Howdy!
First, let me say how refreshing it is to have the Man himself among us... we're not worthy! Totally cool.
I've got an SA/4 that I obtained broken (paid almost nothing, too!). It's in perfect cosmetic shape, and I'd like to try using this amp for awhile.
Initially, it was blowing fuses on one side upon power-up. I discovered a single bad output device on the channel, and changed it. I also checked every other device and resistor on the side. Changing that device solved the problem at idle.
Unfortunately, there is still trouble. At about 1 watt of output on the defective channel, current draw from the mains moves massively up and distortion goes way up, as well. I have been all over the driver board for that channel and measured every passive and every semi (de-soldered), and can't find anything out of sorts. And I'm out of ideas, particularly because I don't have a schematic.
Can anyone help with one? Does anyone have an idea of what this might be?
Appreciate the help, and very glad to be here!
-Pacific
First, let me say how refreshing it is to have the Man himself among us... we're not worthy! Totally cool.
I've got an SA/4 that I obtained broken (paid almost nothing, too!). It's in perfect cosmetic shape, and I'd like to try using this amp for awhile.
Initially, it was blowing fuses on one side upon power-up. I discovered a single bad output device on the channel, and changed it. I also checked every other device and resistor on the side. Changing that device solved the problem at idle.
Unfortunately, there is still trouble. At about 1 watt of output on the defective channel, current draw from the mains moves massively up and distortion goes way up, as well. I have been all over the driver board for that channel and measured every passive and every semi (de-soldered), and can't find anything out of sorts. And I'm out of ideas, particularly because I don't have a schematic.
Can anyone help with one? Does anyone have an idea of what this might be?
Appreciate the help, and very glad to be here!
-Pacific
Hugo,
i bet you're very good at charming les merveilleuse femmes as well.
Pacific friend, send me an email for the SA/4e schematic, courtesy of the one and only who ocassionally does a sleazeball like me a big favor.
Paid almost nothing ? Oh dear, i'm fainting again.
His Holiness himself may be arriving shortly on this stage, has a lot more hair than Tenzin Gyatso, let me just cough 1-2-3-testing in the mic.
i bet you're very good at charming les merveilleuse femmes as well.
Pacific friend, send me an email for the SA/4e schematic, courtesy of the one and only who ocassionally does a sleazeball like me a big favor.
Paid almost nothing ? Oh dear, i'm fainting again.
His Holiness himself may be arriving shortly on this stage, has a lot more hair than Tenzin Gyatso, let me just cough 1-2-3-testing in the mic.
Hi, guys:
Sorry to not check in earlier- shortly after that first post, my main box (sigh- this is the one I do all my audio remastering and video projects on) crashed harder than Humpty Dumpty on crack. Totally hosed Windows, cross-links on data files (on ANOTHER, different partition!), the works.
I am only now coming back to life... Still can't get the install of 2K to work right (may have to give up). Since my practice is always to stay one generation of OSes behind, I guess this is my calling to get on with the business of living with and trying to like XP.
Happily, almost all the data lost was either backed up, or very recent. About the only thing I haven't been able to recover is some recent cover art that I should be able to recreate without too much trouble.
Lesson: Regular back ups. I had gotten lazy and that's a fatal error when things go bad.
Anyway, thanks for the reply! Jacco and Hugo, nice to meet you both. Jacco, look for a private from me for a mailng addy, your generous offer is very much appreciated.
Please let me make one in return:
Along with many hats before then, I was the undertaker for Pacific Stereo when it died in 1986. I eventually ended up with 18,000 paper service manuals, mountains of microfiche, and boxes and boxes of original parts, including semis, lots of them. I've even got new optics for a CDP-101.
Need factory heads for the original Advent cassette deck? Got 'em... You get the idea.
The S/M collection is supplemented by stuff from The Federated Group and other service organizations, and goes to about 1996 for many, many brands.
If anyone here needs a part, a schematic, or anything else along those lines, please PM me and I'll get you fixed up.
Jacco, watch your message box!
-Pacific
Sorry to not check in earlier- shortly after that first post, my main box (sigh- this is the one I do all my audio remastering and video projects on) crashed harder than Humpty Dumpty on crack. Totally hosed Windows, cross-links on data files (on ANOTHER, different partition!), the works.
