[GreenKeys] Tek 485 help?

[drlegendre .]

This is all very familiar..

I've seen that thread before.. in fact, it was just about one year ago that
I came across it. I was t-shooting a very similar issue at that time, and
it turned out to be a shorted tantalum cap on one of the boards. Cap was
pulling too much current and tripping the protection circuit.

It's all coming back to me now. Wonder if there's another dead tantalum in
there? But dang it, how the heck did I ever find the first one? Can't yet
recall how it was that I located it! Sure, yeah, isolate etc. etc. But I
can't recall the exact process.

On Sun, Feb 18, 2018 at 9:28 PM, Steve Ripper <steve.ripper at gmail.com>
wrote:

> Here is a link to a thread for a power supply problem very much like yours.
> Especially tic-tic-tic sound you hear is explained.
>
> http://www.dslreports.com/forum/r25550083-Tektronix-485-no-power-up
>
> And here is a link to the service manual (30MB)
>
> http://bama.edebris.com/manuals/tek/485/
>
>
> Steve R.
>
>
> On Sun, Feb 18, 2018 at 9:27 PM, drlegendre . <drlegendre at gmail.com>
> wrote:
>
>> Anyone here familiar with the power supply voodoo in the Tek 485? I have
>> a scope here that was running ok, then suddenly the display went out of
>> focus - the traces became very wide and indistinct. About a minute later,
>> the entire PSU shut down.
>>
>> About all that's working at this time is the main DC supply, the one that
>> drives a little neon relaxation oscillator. None of the 5V / 15V / 9V etc.
>> points are hot, just a little noise on those. I can also hear a faint
>> 'tic-tic-tic' from one of the PSU boards.
>>
>> This unit is above my pay grade, and I'm not sure how to t-shoot it.
>> About all I know is that the main DC supply is up, and everything else is
>> dead.
>>
>> Thanks for any help.
>>
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>
>
>
> --
> Cheers,
>
> Steve Ripper
> steve.ripper at gmail.com
> 248-787-0705 <(248)%20787-0705>
>
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