Soundcraftsmen Mods & PCR Regulators

I have owned and repaired quite a few of the little Soundcraftsmen PCR-800 & PM 860, pro power series etc amps and found them to be excellent performers.
Even Audio mag reviewed them highley, slightly better then the Adcom 555 amps.

Has anyone else played with these and done any mods?

How about the PCR, Phase Controlled Regulation power supplies? i have never seen another company use such a design? (maybe for a reason?) any thoughts on the PCR design??

I have done some simple mods like upgraded the PSU caps and added bypass caps, cleaned up the internal wiring and upgraded jacks etc.

These ******s can be had really cheap and they sound pretty good. My Bryston 4B had better bottom end, but these seem a but less harsh on the top end.


Zero :cool:
 
I have one that I am trying to get going right now. Mines a PCR800. One of the PS caps is bad and I am having trouble finding an exact replacement. I see that you upgraded yours. What values did you go to and where did you add the bypass caps at?

I'm showing really high VDC right now but someone said that is because of the PCR and the bad cap. Sound right?

Anyway, I would love to hear what you did as well as looking forward to what others have to add.

Blessings, Terry
 
I dont remember what i used exactly, it was some time ago. i think i found some 20,000uf caps, i used 4 per amp and upgraded the SCR's to 15 or 20 amp units. I used some nice teflon foil caps i found for bypass .1 or .01 i dont remember anymore....


I have some original SC PSU caps if you need them.


Zero :cool:
 
Zero Cool said:
I dont remember what i used exactly, it was some time ago. i think i found some 20,000uf caps, i used 4 per amp and upgraded the SCR's to 15 or 20 amp units. I used some nice teflon foil caps i found for bypass .1 or .01 i dont remember anymore....


I have some original SC PSU caps if you need them.


Zero :cool:


Help me out here. What does SC PSU stand for. I might need them.

Thanks, Terry
 
SC = Soundcraftsmen

PSU = Power Supply Unit

I have at least 1 pair if not 2 pairs of Original Power Supply caps if you need them.

In fact, i have a extra transformer, bottom chassis, front plate, rear plate with fan available as well. I would ahve rebuilt that amp but it was missing the top cover!

I have parts Power supply board and a parts mainboard as well!!!


Here in MN we have some pretty good electronic surplus stores! you just never know what your going to find!!!

Plus i ran a home based electronics recycling company for the last 3 years, came across some really fun stuff from local Manufactures etc!


Zero
 
Zero Cool said:
SC = Soundcraftsmen

PSU = Power Supply Unit

I have at least 1 pair if not 2 pairs of Original Power Supply caps if you need them.

In fact, i have a extra transformer, bottom chassis, front plate, rear plate with fan available as well. I would ahve rebuilt that amp but it was missing the top cover!

I have parts Power supply board and a parts mainboard as well!!!


Here in MN we have some pretty good electronic surplus stores! you just never know what your going to find!!!

Plus i ran a home based electronics recycling company for the last 3 years, came across some really fun stuff from local Manufactures etc!


Zero



Hey Zero,

So, when you say Original, are we talking NOS or OLD original stock. I have just replaced the PS caps in two Haflers and my PCR-800 has bad caps as well. I'm a little leary of using old caps. If they are used, do you have any idea how old they are? Wish I could find an electronics surplus store. It's hard enough finding a decent electronics store around here.

Anyway, let me know. I do need caps for this amp.

Blessings, Terry
 
One more question.

When I power up this amp, with the new caps installed, the little green light flashes off and on. The amp sounds fine but i can't imagine they meant fo the light to blink. Also, when I shut the amp off, the two red clip indicator light come on and grow dimmer as time passes until they finally go out.

Any ideas what might be causing this?

Thanks, Terry
 
S4G, the green light is supposed to blink!!!!! Later models they changed this due to customer complaints.

The light blinks at 2 different flash rates. slow is normal. and when you really kick it in the pants, the light flashes very fast and the fan kicks in on high!

This is completly normal operation dont be alarmed.


The clip lights flash when you shut these amps off as well. thats normal, dont worry.

the clip indicators monitor the negative feedback line and anytime there is .1% distortion of more they light up. very accurate. when you power down, the power supply becomes unstable and the light light up!!!


