I bought a used M-50 in Europe (Dual Voltage) and I've had right channel issues from the beginning. A little tap on the top would bring the channel back. The tap became a slap and now the channel is out for good. I'm not a tech and don't know how to check resisters etc. I see nothing damaged, loose or burnt. It happens on both A and B. I wiggled wires and tapped components as this is the extent of my expertise. I've learned here that there is also a capacitor that should be changed? I assume one has nothing to do with the other. How would I go about testing this? I can use a multimeter and solder.
M-50 Lost Right Channel
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Sparkplug
Super Member
Welcome aboard.
Sounds like you have corrosion issues which include but are not limited to, cold solder joints, dirty switches, dirty relays, etc.. It‘s normal for an amp of this age, however, since you mentioned you were not familiar with electronics, I strongly suggest you let an experienced technician in your area look at it lest you might introduce damages that aren’t there now.
In its present state, I think the issues can be easily solved through reflowing solder joints, cleaning selectors, and replacing a few common components.
Sounds like you have corrosion issues which include but are not limited to, cold solder joints, dirty switches, dirty relays, etc.. It‘s normal for an amp of this age, however, since you mentioned you were not familiar with electronics, I strongly suggest you let an experienced technician in your area look at it lest you might introduce damages that aren’t there now.
In its present state, I think the issues can be easily solved through reflowing solder joints, cleaning selectors, and replacing a few common components.
I have reflowed Laptop Motherboards and cleaning doesn't sound difficult. Replacing components might be the difficult part but I have recapped PC Monitors. I just think that if I'm spending money I would rather buy a newer amp with all the modern bells and whistles and use this as a mono amp for my shortwave/scanner system. I'm not out much if I fail; right?
Which relay?
Try wiggling the amplifier input RCA connection for the right channel. Could be a bad solder connection or broken input RCA jack. It might even be a broken interconnect cable from the pre-amp.
Flip one end your main input cable around Left to right and right to left. See if the problem changes channel.
Flip one end your main input cable around Left to right and right to left. See if the problem changes channel.
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Seeing's how the M-50 has separate switches , input attenuators and relays for A & B. It is unlikely these are the issue. If it exhibits the same issue on both A & B.
It has to be something common to both A & B..
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Yes. C607 .47µf/250vac needs to be replaced with and X2 safety rated snubber cap . If you have the clear greenish yellow RIFA cap installed.
Like this one.. ( the burnt one )
If it is not a RIFA cap then it may have already been replaced.
If in doubt -- post a photo..
Replace with something similar to this
Its located on one of the left rear boards that connects directly to the power input cord.
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Sparkplug
Super Member
Then you should be able to handle light repairs if need be which I’d good.
LOL … use an m-50 for short wave scanner? I’d do that with the new ones with all the bells and whistles, but that’s just me. I strongly believe there’s a connectivity issue here due to corrosion of some sorts .
Check your RCA connectors and their solder joints on the board as was stated above. They are all in a row behind the relays by the back panel. You may have to remove the back panel to have good access for a reflow job.
If you have the patience, reflow every solder joint you see, only good can from that. Also, please post a hi-res photo(s) of the solder side of the amp.
Sparkplug
Super Member
This must be it. The link you gave me is $7 with shipping but my amp was bought in Germany and is dual voltage 110-220V. Is this still the correct part?
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No.... Correct part just wrong value.
.22µf instead of .47µf
This would be the correct value..
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