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Marantz 2226 Advanced Diagnosing..

atrelstad

New Member
Hi AK'ers!

Hoping for both some general and maybe more specific advice on diagnosing receivers. I'm fairly new to the vintage audio game, and so far my method has been "recap and listen" with some luck tracking down bad transistors, resistors, etc. The work I've done has so far turned out great, the issue is... I don't really know what I'm doing. I'm handy with a soldering iron and am good at following directions, but when I run into an issue I come to a stop pretty quick. For the general side of things... does anyone have good resources to learn more about what I'm actually doing? Transistor matching, voltage testing, that sorta thing. People on here say things like "I've tested the voltage at Q408 and at the main filter caps, and all looks normal" and I have no idea how they know to test there, or what normal is! Lack of experience I'm sure, but I'm willing to learn!

To get more specific, I'm working on a Marantz 2226 (not the b model) that is getting some distortion in the right channel. I've so far replaced all electrolytic caps, but haven't touched the orange ceramics, films, or the blue tantalum drops. It sounds 90% of the way there, but distorts on high dynamics (the kick in "beat it" reveals it well). I've followed the schematic directions for power amplifier adjustment and power supply adjustments successfully, have replaced half of the transistors on the Pre/Tone Amp Board (I'm waiting on the rest to arrive), and by swapping left/right via Pre Out/Main In's, am fairly certain it is in the preamp section. The distortion switches to the left at least. It is audible both from Phono and Aux channels, the only two I've really critically listened to. I would suspect output transistors as I've not touched any transistors on the main amp board, but as it swaps with the Left/Right switch that seems unlikely.

I'm hoping this next set of transistors just does the trick, but any advice on how to more critically determine what my problem might be? Shoot now check later is getting to be very inefficient, and I'd love to know more about what's actually going on on these boards.

Thanks a ton, you folks are uber knowledgeable and us newbies really appreciate you passing it down!
 
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You're off to great start and already narrowed it down to the preamp section by swapping the Pre Out/Pwr In connections. Now I'm not an expert by any means, but I would start by checking voltages on the schematic, specifically on the transistors you have yet to replace. I would also take a look at any old tantalum caps for leakage or shorts.
 
As Tom said, your on the right track. I wouldn't call myself an expert either, but I did learn a few thing about repairing audio. Best source: it is Audio Karma :bigok:. Well and the trail& error of course, googeling stuff, watching some U-tubes now and then..

A quick way to check out transistors in circuit is to switch the machine on an carefully touch the transistor with your fingertip. If that makes it humm or tick or whatever over the speakers, the transistor is bad. Start at low volume, crank it up a bit if all appears good. Also look for blackened feet of the transistors, and one lag "growing out" of the transistor, leaving it steeped over on the PCB. Google for pictures!

Oh, and get yourself one of those cheap component testers.
 
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