Model 1030 left channel LOUD

[try1256]

I picked this Model 1030 last week. The fellow I got it from said the right channel didn't work. Upon further inspection, I found that the right channel did indeed work. It is just so much lower in volume than the left channel, at center on the balance knob, the right channel is inaudible. I am not sure that the it is the right channel that is the problem though. At idle, the left channel has a loud hum/noise like an amp that is all the way up with no signal. I haven't given it the De-oxit treatment yet but there is not a lot of noise in the pots and switches. Any input on the direction to go in repairing would be appreciated.

Tim

 

[jblmar]

Hum with the volume all the way down indicates a power supply problem.

 

[Lavane]

My 1030 started to hum and recaping the power supply fixed the problem. Next is to recap the rest of it.

 

[Blue Shadow]

I just fixed a 1030 with a nearly inaudible channel. One leg of a cap on the amp board was corroded off the cap. A recap fixed the problem. Check out the thread about better lucky than good here in the Marantz forum for some links. Grab the SM from the AK database and jump in if you are up to it. The hum is as jblmar says maybe the caps there, too.

If you jump into this project, remember to replace the 10 2SC458 transistors that get noisy with age on the preamp board and the phono board.

 

[jblmar]

Defective diodes in the power supply are another culprit.

 

[tonebells]

I pick this 1030 up from Tim. It had some bad caps in the left channel on amp board.

 

[Blue Shadow]

I pick this 1030 up from Tim. It had some bad caps in the left channel on amp board.

We lost where you said it was a bad leg on a cap, exactly as I found in my 1030 which had a low channel volume.

I was guided to try a couple things and neither worked to bring back the channel so the next step recommended was a complete recap which was part of the plan. I unsoldered one leg of a cap and it came away from the board in my hand, leaving its other leg still soldered nicely in place but corroded where it enters the cap itself.

 

[tonebells]

One leg of the 47uf on the left side was gone. The 47uf on the right was 1.5pf. The left was still loud until I replaced all the caps. I am not sure which one caused it to be loud.

 

[tonebells]

I took a second look at the old caps an the legs on C717 22uf were twisted all most backward. I thought the heat shrink was just wrong. Maybe someone knows if C717 being installed backward could make the channel play loud.

 

[tonebells]

I need to learn to look at everything and assume nothing when go through these old units. I thought I was all done with this unit and just needed to adjust, clean it up and put it back together so it sat for a long while. When I tried to adjust I had no luck. After checking everything I had done many times I look at the stuff I did not touch. I found someone had changed H705-708 and swaped the c and b on H705/706. I replace with the correct pinout and all is good.