FPIII Bad Voltage Readings

[Paul Joppa]

It could be that the cathode is still forming - a search on this site will turn up several posts. We seem to have seen this more than a few times, though I don't see much mention of it on other sites. It can take  100 hours or so if that's the case.

"All the way off" means the switch has grounded the output to the tube. If there is a little resistance in the wire, switch contact, or solder joints, then there will be a little leakage. This is the wire from terminal 1 of the Whispers to terminal 16 or 40. It won't affect the balance on the higher switch positions to any measurable degree, so you can ignore it unless it either gets worse or just bothers you.

 

[Laudanum]

Mike, if you swap tubes around and it follows the tube, it is the tube.  But definitely follow Pauls advice and give the tubes some run time.  That may solve it.  Also ... here comes my standard advice ... get yourself a spare or two of each tube.  In the case of FPIII, two of the same type 12AU7's and a spare OD3.  The OD3's are really inexpensive, literally under 10 dollars for new (old stock) tubes like Hytron and RCA brand.  And I paid 3 or 4 dollars for a couple new old stock spares.    The 12AU7's are relatively inexpensive for new production tubes (like the EH included with the kit), maybe 15 dollars or less per tube.  But you can even find some of the New old stock vintage tubes for less than that.  The more highly prized 12AU7's are more but the point is having a couple of spares to troubleshoot or get you up and running should a tube go south.  So grab some spares. 

ps.  If shopping for new old stock tubes, look around and shop wisely (price wise). 

 

[Grainger49]

I agree with all the above.  As I read the problem I had the same thoughts.

 

[Frank Breech]

Thanks, guys.  I'll give these tubes some time, get a set of spares, and let you know if  is any trouble. I'll bee in touch soon most likely. Going to get started on my seduction.
Thanks a lot
Mike

 

[Frank Breech]

Hi Guys,
UPDATE: my FPIII channels are now evened out -- one is not louder than the other any longer and it has been stable for a few weeks. 
Thanks for all help.

Talk to you later