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Marantz 18 Scope Troubleshooting

Thanks guys. It went back on the bench this morning just to set the audio crap, dc and bias. Thank god I checked it, had over 1V on the DC reading. Dug back into to amp driver board, 2 more bad transistors found, got it down to 0V on the speaker terminals and set the bias to .08V. I also forgot to mention- this thing has 2 relays for speaker protection, not just one. So if you have a channel cut out like mine did on the left side, it's the relay contacts that are dirty. As well, anyone with an 18 and the black power switch should pull the bottom panel and check it out, you may see this as I did, the switch was hanging on by a thread of plastic, when I removed it the terminal fell off.

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Great work! :thmbsp: Your 18 looks fantastic! :thmbsp:

Thank you very much for the info about the dial glass. I will order one for my 18. Looking for that for a very long time. Thank again!!! :tresbon:

Jan.

:beerchug:
 
Just to add one more thing to this thread in case anyone finds it trying to fix the ol' scope, I had to look up the transistor #'s for another AK member who was going to fix his 18 before he sold it. I used 2sc1473a transistors that were from a 13 inch toshiba tube tv, I imagine they are pretty common parts.
 
Glad to see your 18 back in service. She's a beauty.
After I picked up a Model 20 Tuner, I had to have a Model 18 Receiver too. I still listen to FM. I pick up WXPN-FM out of Philly. Excellent station; but the signal leaves a lot to be desired. No problem for the Model 20 though.
Once I get into the 18, I'm sure I'll find this thread helpful.
Thanks for sharing.
 
bktheking said:
PB- was the 18 a recent purchase off ebay?
Click to expand...

Not very recent... months ago, actually. It was originally missing the top and the transistor cages on both sides. I didn't ever expect to get the missing parts; but, in face, I did finally receive them along with several extra boards.
It will have to get in line, though, behind a 2270, 19, a pair of 250 and three tuners.
Oh well...:D
Jay
 
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