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CR-2020 No Meters

Nuklhed

Nuklhed

Active Member
Hello friends. I have a 2020 on the bench. Sounds wonderful, but none of the meters work. Here is what I have discovered so far.
Touching the tuning knob…the right channel meter pegs high
Placing the SP-OUT/SIGNAL Q button in SIGNAL Q….the right channel meter pegs high
Neither the left channel meter nor tuning meter respond to anything
No response during the meter calibration procedure
It looks to me like the meters still get signals via the tuner board even when using AUX input, so I started checking voltages to tuner board. +25, -25 and +12 all good.
I’m not sure what kind of signal is supposed to be on the SM pin, so I measured for both AC and DC. Nothing.
This tuner stuff is new to me, so for grins I measured the frequency on the 19khz pin…right on.
I’m really not sure where to go from here. Thanks in advance for any guidance.
 
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Did you remove any wiring to the little circuit board that the SP-OUT/SIGNAL Q button is soldered to? Does the protect relay "click"? Did you do any work on the power supply section? Replace caps?

SP-OUT/SIGNAL Q switch could be dirty.
 
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Hello friends! Thank you for the replies. This unit was a mess when I started. The relay and ecap boards are all new. The tuner and small boards underneath all recapped. Thorough inspection of all backplanes found no heat or mechanical damage. After all that, no left channel unless the low filter switch was down. Removed, disassembled and cleaned/polished. Left channel back and great.
So 2 problems remain that I’m aware of.

None of the meters work. I have had issues with the level meters before, but never all 3. I see nothing coming to the meters on the scope.

The other issue is that the tuner is unresponsive. Constant static all along the dial.

I thought about the SP OUT/SIGNAL Q switch and board, but I don’t see that they affect the tuning meter?
Yes, the protection relay clicks in every time I power up. Unit sounds wonderful with music input through AUX.
No, I did not touch the SP OUT/SIGNAL Q button (except detox and cycle 50 times), nor it’s associated PCB as there were no caps on it.
Thank you so much friends!
 
I agree. Looking at the Meter board on the schematic, it seems that there is power in, level meters out, and then SM and T are the actual signal inputs generated in the tuner section. I looked for AC and DC on the SM pin and got zero…

Isn’t that where I should see an AC signal when I’m doing the meter cal procedure?
 
TR717 and 718 on Power Supply C board 1 . <------ you refer to it as the relay board.
Nuklhed said:
The relay and ecap boards are all new.
Click to expand...
Likely and issue with the new boards. By new do you mean a new after market board or just a different board from a parts unit?
 
Nuklhed said:
Isn’t that where I should see an AC signal when I’m doing the meter cal procedure?
Click to expand...
Your test points appears to be the speaker output binding post for the meter cal. A 1khz audio signal @ 50 watt output into an 8Ω dummy load.
 
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So while I was considering my next move, I decided to go ahead and remove the meter board and thoroughly clean the switch on the board. I must admit I’m about 2 for 50 at successfully disassembling and reassembling 50 year old switches. I’m now 2 for 51…

Another switch on the way.

To answer your question, the relay and ecap board were both filthy and burned with pads and traces missing from previous repair attempts. So I used brand new jay free boards. This is the third 2020 I am using the boards. The first two work very well.

I’m just puzzled by how the meters are driven. DC modulated by the AC? Not my strong area.

I am comfortable with the meter cal procedure thanks to one of your old posts. I connect my 8 ohm resistors to the speaker terminals along with my multimeter. I then input a 1khz signal into AUX and raise volume to get about 20vac, looking for 50 on the meters.

Once I get the new switch installed I will take some readings at TR 717 and TR 718 and post results.

Thank you so much for the help!
 
Feed it a sine signal and measure the voltage going to the meters.
You should see a DC voltage (mV) on the meter pins which follow the volume control.
 
Thank you for the reply Magnus! I will do that today.
BTW, what is the range of these meters? 0 to ? mV DC.
 
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