Marantz 1060 - DC Volts at Speaker Terminals

[markallen]

Got a beautiful perfect-condition 1060, an early model with the engraved faceplate AND original box! Seller didn't know working condition. Upon getting it home, as a precaution I decided to check the voltages at the speaker terminals. 30 volts DC (give or take) on both channels! Not good. I'm thinking the main output transistors are toast. Ouch. One more test to confirm . . .

I plugged it in the dim bulb tester (100w) expecting the bulb to light up - which it did, but only momentarily, then it went dark, just like in a working amp. Hmm, not making as much sense now.

Examining the amp board, everything looks good - no obvious evidence of heat anywhere, and in general this thing is super clean.

So, now I'm wondering where exactly I should start to trouble shoot this thing. Anybody else been there?

 

[tonebells]

It's cap coupled. There will be voltage until speakers are hooked up. Test with something you don't care about just to make sure.

 

[tonebells]

I love 1030 & 1060s

 

[markallen]

Its cap coupled. There will be voltage until speakers are hooked up. Test with something you don't care about just to make sure.

Thanks for the prompt response. I had actually wondered if this could be the case - but consider this:

I already have a 1060 (a later version, much higher serial number) so I tested the outputs at the speaker terminals on that unit for comparison. It started out about 15v, but as I watched the DMM, the volts slowly dropped off to millivolts.

The volts definitely don't drop off (much) on the early model, staying above 26v or so. In addition, other amps/receivers I've seen that are cap-coupled don't typically show 30 volts without speakers.

What am I missing here?

 

[tonebells]

Do you have a dummy load?

 

[restorer-john]

The early 1060s had no capacitor bleeder (to bring the cap up to 1/2 rail voltage) resistors, the later models did. It was done to minimise the almighty 'crack' you'd get pressing speakers main or remote after turning the amp on. Yours is fine, if you want the improvement, look at the two resistors tied onto the tag strip under the speaker coupling caps (on your later model) and make the modification to your early model.

Some people just stick a sacrificial pair of headphones into the jack to absorb the thump.

 

[markallen]

The early 1060s had no capacitor bleeder (to bring the cap up to 1/2 rail voltage) resistors, the later models did. It was done to minimise the almighty 'crack' you'd get pressing speakers main or remote after turning the amp on. Yours is fine, if you want the improvement, look at the two resistors tied onto the tag strip under the speaker coupling caps (on your later model) and make the modification to your early model. Some people just stick a sacrificial pair of headphones into the jack to absorb the thump.

Hey, thanks. Wouldn't have expected such a modification. Good to know!

 

[tranguru]

The amp has 2 big output caps. center line on amp board is at 30 V if I remember correctly.
connect speaker and see what happens

 

[catrafter]

Mark,
Plug something, (a set of 'phones' or even a 1/4 inch to 3.5mm stereo adapter) into the headphone jack. This will put an attenuator on the amp outputs and the voltage should go away.
This also helps to 'tame' the turn on and turn off pops, works on the 2230 as well.

Tom