Req Help/Advice with Tek scope repair

[nicklinn]

Hello guys,

I am no virgin to replairs but I encountered a problem that is a bit above me and I though I would ask around for help on this problem.

I have a Tek 7934 scope with a bad power supply. I have track the problem down to the component that is causing the problem, which is a power transformer that seems to be having a secondary winding shorting to the primary. Here is the deal. No one really carries the parts that I need on this 20year old scope. Since the ferrite core seems to be in good shape I thought the best course of action would be to re-build the transformer. This is something I have never done before and since while tek offers great schematics info I cannot find any info on the winding of the transformer (which's part number is 120-1183-00 if anyone is interested) other then the input and output voltages, I think I will have to reverse engineer it.

Does anyone have any advice or tips to reverse engineering and remanufacturing transformers that may help me?

Thanks a ton,
Nick

 

[echo47]

A power transformer with ferrite? Is it a switcher?

I've seen 7934 scope mainframes sell on eBay for less than $50 US. Maybe buy one as a source of spare parts. However it is a big hulk to have sitting around.

Once upon a time, Tek promised a lifetime warranty on their power transformers. Ask them and maybe get lucky.

Here's a group that discusses Tek scopes:
**broken link removed**

 

[nicklinn]

I got to admit I don't know a heck of a lot about transformers buy yes it has a square type ferrite ring with one edge having the windings. Paper and glue insulation. If you are interested I can shoot a pic of the device?

Unfortunately the cheapest I can find on the bay is in the $500 ballpark. Though I am not in a rush for it to be working I need it within a month or so in the meantime thought I would try fixing it first.

I wasn't aware of that I will have to look into that at the very least they may have the part I need.

Thanks will post on that board.

 

[echo47]

Yes, I don't see any cheap ones on eBay right now.

In case you need a service manual (110 megabytes):
https://bama.edebris.com/manuals/tek/7934/

Dealer of spare parts. Maybe email him and get lucky:
https://www.sphere.bc.ca/test/index.html
https://www.sphere.bc.ca/test/tek-transformers.html

I think the transformer lifetime warranty applies to scopes made before early 1970's. Your scope is probably too new.

 

[nicklinn]

Got the repair manual on paper complete with sweat and tear stains

My scope was made around 86 unfortunately.

I looked at those guys but didn't see the part on the site. Will try emailing them.