Re: 2235 power supply noise

Bert Haskins

On 10/20/2017 7:24 AM, mikepickwell@... [TekScopes] wrote:

Time for another update:

My replacement T906 arrived from Canada this morning. Annoyingly I had
to pay the post office £15 for import duty and handling making the
final cost for the part about £60.

I've just installed it and I was gutted to find that the high pitched
squealing noise coming from the power supply section is just as bad as
ever. Aargh!

The good news is that the recap has obviously done the scope some good
as the trace is now cleaner and sharper than I have ever seen it.

So just to summarise:

I've replaced all of the electrolytic capacitors apart from a few
small 22uF in awkward positions. All of the electrolytics around the
power supply have been changed.

I've also replaced T906 and CR907.

The scope seems to function perfectly as far as I can tell but it
makes a god awful high pitch squealing noise which drives you crazy
after a few minutes.

I'm completely at a loss as to how to proceed now. Is the problem
elsewhere? Is my replacement T906 faulty?

Please help!
Are you sure that the HVO is not running at too low frequency?
It should be running well above the human hearing range.
I would expect it to be about 60Khz.
I would think that you could read the frequency right from the 2235 just
by having the probe near the xformer.
If not just make up a small loop at the end of the probe.

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