Classic Hifi Care

I was playing it the other day and after about an hour I noticed the left channel was gone... dead... the right continued to play along just fine...so I shut it off and figured here is another one that needs work... a week later I turned it back on and both channels play loud and proud.... so what could it be?... the original speaker set up just used a cap and an inductor in line with the speakers... I used a 2 way crossover and now wonder if it is too much for the amp to push the sound through .... I had to use 4 ohm speakers... as 8 ohm would need the speakers with the magnets in front , which are impossible to find... so I figured the crossover would isolate the amp somewhat from the lower impedance of the speakers the worst part about fixing this is , if it is in the amp , it will take longer to disassemble the set than it would take to repair it ....

If your speakers are two-ways (bass & treble) then the problem is before the speaker. Impedance matching isn't a critical issue. Likely you've got some other problem. Do the usual checks of voltages when the problem arises, or even before to see if there's a failed or drifted component that's causing problems. Could be something as simple as cruddy tube pins or sockets. Always check the easiest things first. Wiggle the tubes.

Chris Campbell

Is it tube or solid state? If tube, I agree with Chris. Dirty connections are top suspects. If SS, connections can still be suspects, particularly push-type controls, such as filters and tone controls. It is something simple, since it "fixed" itself, but the simple things can prove the most elusive in troubleshooting......

Unfortunately the allegro 192 was the last of the allegro line and it is solid state ... the 190 was the tube model which I have seen going for about 700 bucks !... mainly because they are rare as hens teeth....

My Pioneer SX-1050 lost its left channel about five years ago. It made a squealing sound, then the left channel quit. I replaced it with another receiver and figured that was that. I would need to get deeper into it. I put it on the bench here awhile back and found it plays just fine. I have tentatively narrowed the suspects down to a bum graphic equalizer I was using to process my music. You may be experiencing something similar. What mode was it in when it played last, then what mode was it in when it lost a channel. Did you change anything before it came back to life? One would think that a bum connection would be logical, since electronics don't just "fix" themselves if there is an actual failure of some kind. Good luck, and let us know what you find.

it was playing an album, so naturally I checked the cart, then the rca input jacks , checked the radio function and the same thing , I even flipped the right speaker over to the left but still nothing.. so I just shut it off and it has sat for a good week and a half untouched . then yesterday I just opened it and turned it on and both channels were working ... I am thinking maybe a bias resistor in the output is going thermal and killing the channel ?...or worst case is an output transistor going thermal....

I haven't had enough experience troubleshooting transistors to speak to that possibility. Does it use germanium transistors?

Yes... that is all they had on early solid state sets. I have a few in my stock to use for replacements ...I thought about changing over to silicon , but some audiofools claim germanium has more warmer sound like a tube than silicon?... who knows... I don't have dog hearing to hear a difference I will play it but only on the left channel to see if it acts up again , if like before it was less than a hour of playing before the channel went dead

Well a little update ... she played just fine ... until I cranked the Bass... then the left channel distorted and went out ... right continued to play fine... now I will shut it down for a few hours and see if it resets itself

Can you determine whether it is dead ahead of the volume control or behind it? That might help narrow it down a bit......

Deox the "deleted" out of the pots. Whenever I run the 500B, I work the volume control back and forth while it warms up...

Quite possibly a resistor is opening when hot.