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

  • Thread starter Thread starter nbarts
  • Start date Start date
oh, and please turn the hum trimmer a bit to whatever side . . .
 
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!
 
The fluctuations of the hum trimmer are not ok.
Please turn it a bit.
Is PIN 3 still going up and down?
 
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.
 
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 . . .
 
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.
 
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.
 
Please adjust the hum trimmer to best results on
channel 3. The setting should be around 11 to
1 o clock position.
 
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.
 
Peter Diezel":267xdk4j said:
Please adjust the hum trimmer to best results on
channel 3. The setting should be around 11 to
1 o clock position.
Click to expand...

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?
 
I don´t think so.

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