Hi Tony. Yes, by all means, do the solder talk and go in as many detailes as possible. I love your explaining methods with practical details as well as doing it on a level all can follow. Not all of us watching and following your channel are the experts. Still a lot to learn. Thank you so much for doing these videos and especially working on vintage hi-fi Pioneer, Maranatz and sinilar designs.
solder and chat yes please. there is always something revealed that is not written or illustrated like what you learn as an apprentice . I appreciate watch the trouble shooting as well. can you sometime work on some equipment that does not have any schematics or service docs available I have some nice sounding old solid state audio equipment that do not have any documentation available. To see your approach to that kind of problem would be very fun I might even learn something thanks for all of your efforts.
Well done! It's interesting to see your design choices explained for the soft start modifications. Thanks for sharing the details. I think I would enjoy seeing you rebuild the second amp module. Can you discuss the part choices, especially the two bias transistors and the emitter resistors (who makes them and what wattage did you choose?). Same goes for the high pwoer resistors and NTC resistors you used in your soft start circuit.
Vote solder and chat. I enjoy seeing what you're doing but I really enjoy just listening to how you narrate about what you're doing along with your thoughts and opinions.
That thing is blown up pretty good-dang!!! I see/understand what they did with the original start up circuit, but I like what you did to it better!!!! :)
Hello, Tony. Please carry on with the solder and chats, there are always little nuggets of information to be had from these, and like you say more or less if you don't like it shut your mouth and by all means use the FF button."
As the owner of 2 'Flame Linear" PL 400's, I know all too well the carnage left behind due to output transistor failures. Both were purchased DOA. I Resurrected one so far, will do some upgrades on the second..(soft start and DC protection). Good info here for those who've never dealt with a direct coupled amplifier. I love the solder amd chat sessions.. so I'll vote yes please =)
Did Pioneer sleeve the resistors as "flame containment" - before the days of flameproof resistors? Really enjoying this one, more than happy for a solder-and-chat 😊
Solder and chat is my preferred way to go. After all, as it's kinda off-the-cuff so to speak, we never know where your conversation will go and generally we all learn something either about electronics or your life (usually both) and that's well worth the watch.
Hi Tony, just to note Q4 is the VAS transistor and Q5 is part of the current source circuit (neither of them is part of the bias circuit). Thank you for the video!
What are you going to use for those 424’s and 554’s? I’d like to see the rebuild of the second module too, this is awesome. This 9090DB on the bench, uses the same transistors. Solder and chat, my friend, solder and chat it right up!
He mentioned in the video that he was using the Onsemi MJ21193G and MJ21194G. The NPN was hard to get last time I saw, the MJ21195G and MJ21196G is equally as good. The 93/94 perform ever so slightly better with lower rail voltages where the 95/96 are slightly better with the higher rail voltages. But they’re essentially the same. If you have trouble finding them there are a couple members over at audiokarma selling authentic devices for a bit more than you’d pay at mouser. I bought a couple hundred each of the 93/94/95 and 96 so if I see someone looking for a few on the forums I try to help them out. Good luck!
Recently recapped my SPEC 4, had to break out the "Holy Hand Grenade of Antioch" 200W bulb for the DBT to work. Wish I had waited now, you're on point. Looking for a Spec 1 preamp now.
Would like to see rebuild of second amp. module. Do you have any comment on the earlier info commented about NTC and bass response? Very interesting rebuild. Enjoyed!! Thanks.
Regarding the softstart: there is a video where you talk about and calculated the resistorvalue for the softstart:) Do you remember witch video??? Great build
I just acquired a Spec 4. Can’t wait to see how this series progresses…. I wonder already if the new bias transistors will have a higher quiescent current. Also, that startup circuit is interesting, how reliable are those ICL parts?
Great video - yes i like to see the detaillering work - so solder and chat :) But a few questions: 1- would mj15004/3 have worked for the outputs - I tend to use those for to3 replacement (the others are hard to get here) 2 - maybe I missed it but what did you do for the 2sa798 dual xtor and why ? 3 - why did replace the small ceramic caps?
