Model 140 rebuild

[rikdekonink]

Hello all,
long long time ago i was 16 and bought a second hand 3200/140 set for 50 euro's and used it for a while in combination with an pm7000 amp to drive my quadral aurum 9 speakers.
but my room on campus was waaaay to small for this setup so i took the pm7000 and a couple of B&O speakers and left the rest at my parents.
fast forward to last month when i visited my parents and saw the 3200/140 in the corner of my old room.
just in time because I was in dire need of a new hobby.
after first startup it was just as i expected, peak light on the right channel lights up, amp does nothing.
the 3200 works fine when used with a different power amp.

so far i've switched the meter circuits to check if it wasn't the usual suspects within that circuit.
one by one disconnecting of the amp boards determined that it is most definitely the right amp, without it the amp powers on and the left channel plays perfectly.

I'm waiting on the ordered DMM and component tester, but any tips on which components are most likely to be the culprits are welcome.

Furthermore, there seems to be some sort of coating on the underside of the PCB's, with the typical old electronics smell, see attached pictures, is this normal? can/should I clean it off, or only where soldering is required?

 

[Dingman]

I'll let others answer the technical questions, but I'll say hello and welcome to AK.
BTW, that black transistor is suspect. Looks like it's burned the thermal goop, that needs attention.

 

[catrafter]

I don't see pictures.

Tom

 

[Steven Tate]

I don't see pictures.

Tom

Same here.

 

[Richs_Trains]

try this:
From my tech: The diodes, 2 per channel, are designated H720, H721. If they are a small black diode, they should be replaced with 1N4148 diodes. Be very careful of the polarity. Also, look for any glue on the top or bottom of the boards. If there is, it has probably turned black and is possibly conductive. Carefully scrape it off. After the repair, set the D.C. offset adjustment R741 for 0 volts D.C. at the speaker outputs. The other adjustment is for bias and is a trickier adjustment. You should not need to adjust this unless the amp tends to run hot with no signal after being on for 10 to 15 mins. The 1N4148 diodes should be available at any electronics shop. Rich

 

[Richs_Trains]

check this thread, it fixed 2 of my 140's .....

http://www.audiokarma.org/forums/index.php?threads/marantz-140-amp-pops.663148/

Rich

 

[rikdekonink]

Same here.

Thanks for the quick replies, I'll link the pictures from another host, hoep that works.
I haven't had any time to work on the amp this week and my component tester is still in transit...
Hopefully i can work more on it during the holidays, not like I'm going anywhere this year, plenty of time.

 

[Lavane]

I've rebuilt two of these amps as well. I kept one, and gave the other to my son with a 1060 integrated to use as a preamp. One other thing to add to your list is to replace the flat gray film caps at the end of the boards. I did an A/B test between the two amps, one with new film caps, one with the original gray caps. There was a difference in sound. For whatever reason, the one with the gray film caps sounded a bit lifeless compared to the other. These are nice amifieres to work on being so moduler. Good luck with the restore. I use mine as a second system with my main system that is most tube based.