Intern Mainboard: F1 (High voltage) 1.6AT blew - Herbert

[duesentrieb]

oh, and please turn the hum trimmer a bit to whatever side . . .

 

[nbarts]

I can see 7 of them, visually they look similar, nothing I can see that would make me believe there is something wrong with one of them.

So those hum trimmer readings were fine?

Your help is very appreciated!

 

[duesentrieb]

The fluctuations of the hum trimmer are not ok.
Please turn it a bit.
Is PIN 3 still going up and down?

 

[nbarts]

I did. It's still going up & down. So are changing the other 2, only very slowly, it's hard to get any accurate measurements, these 2 seem to have decreased by 10v after turning the trimmer a bit.

 

[duesentrieb]

Sorry, I don't get it. You have three bias trimmers and one hum trimmer.

Could be your hum trimmer is bad. If so, turning it a bit should solve the problem for a while. But it could be that you need to replace it (lets wait for Peter's confirmation).

The bias trimmers should be ok. Set them to -50V, put tubes back in, bias to 60-70mA a pair.

Thats all I can do for you at the moment, sorry.

If Peter should call from Japan, I will try to direct him here . . .

 

[nbarts]

The bias trimmers are under the little board ( I'm sure you already know that). The hum trimmer readings is what I'm telling you.

Thanks, I'll try to re-bias it sometimes soon. I'll let know what happened.

 

[duesentrieb]

Peter . . .

 

[nbarts]

Peter . . .

No worries, man. I can wait.

 

[duesentrieb]

I was just kidding, Peter knows that

 

[Peter Diezel]

It´s not on my workbench

 

[nbarts]

So today I finally had time to snap a set of power tubes in the amp & bias it. I have no clue how, but it biased fine & the amp sounds as it should. However I would like your advice on the hum trimmer issue & whether it's safe or not running the amp as is.

 

[Peter Diezel]

Please adjust the hum trimmer to best results on
channel 3. The setting should be around 11 to
1 o clock position.

 

[Dallas Marlow]

I had a bit of an issue with my hum trimmer pot and sometimes it makes noise I think a tube at some point went bad or something and it got a little carbon build up on there... I was getting this buzz/hum a long time ago and had all these techs check it out, and replaced a pre-amp tube socket that had a bent pin, so that was good anyway... but it all turned out to be the hum trimmer was a little dirty i moved it slightly and then back and boom dead quiet like it should be. I'm pretty sure whatever happened to it, occurred when a pre-amp tube went bad.

 

[nbarts]

Please adjust the hum trimmer to best results on
channel 3. The setting should be around 11 to
1 o clock position.

Peter,

I did adjust the hum trimmer, the amp sounds great(God, I've missed this sound!). My question refers to the fluctuations I described above. Does the hum trimmer or anything other need to be replaced?

 

[Peter Diezel]

I don´t think so.

Please note that You have fluctuations from the main power
every second. This will also influence the bias reading.