Can you speak to the 3 and 4 diode packs labeled SV-4? Do they have any special characteristics besides 3x and 4x forward voltage drops? Thanks for this most comprehensive video!
I used a microcontroller PIC with angular timer and triac for my amplifier design. It has zero cross detector which control the triac . I control triac on negative decay of sinuse for positive part sinus wave and opposite for negative part of sinus wave to put a adjusted width on input sinus , with other word i pwm the sinus wave .Transformer is 1000va with 200000 uf at secondary . The idea is to have smal size power resistor as in rush current. In rush are for current is magnetic fields + capacitor currnet . There are also some applications note from ST for microwave oven they use triac and diac . You can find it by writing inrush current for microwaves oven. The problem with NTC is if you turn on off fast still they are warm.
"The problem with NTC is if you turn on off fast still they are warm." Yes, but think a little more - the caps would also be partially charged as well. I do a delayed B+ on my tube amps using solid state rectifiers. You don't want to put B+ on a cold tube. I had the same concern, the amp being turned of and on quickly like from a power hit. But again the tubes would still be hot and thus no issues.
The beauty of this circuit is that it bypasses the ICL in less than 2 seconds. It hardly even has time to get warm. The capacitors take time to discharge, so turning it off and on quickly will result in the caps already being partially pre-charged. If you wait long enough for the caps to discharge long enough for the bypass relay to drop out, the ICL will be cooled down. Thanks for the comment!
Thank you for the handling precautions for for the ntc thermistor.any way to safely clean one that has been mishandled?years ago I had test probe slip on amp that was at least partially direct coupled.what a mess but not quite as much damage as you found.
Man I love your videos, I was thinking about trying to recap my Sansui AU 555 with one of those instructional kits from eBay. What are your thoughts on that? I have no experience so I'm hesitant. Thanks
It’s OK by me to skip the solder & chat, but can you give a report on what you found on the second amplifier board, especially since we think it may be in better shape. I don’t need to know how to solder, but I need to learn more about repairing directly coupled stages, replacement decisions, and testing. I got a lot out of your last Marantz rebuild. I can tell you’re excited to be working on your own stuff, it makes decisions easier, I’m sure. PS: I seems that directly coupled stages require disassembly to properly troubleshoot, or was that the point you were making?
You could. A light bulb is just a resistor. But do you want a 40 to 100 watt light bulb sticking out of the chassis? I use power resistors in my high power amps as well. But I parallel them and in one amp even use a heat sink. I think Tony used the NTC because he didn't want to kludge in larger resistors on his custom PC board, which I totally agree with.
Tony i have the normal US non multivoltage spec 4 model. Mine possibly has a bad transformer and have a chance to buy a multi-viltage transformer from another spec-4 like yours. Would this swap be able to work without too much trouble.
I wondered if you could point me in the right direction... Picked up a Rack mount power amp a couple days ago.. Faulty, to fix... But my knowledge is limited... And its got a fault that ive not come across yet, So unsure where i should be looking... The amp powers up as normal.. No dim bulb needed etc.... Both channel relays click, and both READY Led's come on... But channel B has CLIP light illuminated, But dimly.... and 7.7v at the speaker terminals.. 😂 I find it strange that it all powers up fine... and It allows the relay to click.. It doesnt go into Protect mode, and Protect light doesnt illuminate... green READY light stays ready for a signal.... Also why the CLIP light is very dimly lit up?!?! As i said, I know the basics.. How to check components.. Transistors etc etc... But im curious of where i should be looking at here... Clearly not a dead shorted transistor etc... Because it all powers up fine.... and i cannot find a schematic of service manual anywhere!! thankyou
Every rcvr or amp i do that has A798 in it gets replaced with A733 no matter what. Those transistors are a PITA . I dont want my customers dealing with the inevitable failure .
