Marantz 1200 w/Channel Fading Out

[JJ3810]

I really need some suggestions. The left channel of my Marantz 1200 fades out shortly after I turn it on. It plays fine for a little while and then fades down to almost nothing. Please offer me any help you can. Thanks so much.

[JJ3810]

I'm bumping this for some help. Please.

[Punker X]

Could be many things. You need to try and narrow it down. Try removing the pre-out/main in jumpers. Take the pre-out to a different amp, or use a different sourse to the main in. I sometimes use a small Diskman. You need to figure out if its an amp or pre-amp problem.

X

[ruesselschorf]

Hello,

could be the speaker relay. Does the weak channel 'come back' when you pump up the volume for a few seconds?
Remove the top cover, locate the relay (it has a clear plastic housing, about 1 inch by 1 inch size) IIRC its in the left rear of the amp. Tap on it with a screwdriver-handle while playing low volume music - see what happens...

Helmut

[JJ3810]

I'll look at the relay and Deox again this afternoon. Thank you all for the suggestions.

[SB Marantz]

I'll look at the relay and Deox again this afternoon. Thank you all for the suggestions.


Deox the relais?

You need to unscrew the relais board,pull it upwards en take the plastic cover of, then release the small spring and flip the moving part out, clean the contacts with very fine sandpaper.
If you cannot reach the contacts in the relais itself then desolder it and take it out.

Ready,set,go.....again :smoke:

[JJ3810]

No, I wouldn't ever spray the relays. But I did DEOX the TAPE MONITOR switch and the SELECTOR switch real good again and then I pulled all eight transistors and applied heat sink compound just in case there was a thermal problem. The relay is located on a board that is mounted vertical which makes access to the relay somewhat awkward because of the wiring scheme. I'll pull it and take a look sometime this week. Thanks for the replies.

[jblmar]

Fade out after the set has been on for a while, could suggest a thermal problem. If cleaning the relay/switches is of no help, you'll need some component cooler to find the intermittent component(s).

Ron

[JJ3810]

Lovely. I was hoping to hear leaky capacitor or something a little easier to find. Actually, this is my third experience with this failure on Marantz units so I was hoping there would be a obvious defect that others had found. I guess I'm just one of the lucky few.

[dj2quick]

hey, just wondered about a couple of things.

firstly, did you fix your problem?

and secondly, and this is mainly directed to ruesselschorf,

"Hello,

could be the speaker relay. Does the weak channel 'come back' when you pump up the volume for a few seconds?
Remove the top cover, locate the relay (it has a clear plastic housing, about 1 inch by 1 inch size) IIRC its in the left rear of the amp. Tap on it with a screwdriver-handle while playing low volume music - see what happens...

Helmut"

that is EXACTLY what my Marantz 1060 does, and on the left channel too. its been so frustrating but i have no clue where to start in order to rectify this. so you're saying that if it fades out but comes back when the volume is turned up (and in turn fades back down after a bit) then its the speaker relay? would it be in the same place as on the 1200? thanks so much in advance!

[onplane]

Guys, a fading out problem could also be a cold solder joint or a bad cap AND could be ... ANYWHERE!

Punker has it right. The very first thing to do is find out in what part of the amp you are losing the signal.

Easiest way to do this is to remove the pre-out/main in jumpers and replace with a regular audio patch cord.

Now, turn the receiver on as usual and at a LOW or moderate volume (we want the channel to fade out). Once it fads out, reverse the leads going to main in. That is right pre-out to left main in.

What we want to know is whether the LEFT channel is still the weak one, or did they flip and now the RIGHT channel is the weak one.

This little test will help us narrow down where the problem is.

Let us know what you find.

Regards,
Jerry

PS: One other test you should ALWAYS do is throw the mono switch to see whether the faded channel comes back.

[dj2quick]

ok, and if its still the left side fading then its the main amp and not the preamp right?

ill do this test and post the results.

[dj2quick]

ok WELL, i did what you said and the left channel still fades out, only this time for some reason it was after a long time and with the volume even lower than before. it faded out while they were not crossed ( L - L , R - R) and as soon as i connected the right to the left it came back. then faded back out.

so now, am i correct in assuming that im going to have to fix something in the main amp part? whats to check / look for next?

thanks for all the help guys.

EDIT: Also, tried the Mono switches LOOOOOONG time ago, they do nothing. My Tape Monitor switch is buggy and takes some jiggling, but thats a whole other problem and i know for a fact that it has nothing to do with this fading out.

[onplane]

Yep, the problem has been isolated to the LEFT power amp.

Relays can cause problems, but I'd bet more on a cold solder joint or a bad cap. Do you have the schematic or service manual? Reason I ask is that depending upon the amp design, we might be able to isolate even further.

If you don't have a schematic, I'd recommend that you buy as this investment you can recover when you sell the unit.

Other than that, start looking at the power amp board and re-solder any joints that don't look perfect.


The suggestion to "tap" on the relay once you lose the LEFT channel is a good idea. If you gave a "flakey" relay it should respond to mechanical vibration.

Regards,
Jerry

[dj2quick]

ok, thanks. no i do not have the schematic nor do i have the service manual. ill begin searching the board tomorrow, when i have more time and will let you know of anything else. when this first started happening i thought it could be a capacitor. anyway, ill post more later. thanks.

[Cable Monkey]

Identical symptoms on my Sony was capacitors on the power amp board. The board was isolated by virtue of the fact the channel died regardles of what was selected on the input. 20 minutes with a soldering iron fixed it.

[dj2quick]

yea, i dont think these amps even have speaker relays. im looking through it now.

cable monkey, which capacitors were bad and how much did they run?

[Cable Monkey]

I didn't take analysis that far! My background was as a repair and calibration engineer for telecoms test equipment back in the days when they didn't just throw it away and buy new gear. If one electrolytic was deemed to have failed, we changed the lot as once one goes others invariably followed, especially with old kit.

[dj2quick]

ah, i see.