Been itching waiting for this video to be released. It should be us thanking you Sir for producing such interesting and informative videos. Thank you so much for sparing us your time to make these vids. Just poured a beer and settling down to watch this episode. My firm belief is: Our legacy is not the personal money or fame we gather during our lifetime its what we pass on to the next generation that we will be remembered. Thanks for sharing 👍 👍 👍
Such true words! I actually got into a bit of an email argument with a guy who feels he must charge for any information he provides. This particular guy came up with a list of components to repair an oscilloscope and when I asked for a copy of the list, he wouldn’t give it to me but he would sell me a “kit” of all the components he had listed to make the repairs. I truly think that everyone will be judged some day and the folks that share and are helpful, like Tony and some others, well... I’m sure hoping that they go right to the front of the line!
@@budandbean1 too many people persue wealth and power but die sad and lonely. Just think of the joy of sharing with family, friends, youngsters and people you meet in day to day life. Unfortunately, in todays world people who share, or are educated are seen as some weird race who ought to be extinguished. I say to wealthy and powerful people build libraries, hospitals, parks, tech centres, museums, not only will you receive joy in your lifetime but you will be remembered long after your departure. The other day I was in the supermarket and the lady in front of me was rooting through her purse, pockets and shopping bag looking for $0.10, her shopping came to $30.10; she had only $30. I had a pocket full of change so i gave her the 10c (the super store would not let her fetch it in next time she passed). The lady thanked me and added "I'm in a hurry my mother is very sick only had a few days left to live and that she had purchased the food to cook her mothers favorite lunch. I felt so good that i could help the lady and her mother enjoy a meal together.
I don't know much, but I've learned quite a bit from watching your channel. I know exactly what you mean by sometimes you have to dive right into something to figure it out. Of course, you got to have some basic fundamentals and common sense. I love this channel and thank you for taking time out of your busy life to share your knowledge with us.
Your video about this wonderfull amp made me decide to finally sign up for youtube. I have restored the same amp in 2014 and it was a lot of work. I don't have the knowledge about electronics that you have (not even close) but i succeeded with a lot of patience, self study and perseverance. It took a few months in recapping, cleaning, testing, checking, fault finding and In the end I managed. I have been listening to this amp since then (it is in my main system) and it was a big step from my Sony VFET TA-N7 & TA E88 combo which i regard highly (also restored by me but less complex). Untill now i used it with a Sony PS-B80 turntable (a restoration project that came close to this amp) with a technics EPC205mk4 mm cartridge. The amp is almost in daily use with Yamaha NS 2000 speakers (berillium high and mid domes) I designed and ordered new pcb's for the power amps and i also created my own improved version of the phono motherboard with modern relays. I also had the earlier version of the motherboard just like the amp you are showing. On the new motherboard i used a less complex switching sheme to reduce the numbers of relays. With phono 1 and 2 i switch between MM and MC. I also applied a grounding upgrade that i read about in a restoration thread from a german tech. This grounding upgrade is essentially the same as the grounding upgrade on the phone motherboard as performed by Sansui. You show it somewhere in the video. You can find my restoration link on audiokarma. I even stripped the amp to bare metal and repainted all steel and I even made some mistakes but by checking everything multiple times I was able to correct all of it. There was/is however one cullprit that i cannot solve. The amp is dead quiet. I did the same testing as you did during the rebuild of the amp and after finishing the amp but as soon as i put in my MC cards i get hum on the MC input. Only on the MC input, the MM is dead quiet. Looking at your video you have given me a hint regarding the hum on the MC. I suspect a ground loop but did not find any yet. This was regarding the ground wires on the MC board (which I have on both side of the board :)) and the ground reference for adjusting the pots. I think i used chassis ground for that.
Tony, I miss words how much I am grateful for the materials you upload to CZcams. I do not know electronics. I have no education in this area. However, I love audio equipment produced in the period from the late seventies to the early nineties of the last century. I do not like lamps, I prefer good transistors and thoughtful hybrid constructions who provide me with more musical pleasure. It is easy to find materials on the network from listening tests of equipment, but very rarely videos of a cognitive and didactic nature, allowing to understand how given amplifiers, recivers or other audio equipment actually work. In addition, why they operate in such and no other way. Your didactic approach to the subject, enriched quite often thanks to reverse engineering, even allows such a complete layman how to understand the signal waveforms, the principle of operation and the implementation of sound in a presented device. I can not afford Top Hi-Fi or Hi-End equipment bacause of money lacking, so I am more pleased to see how such devices are repaired and maintained, so that they peoples will enjoy their musical quality for the next several decades. I am very happy that you have the pleasure and satisfaction of creating your films for us. This means that we can still wait for the next episodes. I assure you that for people of my kind, those movies are still too short. I would be able to watch the video production of such or similar quality all day long. Eagerly waiting for the next episode, satisfied with the present one, I would like to send warm greetings from Poland. By the way - healthier fast and do not get caught up to another disease or infection.
Thank you, Tony for sharing your expertise. I've followed your vintage stereo webcasts with much interest since I have a Sansui 9090 (my favorite piece of gear).
Thank you for the SV03 solution , there's a lot of problem restoring vintage on that issue......alternative putting tree diodes have not the same tempearture behaviour like the original .............your solution may them help out of the dilemma !
Thanks so much Tony, I’ve picked up so much watching your videos. It’s amazing the great ideas that I’ve actually been able to use recently to repair several items. Buddy
This stuff is so mind boggling and at the same time so interesting, and the troubleshooting, it's like a hydraulic circuit but much more intense, I'm fascinated by it and enjoying it, thanks for the great know how, I knew I should have went into electronics instead of vibration analysis.
TR 5, 6, 9 and 10 are cascodes wich would not need to be matched if I am not mistaken. If anything they are making the phase margin bigger instead of eroding the stability. Also the bases of Tr05 and 6 are connected to R13 and not flapping around as shown on the schematic in the video. A source for oscillation could be the voltage source for the cascode of the input FET. Connecting 10nF across R6 should help...
Thanks for the tip on the new driver(?) transistors for these phono slave boards. I have the Purple Motherboard that I have populated, but still need to drop into the amp. I have never heard the phono stage on my X1, as I am restoring it veeerrrrrry slowly.....
I own a vintage Sony TA2000F Pre-amp. I re-designed and re-built the line amp side. I am now about to tackle the phono amp side. This pre-amp has two phono inputs. One dediciated to MM (phono2) and one for different impedance cartridges. The phono stage uses a combination of SONY (first generation) FETs and high volatge (150 VDC !) bi-polars. Most of the boards are plug-in modules. Really well built for 1975 ! Recapped the entire unit 10+ years ago and repalced the line amp FETs with MPSA18s. I'll never "sell" it now !
I hear this often in audio forums. Negative feedback causes TIM distortion (another word for slew rate distortion) and does not work due to delay in the feedback loop. Think this thinking is from the early solid state amplifier days with very slow output transistors. Just to put things right: In a proper designed audio amplifier, feedback will not create TIM. TIM will in fact be reduced by negative feedback. Another mistake is the confusion about phase delay and propagation delay. Time of flight in the feedback loop is in the order of a few nsec. Not usec as mentioned. Compared to audio frequencies, propagation delay is not an issue. Please read litterature on the subject (eg. Cordell, Putzeys)
Im lucky enough to have gotten one of the purple phono motherboards. I've just got to get the courage up to populate it, and drop it into my X1! thats not a bad workaround that you did with the relays at all!
those relays were used (among other consumer habits) in the original JVC VCR'S to switch from SP/LP video head output directly from the rotary transformer so the signal level was extremely low and frequency relatively high. They were mounted directly on the video head drum assy. When the contacts became oxidized the pic of course was distorted. We used to just use some cleaner like Deoxit on a piece of paper that we ran through the contacts and resolve the issue without removing the entire drum assy which would have required a tape path alignment. Anyway, we did this to hundreds of those VCRs and never had another issue. So it's possible that might have also worked here. Just a thought.
Like that you mention local and global negative feedback.I use a mm phono riaa stage with no feedback.My power amplifiers are also without feedback.they are very linear.No problem with os at all.They are also the most quiet circuits i have had with no hiss.Way better than many well known brands witch make so much hiss that i can hear it from my listening place 3meters away.With the no feedback amps in my active setup i have to put my ear close to the tweeter to hear some faint hiss.And i use AMT type tweeters 94db 1w 1 meter sensitive.Osillation was a problem with the first versons.Better components and and a small pcb size(groundloops)credit card size etc helped. 120w 8 ohm 240 in 4 ohm etc.Capable to play loads down to 1 ohm.The bias is set higer if i use a 4 ohm contra a 8 ohm drivers.
That Sansui phono stage is extemeley complex. It looks like a discrete op-amp with the RIAA R/C network in-between. You can build a pretty decent phono amp with just 3 npn (low noise) bi-polars and a 24vdc supply. The MC board looks even more complex !
