Re: Unknown Type 547 add-on circuit.

Dave Wise

Beware that the 547 and 549 are susceptible to a high-voltage transformer problem. Tek switched to an epoxy-based winding impregnant which has become lossy. The symptom is loss of high voltage, sometimes after a short time on the order of minutes to a couple hours. Chuck Harris is working on an industrial-grade rewinding operation, or you can try my low-tech DIY approach documented in topic and album titled "453 HV Transformer Rewind". The 547 transformer winding spec is available at TekWiki, .

Dave Wise
From: <> on behalf of Dave Seiter via <>
Sent: Sunday, July 12, 2020 5:55 PM
Subject: Re: [TekScopes] Unknown Type 547 add-on circuit.

A nice haul! I have a 549 around somewhere that I've been meaning to restore; thanks for reminding me!
On Sunday, July 12, 2020, 05:03:39 PM PDT, Martin Hodge <mhodge@...> wrote:

Actually the total bill was $60, for a 535a, 547, 549, 575, 585a and a little Heathkit scope. I was very pleased, but the suspension on my van was not.

I was really after the 575. I'd been wanting a curve tracer and the other units were gravy. The 585a and the heathkit were unfortunately rotted away far beyond saving. But I've got the 575 and the 535a working nicely and calibrated. The 547 I've just finished but haven't calibrated yet. The 549 storage scope is going to have to wait, it needs two 8608 tubes in the vertical amp (gassy) which are very expensive.

The 535a has a beautiful, bright and razor sharp aqua colored trace and is completely transistor free when equipped with a Type 53/54K. I feel like a bolt of lightning could hit it and it would keep right on ticking.

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