Recent Posts

11

Tube Amp Building - Tweaks - Repairs / Re: Blackstar Club 40 - Have you ever seem such a failure?

« Last post by Platefire on September 06, 2025, 12:25:04 pm »

Wow! Looks like pancakes on the grill! Well, you know where to start at---might be a lot more to be found?

12

Tube Amp Building - Tweaks - Repairs / Blackstar Club 40 - Have you ever seen such a failure?

« Last post by jukelemon on September 06, 2025, 11:59:22 am »

Hi all!


So this Blackstar Club 40 comes in. Power/Volume surging in and out.


Open it up and see 10 caps look to have exploded.

Getting high voltage when I probe the top of the power supply caps.

The "have you seen" question is this... I am ALSO picking up 250-400vdc when I probe that rust/brown residue.


It is as if the caps have bonded together on the top of the board?

13

Tube Amp Building - Tweaks - Repairs / Re: Troubleshooting a new build amp

« Last post by Wardy on September 06, 2025, 11:23:04 am »

Thanks People

I’ll try all your suggestions tomorrow. Can’t do anything this evening.
Best

Steve

14

Tube Amp Building - Tweaks - Repairs / Re: Troubleshooting a new build amp

« Last post by kagliostro on September 06, 2025, 11:13:51 am »

Just to know

didnyou swapped V1 with One other tubes, the problema is there also if you do that ?

Franco

15

Tube Amp Building - Tweaks - Repairs / Re: Troubleshooting a new build amp

« Last post by acheld on September 06, 2025, 10:58:57 am »

IF what you're saying is correct, then consider mis-wiring of the input to V1a. 

Pictures of your build would be really helpful, showing wiring of the inputs (both normal and FET), and V1.  High resolution helps greatly.

16

Other Topics / Re: Meme of the day

« Last post by shooter on September 06, 2025, 10:48:35 am »

...

17

Tube Amp Building - Tweaks - Repairs / Re: Troubleshooting a new build amp

« Last post by dogburn on September 06, 2025, 10:39:29 am »

Could it be the input jacks and/or their wiring? Could the FET board have anything to do with it? Have you tried wiring in an isolated input jack and playing through that?

18

Tube Amp Building - Tweaks - Repairs / Re: Troubleshooting a new build amp

« Last post by Wardy on September 06, 2025, 05:04:22 am »

Ok Thanks, Sorry I forgot to attach the voltage chart I made previously.

best

Steve

19

Tube Amp Building - Tweaks - Repairs / Re: Troubleshooting a new build amp

« Last post by Williamblake on September 06, 2025, 04:48:05 am »

Measure DC Voltages at tube pins.
Doesn't sound sexy, but excel is of big help. No more notes flying around, you can see your progress afterwards.

20

Tube Amp Building - Tweaks - Repairs / Troubleshooting a new build amp

« Last post by Wardy on September 06, 2025, 02:14:52 am »

Hi Gang,

I really need some expert help. am reaching the end of my tether with a new build 50W ODS amp.

The situation is that it fires up and all the controls work as expected but the output volume is low. I have traced through the amp with an oscilloscope and narrowed the problem down to V1a. which does amplify but by a factor of 2 when the expected is 45. Its taken me days to get to this stage!

I guess the question is now pretty simple as the problem is specific. What would cause one side of an ecc83 triode (V1a) to output 2x gain when it should output a gain of 45x according to a recent test on another amp thats the same.

I've checked for resistor values. cap values, checked for no dc on wrong side of caps, correct connections, all earths working, tried 3 valves, inspected every joint with a magnifying glass, reflowed some.

What else could possibly cause this? where else to look?

has anyone ever had a similar problem?