Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ACDCG400 on November 16, 2011, 02:17:10 pm

Title: question on vox ac30 cc
Post by: ACDCG400 on November 16, 2011, 02:17:10 pm

Hey guys ive been looking at a friends ac30 cc and it keeps blowing the power tube grid stoppers, the 1.5k ones. they start smoking then the ht fuse blows. any thoughts? i thought it might be dead tubes so i replaced them with good ones, but nothing. is it the ot?

Title: Re: question on vox ac30 cc
Post by: Raybob on November 16, 2011, 03:17:42 pm

What are the voltages at power tube pins with no power tubes in?

Title: Re: question on vox ac30 cc
Post by: phsyconoodler on November 16, 2011, 03:45:28 pm

There is a short somewhere,maybe the tube socket itself.I can't think of anything else that could cause a low voltage grid resistor to burn up.Are you sure they are grid resistors that you are talking about?

Title: Re: question on vox ac30 cc
Post by: ACDCG400 on November 16, 2011, 04:01:22 pm

Raybob, ill check in like 10 minutes, i didnt even think of checking! and im certain, its the resistor on pin 2 of every el84. thats odd tho, a short with every socket?  :w2:

Title: Re: question on vox ac30 cc
Post by: LooseChange on November 17, 2011, 06:48:32 am

Does it happen with the tubes removed?

Title: Re: question on vox ac30 cc
Post by: ACDCG400 on December 16, 2011, 08:35:48 pm

Sorry for the really late reply guys! It doesn't do it with the tubes out, but I replaced the it and still they are smoking. I'm gonna fiddle around with it more but do u guys have any other ideas? Ill check the cathode bias and make sure its working

Title: Re: question on vox ac30 cc
Post by: PRR on December 16, 2011, 10:09:44 pm

>> What are the voltages at power tube pins with no power tubes in?

> ill check in like 10 minutes

Checked yet?

There's way too many things can go wrong, we (and you) need to buy more clues.