Tek 465 with loose position knob -- non straight line sweep with no signal added - Page 1
Forum section: electronics / testgear

author: HarveyCat
author_rank: Newbie
timestamp: July 11, 2014, 08:42:44 pm
content: Hi allI got a used Tek 465 with a loose sweep position knob -- it shows a non straight line sweep with no signal added -- any advice or thoughts -- sweep changes with sweep position knob but doesn't go straight across.ThanksHarvey

author: tautech
author_rank: Super Contributor
timestamp: July 11, 2014, 10:29:14 pm
content: With CRT scopes you will need 2 thingsService manual, you should be able to find it online.And I think this document was written for you:http://www.sphere.bc.ca/test/tek-parts/troubleshooting-scopes.pdfAlways check PSU rails are within spec first.Short trace like this is often a faulty CRT deflection output stage.Transistors in the output stages do fail and it might be an easy fix.Be aware of the voltages present.This might have been better to be placed in the Repair board.Ask a moderator and they can shift it if you wish.

author: HarveyCat
author_rank: Newbie
timestamp: July 11, 2014, 10:55:57 pm
content: Thanks tautechI failed to mention that with the sweep position knob -- besides being very loose -- only allows the sweep to be brought (positioned) half way across the screen.I found the operation manual (50 pages) and the service manual (291 pages) both online -- but that troubleshooting Tek pdf that you posted a link to -- looks like a great help -- kind of flow charts the process. I will also follow your other advice - and if a Mod is seeing this please do move this to the repair area!CheersHarvey

author: GreyWoolfe
author_rank: Unknown
timestamp: July 11, 2014, 11:01:19 pm
content: for the non straight line, did you try to manipulate the trace rotation?

author: HarveyCat
author_rank: Newbie
timestamp: July 11, 2014, 11:09:21 pm
content: Hi GreywolfYes I did -- and that did not solve it for me.-Harv

author: tautech
author_rank: Super Contributor
timestamp: July 11, 2014, 11:47:37 pm
content: QuoteThis is the 'other than visual' symptom of your fault as I have described.

author: PaulAm
author_rank: Frequent Contributor
timestamp: July 12, 2014, 12:51:38 am
content: Once you get the manual, two things to check1 - Check all of the low voltage power supplies. 465s tend to have filter caps that fail open which leads to all sorts of bizarre behavior. That non-straight line, or even the trace on one side could be a symptom. Check both voltages and ripple (which should be somewhere in the mv range). Sometimes the bridge rectifiers fail, but the caps are more common in my experience.2 - Although they don't look like it, all of the transistors are socketed (at least for early 465s). Lack of a centered trace could be a bad transistor in the horizontal section, or it may simply be an oxidized contact in a socket. Simply reseating the transistors could solve the problem. I've fixed a couple of scopes by reseating transistors in sockets.Somewhere along the line Tek got rid of the sockets which improved reliability, but made repair a little more difficult.

author: scopeman
author_rank: Frequent Contributor
timestamp: July 12, 2014, 04:16:39 am
content: Quote from: HarveyCat on July 11, 2014, 08:42:44 pmIf you scope the supplies and find that they are okay I was wondering if it looks like the instrument has been dropped at some point. Dropping these scopes can cause a serious problem due to electron gun alignment.Do you get the same display at all sweep settings? Does the horizontal display change when you move the trace up and down vertically?You can also scope the horizontal plate feed (carefully) with another scope and see if you see a clean sweep and also the vertical plates to see what is there.So you see you can never have too many scopes as you need a scope to fix a scope! I always have a Tek 422 or 453 handy!SamYou can find high resolution service manuals here:http://exodus.poly.edu/~kurt/manuals/manuals/Tektronix/Good luck and let us know how you made out.