Thank you Tony and your family for taking the time to make such interesting restoration videos. Also sorry about your pet passing. Lots of good times I'm sure.
it never seese to amaze me how small components have gotten in comparison to originals made back in the day, oh how tech has advanced thanks for sharing it's appreciated :) 73' k7sce
First I'd like to say I'm sorry to hear about the loss of your cat, I have had dogs pass away and believe me I know how it can hurt. There are still good people in this world but some of the best have 4 legs. I really enjoy following the Sansui amp repair videos as I had an AU-X911DG years back, I had a lot of fun with that amp and it weighed a ton! In the background that speaker looks like a Minimus 77, amazing speakers.
All the black flag caps looked all pitted and horrible in my X1 when I took them out. Interesting comments on the factory soldering - I had to totally reflow my powersupply board as some dry joints in there were causing some major issues.
Tony I am sorry to hear about your cat !!!! As I watch this video My female cat ( Christmas ) is draped over my right shoulder and we are both watching your video. Yup I love both cats and dogs dearly and miss them terribly when they go !!!! I have shed a few tears for your loss of your beloved kitty today !!!!!!!!!!! I found my cat just 3 weeks before Christmas 13 years ago, she was about 2 weeks old as her eyes were just opening up. She is all White but has a Black tail, a small Black round spot on her back and 2 small Black stripes, one at the base of each ear on the top of her head !! they are equal length and almost the same width !!!!!! Even the Veterinarian says " She is uniquely marked!! "
the option for a small trafo drives the input stages on each of my power amp channels and a big one drive the output.i Dont use that otion yet.Have to buy the 2 small toroid trafo,s.The rest of my psu pcb have 2 full bridge rectifiers and 10 000uf pr input stage and 40 000uf for the output stage wich are in use with 2 bigger rectifiers.Fun to se that other gear have used the same setup.i guess why they made it that way is the same.Since i always have done some repair and el builds i learn somthing new and other ways of doing things by watching your videos and eevblog etc.It has made me better at what i do:Thanks
if I remember correctly bang and olufsen were using mylar caps on some of their audio products in the mid to late 1980's shame I don't have a copy of the specs for the mylar types to compare with other types or remember what was special about them and what applications they suited . it is a shame to see how butchered this unit is in places I have a similar issue on a 1970s transistor radio I am working on where pcb tracks have been damaged i think I have mitigated the worst of it I will see next week when I can get time to work on it again. thanks for the video i enjoy watching your careful and thoughtful work.
I missed that video. I’m so sorry to hear of your lovely cats passing. When all said and done they are family and their passing is just as big as a human family member passing. Sending all of you supportive hugs.
Being owned by four cats please accept my condolences. Tony, you have a great way with electronics and people. I'd love to have you recap my Sony's. Both the TA-2650 and the TA-F3A. Stay safe in these COVID 19 times.
Will be following this video series for sure and you sure have your work cut out on this beast. Having worked on and rebuilt a couple of Sansui AU-919's they're complex but no where near the complexity of the AU-X1! And the same black low value capacitors are in them too so all need to go. Have never seen an X1 in the flesh but hope to some day. Always enjoy your videos so keep up the great restorations!
Sorry to hear about your cat, I lost mine nearly 4 years ago, one of the most upsetting things I've been thru, he wasn't just a cat he was my best friend
So sad to hear your kitty passed away - I don’t recall seeing it on any of your videos, but I hope it’s in kitty heaven! 😻 Please consider adopting a black cat from a local animal shelter; they need a forever home! Maybe you could make a video about getting a new cat. 😋
Dont replace the Toshiba 2SA968 and 2SC2238 transistors unless you have to, and if you have to, but some Toshibas NOS in there, they can be found fairly easily, the replacements you used are not suitable due to their low bandwidth, the Toshibas are 100mhz, your replacement is only 4mhz. This will compromise the amplifiers performance by limiting its speed. Good to see you digging into an AU-X1, I have done two of these amps, and they are full of gotcha's. Watching with interest.
I already received an e-mail pointing this out. Definitely a mistake on my part! I have the correct ones on order and will be doing a follow-up video on the transistors in this unit in general. Thanks for bringing this up. It's one of the reasons I enjoy sharing these videos. We all learn!
@@xraytonyb nice one, I admire the work you put into these videos, its hard enough doing this work as it is let alone trying to film it and explain what you're doing along the way!! I have learned a lot from watching your videos, its a great resource...
