RX-5085 Loud rumbling from the right channel only during cassette playback.

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mu1sic2ian3

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Welp, I may have found the problem (I sure hope so). Caps C142 and C242 were completely perfect looking from the top. But as soon as I looked
underneath I saw a nightmare. I'm honeslty shocked the left channel wasnt more effected. C142 which I believe is tied to the left channel was
broken off on one of the leads. I really hope this was the issue. Will report back in a couple days when I get the new caps...IMG_20240602_211153667_HDR.jpg
 
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mu1sic2ian3

Member (SA)
caution said:
I think you found your dirty connection :lol:
Nice work!
Click to expand...
Believe it or not, that wasn't the problem... The noise persists after changing out the Caps. I think I can hear the noise a little on the left channel now too. Oh well, the search continues...
 
hopey

hopey

Member (SA)
I would suggest it is the Rec Bar. You can get al sorts of weird noises due to bad internal contacts. I would sweat it off the PCB and dissemble clean.
 
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mu1sic2ian3

Member (SA)
Well, the saga continues. I don't think its the record bar. I figured if I bridged the contacts for the record bar switch that should create a direct connection bypassing the switch. I tested every set of closed contacts by bridging the connections directly and there was no change in the sound.

I found another suspect capacitor and replaced it. I was celebrating for a minute or so as the sound dissapeered completly for a good 2 minutes and then came right back again. Oddly enough the rumbling sound seems to be in both channels now.

Very perplexing. I think the only thing I can do is study the board more closely and keep looking for bad components.
 
floyd

floyd

Boomus Fidelis
mu1sic2ian3 said:
Well, the saga continues. I don't think its the record bar. I figured if I bridged the contacts for the record bar switch that should create a direct connection bypassing the switch. I tested every set of closed contacts by bridging the connections directly and there was no change in the sound.

I found another suspect capacitor and replaced it. I was celebrating for a minute or so as the sound dissapeered completly for a good 2 minutes and then came right back again. Oddly enough the rumbling sound seems to be in both channels now.

Very perplexing. I think the only thing I can do is study the board more closely and keep looking for bad components.
Click to expand...
Sometimes when you fix one thing all it does is send the problem further down the chain to the next weakest component.
 
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mu1sic2ian3

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Ok here's something weird. I decided to replace some more capacitors in the tape path. I looked at the service manual and ordered the correct values for 2 matching sets of capacitors. I went to replace the caps today and the values don't match whatsoever. So for example according to the service manual one of the capacitors is supposed to be a 50v 10uf and the ones I pulled off the board are 16v 10uf. The other one is supposed to be a 10v 100uf and the ones I pulled are 6.3v 100uf.

Anybody ever run across this? I haven't put the new caps in yet as I wanted to double check the manual but I'm pretty certain I'm right.
 
floyd

floyd

Boomus Fidelis
mu1sic2ian3 said:
Ok here's something weird. I decided to replace some more capacitors in the tape path. I looked at the service manual and ordered the correct values for 2 matching sets of capacitors. I went to replace the caps today and the values don't match whatsoever. So for example according to the service manual one of the capacitors is supposed to be a 50v 10uf and the ones I pulled off the board are 16v 10uf. The other one is supposed to be a 10v 100uf and the ones I pulled are 6.3v 100uf.

Anybody ever run across this? I haven't put the new caps in yet as I wanted to double check the manual but I'm pretty certain I'm right.
Click to expand...
Those caps might have been replaced before but with the wrong values . could also be why they failed . I would use the ones recommend by the service manual.
 
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mu1sic2ian3

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Well anyway, for anyone interested it turns out it was indeed capacitors. I replaced more caps in the tape head path and I am happy to say I have eliminated the rumble. In the process I somehow blew the power supply board. But I am going to try and replace that with a slightly more modern board and then put her back together.

Thanks for all the help everyone.
 
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Superduper

Superduper

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mu1sic2ian3 said:
Well anyway, for anyone interested it turns out it was indeed capacitors. I replaced more caps in the tape head path and I am happy to say I have eliminated the rumble. In the process I somehow blew the power supply board. But I am going to try and replace that with a slightly more modern board and then put her back together.

Thanks for all the help everyone.
Click to expand...
BTW, power supply boards are usually the easiest part of a boombox to refurbish. It's merely 4 ceramic capacitors, and 4 rectifier diodes. If anything blew, it's usually the diodes. If the transformer blew, you can get replacements for that too. Check either Mouser.com or Digikey.com for the transformer.
 
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