Can someone please explain why the Japanese engineers used single pole power switches back then? In conjunction with a non-polarized plug, you have a 50% chance of the hot side not getting interrupted when the unit is turned off. I hope I don't have to explain the resulting danger.
Why don't you tell what transistors replacements you did? You replaced all transistors on the amp board and tell replacements for power transistors and bias but what about others you replaced and thats the only thing missing in your videos. Otherwise probably the best channel for vintage amplifier/receiver refurbishment.
I'd very much appreciate another solder and chat. Y'knever know what stories are bound to come up, but they're always entertaining. 😁👍
Yes, let's do the "solder and chat", Tony. I enjoy it and maybe others too.
Thanks for this one.
I actually enjoy the solder and lip flaps
Of course we want a solder and chat 😊. Thanks Tony enjoying the series.
Hi Tony. Yes, by all means, do the solder talk and go in as many detailes as possible. I love your explaining methods with practical details as well as doing it on a level all can follow. Not all of us watching and following your channel are the experts. Still a lot to learn. Thank you so much for doing these videos and especially working on vintage hi-fi Pioneer, Maranatz and sinilar designs.
I vote for solder and chat, please.
Solder and chat, always good!
Dan
Solder & chat works for me Tony; thank you for your time!
solder and chat yes please. there is always something revealed that is not written or illustrated like what you learn as an apprentice .
I appreciate watch the trouble shooting as well.
can you sometime work on some equipment that does not have any schematics or service docs available I have some nice sounding old solid state audio equipment that do not have any documentation available. To see your approach to that kind of problem would be very fun I might even learn something
thanks for all of your efforts.
Well done! It's interesting to see your design choices explained for the soft start modifications. Thanks for sharing the details. I think I would enjoy seeing you rebuild the second amp module. Can you discuss the part choices, especially the two bias transistors and the emitter resistors (who makes them and what wattage did you choose?). Same goes for the high pwoer resistors and NTC resistors you used in your soft start circuit.
I like the solder and chat sessions.
Vote solder and chat. I enjoy seeing what you're doing but I really enjoy just listening to how you narrate about what you're doing along with your thoughts and opinions.
Solder and chat is good - it's always interesting and if there are people that don't want to listen, they can always skip ahead.
please do solder and chat, if any dont like they dont have to watch. thank you for the video tony
I'd like the solder and chat. You never know what long lost nugget of wisdom will pop up. Plus, it's nice to just hang out and do something fun.
Yes, let's see the rebuild!.
Yes would like to see that
Saludos desde Ayacucho Perú, es usted un excelente restaurador
Hi I'm from UK.
Yes for solder and chat.
That thing is blown up pretty good-dang!!! I see/understand what they did with the original start up circuit, but I like what you did to it better!!!! :)
I vote for the solder and chat version and to follow all the way through the restoration of this amp.
I learn a lot with the solder and chat... I know it takes you lots of time but for me its about the learning and you do teach me tons... so thanks.
Your chats are the best 👌
Hello, Tony. Please carry on with the solder and chats, there are always little nuggets of information to be had from these, and like you say more or less if you don't like it shut your mouth and by all means use the FF button."
As the owner of 2 'Flame Linear" PL 400's, I know all too well the carnage left behind due to output transistor failures. Both were purchased DOA. I Resurrected one so far, will do some upgrades on the second..(soft start and DC protection). Good info here for those who've never dealt with a direct coupled amplifier. I love the solder amd chat sessions.. so I'll vote yes please =)
always do the solder and chats i love those
Did Pioneer sleeve the resistors as "flame containment" - before the days of flameproof resistors? Really enjoying this one, more than happy for a solder-and-chat 😊
Solder and chat is my preferred way to go. After all, as it's kinda off-the-cuff so to speak, we never know where your conversation will go and generally we all learn something either about electronics or your life (usually both) and that's well worth the watch.
Hi Tony, just to note Q4 is the VAS transistor and Q5 is part of the current source circuit (neither of them is part of the bias circuit). Thank you for the video!
