Need some help getting VU's to work (Clairtone 7980)

[Broncos319]

Hi everyone. I just refurbished my 7980. One week ago prior to working on this box more thoroughly, the upper left VUs worked when I played Tape 1 (lower deck). Now that I have reassembled the unit everything works fine except the VU's don't get a signal from Tape 1 anymore. They DO get a signal from the radio (tuning and battery) but do NOT get a signal from Auxillary.

I've checked the connector from the VU's to the PCB and it's good.
I've checked and cleaned the function selector dial (Tape 1, Tape 2, Aux, Radio) and it didn't help.

Can anyone tell me if I'm missing something? What are the other connectors that are sending a signal related to those VU's from Tape 1 or Aux? I guess what I'm asking is what are all the connectors that relate to VU's in a 7980? Thanks SO much

 

[caution]

If you set record mode to manual and record the radio, can you change the intensity of the VU's with the rec level knob?

 

[Broncos319]

If you set record mode to manual and record the radio, can you change the intensity of the VU's with the rec level knob?

Hi - no that doesn't change anything.

 

[caution]

So when you're on the radio, you can see the tuning strength and battery power, but as soon as you press record, the needles fall to zero?

 

[Broncos319]

So when you're on the radio, you can see the tuning strength and battery power, but as soon as you press record, the needles fall to zero?

No it has nothing to do with record. The tuning strength and battery power work (radio). But the VU's don't.

 

[caution]

If you're on the radio and you hit record, the needles change from battery/signal to L/R VU's. Let me know what you see.

 

[Broncos319]

If you're on the radio and you hit record, the needles change from battery/signal to L/R VU's. Let me know what you see.

No that's not the problem. Question: there are some little "posts" on the PCBs that are labelled TP003, TP306, etc. Could it be one of these connections? What do those posts do?

 

[floyd]

Hopefully you labeled all those connections because the plugs will plug into multiple connections. Not sure about the vu meters but some share common connection plugs that's why each connector has to be labeled

 

[caution]

No, those are test points, they mean nothing.
If you don't want to mess with labeling connectors, I developed a wiring diagram here. The Conion schematic is here.

The reason I asked about seeing L/R audio on the needles while recording the radio is that it would tell us whether or not there's any audio getting to the needles at all. If they just sit there doing nothing, like you see on AUX, then that helps diagnose the issue.

The needles plug into one side of the preamp board and travel all the way across to the function switch. The audio feeding into the function switch comes from the play/record switch on the lower deck board. That switch could be the culprit. I know it was incredibly dirty on one I fixed and had to come off the board and disassembled for a deep clean. The long plastic cap over the contacts doesn't easily allow cleaner inside it. The audio also passes through the record mode switch on the mixing board, so you might want to give that one some cleaner.