VU meter in Akai M8

[xtian]

I got an Akai M8 reel-to-reel, and converted the two amps to guitar spec, and they sound quite good, in all their 2.5 watt glory. Remarkably quiet at idle, too, for an SE amp.

I'm trying to get the VU meter working. The schematic shows the VU meter connected to the speaker output, and other end grounded thru a 5K resistor, or, if you follow the switching system, directly to ground. Either case, I'm not seeing the needle budge at all.

I disconnected the VU meter from the circuit, and attached my sine wave generator, which puts out 24v p-p, or 8.2v RMS, and I tried various frequencies. Still cannot get the needle to move at all. I did confirm that the needle is floating and it can move, just not in response to my AC input. I also tried 9vDC, and again, no motion of the needle. I measured 285K resistance between the two terminals of the VU meter.

Any hints?

Here is the schematic: https://analogian.co.za/wp-content/u...1/AKAI_M8_.jpg

The VU meter is just to right of center, near the OT and speaker output jack.

[Enzo]

285k? SOunds like an open meter to me, or a meter with internal circuitry.

[olddawg]

Try momentarily touching a 1.5v battery across the terminals.

[xtian]

Yes, tried applying DC voltage also--no needle movement. What resistance would you expect? Just a few ohms? Strange that the VU meters in both M8 amps burned out, but nothing else was wrong with the amps--even the original filter caps are running nicely!

[Enzo]

Not necessarily "burnt" out. COuld be the unit took a hard drop and the mechanical meters died.

[g1]

Yes, tried applying DC voltage also--no needle movement. What resistance would you expect? Just a few ohms?

Yes, low ohms. One of the old radios I worked on had a meter in series with power supply feed for one of the stages. Bypassed the dead meter with a wire and the radio worked again.