MARANTZ 19 (channel issue)

[copezone]

Ok, so a guy brought a 19 into my shop with the left channel out. Two prior service attempts by others (new caps, yadda, yadda,) and still, no left channel, EXCEPT during "power down". While powering down the left channel kicks in. ANY IDEAS???

 

[tranguru]

my guess is that the channel is dead
why does it come on when you turn it off..
unlike other marantz units, in the 19 the relay is closed so the protection opens the circuit when there is a problem.
so I assume that here the protection opens the circuit (as the circuit gets the power) because there is an issue with the channel.
when you turn the unit off the protection stops working faster than the amp ==> closes the circuit ==> sounds comes.


try measuring the voltages at output when you turn it off


let me know how you progress

 

[clinic-audio]

Bad relay contacts may possible too

 

[tranguru]

Bad relay contacts may possible too

Not sure if audio passes thru at switch off

 

[onemug]

let me know how you progress

On the 19, is there an adjustment inside to shrink the size of the scope display?

 

[rBuckner]

Sometimes an overly large scope display is due to a low high voltage supply. Has your 19 been recapped?

 

[onemug]

Has your 19 been recapped?

Thanks for the suggestion. The 19 has been recapped.

 

[tranguru]

I recapped my HV supply caps
Made a big difference.

I also replaced the Zener diodes and caps of the LV parts

 

[RustyJames]

I have replaced the FET's on the scope board and restored the operation of a very nice, bright scope! I'd like to know if there is any way to adjust the signal levels being delivered to the scope. The display is overly large, but clear, focused and bright. rBuckner suggested that the high voltage supply may be too low. I'm reading -500 and +200 as indicated on the schematic. Any other suggestions? All other voltages seem to be correct and things are sounding really good otherwise.
Thanks to any and all!

 

[tonebells]

What is the source?

Tony

 

[RustyJames]

It seems about the same regardless of the source. I've been comparing FM and AUX using a CD as the source.

 

[tonebells]

You could try the Horiz. Gain adjustment. Full instructions on page 43 in the service manual.

Tony

 

[RustyJames]

I'll look into that, but I'm pretty sure that's only an FM 'thing'. I appreciate the suggestion though. Thanks!