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Marantz 2230 ~ What did I fry?

Landcruiser

Landcruiser

New Member
Hello, All!

This is my first post here on AK, so be gentle..

I recently picked up a minty fresh, *all original* Marantz 2230 from my local Craigslist of all places. I got her home and cranked her up..sounded great aside from a scratchy volume pot. So I figure I'll open it up, clean out the years and years of dust and de-ox all the necessary pots, switches, inputs, etc..

While I had it opened up, I figured I should check the power supply and amplifier bias #'s. I get the power supply to the 35.6VDC number recommended..no problem. I move to one amp, it's running a little high..so I back it down to the recommended 5mV..no problem. I get over to the other amp and it was also running a bit high. So, I ask my wife to give me a hand this time and dial it back for me while I check the resistor and count her down to 5mV. I get to 5.2mV (I should have stopped!) and tell her just to give me a little more.. When she does, my meter goes to 0. And it NEVER came back. I'm assuming I touched something I shouldn't have during the adjustment and ended frying something..but what? No smoke, no smells.. R774 was still resisting (1.5k I think).. But nothing was coming through. I plugged it back into my speakers just to confirm and sure enough, the right channel was full of weak static with only subtle hints of music coming through. Any ideas what I fried?

I had planned on ordering a recap kit anyway..but now I'm wondering.. Will the recap kit fix the (possibly) fried amp?

Thanks for reading, I appreciate the time!

Danny
 
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Danny,
The "recap kit" will not fix your problem, and can actually create a more complex issue. You need to get the problem fixed before you recap anything.
I would check the outputs to see if they are open base to emitter, or one shorted E to C, and the other open B to E. If you only have a digital meter, you can check for an open output by measuring DC volts between Base to emitter. It should be no more than 0.65V. If it is showing a lot higher, it usually indicates an open. But using an analog multimeter to check ohms on the RX1 scale across the base to emitter should give you a mid scale reading in foward direction, and open or infinity in the reverse direction. Base to collector should read the same. Emitter to collector should read open in both directions out of circuit, and probably similar to Base to emitter in circuit, due to the other circuitry involved. You can check those emitter resistors you were measuring against to make sure they didn't open. they should read 0.24 ohms.
Other than than, it could be drivers, pre drivers, diodes, or combinations on anything from the main amp to the outputs on that side. I don't see any fuses, protect relays, or fusable resistors being used than could cause this issue. This is a capacitor coupled output, and if that cap fails you would not have any sound out of that channel, but having no bias volts on that channel says you popped something, and a bad cap would give you ) bias volts. (I have assumed you have the 2230, and not the 2230B. The 2230B does have different amplifier circuitry, and protect relay, and circuits as well.
 
fortunately, the 2230 is the stereo equivalent of a 1 barrel carter carb and points ignition on a ford truck I6 - meaning no repairs aside from some thermal sensing diodes, will be difficult. heck, disassembly will be the hardest.

there are some smart cookies on the marantz board that have BOMs and sage advice and dirty jokes to tell you. I myself have done 2 2230's (B and not B) but I aint considered a smart cookie. so if I can do it, you can do it.

(and besides, the parts you weld in there will be worlds better than the parts you took out....)
 
Tom B said:
Danny,
The "recap kit" will not fix your problem, and can actually create a more complex issue. You need to get the problem fixed before you recap anything.
I would check the outputs to see if they are open base to emitter, or one shorted E to C, and the other open B to E. If you only have a digital meter, you can check for an open output by measuring DC volts between Base to emitter. It should be no more than 0.65V. If it is showing a lot higher, it usually indicates an open. But using an analog multimeter to check ohms on the RX1 scale across the base to emitter should give you a mid scale reading in foward direction, and open or infinity in the reverse direction. Base to collector should read the same. Emitter to collector should read open in both directions out of circuit, and probably similar to Base to emitter in circuit, due to the other circuitry involved. You can check those emitter resistors you were measuring against to make sure they didn't open. they should read 0.24 ohms.
Other than than, it could be drivers, pre drivers, diodes, or combinations on anything from the main amp to the outputs on that side. I don't see any fuses, protect relays, or fusable resistors being used than could cause this issue. This is a capacitor coupled output, and if that cap fails you would not have any sound out of that channel, but having no bias volts on that channel says you popped something, and a bad cap would give you ) bias volts. (I have assumed you have the 2230, and not the 2230B. The 2230B does have different amplifier circuitry, and protect relay, and circuits as well.
Click to expand...
Thanks for the response, Tom. I'll open it back up and start troubleshooting with your suggestions. Time to get the hands dirty! BTW... It's the standard 2230.
 
quaddriver said:
fortunately, the 2230 is the stereo equivalent of a 1 barrel carter carb and points ignition on a ford truck I6 - meaning no repairs aside from some thermal sensing diodes, will be difficult. heck, disassembly will be the hardest.

there are some smart cookies on the marantz board that have BOMs and sage advice and dirty jokes to tell you. I myself have done 2 2230's (B and not B) but I aint considered a smart cookie. so if I can do it, you can do it.

(and besides, the parts you weld in there will be worlds better than the parts you took out....)
Click to expand...
Glad to hear she's not a V12 Rolls Royce! It definitely seems much easier to work on than my Onkyo TX-2500mkii..but I'll have to wait and see how "deep" of a fix this is. Thanks!
 
Petehall347 beat me to it while I was being a smart-a. Change out the trim pot first and see if it solves your problem. In fact, you'll need to change both of them. Bourne trim pots are usually the best replacements.
 
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