Re: Tektronix 2235 grief

BFoelsch <BFoelsch@xxxxxxxxxxxxxxxxxxxxxx> wrote in
news:ju3sf29bov9mhpcuqm7d8uc5l315jhu5d4@xxxxxxx:

Was given a Tek 2235, option 2 (what's that?) in decent shape, with
one problem.

On both vertical channels, there is massive overshoot on rising edges
on the .1 v/cm ranges and higher. The lower voltage ranges are fine.

Poking around inside, I found a little assembly, P/N 307-1013-00 that
is labelled 10X and 100X . Apparently this assembly contains some
compensating capacitors for the attenuator.

In any event, touching this assembly, exerting the slightest force in
any direction clears up the problem, which quickly returns as soon as
I remove the pressure. I don't think the problem is the switch
contacts, as pressing down and wiggling the switch cam doesn't do
much.

Does this sound familiar? and what is the recommended fix. I hate to
start taking stuff apart "looking for trouble" so I figured I'd ask
here first. Or, if you have a manual/schematic of the input section
I'd appreciate that too.

Thanks to all in advance.


Perhaps a bad solder joint at the pin/substrate interface?
Or a fractured SMD cap.
I believe regular solder will not work here,but don't have any
alternatives,either.Possibly some low-temp stuff like Chip-Quik may work
without destroying the metallization on the substrate.

The other alternative is to find a replacement thickfilm.
Sphere in Canada may have new parts for this,or cannabalize from a parts
scope.

(I always wondered if one could make a small PCB using SMD resistors and
caps instead of the ceramic thickfilm,to replace one of these.)

--
Jim Yanik
jyanik
at
kua.net
.