Newbie needs help on Marantz Amp

blitzgritz

Natural Sounds
G'day everyone,

I'm new to all this great vintage audio stuff. I have found a new passion !!

Anyway....I purchased a Marantz 1060 on Ebay and it has just arrived.
I haven't connected any speakers to the amp yet....thought I better do a DC offset reading first.

The reading I'm getting is ....12 volts left channel and zero volts right channel
[Multimeter set to VDC] # note right channel get no reading even when multimeter is set to ma setting too

What does all this mean ?.....thought I'd better ask before I connect my good Luxman speakers into this puppy

Please help

Cheers from down under
 
Welcome to AK! This amp has quasi-complementary outputs, running from an 80V supply to ground. As such, the output must sit at 1/2 of the supply voltage and it swings from 40V up to 80V and down to ground. When there is no signal it sits at 40V. You can't put 40V across your speakers so there is a large capacitor in series with the output to block the DC voltage. With no load connected at the output it is possible for the capacitor to retain some charge, and you will measure a voltage there. If you connect your speaker the voltage will be discharged. It is possible for the capacitor to be leaky, in which case you would get 12V on your speaker; not good. My advice is to connect a set of expendable speakers and measure the voltage. If it drops to 0V, go ahead and connect your Luxman speakers. There is no DC offset adjsutment on this amp, however there is an adjustment for the 40V "center voltage"
Perform these adjustments with the speakers disconnected!
Insulate the meter probe with electrical tape so only the tip is exposed, to avoid shorting something out if you slip!
There are 4 adjustment pots on the poweramp board. The 2 inner ones adjust the center voltage. Measure the voltage on the metal case of the output transistors The 2 inner ones should read 1/2 the voltage of the outer ones. If not, adjust the 2 inner pots so that the voltage on the inner transistor cases is exactly 1/2 of the voltage on the outer ones.
The outer 2 pots adjust the idle current.
On the opposite edge of the pc board from the pots are 4 large resistors The idle current is measured across each of the outer 2 transistors. Pick one of these resistors, clip on toeach end of it with a mini-hook type meter probe. If you don't have one go buy one right now, don't use an alligator clip or you'll be sorry! Adjust the outer pot for each channel for 7.5mV across the respective resistor. Monitor for 20 minutes and touch up as necessary. Recheck the center voltage and adjust as necessary. When it remains unchanged for 5 minutes, you're done.
 
Thank you so much for that prompt reply.

I attached 2 crappy speakers as per your suggestion....left channel is dead....and right channel was bearly audible even with volume way up. [amp set to tuner]

Right channel still reading 12 volts

Also checked voltage to the big massive caps [ elna ceg1w 55v 3000 uf ] and one has no voltage present but both caps ohms increased slowly.

Please help me diagnose

Cheers
Blitz
 
It has no speaker relay. Assume for the moment that the right channel output cap is shorted and needs to be replaced. The other should be replaced also, because it will probably fail soon also.
With the speakers disconnected, check the voltages on the metal cases of the output transistors and report them here, like this:
With the front panel facing me, from left to right, the voltages are: aaV bbV ccV ddV.
 
Sorry for my delay inresponding to your question.

I have taken the amp to a friend who has better equipment to diagnose.

This is where we are at ...

I cant give you the voltage reading of the output transistors because we can't power up long enough to get a reading before blowing other transisters etc.

We have replaced transistors that were found to be bad by comparing to the other side of the power board [ remote ]

My question is how critical are the values across the 4 output transistors to each other.

This amp looks as though it has been worked on before and 2 of the output transistors have a different value on one side.....should I replace all 4 with the same gain or is this not that critical ?
 
The 2 output transistors should be the same, but don't have to be the same as on the other channel. The improtant ratings are Max Voltage (VCBO and VCEO), Max Current Ic, and power dissipation Pw. These must meet or exceed the original transistor specs.
 
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