Left Channel Cutting Out

[SkyChurch]

Hey, My Marantz 2270's left channel has been cutting out for quite awhile now. Maybe ~10 months or so. It could always be temporarily cured (about 40 minutes, then acts up again) by just cranking the volume way up real quick and then bringing it back to the previous volume, but I'm getting sick of doing that and just want to fix it permanently. What happens is I'll be listening to music or something, and it happens in both aux and fm, and after about 20-40 minutes the left channel will start breaking up and it sounds like static and then breaks out and then comes in staticy and breaks out and comes in staticy etc.

My question is what should I do now to isolate the problem? Or should I just assume it's the output transistors and just replace those, or should I go through it with a signal tracer? Possibly the relay?

If you think I need to go through it with a signal tracer then I'll have to buy one. Anyone have any recommendations? I've heard that you don't need to spend any more than 25 dollars on an ST, but the cheapest one I could find on froogle is like 50-60 dollars I think. If you could send me a link to a good cheap one I'd really appreciate it.

As always all advice is appreciated, thank you!

Andrew

 

[Jukin Jay]

My hunch is switches. Exercise the tape monitor, input, and speaker switches. Next time it cuts out, see if it is dead with headphones. That will confirm or eliminate the speaker switch. Have you taken it apart and given the switches a shot of De-Ox-It? If this unit has a preamp out to main in jumper on the back, remove and reinsert it.

 

[SkyChurch]

I'll try working those switches a bit and see if it improves. The problem still does occur with the headphones too. And I also did clean the pots and switches with de oxit a few months ago but I've heard that sometimes it takes several times to get them fully cleaned due to the age. I'll also try reinserting the preamp-mains jumper. Thanks a lot jukin, now off for some trial and error.

 

[EchoWars]

Output relay is also suspect.

This is not a problem with output transistors.

 

[SkyChurch]

Is signal tracing the only way I'll surely find out? The only relay I'm familiar with is the relay in the power supply, but then again I'm hardly familiar with electronics. How could I find out if it's the output relay?

 

[EchoWars]

Follow the signal with a scope. No scope? Change the relay. It probably needs it anyway.

FWIW, it is a true PITA to properly clean switches. Unless you've had some experiance here, chances are you simply didn't get it right.

 

[SkyChurch]

Sorry I didn't keep up with this post for anyone who cared, but I've been busy and didn't get around to messing with the receiver until just now.

I took out the jumpers from the preamp to the mains and cleaned the jumper inputs with some deoxit and worked the tape source and monitor switches back and forth a number of times but the channel is still cutting out.

So Echo you recommend that I just replace the relay in the power supply right? I don't know why, but I dread having to clean the switches again even though I still would have to take the thing apart to replace the relay. But if I replace the relay I'd might as well clean the switches too.

Any other thoughts or advice for this problem, feel free.

 

[skibjr]

Tap the relay lightly while the receiver's playing. If the you get noise in either channel, or the sound cuts in/out, that pretty much clinches it - cruddy relay contacts. I've had good luck cleaning relay contacts on Marantz receivers - you may not have to replace the relay. If you search this forum for "speaker relay", there are several threads outlining how to clean 'em... :thmbsp:

 

[SkyChurch]

Hey skib, I actually tried tapping on the relay cover while the music was playing a few months ago and it didn't affect the music at all. So unfortunately I'm guessing that means it's not the relay. That sucks, the search is still on then.

 

[skibjr]

:dammit:

Make sure that when you do the "tap" test, that the volume is fairly low. Higher volumes move more current through the contacts, which more easily bridges the gunk.

You've mentioned cleaning the switches and the pre out/main in jacks. What about the balance control? Anything signal passes through could be the culprit.

Have you tried to isolate the problem to either the preamp or the main amp yet? If you disconnect the pre out/main in jumpers, and hook the pre outs to another amp, do you still have the problem?

 

[SkyChurch]

OK I just did a slight variation to the tap test considering the tapping wasn't cutting it. Instead I shook the whole damn relay a little bit from side to side and that got some results. After doing that the left channel did actually start to cut out like it was doing, then I moved the balance knob to the right channel only and that side was cutting out too. Thing is the right channel would correct itself immediately whereas the left channel would continue staying staticy and breaking up so in the end it is actually the relay that's the culprit so now I can go ahead and get a new one on digikey. :thmbsp:

Once again thanks a lot for all the advice, yet another problem fixed through audio karma

Update: I have a couple other questions. First, I just did some audio adjustments to my receiver including dc offset, idle current, and voltage adjustment. When I replace the relay am I going to have to make these adjustments all over again?

And also on my relay is printed OMRON Type MY2 24DC LY20240033. I can't find this item in either digikey or mouser. I know digikey carried it several months ago b/c I looked it up but now it seems they don't anymore. Does anyone know where I can find this exact model or if I can substitute with a different model?

