[Test-Equipment] First Tube Restoration Project

[Steven Bender]

Hi Mike,

Gee you don’t know anyone with a working tube tester?  Building a tube tester, seems like a multi-month project in and of itself.

I know the better tube testers seem to be sky high in price $400+ these days, but I have several, sold one untested and as-is about ten months ago, that leaves the working ones, four or five if I recall.  Consider spending a few $$$ mailing the tubes (not CRT) to me, but only as a last resort :-).

Try to get the manual on the set, if it is not available online or at electrotanya, sometimes the manuals show up on eBay.  Said manual will show where the high voltage is - which might be too high for most VOM or DMM meters, can you smell the smoke?  Leaking caps on the AC line input may mean hot chassis problems.  Got a variac or a Sencore PR-57 ?

Old caps are most likely to need replacement, maybe more than the tubes...  Tough to find caps rated over 400 volts these days, some might be way higher, 600V or even 1600V.  Resistors may be carbon comp which might have been 10% or 20% way back when, and they may have drifted way, way off original value, like 40 or 50% off, and they may drift further when powered up from heating.  Modern R’s are typically 1% up to 2 Watts these days, typically 5% for 5 or 10 Watt parts.

Hope these comments helped, good luck with the project.


Steven L. Bender






From: greenkeys-bounces at mailman.qth.net<mailto:greenkeys-bounces at mailman.qth.net> <greenkeys-bounces at mailman.qth.net<mailto:greenkeys-bounces at mailman.qth.net>> on behalf of mwillega <mike at willegal.net<mailto:mike at willegal.net>>
Sent: Monday, June 10, 2019 9:16 AM
To: greenkeys at mailman.qth.net<mailto:greenkeys at mailman.qth.net>
Subject: [GreenKeys] [OT] - First Tube Equipment Restoration Project

Hi all,

I?m about to embark on my first restoration of a piece of tube based test gear.  It?s an old Heathkit Oscilloscope from the early 70s.  I am looking for recommendations for approaches to tube testing.  Do I seek out  or build a tube tester or just test in circuit.  Anything else that I should look out for, besides the usual concerns about high voltages on the chassis, and old degraded components.

Regards,
Mike Willegal