I am sorry to hear of the loss of your cat, it is always a hard thing when a pet passes. I will be following the series on this amp with interest. There where was some bodged work on that beast. Some models of Sansui are known for factory wiring errors, my one friend fixed one model and found over 30 factory wiring errors. I also wonder if this amp is going to have issues with the Hitachi transistors that go noisy as they age, or the other issue that some of them have, loss of gain with age.
I like this pair, but the Pioneer and me have history. Sansui not so much, but the 9090db and this group you have are nice. The BA-3000 Amplifier was the japanese Krell.
Have you ever restored an AU-9900? I have one with intermitant sound on left and right channel. I would like to try changing only parts that could relate to such a problem. I think it happens on all inputs, but I have only used the PHONO 1 and 2 inputs. I want to do a FULL re-cap one day but would love to see a video of it being done. I would love to upgrade any parts that would improve the sound, too! Same with my SA-7500 and SL-1700MKII.
The output transistors on my AU-X1 are all 2SC2493N and 2SA1068N. HFE ranges from 72 to 172. Vbe is 0.6. They have the same tarnish etc. I think mine is a later revision and seems to be untampered.
Sorry to hear that you lost your kitty cat. I lost my Cleopatra 20 years ago and yet I still miss her. She was my baby. GHETTO RIGGED is the proper scientific term for the previous repair attempts on this device.
@@xraytonyb They are really high quality and have a amazing temperature coefficient with very stable value. Their one major disadvantage is they are very easily damaged by heat. You must use caution when soldering them. If the capacitor itself reaches a temperature above 70°C the capacitor will start to change value and stay there when it cools back down. Basically because the polystyrene is starting to melt.
About fifteen years ago, I found out that if you put too much voltage on them (like in tube gear), they really make a loud POP when they blow :) Don't ask..... :P
Been several years since I blew up a capacitor. The last one I did was a 100uF 675V cap in a tube type RF amplifier. They had a dozen of them in series parallel to get the capacitance value and 1200 Volt rating they needed. I accidently connected one backwards. I keyed the microphone on the radio and the cap in the amplifier went BOOM!!!!! I had paper fuzz and aluminum foil fragments everywhere. Thing went off like a M80 firecracker. Let's just say I have been a lot more careful when installing high voltage electrolytics since then. Especially ones in series parallel configuration.
Good question! It can be a bit confusing, but the DCA does two different tests. The "Ic" displayed is the collector current used for the Hfe test. The "Ib" displayed is for the Vbe test. Also, I only consider the DCA as a quick test for these transistors to make sure there are no shorts, etc. The Hfe of a power transistor can be quite different when it is operating closer to its rated power. The DCA only uses very small voltages and current in the tests. To properly test these, I would need to use my curve tracer, which can apply up to 500 volts and 10 amps (not at the same time) to the transistor.
Oh also replace R31 and R34 on the driver boards, they are fusible resistors and drift quite badly. Its all coming back now, these amps are a huge amount of work!!
@@xraytonyb Its a Sansui thing, most their biasing circuits have fusible resistors in that particular position, the G series receivers comes to mind, a lot of the DC coupled intergated amps... I always watch your videos, I always enjoy them!!
Sorry about your cat I miss my cat she's only 8 months old but she was very affectionate never had a cat like that before more like a dog than a cat. What was so special about these black capacitors... and if you're changing them surely this affects the sound of the amp how do you decide what to replace it with. But using ceramic is a noisy capacitor surely this is not good, I would of sort the polystyrene would be better choice. Why did you take the induction coil out what's the reason for that....?
Those STV3H and STV4H diodes are a pain. You are right, they may be replaced by 3 of 4 small diodes in series. You can encapsulate those diodes together in one small block of epoxy resin, since thermal stability and heat transfer is an issue.
They're a special type of bipolar. I believe that they are ring emitter transistors (more on that on the next video), but I'm not sure. Datasheets for these are pretty sparse. The big difference form other power transistors is that they have a transistion frequency of 60MHz. Most of the common power transistors only have Ft of a few MHz or even less than 1 MHz. They were one of the selling points of this amp.
