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Any Soundcraftsmen owners in here?

I want to give props to Erik, Stereo Pheonix, for the really nice work he did for me to produce a bridging box. The AB-1 is next to unobtanium and I don't have the skills to fabricate a board so Erik was kind enough to offer to build me a plug and play bridging box. The finished product has labels as well. VERY NICE WORK in my opinion!!
 

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Bob Weber said:
I want to give props to Erik, Stereo Pheonix, for the really nice work he did for me to produce a bridging box. The AB-1 is next to unobtanium and I don't have the skills to fabricate a board so Erik was kind enough to offer to build me a plug and play bridging box. The finished product has labels as well. VERY NICE WORK in my opinion!!
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Thanks, Bob. I appreciate the kind words. For those wondering, the case, transformer, fuse, and power cord / grommet, are all recycled Soundcraftsmen parts!

The bridging box tested well, with 104dB S/N @2V and .0015% THD. Which is about the THD sensitivity of my test gear. Modern test equipment usually shows it much lower than mine will show when it gets there. 104dB is about what a Soundcraftsmen DX series preamp will be when I'm done with it. They are usually around 98-100dB stock, and will be 104-106dB after electrolytic cap and opamp replacement, and local film caps tacked on to each opamp IC directly. Then wires are moved to the lowest noise level while being monitored. My input board uses a TL084 IC like the Soundcraftsmen input boards use. This is with a regulated +/-15V supply. I usually install the board in the amplifier and use the power from that. Resistors are sized to the voltage needs. The bridging box is chassis grounded, but signal ground is isolated.
 
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PabloTincho said:
Erik's in action

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That RA7503 turned out well, but the channel A S/N would have been much better if he had installed the gain pot shield before the tests. I later found that the RA7503 with the analyzer, lets some clock signal from the display leak in to the gain pot. It can be heard close up when the input jacks are not connected to a preamp. After some playing around, I found putting a chassis grounded shield between the two, made it go away. I have used aluminum tape with success since then. I wrap both pots.
 

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I have a PCR-800 power amp someone gave me. Works fine. Am looking into the upgrades proposed by XRayTonyB on YouTube for the PCR-860, which appears to be a slightly modified PCR-800. The PCR-800 has great sound, lots of low bass and clean highs. Like it a lot! Does anyone have a service manual for one? All I can find online is a hand-drawn schematic that leaves out the power supply.
 
RealGoodSnd said:
I have a PCR-800 power amp someone gave me. Works fine. Am looking into the upgrades proposed by XRayTonyB on YouTube for the PCR-860, which appears to be a slightly modified PCR-800. The PCR-800 has great sound, lots of low bass and clean highs. Like it a lot! Does anyone have a service manual for one? All I can find online is a hand-drawn schematic that leaves out the power supply.
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I don't remember what the upgrades were in that video, but that he didn't seem to understand how the PCR system works. I would do research before following it.
 
Just picked up a Pro-Control 422 at a recent garage sale, apologies for the pictures. I do like the looks of it, except for the one broken slider. I'll check it for operation tomorrow if I have time.

Soundcraftsmen Pro-Control 422.jpg

Soundcraftsmen Pro-Control 422 2.jpg
 
I thought about selling the Pro-Control 422 for a profit. After playing it, I think it's a keeper (at least for a little while!).
 
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Racingh11 said:
That RA7503 turned out well, but the channel A S/N would have been much better if he had installed the gain pot shield before the tests. I later found that the RA7503 with the analyzer, lets some clock signal from the display leak in to the gain pot. It can be heard close up when the input jacks are not connected to a preamp. After some playing around, I found putting a chassis grounded shield between the two, made it go away. I have used aluminum tape with success since then. I wrap both pots.
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Speaking of S/N upgrades, I have now started to replace the SCR IC that triggers the triac, with a zero-crossing triac IC. This means it will power up softer starting at zero volts, instead of where ever in the voltage phase it may end up. It also means the SCR IC rectifier diodes can be removed and jumpered where necessary. Removing those diodes means it will fire about 1.2V earlier, and eliminating the noise it creates. It only requires removing 4 diodes, 1 capacitor, and 1 resistor. Then cutting 1 trace, and adding 2 jumpers. And in some cases a new IC socket. There is a certain type that has contact issues with the new IC leads. I change it from 8 pin to 6. Two were always unused.
 
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