Yo Tony, you can twist two bits of wire together to make 6 pf, you'll need a decent C meter and if you're really fussy you can use PTFE insulated wire. Keep up the good work!
25:22 : Placing back-to-back polar electrolytics was often used back in the days when non-polar were not available. I don't know what the sonic advantages of this technique but I suspect there must have been some - probably a search in old forums will reveal it.
52:22 : If they're that temperature sensitive, chances are the bias point will change after you put the cover on. In cases like these it helps if you can find a trick that allows you to adjust the pots with the cover on and, ideally, screwed down tight.
If you look at the schematic, right under the FET input stage, there are two BJTs; one PNP and one NPN wired as a self-latching circuit (a.k.a. an SCR); if you apply a positive voltage to the base of the NPN, or a negative voltage to the base of the PNP, they’ll keep each other turned on. I can only presume they meant it to do that; maybe it’s some weird input protection circuit?
I do not touch these matched pairs of transistors when they are good . But I couple them together with some copper foil to stabilize their temperature .
I have to wonder how much solder was on the pad before you soldered the bolt down. My thoughts lean towards how soft solder is. Tightening the bolt onto the transistor will compress the solder by some amount. Since solder is very pliable it will compress and not spring back. Would it make sense to use a split lock washer? Just something to apply a small amount of spring force to keep the bolt tight(er). Also, compression of the solder would tend to create micro cracks into the newly applied solder. I don't think this would be a huge problem, but will eventually (years "decades" likely) lead to a similar issue, especially with heat/cold contraction, and the bolt will be loose again. Edit: just to be clear, the idea to solder the nut into place is a great idea, this is no criticism. I am thinking out loud is all.
What I think about T03 packages is that the electrical collector connection is always through dubious mechanical friction fits of nuts and bolts using different metals. Must have effects on the sound quality.
For the out capcitors back to back .............those who have still some stock of BG-non polar ( the red ones ) may use them here !............or even use them in super E configuration ....than they are non inductive .......
@xraytonyb : In case you rethink your relay board mod, the 12V version of that relay is still available in limited quantities from rfparts, at a reasonable price. Add a resistor, and you're in business.
Yes, I agree on that, it adds peace of mind in the long-term. I also do the same with tiny traces in the power supply area. Some traces are too narrow to save PCB space.
16:54 : Painted subchassis screwed togethrer without the paint being removed equals poor quality control. Often the designer relies on the grover nut removing the paint when tied down, however, these metal parts being aluminium (which oxidises i.e. forming an insulator) and these amps being of a certain age and possibly having been disassembled for repair are things to take note of when restoring. With many quality manufacturers we often see these points where the subchassis meet and are screwed together having been sanded down to remove the paint, copper screws being used etc.
I suppose it would work to replace the NPN transistors with BC182L and the PNP transistors with BC212L, Class A power amps can run very hot and unless it is done properly the output transistors can burn out very quickly so lets just let #xraytonyb do his own thing.
Hey man don't knock the FM (wildcard) Multiplex harmonics 😅 which later on Sony and Sansui would formulate to the modern day EFM CD encoding standard. I can see how today's phono amps took this circuitry developed replacement op amps as to clean up the cheapie transistors and capacitors. As a Sansui and Sherwood (similar FM sound blaster 70's tech) operator those signals can get noisy. If it becomes too much of a hassle switch the knob to 'AUX' get a good 100$ RIAA/DAC/FM based multiplexer, run to the record player and enjoy probably best output amplifier (kicking out the quad) ever made..
10:54 : The downside with modular amps is for every one that is modular there are 20 out there which are not. So it's back to frustration and wondering: why can't they just make them all modular? Let's hope the R2R (right to repair) trend becomes mainstay! 11:24 : While a modular design can make the design of proper grounding implementation harder it's not a necessity that this be the case. After all, the grounding can also be implemented in a modular fashion, albeit at a huge cost increase. It' all comes down to implementation and design refinement. The same argument could be made against the use of PCB's since they restrict the routing of the ground bus. We would need to resort to point-to-point wiring if this was the only way to eliminate grounding issues, yet we have ultra high frequency precision instruments where these issues are being tackled successfully. Usually these are both modular and built with PCB's! One extra point is that it's probably worth checking and cleaning the contacts when putting the boards back together.
