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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

Reply to
cajuncalibration
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cajuncalibration wrote in news: snipped-for-privacy@4ax.com:

Cam drum

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.

It's a common problem.

--
Jim Yanik
jyanik
at
kua.net
Reply to
Jim Yanik

cajuncalibration wrote in news: snipped-for-privacy@4ax.com:

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

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
Reply to
Jim Yanik

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

Reply to
cajuncalibration

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

Reply to
cajuncalibration

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

Reply to
Chris Jones

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