Precision 660 tube tester Meter

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RalphC
Member
26
Jul Sat 16, 2022 11:15 am
Danvers MA. 01923

Precision 660 tube tester Meter

Post by RalphC »

A month ago the tube tester was working fine. The other day I turned it on and the meter goes all the way to the right. What should I be looking at?
Ralph
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jimtech
Member
1272
Nov Sun 29, 2020 4:59 pm
Carol Stream, Illinois 60188

Re: Precision 660 tube tester Meter

Post by jimtech »

Intermittent, wild meter swings on my 660 were found to be caused by poor oxidized connections inside a few of the wire-wound calibration potentiometers.

First, with the power off, try vigorously exercising all external switches and controls a bunch of times to provide some wiping/cleaning action.

If that fails, try tapping on each of the internal pots with an insulated tool and see if it makes any difference. If the meter is hard pegged to the right, it might be be best to disconnect it and substitute a DMM (set to measure DC current) until you find the cause, to avoid the possibility of damage to the tester's meter.

Problems with mine may have been spurred along by some past environmental influence, as the cadmium plated parts in the interior were almost totally covered with fluffy yellow powder. It was a mini superfund site in a box. :cry:

- JIM
RalphC
Member
26
Jul Sat 16, 2022 11:15 am
Danvers MA. 01923

Re: Precision 660 tube tester Meter

Post by RalphC »

That worked Jim.
It was the load selector switch “D” working fine now. All I did was vigorously turned all of the knobs.

Ralph
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jimtech
Member
1272
Nov Sun 29, 2020 4:59 pm
Carol Stream, Illinois 60188

Re: Precision 660 tube tester Meter

Post by jimtech »

Glad to hear that it's working again :D

I find it to be good practice to exercise all of the switches and controls on older gear once in a while, as the wiping action tends to cut through any oxide layer that may begin to form on contact surfaces. It's usually functions that are seldom used that tend to cause the most grief.

As you may have heard others state, avoid the use of contact cleaners on tube tester switch wafers and controls whenever possible, as residue can be absorbed by porous surfaces and create leakage paths that can be difficult or even impossible to remove.

- Jim
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