Those little black capacitors are a real trouble marker. I changed them all those with modern ones . Hum is problem with this amp I always have tried to solve
Perhaps the relays were designed that way to get around a patent; to create enough of a difference. I cannot see someone deliberately designing a relay that way. Cheers, - Eddy
7:54 : Wow, talk about mirror design PCB's! I will always wonder why amp manufacturers do this. I guess it's to make sure that when your left channel blows that'll you have to order one from them rather than be able to just substitute a second hand one from another half-blown amp. Or it could be that technical support staff is divided into right and left brain types ; )
Great tip this fiber-tip pen (pun intended). Until seeing this I was sure it was just another useless gimmick. How do you go about finding original manufacturer (or identical replacements) for obsolete semiconductors? I'm pulling my hair out trying to guess whether online vendors are actually selling the real deal or just reselling knock-offs. I wouldn't have a problem ordering a sample and trying it out but when you have to order from ten different suppliers abroad - who you don't know whether they're stocking knock-offs or not - suddenly postage costs become a big issue. I wish there was a site out there listing all various vintage transistors (as there is for vacuum tubes). That would be a start when trying to find suitable replacements.
55:20 Do you know how the noise is getting coupled from your lamp to the system? I'd be concerned that power line noise is getting though the power supply.
I think that the noise from the lamp is interfering with the area(s) of the circuit outside of the power supply area, like little antennas spread throughout the volume of the receiver then taking little spikes of magnetic field from an outside source. It should reduce or disappear when the receiver is shielded by its top and bottom covers. The capacitors of the power supply should filter those and it is easy to verify if that is happening with an oscilloscope on the DC rails. If the power supply is not filtering that kind of noise, then something like a 10 uF, 250 VAC film capacitor for each DC rail should solve it, if one can fit those capacitors inside the equipment. I have done that with very good results. One can imagine what happens with the receiver in that condition close to a kitchen... (blender, dishwasher, refrigerator interferences...).
@@kylesmithiii6150 If it's magnetic, then that suggests a "loop" of some kind in the receiver (ground loop?). Depending on what the panels are made of, they won't do any magnetic shielding. (Short of Mu-metal, the shielding will be minimal.) To me, the noise is concerning. There's any number of devices in an audio system that may be turned on or off with the amp on. For example, what happens when your turntable shuts off at the end of the record? I think the test should be run again after the amp is assembled and any problems tracked down.
I think that whoever designed this first thought of a transistor curve and its bias, then found a transistor that matched that design, which happened to be a power transistor operating at certain quiescent point.
It is unfortunate prior meltdowns involving tubes caused the FET/small caps to appear, which can be seen even in these low voltage phono inputs. However in the power amp stage Sansui set the standard. Well into the 80's rebuilt Sansui amps were still sought after in hi fi stores selling higher than new models...
hello, I wanted to know an information for favore.io I own an amp sansui au-x1, I have problem on stage phono after 20 minutes of work begins a buzz..... if I untangle the turntable signal cables it does not show up. I tried to change turntables but the problem persists, you know give me some tips? everything else works perfectly... Thank you.....
Been itching waiting for this video to be released.
It should be us thanking you Sir for producing such interesting and informative videos.
Thank you so much for sparing us your time to make these vids.
Just poured a beer and settling down to watch this episode.
My firm belief is:
Our legacy is not the personal money or fame we gather during our lifetime its what we pass on to the next generation that we will be remembered.
Thanks for sharing
👍 👍 👍
Such true words! I actually got into a bit of an email argument with a guy who feels he must charge for any information he provides. This particular guy came up with a list of components to repair an oscilloscope and when I asked for a copy of the list, he wouldn’t give it to me but he would sell me a “kit” of all the components he had listed to make the repairs. I truly think that everyone will be judged some day and the folks that share and are helpful, like Tony and some others, well... I’m sure hoping that they go right to the front of the line!
@@budandbean1 too many people persue wealth and power but die sad and lonely. Just think of the joy of sharing with family, friends, youngsters and people you meet in day to day life. Unfortunately, in todays world people who share, or are educated are seen as some weird race who ought to be extinguished. I say to wealthy and powerful people build libraries, hospitals, parks, tech centres, museums, not only will you receive joy in your lifetime but you will be remembered long after your departure.
The other day I was in the supermarket and the lady in front of me was rooting through her purse, pockets and shopping bag looking for $0.10, her shopping came to $30.10; she had only $30. I had a pocket full of change so i gave her the 10c (the super store would not let her fetch it in next time she passed). The lady thanked me and added "I'm in a hurry my mother is very sick only had a few days left to live and that she had purchased the food to cook her mothers favorite lunch.
