Allied 435 weak right channel

[rmunson]

Hey guys -
I have a nice old Allied 435 - it's working fine except the right channel is weaker than the left. On headphones the left/right sound fine -- but on speakers - main and remote, the sound is weak on the right channel

I have the original operating manual and schematic for the receiver.

would recapping the power board and amplifier board be a good place to start for addressing this issue? Or is it more likely to be something else?

Any advise would be greatly appreciated --
Reed

 

[avionic]

I would get the right channel straightned out first before recapping. But thats just me.Have youtried cleaning the switches and controls with a healthy dose of deox-it yet?

 

[avionic]

Not familiar with this unit.If it is a tube unit you my also have a weak tube in the right channel final amplifier or loose tube socket..

 

[rmunson]

yes - it has been de-oxit'ized -- all pots are quiet --

The volume pot is a split volume knob -- front half for main speakers, back half for remote speakers --

this is a all solid state little receiver --

Thanks!
Reed

 

[avionic]

I may be able to shed some more light if I had a schematic to view. Does this unit have a protect relay,dirty contacts on the relay could be a cause for low volume. I'm not sure where they tap off for the headphones.

 

[rmunson]

I'll post the schem - looking at the o/m some more: "This is a dual control; the front section adjusts the left channel, and the rear section adjusts the right channel. When the sound volume of the left and right channels, speakers needs to be balanced, or when the volume of only one speaker needs to be raised, this dual control function may be used. In this case, adjust either section of the control while holding the other section."

I'll try working on the volume control some more -- it is not moving freely as a split, dual control, but is stuck together in one place and only turns as one unit.

 

[rmunson]

a scan of the OM

 

[avionic]

I'd say you have and issue with the headphone jack contacts or switch S7.Speaker connection or a problem with a speaker itself.Swap the speakers around. Speaker wires?

 

[rmunson]

ok - some further troubleshooting

scratchy right channel on both main and remote speakers --

I tried switching/flipping speaker connectors on both pairs of speaker connectors and with each combination the speaker connected to the right channel consistantly was scratchy --

I was able to deoxit and clean up the split volume knob -- back half controls volume for left channel, front half controls volume for right channel -- I was able to increase/decrease scratchy right channel with the split volume control --

Looking at two large capacitors directly under the power supply pcb I notice one cap noticably browner --- it measures 14.5 V -- the other less browned cap measures 15 V

Should I start with replacing these two capacitors?

 

[avionic]

On headphones the left/right sound fine -- but on speakers - main and remote, the sound is weak on the right channel

And you say it sounds OK with headphones ? Or is the right channel mess up with the headphones as well..

 

[rmunson]

yes -- listening through headphones, both left and right channel sound fine

Thanks for any insight on this puzzler --

 

[avionic]

Look on the last page of your 5-8 pdf. Note where the headphones tap off of the final output.The headphone jack has 6 contacts.4 of which are being used.You have eliminated the final amplifiers (with the headphones) and the speakers.(by swapping them around)So the problem is somewhere in between.That leaves wiring,the headphone jack, S7 speaker select switch,binding posts or poor solder connection(s).