Yes, do a solder and chat on that second amp board.
Selfishly I want a solder and chat because I have a spec 2 and I really want to refurbish it
I vote for solder and chat.
What are you going to use for those 424’s and 554’s? I’d like to see the rebuild of the second module too, this is awesome. This 9090DB on the bench, uses the same transistors. Solder and chat, my friend, solder and chat it right up!
He mentioned in the video that he was using the Onsemi MJ21193G and MJ21194G. The NPN was hard to get last time I saw, the MJ21195G and MJ21196G is equally as good. The 93/94 perform ever so slightly better with lower rail voltages where the 95/96 are slightly better with the higher rail voltages. But they’re essentially the same. If you have trouble finding them there are a couple members over at audiokarma selling authentic devices for a bit more than you’d pay at mouser. I bought a couple hundred each of the 93/94/95 and 96 so if I see someone looking for a few on the forums I try to help them out. Good luck!
Sure, solder & chat is fun. Add my vote 👍
yeah buddy, 2nd block and solder and chat
Recently recapped my SPEC 4, had to break out the "Holy Hand Grenade of Antioch" 200W bulb for the DBT to work. Wish I had waited now, you're on point. Looking for a Spec 1 preamp now.
Thanks Tony! I vote solder and chat!
Yes - Solder and chat.
Yes on solder & chat
Would like to see rebuild of second amp. module. Do you have any comment on the earlier info commented about NTC and bass response? Very interesting rebuild. Enjoyed!! Thanks.
Yes on solder and chat!
Regarding the softstart: there is a video where you talk about and calculated the resistorvalue for the softstart:) Do you remember witch video???
Great build
Found it: czcams.com/video/CqL1BZpiFHA/video.htmlsi=VxjHMlLe_yUbEzj1
Please do the solder and chat for the second amp.
I just acquired a Spec 4. Can’t wait to see how this series progresses…. I wonder already if the new bias transistors will have a higher quiescent current. Also, that startup circuit is interesting, how reliable are those ICL parts?
Solder and chat please still learning..
Another vote for a solder and chat!
I'm also for solder&chat video ..
Great video - yes i like to see the detaillering work - so solder and chat :)
But a few questions:
1- would mj15004/3 have worked for the outputs - I tend to use those for to3 replacement (the others are hard to get here)
2 - maybe I missed it but what did you do for the 2sa798 dual xtor and why ?
3 - why did replace the small ceramic caps?
Hi Tony, Thanks. Do you have a part number for that ICL thermistor? Any concerns about a stuck-open relay?
Can you speak to the 3 and 4 diode packs labeled SV-4? Do they have any special characteristics besides 3x and 4x forward voltage drops? Thanks for this most comprehensive video!
👍
I used a microcontroller PIC with angular timer and triac for my amplifier design. It has zero cross detector which control the triac . I control triac on negative decay of sinuse for positive part sinus wave and opposite for negative part of sinus wave to put a adjusted width on input sinus , with other word i pwm the sinus wave .Transformer is 1000va with 200000 uf at secondary . The idea is to have smal size power resistor as in rush current. In rush are for current is magnetic fields + capacitor currnet .
There are also some applications note from ST for microwave oven they use triac and diac . You can find it by writing inrush current for microwaves oven.
The problem with NTC is if you turn on off fast still they are warm.
What are you compensating for with the 200k uF?
@@mitkothemacedonian🎉low bass 20 Hz , no bass limitation down to 1 ohm
"The problem with NTC is if you turn on off fast still they are warm."
Yes, but think a little more - the caps would also be partially charged as well. I do a delayed B+ on my tube amps using solid state rectifiers. You don't want to put B+ on a cold tube. I had the same concern, the amp being turned of and on quickly like from a power hit. But again the tubes would still be hot and thus no issues.
The beauty of this circuit is that it bypasses the ICL in less than 2 seconds. It hardly even has time to get warm. The capacitors take time to discharge, so turning it off and on quickly will result in the caps already being partially pre-charged. If you wait long enough for the caps to discharge long enough for the bypass relay to drop out, the ICL will be cooled down. Thanks for the comment!
Thank you for the handling precautions for for the ntc thermistor.any way to safely clean one that has been mishandled?years ago I had test probe slip on amp that was at least partially direct coupled.what a mess but not quite as much damage as you found.
Man I love your videos, I was thinking about trying to recap my Sansui AU 555 with one of those instructional kits from eBay. What are your thoughts on that? I have no experience so I'm hesitant. Thanks
Thank you for this video. Very interesting your feedback. Did you paint the bells with a brush or spray please?
A brush. Nothing but the best😏
Here we go.
tony deals with nuclear arc welder. details in part three!
Solder and chat please. Thank you
Are those Kemet split film capacitors did you use split film capacitors?
When you purchased the Kemet caps, what parameters did you specify in the purchase specs?
It’s OK by me to skip the solder & chat, but can you give a report on what you found on the second amplifier board, especially since we think it may be in better shape. I don’t need to know how to solder, but I need to learn more about repairing directly coupled stages, replacement decisions, and testing. I got a lot out of your last Marantz rebuild. I can tell you’re excited to be working on your own stuff, it makes decisions easier, I’m sure.
PS: I seems that directly coupled stages require disassembly to properly troubleshoot, or was that the point you were making?
I'm interested in the safe power up sequence for a direct coupled amplifier. Obviously you use can't dim bulb or just turn it on.... or can you.
You could. A light bulb is just a resistor. But do you want a 40 to 100 watt light bulb sticking out of the chassis? I use power resistors in my high power amps as well. But I parallel them and in one amp even use a heat sink. I think Tony used the NTC because he didn't want to kludge in larger resistors on his custom PC board, which I totally agree with.
Tony i have the normal US non multivoltage spec 4 model. Mine possibly has a bad transformer and have a chance to buy a multi-viltage transformer from another spec-4 like yours. Would this swap be able to work without too much trouble.
I wondered if you could point me in the right direction...
Picked up a Rack mount power amp a couple days ago.. Faulty, to fix... But my knowledge is limited...
And its got a fault that ive not come across yet, So unsure where i should be looking...
The amp powers up as normal.. No dim bulb needed etc....
Both channel relays click, and both READY Led's come on... But channel B has CLIP light illuminated, But dimly....
and 7.7v at the speaker terminals.. 😂
I find it strange that it all powers up fine... and It allows the relay to click.. It doesnt go into Protect mode, and Protect light doesnt illuminate...
green READY light stays ready for a signal....
Also why the CLIP light is very dimly lit up?!?!
As i said, I know the basics.. How to check components.. Transistors etc etc... But im curious of where i should be looking at here...
Clearly not a dead shorted transistor etc... Because it all powers up fine....
and i cannot find a schematic of service manual anywhere!!
thankyou
Solder and chat please :-)
Why are the resistors wearing shrouds? Skip ahead is fine.
i cant find any 0.5ohm 5watt where did you get yours ?
S&C please
Tony, please do 'em in 4k, the schematics are too blury on my 75" bravia.
Get a Mac.
Every rcvr or amp i do that has A798 in it gets replaced with A733 no matter what. Those transistors are a PITA . I dont want my customers dealing with the inevitable failure .
Can someone please explain why the Japanese engineers used single pole power switches back then? In conjunction with a non-polarized plug, you have a 50% chance of the hot side not getting interrupted when the unit is turned off. I hope I don't have to explain the resulting danger.
Why don't you tell what transistors replacements you did?
You replaced all transistors on the amp board and tell replacements for power transistors and bias but what about others you replaced and thats the only thing missing in your videos. Otherwise probably the best channel for vintage amplifier/receiver refurbishment.
Perhaps you should watch part 3 when I release it.
I would at least like to see it bench tested for output power. 150W seems on the low side for what you've shown so far.