The power supply caps i have are pulled from an amp i upgraded. so they are old caps, but i have used them for bench experiments just fine. i have not done any other checking of them. but they would get you up and running in a pinch until you could fine something better.


Also, check the power supply circuit board where it mounts to the caps, the board likes to crack and you will lose connection to the power supply caps causing lots of hum!


Zero
 
I just bought a non-working PCR800. After inspection I can see that some of the drive transistors are falling off the PCB. They are 2N3440 and MM4003. I can't find the MM4003's. Is there a replacement? Should I upgrade both types with something newer?

Any suggestions greatly appreciated.

Blessings, Terry
 
Good luck finding MM4003's! i have found a grand total of 3 in the whole US still left anywhere! and they want 16.00++ each! been looking for years!

Here is the funny thing...the 2N5416 is the actual device match to a 2N3440, but SC choose to use the 4003 which has half the current rating of the 5416...why? best i can figure is they were trying to speed macth the differences in gate cap charge time. but that is just a guess on my part. maybe they choose that device because it is more linear...who knows....


when i repair these, i just use 5416's and i have never heard any real differences. However. i sure would like to find a NOS stash of MM4003's just to do some testing with...

Oh yeah, only use Motorola devices, the others are NOT the same! they sound different.


Zc
 
Hi Zc,

In another thread you mentioned having the schematic for the PCR800. Would you still be willing to email it? If so, i would really like to have that. The main board in this amp I just bought looks as though it was under water or something at some point. manyt of the leads to the resistors are corroded. I should probably replace them as well. I would rather replace them with the correct values rather than trying to measure them.


Thanks so much, Terry

still4given@yahoo.com
 
A friend had mailed copies of the schematic a while back. I had forgotten I had them. Now to figure out how it relates to the PCB. Not as easy as I had thought it would be.

I've got a couple of questions if I may impose on some of you. Quite a few of the components have that greenish corrosion on their leads. Is there some type of cleaner that will remove that? I tried scraping them but ended up breaking one of the leads to a diode. Now I have to figure out what it is so I can replace it.

What's weird is that only some of the components have the corrosion on them. Others that are right next to them are fine. Could this be some sort of electrolysis? The little TO-39's are all just falling off the board. It's like something just ate away the leads on them. Very strange. Except for a few diodes the rest of the components seem to be fine.

Is there a trick to tracing out the schematic on the PCB? Anything to look for that would make it easier?

Thanks, Terry
 
RE; Soundcraftsmen shoebox amps

Hey guys,

I was brought a partially-disassembled PM840 for service. The main problem is, that someone disconnected all of the wires on the front of the power amp board, going to the power supply board. Anybody have photos from the top down, showing which colors go where?, or even a list from left to right as to which color wires go to which pins, on the amp board. I think I have it figured out, but want to be sure. Also, anyone have a good source for the S.C.R's in the power supply, as two of them seem to be blown. Thanks everyone!
 
Hey guys,

I was brought a partially-disassembled PM840 for service. The main problem is, that someone disconnected all of the wires on the front of the power amp board, going to the power supply board. Anybody have photos from the top down, showing which colors go where?, or even a list from left to right as to which color wires go to which pins, on the amp board. I think I have it figured out, but want to be sure. Also, anyone have a good source for the S.C.R's in the power supply, as two of them seem to be blown. Thanks everyone!

I know this thread is old, I just hate seeing unanswered questions. I have a PCR 800 and A Propower 1 which I could send a photo of if you still happen to need it.
 
I have owned and repaired quite a few of the little Soundcraftsmen PCR-800 & PM 860, pro power series etc amps and found them to be excellent performers.
Even Audio mag reviewed them highley, slightly better then the Adcom 555 amps.

Has anyone else played with these and done any mods?

How about the PCR, Phase Controlled Regulation power supplies? i have never seen another company use such a design? (maybe for a reason?) any thoughts on the PCR design??

I have done some simple mods like upgraded the PSU caps and added bypass caps, cleaned up the internal wiring and upgraded jacks etc.

These ******s can be had really cheap and they sound pretty good. My Bryston 4B had better bottom end, but these seem a but less harsh on the top end.


Zero :cool: