Marantz Model 140 Meter Help

dneu201

Well-Known Member
I just got a really good deal on a stereo system that included a Model 140/3200. Both units work, but one of the meters is damaged. When I cranked the stereo up to peak levels it finally moves. I wanted to see if anyone knows how to fix it or could recommend someone who works on them?

Thanks.
 
Does it seem to be sticking?

If not, there are meter driver boards on the 140 that can be repaired and also adjusted as it states in the service manual.
 
Not sticking, just doesn't seem to be set right. I have to really crank it to get the meter to start moving on the left channel. Should I follow the service manual and try adjusting the the voltage to the meters?
 
Note that you don't need dummy loads while you set the meters as per the service manual. While we think of them as 'watt' meters, they are, in fact, AC voltmeters.

Tom
 
Attempting to adjust the meter is a fine idea.
If it won't adjust, it may be due to old tired electrolytic capacitors on the meter circuit.
The small electrolytic capacitors in audio gear can cause the biggest problems. They are small because they are used in areas where small signals occur and small signals are more "fragile" to the system. So to speak.
Every LED meter I've ever worked on was fixed by replacing the electrolytic capacitors in the meter circuit.

Just tossing that out there.
Your mileage may vary.
 
Attempting to adjust the meter is a fine idea.
If it won't adjust, it may be due to old tired electrolytic capacitors on the meter circuit.
The small electrolytic capacitors in audio gear can cause the biggest problems. They are small because they are used in areas where small signals occur and small signals are more "fragile" to the system. So to speak.
Every LED meter I've ever worked on was fixed by replacing the electrolytic capacitors in the meter circuit.

Just tossing that out there.
Your mileage may vary.

Good idea. I may tackle the recap first to see if that fixes the issue.
 
Quick update. My capacitors came in today and I recapped both meter boards, the power board, and the left power amp. This didn't fix my left meter. I checked the two resistors next to the trimmers on the meter board on both sides and they are definitely reading different. The right meter board resistor voltage jumps around with the input voltage and the left side stays constant. Any suggestion where I could start looking? I have to turn the left gain all the way up to get it to barely move.

Thanks.
 
Have you tried the alignment procedure? You'll need a signal generator or similar app on a smartphone to produce the 1khz test signal. You'll also need a dVM capable of RMS.

While you're in there bring the DC and bias within spec.

This would be my next step.
 
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I was able to fix the meter yesterday. Last night I tried the alignment procedure with my multimeter, which doesn't measure RMS. Before I purchase a new multimeter that measured RMS, I wanted to see if there was a way to measure the same voltage on either side to set the left meter exactly the same as my right meter. Adjusting the trimmer pots at RX03 and RX07 didn't yield any results again, so I thought I would try blowing air and some deoxit at the pivot just in case some dirt could of been causing the needle to stick. Sure enough after barely loosening the screw up front that turns the pivot and spraying a small amount of deoxit, the meter loosened up. Since the meter worked, I adjusted it with the 1khz sine wave to get it to react the same as my right meter. I still need to get them set up correctly at peak volumes.

1.Will any harm be done If the meters aren't set correctly? I probably won't buy a new MM until this weekend.
2. I adjusted the DC offset to <1mv on each channel, but am confused how to adjust the bias. I have adjusted bias on other amplifiers before, but I was instructed a point on the power amp board to measure from to get the desired Bias reading. The service manual mentions using a variac, which I don't have. Can anyone instruct me on a simple way to set the bias?

Thanks again for all the help so far.
 
Can I skip steps 1-4 and just set each side to 10mv from points J701 and J702 by turning R742?

upload_2017-4-24_14-10-1.png
 
Just set bias on both sides to 10 mv. The left channel was at 2.8 while the right was spot on already.

Now I just have the meters to set and will be going to get a new meter this week that measures rms. Could someone explain step 4 for setting the meter? I don't under stand what it means by the meter "hitting the full scale stopper."

Would any damage be done if these aren't set correctly and I use the amp? I wouldn't mind hooking this thing up and testing it out with the 3200 now both fully recapped.
 
Just finished setting the meters today and reset bias with a new voltage meter. This setup is ready to rock.

Hard to believe I only paid $75 for these WITH a Dual 1226, and Cerwin Vega's. I sold the speakers for $60 and refurbished the turntable without spending anything.

Working on buying a set of Advents now to pair up with these.
 

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Did you ever figure out what "hitting the full scale stopper." meant? Is that +3 on the meter? I tried meter alignment and they are not as active as prior.
 
The 'full scale stopper' is the mechanical limit that stops the needle from moving further at the upper end. It is above the +3dB mark.

Tom
 
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