I felt so good that i could help the lady and her mother enjoy a meal together.
I don't know much, but I've learned quite a bit from watching your channel. I know exactly what you mean by sometimes you have to dive right into something to figure it out. Of course, you got to have some basic fundamentals and common sense. I love this channel and thank you for taking time out of your busy life to share your knowledge with us.
Your video about this wonderfull amp made me decide to finally sign up for youtube. I have restored the same amp in 2014 and it was a lot of work. I don't have the knowledge about electronics that you have (not even close) but i succeeded with a lot of patience, self study and perseverance. It took a few months in recapping, cleaning, testing, checking, fault finding and In the end I managed. I have been listening to this amp since then (it is in my main system) and it was a big step from my Sony VFET TA-N7 & TA E88 combo which i regard highly (also restored by me but less complex).
Untill now i used it with a Sony PS-B80 turntable (a restoration project that came close to this amp) with a technics EPC205mk4 mm cartridge. The amp is almost in daily use with Yamaha NS 2000 speakers (berillium high and mid domes)
I designed and ordered new pcb's for the power amps and i also created my own improved version of the phono motherboard with modern relays. I also had the earlier version of the motherboard just like the amp you are showing. On the new motherboard i used a less complex switching sheme to reduce the numbers of relays. With phono 1 and 2 i switch between MM and MC.
I also applied a grounding upgrade that i read about in a restoration thread from a german tech. This grounding upgrade is essentially the same as the grounding upgrade on the phone motherboard as performed by Sansui. You show it somewhere in the video.
You can find my restoration link on audiokarma. I even stripped the amp to bare metal and repainted all steel and I even made some mistakes but by checking everything multiple times I was able to correct all of it.
There was/is however one cullprit that i cannot solve. The amp is dead quiet. I did the same testing as you did during the rebuild of the amp and after finishing the amp but as soon as i put in my MC cards i get hum on the MC input. Only on the MC input, the MM is dead quiet. Looking at your video you have given me a hint regarding the hum on the MC. I suspect a ground loop but did not find any yet. This was regarding the ground wires on the MC board (which I have on both side of the board :)) and the ground reference for adjusting the pots. I think i used chassis ground for that.
I have watched all the videos from this Sansui series so far, great stuff mate ! Bless you mate !!! I reallly appreciate your work!
Oh mate, introduction of Bella was so nice !
Tony, I miss words how much I am grateful for the materials you upload to CZcams. I do not know electronics. I have no education in this area. However, I love audio equipment produced in the period from the late seventies to the early nineties of the last century. I do not like lamps, I prefer good transistors and thoughtful hybrid constructions who provide me with more musical pleasure.
It is easy to find materials on the network from listening tests of equipment, but very rarely videos of a cognitive and didactic nature, allowing to understand how given amplifiers, recivers or other audio equipment actually work. In addition, why they operate in such and no other way. Your didactic approach to the subject, enriched quite often thanks to reverse engineering, even allows such a complete layman how to understand the signal waveforms, the principle of operation and the implementation of sound in a presented device. I can not afford Top Hi-Fi or Hi-End equipment bacause of money lacking, so I am more pleased to see how such devices are repaired and maintained, so that they peoples will enjoy their musical quality for the next several decades.
I am very happy that you have the pleasure and satisfaction of creating your films for us. This means that we can still wait for the next episodes. I assure you that for people of my kind, those movies are still too short. I would be able to watch the video production of such or similar quality all day long.
Eagerly waiting for the next episode, satisfied with the present one, I would like to send warm greetings from Poland.
By the way - healthier fast and do not get caught up to another disease or infection.
Thank you, Tony for sharing your expertise. I've followed your vintage stereo webcasts with much interest since I have a Sansui 9090 (my favorite piece of gear).
I love these amplifier, awesome how much effort they put into the phonostage... Thanks for your informative video's! Greetings from Belgium
Thank you for the SV03 solution , there's a lot of problem restoring vintage on that issue......alternative putting tree diodes have not the same tempearture behaviour like the original .............your solution may them help out of the dilemma !
Thanks so much Tony, I’ve picked up so much watching your videos. It’s amazing the great ideas that I’ve actually been able to use recently to repair several items. Buddy
This stuff is so mind boggling and at the same time so interesting, and the troubleshooting, it's like a hydraulic circuit but much more intense, I'm fascinated by it and enjoying it, thanks for the great know how, I knew I should have went into electronics instead of vibration analysis.