I would totally take out the boards I would change all the capacitors in the amp. It is a mess for sure. Change all please what a chore .over my grad level
I'm sad to hear about your cat... I also had a cat who died a few years ago and understand your pain. It's a family member whose loss is hard to ignore. I wich time and maybe another pet friend will help you and your family to have better moments. We are many collectors and hobbyists to consider Sansui as a reference in Japanese audio equipment. But we all know the company made quality amps and from time to time fairly ugly monsters. I'd say the 1980' to early 1990 was a deceptive period, as many other renowned ones. With Sansui, from times to times was a reminiscence of lost splendors, and some series were high above the rest. Here we have something looking far more like a prototype, with different circuits, many added wires, added or maybe surplus component and a long history of fails and repair stations. All that does not sound as high quality model like earlier AU 11000. These monsters had no serious competitors then, even if others were close to achieve such level only a few years later. Many used also special early design special transistors, like Sony's famous VFets, that are still considered absolute reference in terms of quality and difficulty to obtain. Nelson Pass, audio guru of olde times, also conceived a kit with these 2SJ18 and 2SK60, so they get even and faster impossible to obtain! You say that these power transistors were mismatched and that is not necessary a bad case, but I don't believe a high stability and thermal equilibrium can be reached with this. I think many early high speed large bandwidth amps were deliberately deprived from a good counter reaction to get even better phasis and linearity results. I've read many Engineers disputing about the ideal goal of making without counter reaction, and thus using minimum circuitry, or including components whose failure could destroy the total power stage. Also seen that in tube amps.... However, I believe the people who repaired this amp should have replaced all three PNP to get similar curbs. In that case, knowing they had some access to these Unobtanium, the choice was clear. I don't know if the second amp suffered of the same problems, but maybe it's still possible to get a complete set? You and I suppose the initial design was good enough to compensate for such differences, but if power load resistors are failing, you can get another destruction. We can also guess it can contribute to noise or distortion including HF oscillations if these black mylar caps are failing to compensate electrolytics in HF decoupling and filtering. These kind of amps require specially well designed power supply, with high caps values and or coiled snubber circuits. Last thing is I don't understand how the second load resistor came unconnected! Another way to question the design of this amplifier or the way it was repaired. A hard job with lots of questions and surprises. I'm confident you'll make another success of this one and surely make it a far better and safer amp than when it was produced in Japan 40 years ago!
I agree. The whole thing for me is a bag of worms. The age is no reason to restaurate a device. And by the way.... Sansui in Germany had a very bad reputation. Old shit and new shit have something the same: shit! Throw it into the trash bin.
You guys try producing a boundary-pushing flagship amplifier with the means of 1978 (no physical checks in CAD!) as a medium-size manufacturer and come up with something better. These units are the equivalent of an exotic supercar or luxury sedan, and anyone watching corresponding car channels should be able to tell you that those can be a real pain in the rear end, especially when they get on in years. Ferraris with a penchant for engine fires, Audi R8 with frame issues right from the factory, and I wouldn't wish a badly-kept mid/late-2000s S-Class with loads of electronics problems on my worst enemy. Yet people still want these, despite the likes of a Toyota Corolla giving better gas mileage and reliability. So don't be silly. I mean, I would prefer using something more basic but reliable and "good enough", too. It's still nice to be seeing these exotic models come in though. I would advise having a look at the specifications, block diagram and schematic for a better understanding of why these are respected the way they are. Between the overbuilt power supply, low distortion (also thanks to high slew rate), two-stage volume control and very low-noise MM/MC preamps, these would still be considered a very respectable performer today.
@@PileOfEmptyTapes hit pretty much every point that I'd try to make. Sansui did start to have a lot of hit and miss gear in the late 70s to early 80s when they began to really switch over with their junk gear. This amplifier was well designed but early revisions of gear sometimes had problems. Remember all of this stuff was designed mostly by hand. A lot of the other issues are also little unforeseeable ones (conductive glue) and production quality problems. Even some of Sansui's early 80s lesser regarded gear, though built to a price, often performed quite well. I had one particular receiver from the early 80s that most would over look and throw in the bin. Performance and sound characteristics however make it a very decent little unit. It's missing some things like a proper delayed / protection circuit to cut costs, which I added later with an upgraded power supply. I had another integrated years ago that was built similarly, but had re-used one of their earlier MOSFET output stage designs. It seems they were cutting costs where possible when it _wouldn't_ affect overall sound quality. People often overlook little things like this and just write the whole piece of gear off as junk but a lot of the times the engineers had a specific goal in mind -- keeping the gear sounding and performing well while sacrificing what they could to meet marketings stringent cost requirements. In my opinion, Sansui had some of these rare engineers working that actually kept these things in mind and tried to produce something worth purchasing.
