Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 72Blazer on September 04, 2021, 08:53:33 pm

Title: Acceptable voltage loss?
Post by: 72Blazer on September 04, 2021, 08:53:33 pm
I have some NOS 25uf 25v electrolytics I want to install on a AB763 circuit board.  They are all measuring a little over 3 volt loss.  Is this acceptable not for this application?  Thanks

Edit:  For clarification, the vloss was measured using TC-1 multi-function tester.

Vr
J.
Title: Re: Acceptable voltage loss?
Post by: tubeswell on September 04, 2021, 09:47:05 pm
Quote from: 72Blazer on September 04, 2021, 08:53:33 pm
some NOS 25uf 25v electrolytics ... measuring a little over 3 volt loss.  Is this acceptable


What starting voltage are you putting on which pole?
Title: Re: Acceptable voltage loss?
Post by: 72Blazer on September 04, 2021, 10:24:22 pm
Quote from: tubeswell on September 04, 2021, 09:47:05 pm
Quote from: 72Blazer on September 04, 2021, 08:53:33 pm
some NOS 25uf 25v electrolytics ... measuring a little over 3 volt loss.  Is this acceptable


What starting voltage are you putting on which pole?
Unsure...with the TC-1, you just insert both leads of the cap in the slots and it gives the reading.  My newer sprague 25uf 25v electrolyrics measure 0.0 vloss with this device.


Title: Re: Acceptable voltage loss?
Post by: sluckey on September 04, 2021, 10:36:42 pm
Vloss is displayed as a %, not an actual voltage. That doesn't mean anything to me and the user manual doesn't explain.
Title: Re: Acceptable voltage loss?
Post by: HotBluePlates on September 10, 2021, 10:17:01 pm
Quote from: 72Blazer on September 04, 2021, 08:53:33 pm
some NOS 25uf 25v electrolytics ... measuring a little over 3 volt loss.  Is this acceptable
Quote from: 72Blazer on September 04, 2021, 10:24:22 pm
Unsure...with the TC-1, you just insert both leads of the cap in the slots and it gives the reading.  My newer sprague 25uf 25v electrolyrics measure 0.0 vloss with this device.

Personally, I would say "No."

As an interesting comparison, I replaced the power supply electrolytics in a 1964 AC30 I bought.  Kept the old caps in a bag cause, you know, old parts.  I got a Sencore LC75 and checked the leakage of the AC30's original electrolytic caps: with 400vdc applied, leakage was down in the 1-2ľA range.  That was better than some tweak "paper-in-oil" coupling caps I had!

I wouldn't assume old caps are good, but sometimes when you actually measure them they will surprise you.  But when you do measure and they show anything other than great results, be wary.
Title: Re: Acceptable voltage loss?
Post by: 72Blazer on September 11, 2021, 07:34:43 am
I'm definatley not going to use these on this new FSR AB763 new build.  I suppose once I get this built and working properly I could play around/alligator clip them in to see if there is any negative effects.