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Help with 1180DC problems!

dyche01

dyche01

"Buy high. Sell low"
Subscriber
Dear Marantz community. I have been struggling with an intermittent channel on my trusty old Marantz 1180DC. I did my best to track down the problem but I was spending too much time on it so I turned it over to a professional (old school) repair shop here in the Bay Area. After several weeks (and several different stories about what was wrong) the shop declared that they couldn't fix the problem. Initially they assured me it was dirty contacts (even after I told them that all the contacts had been recently cleaned with Deoxit). Next, they told me that there was damage to the 'input board' and that they were just fixing a few cracked traces. After a few weeks they told me that the problem was a bad capacitor. When I said that all the electrolytic capacitors had recently been changed, the tech said "Oh, did I say capacitor? I meant transistor. There is a bad transistor."

"Power transistor?" I asked.

"Umm, no. A transistor on the pre-amp board." was the reply. I asked how a bad transistor could produce an intermittent channel that is occasionally fixed by tilting or jiggling the unit. "Sometimes a lead comes loose inside the transistor." Hmmm.

Today I got a call from the shop saying that they are giving up on fixing the unit. The current story is that the problem is in the 'channel reverse' switch, by which I assume they mean the rotary selector that switches between 'reverse' 'stereo' 'L+R' ...etc. I suggested that they just bypass the switch and hardwire the 'stereo' mode, but they claimed that this is impossible.

I am going to pick up the unit later in the week and (if it really is the selector switch) try rebuilding it or hardwiring the connection. Anyone here have any experience with such problems?
 
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Get it out of there before they make matters worse. If it's fixed by tilting or torqueing the chassis you most likely have a intermittent soldering joint connection. This unit isn't for the faint if heart. There are many many solder joints that connect the boards here.

I seriously doubt it's your stereo switch and yes it can be bypassed.

Get it to a pro. It's a rare, powerful model and it deserves a skilled hand. I would recommend Bob here in upstate NY, I'm sure he has mended many of this series units! Mech986 I believe. Also recommend Randy aka RBuckner and catrafter.

Don't be impatient and bring it to the first person you find with an empty workbench. Great techs don't have empty workbenches and ARE worth waiting for.
 
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poking it with a wooden stick might well get closer to the fault ..
needs someone with dedication and likes a good challenge to fix it . i would take up the challenge if i was closer .
 
Thanks! I appreciate the comments. This shop has been around for more than 30 years; specializes in vintage gear; and comes highly recommended (both by Yelp and by Bay Area members of AK), so I was really surprised by the changing stories and the general runaround they gave me.

I also doubt that the stereo switch is causing the fault but I will check it out myself when I get it back from the shop.
 
I'm curious.. You say it has been completely recapped. Who did it and how long ago? If you have only a few hours on it since the recap, I would follow up with whoever did the work.
 
Ha! I did the recap myself, in the course of trying to find/fix the source of the intermittent channel. I was checking and re-flowing so many joints that I decided to go ahead and recap the entire unit (except for the main filter caps). I never found the source of the problem but, on the bright side, I didn't make it any worse. As I mentioned above, I was spending too much time trying to fix this unit myself, so I finally decided to let somebody else have a crack.
 
capacitors will very rarely cause intermittent faults . they are bad or good .ambient temperature can however make them work for a while . saying that changing them is ok if no faults are added .
 
petehall347 said:
capacitors will very rarely cause intermittent faults . they are bad or good .ambient temperature can however make them work for a while . saying that changing them is ok if no faults are added .
Click to expand...


Yeah, the problem was the same before and after the recap. I didn't expect the recap to fix anything, I just though that since I was resoldering everything I might as well replace the electrolytics. The upside is that, when both channels are playing, it sounds better than ever.
 
When you get it back, get it under bright light with a magnifying glass and go over all visible solder joints on the top foil side. If nothing visible here, I would get to the foil side of the power supply board and reflow everything. I found bad cold joints on my 1152dc on the relay center pins. Replace the relay while your in there and reflow everything. The 1152, 1180 etc are known for cold solder joints and not just at the edge connectors.

Good luck!
 
About the relay : when the channel is out, try tapping it with a wooden stick or similar. Or also when the channel is out try turning the volume high for a split second. If either of these tricks bring the channel back, the relay is suspect N°1.
Good luck.
 
Another place to look would be the jumpers on the back panel. Insert a patch cord or RCA cables across the pre-amp to main-amp inputs. They at times need to be cleaned. Also there is a row of pin connections on the back of the mode switch (IIRC) that may be in need of attention. Sometimes the 90* connections will need to be soldered to insure a good connection.



Barney
 
I just fixed what seemed to be a mechanically intermittant issue by replacing two transistors (TO-92) in a 2230. When I suspected them as narrowed down by soldering on a long wire to attach a scope probe and seeing where the issue started, I pushed them around with a wooden stick and no noise occurred. Replacing them did fix it though! So it can happen. It was a noise not caused by chassis flexing, only dropping one side about 2 inches from the workbench surface. The only reason I ever did that was that there was an occasional loud pop on one channel.

BTW, Dyche, I'm a native of Alameda across the bay!
 
Thanks for the suggestions. I have not swapped out the relay but that is not a bad idea.

I just picked up the amp from the shop this morning and talked to the actual tech (as opposed to the somewhat surly front-desk man). He seemed to know something about what he was doing, and said that there were two problems. One problem was a damaged board at the rear, with multiple detached traces and cracked solder joints. He fixed this problem and said that the intermittancy that could be fixed by tilting the unit went away. According to him, however, there is a second problem, which he traced to the stereo selector switch. This makes some sense because sometimes, when tilting the amp didn't fix it, cycling various switches on the front panel did the trick.

On the bright side, they didn't charge me for any work - only a nominal diagnostic fee.
 
By stereo switch could that be mode? If so then check the boards on the back of it. The boards connect with a row of pins at 90* IIRC and can loosen over time. Carefully wiggle it a see if the problem occurs. You can solder the board and pins if adjustment and tightening fail to fix.


Barney
 
mmm'kay.

Tonight I opened up the 1180DC, just to see what's what. I pulled off front and back panels and removed the rear board (the one attached to all the RCA connectors). Beneath the EM shielding I found some clumsy repairs that probably predate the trip to the repair shop. It looked like someone intentionally cut traces connecting the "pre-out" and "main in" jacks and then came back later and fixed them. I removed some of the excess solder and wire from the board and then tested to make sure the switches inside the "main in" jack still work. Next, I poked around on the front panel board to see whether the shop was right about the 'stereo reverse' switch being bad. I couldn't find any evidence that this was the case, so I just cleaned the contacts with Deoxit and buttoned everything back up.

You guessed it.

Now both channels work perfectly. Here are my current hypotheses: (1) There is still a broken trace somewhere and all the fiddling just mushed the parts back into contact. (2) The 'main in' cutout switch on the right side was stuck and cycling it with an RCA plug fixed the problem. (3) The 'stereo select' switch really was bad (or at least dirty) and the Deoxit solved the problem.

Regardless, I am currently enjoying the amp, back in its rightful place.
 
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Nice ! I have had the pre-out to main in contacts loose a channel even after deoxit (2226B) and just pushing an rca jack in and out a few times fixed it.
 
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