TR 5, 6, 9 and 10 are cascodes wich would not need to be matched if I am not mistaken. If anything they are making the phase margin bigger instead of eroding the stability. Also the bases of Tr05 and 6 are connected to R13 and not flapping around as shown on the schematic in the video. A source for oscillation could be the voltage source for the cascode of the input FET. Connecting 10nF across R6 should help...
Thanks for the tip on the new driver(?) transistors for these phono slave boards. I have the Purple Motherboard that I have populated, but still need to drop into the amp. I have never heard the phono stage on my X1, as I am restoring it veeerrrrrry slowly.....
I own a vintage Sony TA2000F Pre-amp. I re-designed and re-built the line amp side. I am now about to tackle the phono amp side. This pre-amp has two phono inputs. One dediciated to MM (phono2) and one for different impedance cartridges. The phono stage uses a combination of SONY (first generation) FETs and high volatge (150 VDC !) bi-polars. Most of the boards are plug-in modules. Really well built for 1975 ! Recapped the entire unit 10+ years ago and repalced the line amp FETs with MPSA18s. I'll never "sell" it now !
I hear this often in audio forums. Negative feedback causes TIM distortion (another word for slew rate distortion) and does not work due to delay in the feedback loop. Think this thinking is from the early solid state amplifier days with very slow output transistors. Just to put things right: In a proper designed audio amplifier, feedback will not create TIM. TIM will in fact be reduced by negative feedback. Another mistake is the confusion about phase delay and propagation delay. Time of flight in the feedback loop is in the order of a few nsec. Not usec as mentioned. Compared to audio frequencies, propagation delay is not an issue. Please read litterature on the subject (eg. Cordell, Putzeys)
Im lucky enough to have gotten one of the purple phono motherboards. I've just got to get the courage up to populate it, and drop it into my X1! thats not a bad workaround that you did with the relays at all!
When you get around to it you will wonder why you hadn't done it earlier (☞ﾟヮﾟ)☞
You sure surpass your knowledge and skill far out pass my skill set. I just love Sansui integrated amp. Keep fishing
those relays were used (among other consumer habits) in the original JVC VCR'S to switch from SP/LP video head output directly from the rotary transformer so the signal level was extremely low and frequency relatively high.
They were mounted directly on the video head drum assy.
When the contacts became oxidized the pic of course was distorted.
We used to just use some cleaner like Deoxit on a piece of paper that we ran through the contacts and resolve the issue without removing the entire drum assy which would have required a tape path alignment.
Anyway, we did this to hundreds of those VCRs and never had another issue. So it's possible that might have also worked here.
Just a thought.
Like that you mention local and global negative feedback.I use a mm phono riaa stage with no feedback.My power amplifiers are also without feedback.they are very linear.No problem with os at all.They are also the most quiet circuits i have had with no hiss.Way better than many well known brands witch make so much hiss that i can hear it from my listening place 3meters away.With the no feedback amps in my active setup i have to put my ear close to the tweeter to hear some faint hiss.And i use AMT type tweeters 94db 1w 1 meter sensitive.Osillation was a problem with the first versons.Better components and and a small pcb size(groundloops)credit card size etc helped. 120w 8 ohm 240 in 4 ohm etc.Capable to play loads down to 1 ohm.The bias is set higer if i use a 4 ohm contra a 8 ohm drivers.
That Sansui phono stage is extemeley complex. It looks like a discrete op-amp with the RIAA R/C network in-between. You can build a pretty decent phono amp with just 3 npn (low noise) bi-polars and a 24vdc supply. The MC board looks even more complex !
EVERYTHING re: this receiver is complex! :)
Break out boards are awesome !!!
Yo Tony, you can twist two bits of wire together to make 6 pf, you'll need a decent C meter and if you're really fussy you can use PTFE insulated wire.
Keep up the good work!
25:22 : Placing back-to-back polar electrolytics was often used back in the days when non-polar were not available. I don't know what the sonic advantages of this technique but I suspect there must have been some - probably a search in old forums will reveal it.
52:22 : If they're that temperature sensitive, chances are the bias point will change after you put the cover on. In cases like these it helps if you can find a trick that allows you to adjust the pots with the cover on and, ideally, screwed down tight.
If you look at the schematic, right under the FET input stage, there are two BJTs; one PNP and one NPN wired as a self-latching circuit (a.k.a. an SCR); if you apply a positive voltage to the base of the NPN, or a negative voltage to the base of the PNP, they’ll keep each other turned on. I can only presume they meant it to do that; maybe it’s some weird input protection circuit?
