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Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: frank57 on January 04, 2012, 10:57:02 am

Title: What does continuity to ground on both sides of cathode bias cap mean?
Post by: frank57 on January 04, 2012, 10:57:02 am
I was poking around my screwy amp and what I noticed was:
 I am getting a continuity to ground on both sides of the cap on v1 cathode and the resistor there.
It's not as strong on the positive sideas the negative but it is a beep.
Even with the wire to pin 8 disconnected.
What problems can this cause?
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: kagliostro on January 04, 2012, 11:16:46 am
You must disconnect also the resistor or the cap before to measure

the beep you hear is from the capacitor charge

Kagliostro
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: frank57 on January 04, 2012, 12:40:39 pm
so take out the resistor and check again?
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: sluckey on January 04, 2012, 12:50:25 pm
Why are you using a continuity checker on an amp? Your checker is seeing the 2.2K resistor. You should be using an ohm meter for these kind of checks. Then you would see a resistance of 2.2K rather than just hearing an ambiguous beep.

Continuity simply means there is a path for current flow between two points. It could be zero ohms, 100 ohms, 2200 ohms, 2M ohms, etc. Cheap continuity testers can distinguish a short circuit from an open circuit, but can't always figure out 'in between' resistances.
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: frank57 on January 04, 2012, 01:11:54 pm
I'm using a multimeter and I have the audible beep setting on.
So check both sides and see what the ohms is?
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: sluckey on January 04, 2012, 01:22:42 pm
Quote from: frank57 on January 04, 2012, 01:11:54 pm
I'm using a multimeter and I have the audible beep setting on.
So check both sides and see what the ohms is?
Yes. And turn the beep off. One side of the cap should read zero ohms (or close) because one side of the cap is connected to ground. The other side of the cap should show 2.2K (or close) because that side of the cap connects thru a 2.2K resistor to ground.
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: frank57 on January 04, 2012, 02:43:15 pm
On one side I get about .2 or .3 and the other about 2.16k.
With the resistor I get .1 and 2.16k.
If there was something funny going on what would it do?
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: sluckey on January 04, 2012, 02:47:18 pm
Quote
If there was something funny going on what would it do?
It would make me smile, maybe even laugh out loud.   :laugh:
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: HotBluePlates on January 04, 2012, 05:48:21 pm
Despite Steve's smile, there's nothing funny going on.

As far as I'm concerned, this is no laughing matter!
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: TubeGeek on January 05, 2012, 12:10:27 am
Quote from: frank57 on January 04, 2012, 02:43:15 pm
On one side I get about .2 or .3 and the other about 2.16k.
With the resistor I get .1 and 2.16k.
If there was something funny going on what would it do?

That is exactly what Steve was saying it should read.  Your readings are correct.
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: TubeGeek on January 05, 2012, 12:11:33 am
Quote from: sluckey on January 04, 2012, 02:47:18 pm
Quote
If there was something funny going on what would it do?
It would make me smile, maybe even laugh out loud.   :laugh:

Gotta admit, this made me crack up!  Have a sense of humour eh!
Title: Re: What does continuity to ground on both sides of cathode bias cap mean?
Post by: sluckey on January 05, 2012, 07:49:43 am
And a touch of insanity!