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Channel Fades In An Out

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Channel Fades In An Out

Postby NW_Ryker » 03 Aug 2011 04:56

Hey all,
I recently bought my first setup. It works great except for one problem. One channel fades in and out. Swapping the RCA cables doesn't move the problem from one speaker to another. My receiver is only rated at 20 W, could this be the problem? I play it from about 1/4 to 1/2 volume and it happens all through the range. Could it just be that there isn't enough power? I've played around with two sets of speakers and both exhibit the same problem on the same side (right speaker while facing receiver). I've made sure the speaker wires were making good connections. The receiver is a Harmon Kardon HK-350i.
Thanks in advance for any help you can give.
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Receiver Fading In And Out

Postby josephazannieri » 03 Aug 2011 05:15

Yo NW_Ryker:

You need to describe what it does when it fades out. You appear to have isolated the problem to the receiver, but you can go a little further. Plug a CD player into an auxiliary input on the receiver and see if the problem persists. If the problem persists, the problem is in the high level section of receiver. If the problem is not present with the CD player, the problem is in the phono stage. Is the fading channel left or right? Does it just die out slowly, or does it jump in volume? Does it make noises before it fades? Does it distort while it fades? Does it distort in the low-volume mode? Does it reduce in volume or go completely dead? Answering these questions will help identify whether it is a power supply problem or a problem in the signal path. You can have a bad device, a bad power supply, or a device that is erratic.

You have one good channel. You can compare voltages and signal passage between the good channel and the fading channel, and this will identify the problem stage. Most old receivers use discrete devices rather than IC chips, making them relatively easy to service. Open it up, wait till it fades, and then spray some circuit cooler on the likely devices and see if it comes back. The device that brings it back when you spray it with circuit cooler is the bad one.

Not much help here, but a further description of problem might assist. Service Manual available here:
http://cgi.ebay.com/Original-Service-Ma ... 3ca6f18c9e

Don't know this vendor, but might be a help to have manual if you want to fix it. Schematic provides aid in diagnosis.

Good luck from the old inquisitor,

Joe Z.
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Postby NW_Ryker » 03 Aug 2011 20:00

Thanks for the reply. It was a little late when I wrote that last night. The volume decreases and a muffled popping occurs. I'll try to get a video of it when it happens next. Usually it's just on the right side if your facing the speakers but just before I write this, it happened on both sides at the same time. The weird thing is a good smack to the speaker fixes the problem. The more I think about it the more I start to believe it might be my cart. Also, my TT is missing the ground (ordered one) could that be the problem?
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Possible Suggestions

Postby josephazannieri » 03 Aug 2011 22:27

Yo NW_Ryker:

Based on your descriptions, I do not think your problem is the cartridge or the ground. If it were the cart, it would switch sides when you switch the turntable RCA connectors. A bad ground wire will cause a buzzy hum that is present all the time. You might have that too, but it's not going to cause the fading. You can always try the turntable in another receiver.

You say that whacking the speaker makes it stop, but you also said that changing speakers didn't change the problem. I think that the change when you whack the speaker might be coincidental.

Your description, which is that it fades and there is a muffled popping sound, suggests a defective capacitor somewhere, perhaps in a signal path. Might also be a bad transistor. I think you will need a schematic diagram and a decent DVM to fix this thing.

Does it stop fading when you are using a CD player or some other auxiliary source? Does it fade in and out when you are playing the radio? Try taking the cover off of it and twisting the chassis while it is playing. Be careful not to touch components on chassis with your fingers while twisting. Twisting chassis may move components enough to trigger the problem.

You can also take a wooden pencil or some other nonconductive item and touch components with the eraser end, and see if there is a component that triggers or cures the problem. Just don't let the metal eraser shield touch anything. Cover the metal with electrical tape so nothing gets zapped.

Might also be that you have a number of comonents that are starting to fail, and that is why the problem is now on both channels. Maybe the same failure on both sides.

Anyway, hope this helps, and good luck from the old twister,

Joe Z.
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Postby NW_Ryker » 03 Aug 2011 22:59

The sound isn't present when I use the radio. Only the phono function. Would it even be worth trying to fix? I only paid $15 for the thing and have zero idea what I'm doing.
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Postby analogaudio » 03 Aug 2011 23:27

If it only cost you $15 I say can it. No disrespect to Josepha but don't let this turn into DIY repair shop, instead spend the time enjoying music with a receiver that does work OK.

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Postby NW_Ryker » 03 Aug 2011 23:36

Any suggestions what to look for? Under $100 please.
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Postby NW_Ryker » 03 Aug 2011 23:51

With a quick look through CL, I found this. I figured I might be able to get him down to around $50. Tell me what you think.

EDIT: A link would be helpful :oops:

http://seattle.craigslist.org/see/ele/2527330076.html
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Funeral Music

Postby josephazannieri » 04 Aug 2011 04:11

Yo NW_Ryker:

Analog Audio has a point.

If it were mine, I'd fiddle with it, but then I'm always fiddling with anything. BUT, if the tuner doesn't work, and you only paid $15.00 for it, it may be dumpster food. This thing has too many problems, and you could spend a year hassling with it and not getting it right. Better to spend $50.00 on a used receiver or integrated amplifier that works in all regards than to spend $50.00 in parts and a year of hassles and have a unit that still might be bad.

Here is a sample off Ebay that might suit your purpose. You might want to ask seller to be sure everything works. It has a phono input.

http://cgi.ebay.com/Pioneer-Stereo-Rece ... 1c1d4ff7b6

There are lots of these things floating around, and most of them still work. I just spent $45.00 including shipping for an amplifier for a friend that has a dance studio, 40 WPC Pioneer. Works great and looks decent. Just stick to the ones that work COMPLETELY, TUNER AND ALL.

Craiglist is OK too if you live in a metropolitan area where these things come up for sale. Advantage is that you can look at it and try it. But you may wait a while or get lesser gear.

And good luck from the old EBay purchaser,

Joe Z.
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Postby NW_Ryker » 04 Aug 2011 05:04

The tuner works perfectly. Never had a problem with it. The only thing I have hooked up to it is the TT. The problem only occurs on the phono setting. I have a video of it, I'm having trouble uploading it though. I'll swap the RCA cables when the problem is happening and see what happens.
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Boy Am I Dumb!

Postby josephazannieri » 04 Aug 2011 05:45

Yo NW_Ryker:

I misunderstood. I thought you were saying that there is no sound when tuner is being used. If the tuner works perfectly and the problem only occurs when phono is operating, then the problem lies in the phono preamp. There is a quick'n'dirty solution. Buy an inexpensive phono preamp such as MCM Electronics part number 40-630 ($19.95 plus shipping). http://www.mcmelectronics.com. Plug phono into preamp and preamp into an auxiliary input. You can check phono cart and leads by switching RCA plugs when problem is occurring to be sure that fading doesn't switch, but I thought you had said previously that it didn't switch.

Maybe it's not dumpster food, since $19.95 or less on Ebay for a cheap phono preamp will get you working, and be cheaper than a new receiver.

And good luck from the old guy who changes his mind with each new piece of information,

Joe Z.
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