I do not touch these matched pairs of transistors when they are good . But I couple them together with some copper foil to stabilize their temperature .
Isn't that a Fairchild logo on the original relay? They were one of the higher end brands in the '70's and '80's.
To replace the wires that shunt/bridge over the circuit board and components I use solid silver wire ( on the back like you do )............faster .
I have to wonder how much solder was on the pad before you soldered the bolt down. My thoughts lean towards how soft solder is. Tightening the bolt onto the transistor will compress the solder by some amount. Since solder is very pliable it will compress and not spring back. Would it make sense to use a split lock washer? Just something to apply a small amount of spring force to keep the bolt tight(er). Also, compression of the solder would tend to create micro cracks into the newly applied solder. I don't think this would be a huge problem, but will eventually (years "decades" likely) lead to a similar issue, especially with heat/cold contraction, and the bolt will be loose again.
Edit: just to be clear, the idea to solder the nut into place is a great idea, this is no criticism. I am thinking out loud is all.
What I think about T03 packages is that the electrical collector connection is always through dubious mechanical friction fits of nuts and bolts using different metals. Must have effects on the sound quality.
In that case I use Carbon Conductive Thermal Compound to help the electrical connection.
For the out capcitors back to back .............those who have still some stock of BG-non polar
( the red ones ) may use them here !............or even use them in super E configuration ....than they are non inductive .......
@xraytonyb : In case you rethink your relay board mod, the 12V version of that relay is still available in limited quantities from rfparts, at a reasonable price. Add a resistor, and you're in business.
Thanks Tony!
Oh Tony, you should learn to love Kicad! I have, but must admit I have made the air turn blue few times using it.
What a lovely dog!
3:55 - I'd solder jumpers from the middle conductor of each of those transistors to their corresponding tracings on the PC board, just to be safe!
Yes, I agree on that, it adds peace of mind in the long-term. I also do the same with tiny traces in the power supply area. Some traces are too narrow to save PCB space.
Funny story about the new tech as a systems tech with AT&T I can relate.
28:30 - This behavior is just a couple of steps up from 'magical thinking' :)
16:54 : Painted subchassis screwed togethrer without the paint being removed equals poor quality control. Often the designer relies on the grover nut removing the paint when tied down, however, these metal parts being aluminium (which oxidises i.e. forming an insulator) and these amps being of a certain age and possibly having been disassembled for repair are things to take note of when restoring. With many quality manufacturers we often see these points where the subchassis meet and are screwed together having been sanded down to remove the paint, copper screws being used etc.
I suppose it would work to replace the NPN transistors with BC182L and the PNP transistors with BC212L, Class A power amps can run very hot and unless it is done properly the output transistors can burn out very quickly so lets just let #xraytonyb do his own thing.
Hey man don't knock the FM (wildcard) Multiplex harmonics 😅 which later on Sony and Sansui would formulate to the modern day EFM CD encoding standard. I can see how today's phono amps took this circuitry developed replacement op amps as to clean up the cheapie transistors and capacitors. As a Sansui and Sherwood (similar FM sound blaster 70's tech) operator those signals can get noisy. If it becomes too much of a hassle switch the knob to 'AUX' get a good 100$ RIAA/DAC/FM based multiplexer, run to the record player and enjoy probably best output amplifier (kicking out the quad) ever made..
Nice work on the Phono boards Tony, I thought you'd end up replacing those transistors. Those relays are awful, no doubt about it!!
Give a man a fish and he will eat for a day. Teach a man to fish and he will sit in a boat and drink beer all day.
10:54 : The downside with modular amps is for every one that is modular there are 20 out there which are not. So it's back to frustration and wondering: why can't they just make them all modular?
Let's hope the R2R (right to repair) trend becomes mainstay!
11:24 : While a modular design can make the design of proper grounding implementation harder it's not a necessity that this be the case. After all, the grounding can also be implemented in a modular fashion, albeit at a huge cost increase. It' all comes down to implementation and design refinement. The same argument could be made against the use of PCB's since they restrict the routing of the ground bus. We would need to resort to point-to-point wiring if this was the only way to eliminate grounding issues, yet we have ultra high frequency precision instruments where these issues are being tackled successfully. Usually these are both modular and built with PCB's!
One extra point is that it's probably worth checking and cleaning the contacts when putting the boards back together.