I am only now coming back to life... Still can't get the install of 2K to work right (may have to give up). Since my practice is always to stay one generation of OSes behind, I guess this is my calling to get on with the business of living with and trying to like XP.
Happily, almost all the data lost was either backed up, or very recent. About the only thing I haven't been able to recover is some recent cover art that I should be able to recreate without too much trouble.
Lesson: Regular back ups. I had gotten lazy and that's a fatal error when things go bad.
Anyway, thanks for the reply! Jacco and Hugo, nice to meet you both. Jacco, look for a private from me for a mailng addy, your generous offer is very much appreciated.
Please let me make one in return:
Along with many hats before then, I was the undertaker for Pacific Stereo when it died in 1986. I eventually ended up with 18,000 paper service manuals, mountains of microfiche, and boxes and boxes of original parts, including semis, lots of them. I've even got new optics for a CDP-101.
Need factory heads for the original Advent cassette deck? Got 'em... You get the idea.The S/M collection is supplemented by stuff from The Federated Group and other service organizations, and goes to about 1996 for many, many brands.
If anyone here needs a part, a schematic, or anything else along those lines, please PM me and I'll get you fixed up.
Jacco, watch your message box!
-Pacific
I don't have SA4e schematics, but I do have the SA12e
which is very similar. I have uploaded the 15 pages of the service
manual to www.passlabs.com/np
which is very similar. I have uploaded the 15 pages of the service
manual to www.passlabs.com/np
PacificStereo said:
How old is the SA/4? If its anywhere near 20 yrs Id replace all the electrolytics.. Unless you have a method for testing... I am the person to blame for the 400a repair thread but its nothing like the symptom you have... I think the SA/4 is a predecessor to the 400a and very similar.. if it took out a output transistor did you replace all the emitters? mine were all cooked and had 3-4 bad output devices.. you might have a few bad emitters... better check em.
Send pics, I wanna see the guts!
Hi, Barchetta:
Yes, I tested every output device on that channel, and measured every emitter resistor- everything is good.
I don't know the age of the amp (it's not with me, here).
And I agree, replacing electrolytics is a good idea, if for no other reason that good Panasonic FG or FM series parts have ultralow ESR, very long life and sound great! I haven't done that on the bad channel (or the good one, for that matter) but might try that as a next step, since it's so easy and cheap to do.
I've lived the life of bad electrolytics- I was right in the middle of the "bad Nichicon/Panasonic SMD capacitors" phenomenon in the 90's. Ever replaced every single SMD cap in a camcorder? I have, hundreds of times. There are 103 in a Sony CCDF55. Plus, boards often had to be repaired because of the damage done by leaking electrolyte. Man, does that stuff stink when it gets heated.
And don't get me started on that nasty yellow glue that turns to carbon and traps moisture underneath... Great stuff. It conducts all by itself AND corrodes boards and parts at the same time. It was so notorious in my shop that we even made a song up about it. Gah!
Anyway, I may not make it to the lab until next week. (I live a dual life- LA area weekdays, central CA weekends, and the GF wants me here this weekend.) If I don't, I'll snap pictures next week.
This is an odd symptom, indeed. I was really hoping someone here had run across it before. However, a schematic will really help. Sometimes, you just gotta have one!
I'll keep ya'll posted.
-Pacific
Yes, I tested every output device on that channel, and measured every emitter resistor- everything is good.
I don't know the age of the amp (it's not with me, here).
And I agree, replacing electrolytics is a good idea, if for no other reason that good Panasonic FG or FM series parts have ultralow ESR, very long life and sound great! I haven't done that on the bad channel (or the good one, for that matter) but might try that as a next step, since it's so easy and cheap to do.
I've lived the life of bad electrolytics- I was right in the middle of the "bad Nichicon/Panasonic SMD capacitors" phenomenon in the 90's. Ever replaced every single SMD cap in a camcorder? I have, hundreds of times. There are 103 in a Sony CCDF55. Plus, boards often had to be repaired because of the damage done by leaking electrolyte. Man, does that stuff stink when it gets heated.
And don't get me started on that nasty yellow glue that turns to carbon and traps moisture underneath... Great stuff. It conducts all by itself AND corrodes boards and parts at the same time. It was so notorious in my shop that we even made a song up about it. Gah!