I've been a Sansui collector for years.
That Serial Number should break down as:
23 - AU-X1
8 - 1978
12 - December
0079 - Sequential Number
The serial number for mine starts with: 21906... I assume the 21 vs 23 defines region. Mine is a Japan 100V version
Thank you Tony and your family for taking the time to make such interesting restoration videos. Also sorry about your pet passing. Lots of good times I'm sure.
it never seese to amaze me how small components have gotten in comparison to originals made back in the day, oh how tech has advanced
thanks for sharing it's appreciated :)
73' k7sce
And to think, those tiny caps are rated for 200 volts!
You had me at "parasitic oscillation".
First I'd like to say I'm sorry to hear about the loss of your cat, I have had dogs pass away and believe me I know how it can hurt. There are still good people in this world but some of the best have 4 legs. I really enjoy following the Sansui amp repair videos as I had an AU-X911DG years back, I had a lot of fun with that amp and it weighed a ton! In the background that speaker looks like a Minimus 77, amazing speakers.
All the black flag caps looked all pitted and horrible in my X1 when I took them out. Interesting comments on the factory soldering - I had to totally reflow my powersupply board as some dry joints in there were causing some major issues.
Awesome video, thank you for showing!
Tony I am sorry to hear about your cat !!!! As I watch this video My female cat ( Christmas ) is draped over my right shoulder and we are both watching your video. Yup I love both cats and dogs dearly and miss them terribly when they go !!!! I have shed a few tears for your loss of your beloved kitty today !!!!!!!!!!! I found my cat just 3 weeks before Christmas 13 years ago, she was about 2 weeks old as her eyes were just opening up. She is all White but has a Black tail, a small Black round spot on her back and 2 small Black stripes, one at the base of each ear on the top of her head !!
they are equal length and almost the same width !!!!!! Even the Veterinarian says " She is uniquely marked!! "
Your cautious approach reminds me of the Oath of Hypocrites: "Do no harm." :)
the option for a small trafo drives the input stages on each of my power amp channels and a big one drive the output.i Dont use that otion yet.Have to buy the 2 small toroid trafo,s.The rest of my psu pcb have 2 full bridge rectifiers and 10 000uf pr input stage and 40 000uf for the output stage wich are in use with 2 bigger rectifiers.Fun to se that other gear have used the same setup.i guess why they made it that way is the same.Since i always have done some repair and el builds i learn somthing new and other ways of doing things by watching your videos and eevblog etc.It has made me better at what i do:Thanks
Very cool Tony, I love watching.
if I remember correctly bang and olufsen were using mylar caps on some of their audio products in the mid to late 1980's shame I don't have a copy of the specs for the mylar types to compare with other types or remember what was special about them and what applications they suited . it is a shame to see how butchered this unit is in places I have a similar issue on a 1970s transistor radio I am working on where pcb tracks have been damaged i think I have mitigated the worst of it I will see next week when I can get time to work on it again. thanks for the video i enjoy watching your careful and thoughtful work.
Mylar in theory don't absorb moisture and are very stable over temperature changes,,,
I missed that video. I’m so sorry to hear of your lovely cats passing. When all said and done they are family and their passing is just as big as a human family member passing. Sending all of you supportive hugs.
Thanks Tony! Sorry to hear about your kitty. It sucks losing a good pet!
Being owned by four cats please accept my condolences. Tony, you have a great way with electronics and people. I'd love to have you recap my Sony's. Both the TA-2650 and the TA-F3A. Stay safe in these COVID 19 times.
What a great channel! Sorry about your kitty....my condolences.
Sorry about cookie. Love your channel!
Will be following this video series for sure and you sure have your work cut out on this beast. Having worked on and rebuilt a couple of Sansui AU-919's they're complex but no where near the complexity of the AU-X1! And the same black low value capacitors are in them too so all need to go. Have never seen an X1 in the flesh but hope to some day. Always enjoy your videos so keep up the great restorations!
