Jim,
At one time, we would remove the attenuator and send it to the factory
in Beaverton, if we couldn't clean them and fix the problem. One of
the best scopes ever made...
Jim Yanik wrote:
wrote in
oups.com:

Hi all,

I got hold of this cheap ($100) Tek 485 that is working fine except for
three things: The variable volts/div pot on channel B doesn't pop up
smoothly, and when it does it doesn't turn at all; the lights on the
100M/50R selection on channel B don't work (the switch works though),
and the variable timing pot doesn't turn.

Never having done anything on a 485 I opened up the case, turned it
upside down, and I can see the two aluminum "boxes" for the channel
attenuators. I removed the knobs from the B channel and a few screws,
and I can "pop" the attenuator back, but not enough for me to actually
pull it up and get to it -- it meets the power supply board too soon
(there's also a little aluminum "T" connecting the A and B boxes).

Is there any way for me to get to the attenuator circuitry without more
serious dismantling? I downloaded a copy of the service manual but it
didn't help much.

Best,

- Cesar


You pull out the entire atten. module,not just the top PCB.

After removing the atten knob,there's a nut on a bushing that must be
removed. Then there's a screw on the rear side to be removed,and a hex-
nut/spacer in between the two atten assemblies,on that "T" bracket. Then
you have to pull the Peltola cables out from their jacks,then the harmonica
connector.Then the atten module tilts out.

The serivce manual has the procedure in it.Maybe your 'copy' omitted it.


--
Jim Yanik
jyanik
at
kua.net