 

[EchoWars]

http://audiokarma.org/forums/showthread.php?t=90275

 

[SkyChurch]

Hey Echo, My relay says Type MY2, but then the part number is LY20240033 so I don't kn ow if that makes it an LY2 or an MY2. Plus nowhere on the relay is it listed as XY2-02-DC24. So I'm confused on this one. I know digikey carried my exact model several months ago b/c when I typed in LY20240033 in the search it came up but now it doesn't. Even after I do a search for 24vdc pcb Omron relays in both the general purpose relay section and the power relay section I can't find it so I'm stumped.

Also do you think I'll have to perform all those audio adjustments again after I replace the relay?

 

[SkyChurch]

Anyone have any idea? I'm pretty sure it's an MY2 model but I don't know if it's a 5a or a 10a. Anyone with marantz 2270 experience know what to use?

 

[skibjr]

So you're not going to even try to clean the contacts on the old relay? I've repaired at least a dozen Marantz receivers with the exact problem you're describing, and I've never had to replace a relay yet. There are many variations on this theme, but I've had 100% success with the procedure below.

1.) Desolder the relay connections and remove the relay.
2.) Remove the relay's plastic outer cover. There are usually little snap-in catches on each side; work a thin piece of metal under each (kind of like shimming a door latch with a credit card) and pull the cover up and away from the base.
3.) Locate the relay contacts. There will be two sets of four contacts on either side of a flexible center arm containing four additional dual-sided contacts.
4.) Cut a small, .25" by 1.5" rectangle from a sheet of #600 wet/dry sandpaper. Fold the rectangle lengthwise so that you have a .125" x 1.5" section, with abrasive on both sides.
5.) Spray a little Deoxit on the both sides of the sandpaper to moisten it.
6.) Gently move he center arm containing the two-sided contacts so that you can slide the sandpaper between the four sets of closed contacts.
7.) Release the center arm so that the sandpaper is squeezed between the four sets of closed contacts, then apply a gentle back and forth motion (about 10-15 back & forth cycyles) to relap that set of contacts.
8.) Repeat steps 6 and 7, but for the other set of contacts; the ones that are normally open when the relay is de-energized. Gently press the center arm against this second set of contacts as you sand between them so that all contact surfaces are relapped.
9.) Remove the sandpaper and spray all contacts thoroughly with Deoxit, AVOIDING THE RELAY COIL as you spray, then blast any excess Deoxit off of the contacts and out of the relay with a can of compressed air.
10.) Reassemble relay and reinstall.

You should be able to knock this whole procedure out in less than 30 minutes, including desoldering and resoldering, and the relay will not not need for further maintenance for years. I haven't had to clean the same relay twice in over five years, anyway.

Good luck if you decide to give it a go! :thmbsp:

 

[SkyChurch]

Thanks Skib, I was thinking if I have to take a relay off to clean it I might as well replace it with a new one but I can't find it anywhere so I'm just going to clean it like you said. I like the step by step instructions too, nice.

I also have a damaged 2270 from shipping that I keep around for spare parts and the contacts on its relay look very shiny and clean so that's another option but I'll probably just keep the original that way the audio adjustments I made won't be off at all.

By the way do you work on electronics for a living? That's something I'm interested in doing myself just don't know how to go about doing it. As far as opening a little shop goes.

 

[skibjr]

...By the way do you work on electronics for a living? That's something I'm interested in doing myself just don't know how to go about doing it. As far as opening a little shop goes.

I do a little "flipping" (buy/fix/sell) in the evenings just to keep the bills paid and to sock a little extra away in my kid's college fund, but that's about it.

Electronic repair full time is a tough business... and getting tougher - in fact, our very own Karma16 started a great thread on that very subject here. I fixed my first clock radio when I was 10, took a few college classes, and the rest I picked up out of sheer stubbornness (trying yet again, after the smoke clears ). I've also learned quite a bit by just hanging around here! :thmbsp:

 

[SkyChurch]

I don't know if it's these model of relays but getting the cover off is an incredible PITA. So I just took the nice relay out of the spare 2270 and swapped that in and so far the receiver's been playing trouble free. I've only played a couple albums but so far so good.

Also I don't know if it's just me but I think the sound quality has actually improved since putting the other relay in. The sound is cleaner (not as distorted), and even the tape hiss on old recordings seems to be not as apparent as it was before. :scratch2:

That's interesting skib about flipping receivers. I've seen it talked about a lot on the forums. I'd be interested in doing that too. How exactly did you learn to troubleshoot the receivers though? Did you just use an oscilloscope or signal tracer? Any books in particular you recommend? Thanks for all the help!

 

[Whaleman]

Not to revive this old thread, but after cleaning the relay on my 2270, a similar problem continued with the left channel. It would work well for a few minutes, then loud static, and then the relay would disengage.

Turns out, I had bad input pair transistors or main driver pair. I replaced both and problem solved.

Echo and Fred helped identify.

 

[wank]

Bumping this thread with appreciation for Skibjr's instructions. Had a 2270 collecting dust for almost a year. Just tested with the relay tap - pulled it, lapped it, and reinstalled it, and it's like new.