1176LN meter warmup?

[jwhmca]

I'm working on an original 1176LN (H)

When I first power it on, the meter starts off about 2-4 db low, then slowly climbs up as the unit warms up.

Is that normal for these... or do I have something failing?

 

[Brian Roth]

Most 1176 units I've seen have a warm-up period for the "GR 0" mode, but I don't recall any being 2-4 dB low when cold.  1 dB low when cold would be more typical, IIRC.

Bri

 

[jwhmca]

When I press on R81 it jumps (and then stays) all over the place...

Is R81 for sure the Q-bias control? It doens't effect the output at all when I move it around... only the meter

 

[Brian Roth]

I looked at the "H" schematic from the JBLPro website and it shows R81 as Q-bias.  Dunno what may be happening with your unit.  Bad pot would explain jumpiness, but adjusting Q-bias should affect audio levels, since it varies the gate voltage on the control FET.

Bri