11:40 - Tony, Molex connectors are HORRIBLE for audio! At least clean them like you did to those power transistors.
Why?
Those connectors look too much like the ones in equipment that I always had to fiddle with because the connectors were high resistance and unreliable.
Those little black capacitors are a real trouble marker. I changed them all those with modern ones . Hum is problem with this amp I always have tried to solve
;) SWMBO: Behind any great man there is a strong woman (sometimes rolling her eyes!)
Perhaps the relays were designed that way to get around a patent; to create enough of a difference. I cannot see someone deliberately designing a relay that way.
Cheers,
- Eddy
7:54 : Wow, talk about mirror design PCB's! I will always wonder why amp manufacturers do this. I guess it's to make sure that when your left channel blows that'll you have to order one from them rather than be able to just substitute a second hand one from another half-blown amp. Or it could be that technical support staff is divided into right and left brain types ; )
03:07 - A resistor, or an open circuit!
Could your use nylock nuts on the transistor bolts?
This one I liked.
Great tip this fiber-tip pen (pun intended). Until seeing this I was sure it was just another useless gimmick.
How do you go about finding original manufacturer (or identical replacements) for obsolete semiconductors? I'm pulling my hair out trying to guess whether online vendors are actually selling the real deal or just reselling knock-offs. I wouldn't have a problem ordering a sample and trying it out but when you have to order from ten different suppliers abroad - who you don't know whether they're stocking knock-offs or not - suddenly postage costs become a big issue.
I wish there was a site out there listing all various vintage transistors (as there is for vacuum tubes). That would be a start when trying to find suitable replacements.
Great video for the dud
Hi Tony, where do you get those fiber brushes? Been looking and haven't located one. Maybe not using the correct description.
Found them!
55:20 Do you know how the noise is getting coupled from your lamp to the system? I'd be concerned that power line noise is getting though the power supply.
I think that the noise from the lamp is interfering with the area(s) of the circuit outside of the power supply area, like little antennas spread throughout the volume of the receiver then taking little spikes of magnetic field from an outside source. It should reduce or disappear when the receiver is shielded by its top and bottom covers. The capacitors of the power supply should filter those and it is easy to verify if that is happening with an oscilloscope on the DC rails. If the power supply is not filtering that kind of noise, then something like a 10 uF, 250 VAC film capacitor for each DC rail should solve it, if one can fit those capacitors inside the equipment. I have done that with very good results. One can imagine what happens with the receiver in that condition close to a kitchen... (blender, dishwasher, refrigerator interferences...).
@@kylesmithiii6150 If it's magnetic, then that suggests a "loop" of some kind in the receiver (ground loop?). Depending on what the panels are made of, they won't do any magnetic shielding. (Short of Mu-metal, the shielding will be minimal.) To me, the noise is concerning. There's any number of devices in an audio system that may be turned on or off with the amp on. For example, what happens when your turntable shuts off at the end of the record? I think the test should be run again after the amp is assembled and any problems tracked down.
@@russellhltn1396 Yes indeed, I agree, that kind of interference needs to be eliminated.
You really should fix the spelling error in "weird" in the intro roll...
Are the blue resistors 1% tolerance?
Hmmm., Why does a phono stage need power transistors?
I think that whoever designed this first thought of a transistor curve and its bias, then found a transistor that matched that design, which happened to be a power transistor operating at certain quiescent point.
@@kylesmithiii6150 Yeah I thought about this a bit. This amp has to be FAST so there's a lot of voltage involved (+/- 47.5V supply).
I was wondering that myself. I thought maybe it was on-board power regulation, but I'm not seeing it in the schematic.
It is unfortunate prior meltdowns involving tubes caused the FET/small caps to appear, which can be seen even in these low voltage phono inputs. However in the power amp stage Sansui set the standard. Well into the 80's rebuilt Sansui amps were still sought after in hi fi stores selling higher than new models...
I'm guessing that Sansui sold so few of these units, that a recall wouldn't have been warranted :) This product just looks horribly complex!
Hey Tony, my stuff's broken... why?
My eyes are too old to work with smd without serious magnification! 🤓🤓🤓
Shit, wow ground loops
hello, I wanted to know an information for favore.io I own an amp sansui au-x1, I have problem on stage phono after 20 minutes of work begins a buzz..... if I untangle the turntable signal cables it does not show up. I tried to change turntables but the problem persists, you know give me some tips? everything else works perfectly... Thank you.....
That phono stage is definitely over engineered . The sound is definitely colored by all that stuff