Tek 465M vert problem
 

I have a 465M w/ a problem. When you wiggle the Ch1 V/Div knob, the
display shrinks about .4 div from the correct calibrated position. I
thought dirty contacts, I pulled the assembly completely apart and
cleaned all contacts w/ 99.957% alcohol, all the fingers are in fine
shape, and there visually isn't anything wrong. However, I still have
the same problem. Now that I look back, is it a possibility that the
black rod that switches the reeds has gotten worn? I was just
wondering if anyone had this problem before, and if that was a
possibility. Everything on the scope works fine, and if you turn the
knob to the extremes of the detent, it works fine. Sorry for the
vagueness, I just wanted some advise before I tear it apart again.

Thanks,
Steve

cajuncalibration wrote in :

I have a 465M w/ a problem. When you wiggle the Ch1 V/Div knob, the
display shrinks about .4 div from the correct calibrated position. I
thought dirty contacts, I pulled the assembly completely apart and
cleaned all contacts w/ 99.957% alcohol, all the fingers are in fine
shape, and there visually isn't anything wrong. However, I still have
the same problem. Now that I look back, is it a possibility that the
black rod

Cam drum

that switches the reeds has gotten worn?

Not really.
It's more of a loss of spring tension in the spring contacts.
These HF cam switch contacts have a very low wiping force.
Also,outgassing from plastic parts may have left a hard film on the PCB
contacts,a light cleaning with a pencil eraser will help there.
Don't go so hard you remove the gold plating.

I was just
wondering if anyone had this problem before,

It's a common problem.

and if that was a
possibility. Everything on the scope works fine, and if you turn the
knob to the extremes of the detent, it works fine. Sorry for the
vagueness, I just wanted some advise before I tear it apart again.

Thanks,
Steve




--
Jim Yanik
jyanik
at
kua.net

cajuncalibration wrote in
:

On 5 Aug 2005 15:05:28 GMT, Jim Yanik . wrote:

cajuncalibration wrote in
m:

I have a 465M w/ a problem. When you wiggle the Ch1 V/Div knob, the
display shrinks about .4 div from the correct calibrated position.
I thought dirty contacts, I pulled the assembly completely apart and
cleaned all contacts w/ 99.957% alcohol, all the fingers are in fine
shape, and there visually isn't anything wrong. However, I still
have the same problem. Now that I look back, is it a possibility
that the black rod

Cam drum

that switches the reeds has gotten worn?

Not really.
It's more of a loss of spring tension in the spring contacts.
These HF cam switch contacts have a very low wiping force.
Also,outgassing from plastic parts may have left a hard film on the
PCB contacts,a light cleaning with a pencil eraser will help there.
Don't go so hard you remove the gold plating.

I was just
wondering if anyone had this problem before,

It's a common problem.

and if that was a
possibility. Everything on the scope works fine, and if you turn
the knob to the extremes of the detent, it works fine. Sorry for
the vagueness, I just wanted some advise before I tear it apart
again.

Thanks,
Steve


I used a pink eraser on the contacts, maybe I didn't do a through
enough job. I guess I can pull it back apart, maybe get lucky this
time.

Also, just out of curiousity, what kind of material is the board made
out of? Also, I've read many times not to use any cleaners that leave
residue, not to clean anything but the contacts, not to breathe on the
vertical attenuators etc. etc., is this just due to the extreme
sensitivity of the components?

Due to the very low wiping force of the HF contacts,and effects of solvents
on plastics.



Thanks for the reply,
Steve


If the atten PCB is translucent,it's polystyrene,melts easily,and most
solvents affect it.(microcracks)
Some atten PCBs were ordinary epoxy-glass,I don't recall about the 465M.
The similar 455 atten PCBs were epoxy-glass.

--
Jim Yanik
jyanik
at
kua.net

On 5 Aug 2005 15:05:28 GMT, Jim Yanik . wrote:

cajuncalibration wrote in :

I have a 465M w/ a problem. When you wiggle the Ch1 V/Div knob, the
display shrinks about .4 div from the correct calibrated position. I
thought dirty contacts, I pulled the assembly completely apart and
cleaned all contacts w/ 99.957% alcohol, all the fingers are in fine
shape, and there visually isn't anything wrong. However, I still have
the same problem. Now that I look back, is it a possibility that the
black rod

Cam drum

that switches the reeds has gotten worn?

Not really.
It's more of a loss of spring tension in the spring contacts.
These HF cam switch contacts have a very low wiping force.
Also,outgassing from plastic parts may have left a hard film on the PCB
contacts,a light cleaning with a pencil eraser will help there.
Don't go so hard you remove the gold plating.

I was just
wondering if anyone had this problem before,

It's a common problem.

and if that was a
possibility. Everything on the scope works fine, and if you turn the
knob to the extremes of the detent, it works fine. Sorry for the
vagueness, I just wanted some advise before I tear it apart again.

Thanks,
Steve


I used a pink eraser on the contacts, maybe I didn't do a through
enough job. I guess I can pull it back apart, maybe get lucky this
time.

Also, just out of curiousity, what kind of material is the board made
out of? Also, I've read many times not to use any cleaners that leave
residue, not to clean anything but the contacts, not to breathe on the
vertical attenuators etc. etc., is this just due to the extreme
sensitivity of the components?

Thanks for the reply,
Steve

On 5 Aug 2005 22:26:08 GMT, Jim Yanik . wrote:

snip

Due to the very low wiping force of the HF contacts,and effects of solvents
on plastics.



Thanks for the reply,
Steve


If the atten PCB is translucent,it's polystyrene,melts easily,and most
solvents affect it.(microcracks)
Some atten PCBs were ordinary epoxy-glass,I don't recall about the 465M.
The similar 455 atten PCBs were epoxy-glass.

Problem fixed, thanks for the reply. I cleaned the contacts very well
again, but it still had the same problem, so i lightly pushed on the
tops of the contacts w/ a paper stick until I found the two that were
the problems, and just slightly tweaked the contacts back down. It
works perfect now. The board is translucent, which is what made me
wonder. It didn't seem like typical epoxy-glass board. Thanks for
the reply again, and now I finally have a fully functional scope that
I bought on ebay for a buck plus s&h (I have 4 scopes, all bad in one
way or another).

Thanks,
Steve

cajuncalibration wrote:

I have a 465M w/ a problem. When you wiggle the Ch1 V/Div knob, the
display shrinks about .4 div from the correct calibrated position. I
thought dirty contacts, I pulled the assembly completely apart and
cleaned all contacts w/ 99.957% alcohol, all the fingers are in fine
shape, and there visually isn't anything wrong. However, I still have
the same problem. Now that I look back, is it a possibility that the
black rod that switches the reeds has gotten worn? I was just
wondering if anyone had this problem before, and if that was a
possibility. Everything on the scope works fine, and if you turn the
knob to the extremes of the detent, it works fine. Sorry for the
vagueness, I just wanted some advise before I tear it apart again.

Thanks,
Steve
I'm glad to hear that you fixed it.
I had a similar problem with a 475, and it was a poor contact on one of the
little attenuator modules which plug into the attenuator PCB if I remember
correctly. I had to unplug and reinsert the attenuators to fix it.

Chris