![]() We used the 2N4124 or 2N4126 transistors, but I'd imagine a 2N3904/2N3906 would also work. On the circuits where you can make out the transistor bodies inside the conformal outer coating, I've had (very limited) luck scraping off the ceramic coating and tacking in new transistors - you have to use a low heat iron and be quick. It'll be an encapsulated circuit/PEC/Bulplate, 7,8 or 9 pins, with a 130XXX or 132XXX or 134XXX part-number (I don't remember the drawing numbers actually on the devices anymore.) No component values in the RCA manuals, as it's all encapsulated. That's the weakness of Sams - RCA's service data shows the MPX Detector to be the ubiquitous discriminator diodes and a preamp ("matrix amp") stage, something Sams doesn't. Last edited by Tbirdkid on Aug 4:31 pm, edited 2 times in total. I also get a lot of 'snow' sound at times on that left channel and some in the right.sounding like the silver mica disease. It uses the dreaded RCA 'encapsulated circuit' modules which are a pain and had a history of failures. If I know where the signal actually splits that will help me figure a plan. I've attached a poor copy of the circuit.sorry it's not great to start with and this posting is even poorer. ![]() My question is-Where is this left/right separated signal developed in the de-mod circuit? I assume that is where I lose some of the signal. ![]() The pre- amp and amp is OK because when I switch it into Mono mode, both channels have equal volume and this switch is in the tone/volume/balance pre- amp, just before the main amp section.and the phono circuit is balanced stereo also. I'm getting a weak stereo left channel signal coming into my pre- amp section of an RCA VPT-50-W 1970 console. ![]()
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