Sorry to hear about your cat, I lost mine nearly 4 years ago, one of the most upsetting things I've been thru, he wasn't just a cat he was my best friend
So sad to hear your kitty passed away - I don’t recall seeing it on any of your videos, but I hope it’s in kitty heaven! 😻 Please consider adopting a black cat from a local animal shelter; they need a forever home! Maybe you could make a video about getting a new cat. 😋
Dont replace the Toshiba 2SA968 and 2SC2238 transistors unless you have to, and if you have to, but some Toshibas NOS in there, they can be found fairly easily, the replacements you used are not suitable due to their low bandwidth, the Toshibas are 100mhz, your replacement is only 4mhz. This will compromise the amplifiers performance by limiting its speed.
Good to see you digging into an AU-X1, I have done two of these amps, and they are full of gotcha's. Watching with interest.
I already received an e-mail pointing this out. Definitely a mistake on my part! I have the correct ones on order and will be doing a follow-up video on the transistors in this unit in general. Thanks for bringing this up. It's one of the reasons I enjoy sharing these videos. We all learn!
@@xraytonyb nice one, I admire the work you put into these videos, its hard enough doing this work as it is let alone trying to film it and explain what you're doing along the way!! I have learned a lot from watching your videos, its a great resource...
My guess on the added black wire was to change the inductance of that trace. Either that, or lower the resistance.
What a mammoth task you have there Anthony.
It's a shame Sansui put some junky parts in such a high end unit..
i still have both of the, good working, only1 or 2 leds must be renewd....., Speakers connected are the ESS-am1
I am sorry to hear of the loss of your cat, it is always a hard thing when a pet passes.
I will be following the series on this amp with interest. There where was some bodged work on that beast. Some models of Sansui are known for factory wiring errors, my one friend fixed one model and found over 30 factory wiring errors.
I also wonder if this amp is going to have issues with the Hitachi transistors that go noisy as they age, or the other issue that some of them have, loss of gain with age.
I like this pair, but the Pioneer and me have history. Sansui not so much, but the 9090db and this group you have are nice. The BA-3000 Amplifier was the japanese Krell.
Maybe the little split in the solder pad is for thermal relief?
Have you ever restored an AU-9900? I have one with intermitant sound on left and right channel. I would like to try changing only parts that could relate to such a problem. I think it happens on all inputs, but I have only used the PHONO 1 and 2 inputs. I want to do a FULL re-cap one day but would love to see a video of it being done. I would love to upgrade any parts that would improve the sound, too! Same with my SA-7500 and SL-1700MKII.
The output transistors on my AU-X1 are all 2SC2493N and 2SA1068N. HFE ranges from 72 to 172. Vbe is 0.6. They have the same tarnish etc. I think mine is a later revision and seems to be untampered.
What is the best way to clean old corrosive capacitor glue off the boards?
Tony, just a thought. This Amp is very tightly packed and likely gets very hot when playing. Some cooling arrangement would likely be very helpful.
Sorry to hear that you lost your kitty cat. I lost my Cleopatra 20 years ago and yet I still miss her. She was my baby. GHETTO RIGGED is the proper scientific term for the previous repair attempts on this device.
is there any protection circuits that shut down this monster from parasitic occilations self destruct mode when parts fail ?? mmmm?
I am sorry about cookie. I lost 3 dogs too, I feel your pain, but know cookie is in heaven with my dogs too.
I do miss Sansui!!!!
My condolences to your cat!!!
if you read the history about Sansui there was a lot of miss management etc
by the way your a great teacher tony high school would been more cool with a electronics class *!
Will you have to climb inside to fix it?
I have an untouched AU-X1. What would be an estimated cost to restore?
I am right there with you with the furry pets...lost 2 since 2015, and believe my last friend is on his way...this is 3.16.2019.
Sorry about the loss of your kitty
nightmare to work on
39:10 - I see two UNSOLDERED leads (upper-right)!
Looks like a component Tony has desoldered for removal, no biggie. It might be a resistor or cap he was swapping out..
Yes, it was desoldered for replacement. It was fixed after I shot the vidoe clip.
Thanks for watching!
Man what a mess. That thing needed a ton of work
The radial lead capacitors with clear bodies look like polystyrene capacitors.
That's the name I was trying to remember!!
@@xraytonyb
They are really high quality and have a amazing temperature coefficient with very stable value. Their one major disadvantage is they are very easily damaged by heat. You must use caution when soldering them. If the capacitor itself reaches a temperature above 70°C the capacitor will start to change value and stay there when it cools back down. Basically because the polystyrene is starting to melt.