Anyway, I may not make it to the lab until next week. (I live a dual life- LA area weekdays, central CA weekends, and the GF wants me here this weekend.) If I don't, I'll snap pictures next week.
This is an odd symptom, indeed. I was really hoping someone here had run across it before. However, a schematic will really help. Sometimes, you just gotta have one!
I'll keep ya'll posted.
-Pacific
PacificStereo said:Hi, guys:
Along with many hats before then, I was the undertaker for Pacific Stereo when it died in 1986. I eventually ended up with 18,000 paper service manuals, mountains of microfiche, and boxes and boxes of original parts, including semis, lots of them. I've even got new optics for a CDP-101.
-Pacific
Very interesting PacificStereo! You may want to check in at the Vintage Forum of the AudioKarma site (Audiokarma.org). There are quite a few fans of the Concept line of receivers on that site and I'm sure they would be very happy to hear from you. Any service manuals or even parts would be cool. There are many there that feel that the Concept 16.5 was one of the best receivers ever.
hope you check in,
Steve.
Hi, guys:
Spind:
That Concept line of products really shone. I've got two 12.0Ds sitting around that I just love the sound on.
There never were what I would call "real" service manuals for the Concept line, at least as far as I know. It's odd- we made all these products, but the documentation was terrible. What literature there is is almost all microfiche, with a few paper service bulletins. For example, the only thing I have for the 12.0D is a microfiche of the schematic, and a typed-up, Xeroxed alignment procedure for the FM section.
But I will definitely head over there and check the place out. I've got a lot of Concept, Calibre, Quadraflex and Transaudio parts and info- thanks for the suggestion!
Hugo:
I did not check the zobel. Is this something that tends to fail? This is where a schematic starts to help... heh. Since the amplifier seems to work well on the affected channel up to about 1 watt of output, a static check of the zobel components might not reveal much, but I'll take a look this weekend and report in.
Talk with ya'll soon.
-Pacific
Spind:
That Concept line of products really shone. I've got two 12.0Ds sitting around that I just love the sound on.
There never were what I would call "real" service manuals for the Concept line, at least as far as I know. It's odd- we made all these products, but the documentation was terrible. What literature there is is almost all microfiche, with a few paper service bulletins. For example, the only thing I have for the 12.0D is a microfiche of the schematic, and a typed-up, Xeroxed alignment procedure for the FM section.
But I will definitely head over there and check the place out. I've got a lot of Concept, Calibre, Quadraflex and Transaudio parts and info- thanks for the suggestion!
Hugo:
I did not check the zobel. Is this something that tends to fail? This is where a schematic starts to help... heh. Since the amplifier seems to work well on the affected channel up to about 1 watt of output, a static check of the zobel components might not reveal much, but I'll take a look this weekend and report in.
Talk with ya'll soon.
-Pacific
I'm baaaack!
Wow, it's really been a long, long time. This SA/4 has been languishing on a shelf for nearly three years. Shortly after Nelson was kind enough to put up the schematics for the 12, a bunch of things occurred that diverted my attention away from audio repair. Fast-forward to now.
It's fixed!
This poor beauty has been sitting long enough, and I decided to get my head back into it. Nothing has changed since the last post- at about 1 watt, the amp would draw lots of mains current and blow the rail fuses if I asked it for more than that.
So, today I unshelved the amplifier and started looking again.
The first thing I did was eliminate the driver board as the cause of the problem. I moved it to the other operational channel, and it worked just fine. So I returned it to its original channel.
I went and measured across all the emitter resistors on the channel, and everything seems to be nominal. What could possibly be going on here? Then I discover that the problem is independent of load. If I disconnect the load from the output terminals and simply drive the input with the test signal, the problem is still there.
Never seen THAT before. HUH? I'm stumped. Then I churn some more. "Hmmm... No zobel on this amp... what's left? A short across the output?"
So I measure across the terminals, and sure as Shinola, they're shorted. Collector to ground short on that channel. WTF? Really? Where could it be?
So I start looking. Don't see anything unusual. So I lift the wires on each board half that go to the + output terminal. I find the short. It's on the half that had the bad output device. Well, I've only disturbed ONE THING on that side- so I unsolder the replacement device and unfasten it. I see a spot on the Silpad. Ruht-roh. I turn the device over, and I see a spot on IT, too. There's a... a... PROTRUSION on the bottom of the device! It's poked through the Silpad and created the short. Good Lord. EUREKA!!!
I surmise that the protrusion started its life as a very small solder-ball. Dunno how it got there.
Unbelievable.
A scrape and smooth, and a new Silpad, and we're in business. The SA/4 makes music again. Yay!
Many, many thanks to Nelson and whoever it was at Pass Labs that taught me how to determine which device(s) in the array needed to be unsoldered (as opposed to unsoldering them ALL!), and everyone here who gave me ideas.
Now, It's Miller time!
Wow, it's really been a long, long time. This SA/4 has been languishing on a shelf for nearly three years. Shortly after Nelson was kind enough to put up the schematics for the 12, a bunch of things occurred that diverted my attention away from audio repair. Fast-forward to now.
It's fixed!
This poor beauty has been sitting long enough, and I decided to get my head back into it. Nothing has changed since the last post- at about 1 watt, the amp would draw lots of mains current and blow the rail fuses if I asked it for more than that.
So, today I unshelved the amplifier and started looking again.
The first thing I did was eliminate the driver board as the cause of the problem. I moved it to the other operational channel, and it worked just fine. So I returned it to its original channel.
I went and measured across all the emitter resistors on the channel, and everything seems to be nominal. What could possibly be going on here? Then I discover that the problem is independent of load. If I disconnect the load from the output terminals and simply drive the input with the test signal, the problem is still there.
Never seen THAT before. HUH? I'm stumped. Then I churn some more. "Hmmm... No zobel on this amp... what's left? A short across the output?"
So I measure across the terminals, and sure as Shinola, they're shorted. Collector to ground short on that channel. WTF? Really? Where could it be?
So I start looking. Don't see anything unusual. So I lift the wires on each board half that go to the + output terminal. I find the short. It's on the half that had the bad output device. Well, I've only disturbed ONE THING on that side- so I unsolder the replacement device and unfasten it. I see a spot on the Silpad. Ruht-roh. I turn the device over, and I see a spot on IT, too. There's a... a... PROTRUSION on the bottom of the device! It's poked through the Silpad and created the short. Good Lord. EUREKA!!!
I surmise that the protrusion started its life as a very small solder-ball. Dunno how it got there.
Unbelievable.
A scrape and smooth, and a new Silpad, and we're in business. The SA/4 makes music again. Yay!
Many, many thanks to Nelson and whoever it was at Pass Labs that taught me how to determine which device(s) in the array needed to be unsoldered (as opposed to unsoldering them ALL!), and everyone here who gave me ideas.
Now, It's Miller time!
Last edited:
I have one other question, and that is bias setting for this amp. As I understand the procedure, I want the amp to sit for an hour with the cover on and then am looking for a temp of between 40 and 50 C by sticking a thermometer down the back heatsink top screw hole (the same screw the cover is attached with, yes?). Is that correct? I can easily see the effect of current consumption at idle by moving bias around.
How long do I need to wait between adjustments for the heatsink temp to stabilize?
How long do I need to wait between adjustments for the heatsink temp to stabilize?
Thanks, Nelson. Appreciate the help.
Ah... it seems that bias keeps wanting to creep up. My little thermometer stuck in the back heatsink holes sits at about 130F for each side, give or take a couple of degrees. 50C is about 122F, so this definitely seems hot. At idle with no signal, the amp wants to draw about 3.5 amps from the mains. Each half hour, I have been returning to the amp and taking bias down a smidge to bring current consumption down to 3 amps. Each time I return, the amp is back up to 3.5 amps or so. No way can I do ten seconds of heatsink contact- more like 4.
I should be waiting longer between adjustments? The bias pots are quite a ways counter-clockwise already.
Ah... it seems that bias keeps wanting to creep up. My little thermometer stuck in the back heatsink holes sits at about 130F for each side, give or take a couple of degrees. 50C is about 122F, so this definitely seems hot. At idle with no signal, the amp wants to draw about 3.5 amps from the mains. Each half hour, I have been returning to the amp and taking bias down a smidge to bring current consumption down to 3 amps. Each time I return, the amp is back up to 3.5 amps or so. No way can I do ten seconds of heatsink contact- more like 4.
I should be waiting longer between adjustments? The bias pots are quite a ways counter-clockwise already.
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