Need some help with a 1050 problem

Jefferylu98

Active Member
hello all, I accuired a new 1050 recently. I was horribly filthy outside. Looked like it was in a smokers basement or something. I got it all cleaned up, an it looks great. I deoxed all switches and pots and took all push buttons completely apart and cleaned them too ( that sucked). I have an issue with the right channel not having very much out put at all, unless I turn balance to right and crank the volume. Then I get a distorted but am able the hear the music. I started by checking the power on the power supply board and they seem to all be within 10% of the schematics. I checked the dc balance on both channels and was able to regulate to 0v, went to set the idle current, left is at 50mv and the right is -2.5mv and will not adjust at all? That is all the testing I was able to do today, just wondering which direction to go now. I will print off a service manual at work tomorrow.
 
First off, see the jumpers at the back that should be connected? (pre out, power in). Disconnect those and use a simple music source like an ipod to run a (very low level!) music signal straight to the power amp stage.

The bias issue you describe sounds like the problem is only in the power amp stage, but lets confirm this as it will eliminate the pre-stage as also being a possible problem.
 
I would at the very least suggest you perform a power supply refresh on the unit to ensure you've got reliable clean power going throughout the unit. From that point I would then start looking at what slimecity has suggested and start looking at the power amp stage for the right channel. I just did a complete recap and transistor replacement on the 1050 and isn't really hard at all and it works fantastic. I suggest in the interest of reliability that you do the same if you can.
 
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I own one of those and I can tell you those 30hz and high filter push in buttons have been my biggest trouble.

Whenever I have trouble I play with those 2 buttons and it clears right up.

Not sure why but it works for me.
 
I would perform a visual check of the bottom trace side of the amp board looking for any signs of overheating at the solder connections. This receiver is not known for heating to the point of melting solder but it could of had a previous repair where some integrity was lost. Even a cold solder joint?
Then if nothing is found visually (On both sides or the amp board), I would check all emitter resistors and then the transistors in the driver stage looking for some clues.
Probability wise, there's a broken connection somewhere.
 
+1 on the filter switches. This is a well known issue. The next time I open mine up, they will be jumpered.
 
If you disassembled the pushbutton switches, and got them back together without damage and drama, ... I want to shake your hand.

Check the speaker B output, it might still be your speaker switch. Can also be the very common failure of the speaker protection relay.

As slimecity has noted, you need to isolate the problem to either amp or preamp. If you use a pair of RCA cables to cross over the pre-out/main-in, see if the problem stays with the same channel (amplifier, speaker switch, or protection relay problem) or switches channels (preamp or switch problem).
 
Thanks for all your replays, I pulled the jumpers and connected a m-80 Yamaha amp, walaaaaa both channels work. So assume the problem is in the right channel amp board? I'll start going thru the schematics and see what's up. I should be able to compare voltages with left channel I believe? BTW saturationPT. I did in fact take every one of the push buttons apart completely and clean with toothbrush and detox, it was horrible (especially the triple tab copper sliders) lol I did the same on a previous stereo and I actually can do it relatively efficient now, but still a dreaded task. I will update after some meter testing. Ok, gonna tape my tester probs now, and off I go.. thanks again for all the input
 
Stands to reason with no Bias/Idle adjustment available.
Looking for voltages will only waste time and can cause extra trouble. Unless your an amp designer and understand the circuits will you be able to find the culprit.
The amp components work in a symbiotic way, any one of which can cause the issue.
Use the visual check approach first. Mainly but not limited to an issue in the driver circuit.
See post five for more detail.
So far you have done a good job narrowing down the location. And yes, cleaning/lubing the switches by taking them apart is the ultimate way to go. It makes a difference and brings the set to the top level of performance.
 
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I did these reading prior to getting the last feedback. I will shut her down and take a hard look at the amp board n both sides. Thanks zubulon1 for your helpIMG_0142.JPG
 
IMG_0144.JPG IMG_0143.JPG Re flowed about 6 solder joints on the right channel and 1'on the left channel. She is singing on both channels now, and sound great. Thanks for all your help, again. I'll finish cleaning and re assemble this one and put her on the shelf with the others. I have a 850 with some issues to look at next. Love this stuff. I'll attach a picture of my collection so far, not many missing.
 
Wow!
Nice work!
Nice collection!
Looks like you have some chops for this.
Never mind! Your just as Kooky as the rest of us!
 
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