About fifteen years ago, I found out that if you put too much voltage on them (like in tube gear), they really make a loud POP when they blow :)
Don't ask..... :P
Been several years since I blew up a capacitor. The last one I did was a 100uF 675V cap in a tube type RF amplifier. They had a dozen of them in series parallel to get the capacitance value and 1200 Volt rating they needed. I accidently connected one backwards. I keyed the microphone on the radio and the cap in the amplifier went BOOM!!!!! I had paper fuzz and aluminum foil fragments everywhere. Thing went off like a M80 firecracker. Let's just say I have been a lot more careful when installing high voltage electrolytics since then. Especially ones in series parallel configuration.
sorry about your cat dear friend...from mauritius
How is that Atlas DCA giving you beta = 303, when Ic = 2.50mA and Ib = 4.79 mA?
Good question! It can be a bit confusing, but the DCA does two different tests. The "Ic" displayed is the collector current used for the Hfe test. The "Ib" displayed is for the Vbe test. Also, I only consider the DCA as a quick test for these transistors to make sure there are no shorts, etc. The Hfe of a power transistor can be quite different when it is operating closer to its rated power. The DCA only uses very small voltages and current in the tests. To properly test these, I would need to use my curve tracer, which can apply up to 500 volts and 10 amps (not at the same time) to the transistor.
Oh also replace R31 and R34 on the driver boards, they are fusible resistors and drift quite badly. Its all coming back now, these amps are a huge amount of work!!
Already done. Just didn't make it into the video. Thanks for watching!
@@xraytonyb Its a Sansui thing, most their biasing circuits have fusible resistors in that particular position, the G series receivers comes to mind, a lot of the DC coupled intergated amps... I always watch your videos, I always enjoy them!!
I have a AUX1 in need of repair
bias pots go bad in theses and the transistors get tin whiskers disease
Sorry about your cat I miss my cat she's only 8 months old but she was very affectionate never had a cat like that before more like a dog than a cat.
What was so special about these black capacitors... and if you're changing them surely this affects the sound of the amp how do you decide what to replace it with. But using ceramic is a noisy capacitor surely this is not good, I would of sort the polystyrene would be better choice.
Why did you take the induction coil out what's the reason for that....?
Sorry about your Cat . We lost owner dog sparky He was Jack Russell.
on 1-6-18 age 14 . We now have new dog Poppy . Very Sad when Lost or Cat
Lot number.
Loose a pet really hurts.
Oh god, they replaced the SV03 diodes. The ONLY THING that follows those closely are 3x 1N4150. That 1068N looks like a chinese fake to me.
Those STV3H and STV4H diodes are a pain. You are right, they may be replaced by 3 of 4 small diodes in series. You can encapsulate those diodes together in one small block of epoxy resin, since thermal stability and heat transfer is an issue.
So are the outputs bipolar or mosfet?
Bipolar - high speed. They operate at 100mHz. They are no longer obtainable - making this amplifier even more special
They are NPN and PNP type transistors, epitaxial planar type.
@@simonbarr9476 Incorrect, they operate at 60mhz.
They're a special type of bipolar. I believe that they are ring emitter transistors (more on that on the next video), but I'm not sure. Datasheets for these are pretty sparse. The big difference form other power transistors is that they have a transistion frequency of 60MHz. Most of the common power transistors only have Ft of a few MHz or even less than 1 MHz. They were one of the selling points of this amp.
Pets aren't friends they are family. Terribly sorry for your loss.
I am so sorry my dear dog Bear did yesterday and your cat I am so sad and lonely. He was with me everywhere and your cat was the same friend
I would totally take out the boards I would change all the capacitors in the amp. It is a mess for sure. Change all please what a chore .over my grad level
I was watching a video by another author .. he saw this kind of thing, and called it “San-Sewage” ...
I'm sad to hear about your cat... I also had a cat who died a few years ago and understand your pain. It's a family member whose loss is hard to ignore. I wich time and maybe another pet friend will help you and your family to have better moments.
