View Single Post
Old 17th Mar 2020, 8:10 pm   #8
Skywave
Rest in Peace
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
Arrow Re: Tektronix 465 not sweeping

It's been my experience with repairing Tek. 'scopes in the range 455 → 475 that a lot of patience, perseverance, persistence (the 'Three Ps') and much time is required: there is lots of complicated circuitry to analyse. Yes, you can have the service manual in front of you and spend ages going back and forth though its pages and wandering around the pcbs trying to interpret the cct. descriptions and wandering around said defective 'scope with another 'scope, a DMM and a component tester. I'm sure that there are a few people who are absolute whizzos with the manual and a few instruments & get it fixed relatively quickly. Me? I'm not and never have been that clever. I've always used the "this item looks like it could be the trouble: I'll test it".

It's failure of a transistor (or more) that is often the culprit - with regard to your described fault.
My fault-finding approach would be as follows.

The first place I would look at is the A & B sweep generator / A9 interface board. It features transistors Q1012, 1014, 1002, 1024, 1030, 1036, 1038, and various diodes. I would remove each one in turn and check it in the traditional manner (some of those are FETs). If any are found to be defective, replace with suitable alternatives.

Next, the sweep & Z axis logic / A8 trig. gen. & sweep control. U870 is featured here, along with many transistors & diodes. Although you could remove each one in turn and test it, I would look at Q862 / 864, 854, 1052 / 1054 / 1042 / 1044 first.

Of course, this approach is the 'blindly test (almost everything)' method , but for reasons stated at the start of this post, overall, it has usually caused me less headaches than the alternative & has (usually) restored normal operation.

Best of luck with it: there's a failed component(s) in there somewhere - just a matter of finding it! The 'Three Ps' are your best tools with this generation of Tek. 'scopes.

Al.
Skywave is offline