Re: 577 magic smoke :-(


Auto transformers can damage switch mode power supply if you set them below the regulation voltages. Sounds like a cap went. Note serial number on the serice manual there was a lot of revisions to this one. The 177 comes apart pretty easy I have a late model one so don't know if it has changed but detach it from the 577, just pull "gently" Not screwed in like the 576. Then it is side panels first then bottom cover if I remember correctly. There is HV ever ware in one of there and the collector supply is isolated from chassis ground.  Did you get the D1 or the D2? The storage tube has a weird power on sequence if it has been off for a while "2 weeks" If I recall correct


On 5/7/2020 9:46 AM, Reginald Beardsley via wrote:
I picked up an ebay 577 from a seller who got a big lot of stuff from a company merger. He got into this because a neighbor who worked there. He knows nothing about electronics. The neighbor has since moved. A lot of the other stuff he had looked like old lab closet queens complete with 1990 inventory labels. Serial number on the 577 is B105527

The 577 was shown on ebay with a screen trace. So I was hopeful it might be working.

I just powered it up and got a trace, fiddled with a few knobs moving trace position, width, etc. Noting erratic behavior I concluded I'd need to clean the controls before proceeding further and powered it off.

Then I got the nasty scent of magic smoke. The really acrid variety. I've pulled the covers from the top/sides and base, but don't see anything obvious. The smoke seemed to come from the 177 fixture and the smell is strongest in the front of the instrument. There is a label "Interlock Disabled Internally. 25 V Max". I've not yet figured out how to open the 177.

So where to start? Obviously I don't want to apply power again until I locate the fault and correct it. I do have an isolation and autotransformer if those are potentially useful in diagnosing the source of the smoke.

I have no experience with any of the Tek curve tracers. I've worked with HV CRT supplies. A long time ago, so I'm being especially cautious as I've learned how much I've forgotten.

I'm off to track down a service manual.


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