2250B problem

[quartersaw]

Greetings,
I agreed to take a look at a friend's 2250B, which has an intermittent left channel. There are a few problems with that channel, as the 'Loudness' button does not work, (the right channel loudness does work) and the left channel also sounds like the Treble control is all the way to the left.
When I tweak the volume control, the left channel crackles back to life. I changed the 250K pot with a 250k Alps pot, to no avail. Internals appear to be all original, so some servicing is in order, anyway.
I tapped on the relay during one of the outages, and nothing changed. Visually, the relay looks fine. Pushing the loudness button repeatedly also brings back output to both channels. It seems like a mechanical issue, but the muffled output of the left channel tells me otherwise.
I was wondering if anyone has any suggestions about what might be ailing this receiver?

 

[petehall347]

corroded contacts . try the deoxit treatment

 

[quartersaw]

corroded contacts . try the deoxit treatment

Should've mentioned, that I DeOx'd the unit. (But not the relay) No change.

 

[petehall347]

do the relay or replace it ..its classic signs of bad contacts in the relay

 

[bryans12v]

I would do another round of any switch that brings a channel back to life. Are you cleaning the switches from the very small opening of the bottom of the switch body? Flood it till you see it coming out of the back corners. Do this while it's on its side and have a shop tag underneath to catch the runoff.


Check the tone control board for cracked traces. Someone's these boards are very close to the bottom panel screws.

Was the tone board removed to clean the tone pots? Look for wires busted off of the posts.

 

[quartersaw]

I would do another round of any switch that brings a channel back to life. Are you cleaning the switches from the very small opening of the bottom of the switch body? Flood it till you see it coming out of the back corners. Do this while it's on its side and have a shop tag underneath to catch the runoff.


Check the tone control board for cracked traces. Someone's these boards are very close to the bottom panel screws.

Was the tone board removed to clean the tone pors? Look for wires busted off of the posts.

I did not remove the tone board, but it looks like that will be next.
I pulled the left amp, and replaced a couple of caps that 'looked' faded. (The orange caps) It was just a shot in the dark, since I don't have a Scope. No difference.
I'll report back with my findings on the tone board.
I appreciate the suggestions, as I am a bit out of my comfort zone.

 

[Mike Sweeney]

I hate to suggest this as it will be the cause of much drinking and blood pressure The best way to fix the switches is to take them apart, clean them and then use the DeOxit grease. I've a couple of speaker switches and a loudness switch magically be fixed after such an effort and it is an effort. The resistance on the two speaker switches went down by .5 ohms. No crackles.. no mess. You can always hook some clips on the switches and verify they are actually working before all of this. My own 2285B relay was bad.. it worked for about 4 times when I got it and then died. The relay actually cracked at the base. Also, something else I had an issue with on the 2285B were some bad caps on the tone board. They were new but cheap imported crap as it turns out. They gave low volume and like the treble was all the way up. Just some thoughts

 

[quartersaw]

I hate to suggest this as it will be the cause of much drinking and blood pressure The best way to fix the switches is to take them apart, clean them and then use the DeOxit grease. I've a couple of speaker switches and a loudness switch magically be fixed after such an effort and it is an effort. The resistance on the two speaker switches went down by .5 ohms. No crackles.. no mess. You can always hook some clips on the switches and verify they are actually working before all of this. My own 2285B relay was bad.. it worked for about 4 times when I got it and then died. The relay actually cracked at the base. Also, something else I had an issue with on the 2285B were some bad caps on the tone board. They were new but cheap imported crap as it turns out. They gave low volume and like the treble was all the way up. Just some thoughts

.......Appreciate the thoughts, and what you are saying is more food for thought!