Fisher Allegro

[hermitcrab]

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 ....

[TC Chris]

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

[electra225]

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......

[hermitcrab]

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....

[electra225]

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.

[hermitcrab]

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....

[electra225]

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

[hermitcrab]

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

[hermitcrab]

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

[maxidyne]

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

[walyfd]

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.