Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on February 08, 2021, 05:09:19 pm
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I have at least 20 old Mallory cans, they all check out good with readings, within 20%. They all haven’t had voltage in many years most likely. Is it worth trying to bring up the voltage slowly or toss them...? With prices being $25 to $35 a can, l’m wondering..?
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... Is it worth trying to bring up the voltage slowly or toss them...? ...
Hard to say.
I just got a Sencore LC75 and tested a few caps, including a handful of electrolytics I replaced in a 1964 AC30. After giving the caps a minute or so to re-form, the originals had leakage (at 400v) and ESR as low as most modern electrolytics. So I found those particular original 1964 caps (Bianchi & TCC brands) could really go back into the AC30.
But testing for value alone won't get you there. You could use a Conductance scale if your DMM has one to test for leakage, though you won't be quite as-sure the cap will stand up to higher voltage, or is completely re-formed.
Ironically, the only cap I've had test "bad" so far was an expensive paper-in-oil type I got many years ago. It tested bad for leakage with both the DMM and Sencore.
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I use Heatkit IT-28 capacitor checker, it do a good job
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I don’t have the equipment to test satisfactory, or a variact either. Perhaps it might be worth taking them to someone who has the correct testing equipment.
Thanks
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You can use lamp bulb current limiter.