We are many collectors and hobbyists to consider Sansui as a reference in Japanese audio equipment. But we all know the company made quality amps and from time to time fairly ugly monsters. I'd say the 1980' to early 1990 was a deceptive period, as many other renowned ones. With Sansui, from times to times was a reminiscence of lost splendors, and some series were high above the rest. Here we have something looking far more like a prototype, with different circuits, many added wires, added or maybe surplus component and a long history of fails and repair stations. All that does not sound as high quality model like earlier AU 11000. These monsters had no serious competitors then, even if others were close to achieve such level only a few years later. Many used also special early design special transistors, like Sony's famous VFets, that are still considered absolute reference in terms of quality and difficulty to obtain. Nelson Pass, audio guru of olde times, also conceived a kit with these 2SJ18 and 2SK60, so they get even and faster impossible to obtain!
You say that these power transistors were mismatched and that is not necessary a bad case, but I don't believe a high stability and thermal equilibrium can be reached with this. I think many early high speed large bandwidth amps were deliberately deprived from a good counter reaction to get even better phasis and linearity results. I've read many Engineers disputing about the ideal goal of making without counter reaction, and thus using minimum circuitry, or including components whose failure could destroy the total power stage. Also seen that in tube amps.... However, I believe the people who repaired this amp should have replaced all three PNP to get similar curbs. In that case, knowing they had some access to these Unobtanium, the choice was clear. I don't know if the second amp suffered of the same problems, but maybe it's still possible to get a complete set? You and I suppose the initial design was good enough to compensate for such differences, but if power load resistors are failing, you can get another destruction. We can also guess it can contribute to noise or distortion including HF oscillations if these black mylar caps are failing to compensate electrolytics in HF decoupling and filtering. These kind of amps require specially well designed power supply, with high caps values and or coiled snubber circuits.
Last thing is I don't understand how the second load resistor came unconnected! Another way to question the design of this amplifier or the way it was repaired.
A hard job with lots of questions and surprises. I'm confident you'll make another success of this one and surely make it a far better and safer amp than when it was produced in Japan 40 years ago!
Y
Why do you start out saying this amp is a top quality unit when everything in the video say otherwise? It seems like a real piece of junk to me.
I agree. The whole thing for me is a bag of worms. The age is no reason to restaurate a device. And by the way.... Sansui in Germany had a very bad reputation. Old shit and new shit have something the same: shit! Throw it into the trash bin.
You guys try producing a boundary-pushing flagship amplifier with the means of 1978 (no physical checks in CAD!) as a medium-size manufacturer and come up with something better. These units are the equivalent of an exotic supercar or luxury sedan, and anyone watching corresponding car channels should be able to tell you that those can be a real pain in the rear end, especially when they get on in years. Ferraris with a penchant for engine fires, Audi R8 with frame issues right from the factory, and I wouldn't wish a badly-kept mid/late-2000s S-Class with loads of electronics problems on my worst enemy. Yet people still want these, despite the likes of a Toyota Corolla giving better gas mileage and reliability. So don't be silly.
I mean, I would prefer using something more basic but reliable and "good enough", too. It's still nice to be seeing these exotic models come in though. I would advise having a look at the specifications, block diagram and schematic for a better understanding of why these are respected the way they are. Between the overbuilt power supply, low distortion (also thanks to high slew rate), two-stage volume control and very low-noise MM/MC preamps, these would still be considered a very respectable performer today.
@@PileOfEmptyTapes hit pretty much every point that I'd try to make. Sansui did start to have a lot of hit and miss gear in the late 70s to early 80s when they began to really switch over with their junk gear. This amplifier was well designed but early revisions of gear sometimes had problems. Remember all of this stuff was designed mostly by hand. A lot of the other issues are also little unforeseeable ones (conductive glue) and production quality problems. Even some of Sansui's early 80s lesser regarded gear, though built to a price, often performed quite well. I had one particular receiver from the early 80s that most would over look and throw in the bin. Performance and sound characteristics however make it a very decent little unit. It's missing some things like a proper delayed / protection circuit to cut costs, which I added later with an upgraded power supply.
I had another integrated years ago that was built similarly, but had re-used one of their earlier MOSFET output stage designs. It seems they were cutting costs where possible when it _wouldn't_ affect overall sound quality. People often overlook little things like this and just write the whole piece of gear off as junk but a lot of the times the engineers had a specific goal in mind -- keeping the gear sounding and performing well while sacrificing what they could to meet marketings stringent cost requirements. In my opinion, Sansui had some of these rare engineers working that actually kept these things in mind and tried to produce something worth purchasing.
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