FPIII Bad Voltage Readings

[Doc B.]

OK clip the black lead to H1. Now take a VDC reading with the red lead at each end of the white resistor, H2 and H5.

[Frank Breech]

H1 to H2 --  1.6VDC (see next post)
H1 to H5 --  1.8VDC (see next post)

Interesting.  Earlier today, when I did H1(black lead) to H2 (red lead) I got a reading of zero.  see post Today at 05:20:20 AM Posted by: Frank Breech

[Frank Breech]

Ok, found a loose connection at the heater.

My I am editing the above readings, the new readings are:

H1 to H2  6.75 VDC
H1 to H5 6.75  VDC

still no light at the LEDs at the tube sockets.

[Doc B.]

So you must now go back and see if that voltage is actually at the tube sockets too - 4/5 and 9.

[Frank Breech]

The voltage is at the tube sockets.  The LEDs are lit.  The 12Au7s are lit.

I feel that everything should be ok now.

That bad solder at H1 must have been the culprit. 

I will bring the unit home and post the result.

Thank you for all the guidance.

Mike

[Doc B.]

Now you see why my first post in a troubleshooting thread is most often -

http://www.bottlehead.com/smf/index.php/topic,3284.msg28329.html#msg28329  

Carefully reheating every solder joint and visually inspecting it with a magnifier to make sure everything is properly coated with solder and secure in the joint is the best way to start to sort out a "not working" issue, particularly one where the circuit was working initially. It can save a lot of other testing and probing.

[Frank Breech]

Please refer anyone to me who might doubt this.

I will let you know what happens this evening when I get it hooked up.  I'm hoping I'm not back to square one with the noisy right channel.  I did rewet all sweetest whispers connections and cleaned the tube sockets with Grainger's method (dental brush and contact cleaner).

I might put on Tom Waits's Heart of Saturday Night on a Friday.  Unheard of, but possible.

I did also enjoy the troubleshooting as it got me realizing what was what better that before - even if just a little bit.

Thanks Again
Mike

[Grainger49]

I should have described the black stripe on the capacitor differently.  I was looking at the first picture on page 28 of the manual.  I see now that the input RCA jacks are to the right, the output RCA jacks are to the left.  The black stripe should be to the left.

Two things you have measured point to the diode string.  You got 0V H1-H2, which is where the cap is, and you got 6.1V AC on the transformer.  The diodes are all that connect those two points.  Of course the diodes are what make DC out of AC and smoothing it gives you a little more than the RMS AC value.  

You are right on top of it now.  This has got to be it.

Edit: I now see all the back and fourth that I missed where you and Dan figured out the missing/loose connection at H1.

[Frank Breech]

Grainger,
Thanks for the follow-up.

I'm at home, the amp is sounding very nice.  No more noise on the right channel when touching that side of the chassis.  I'm having just one issue (which might even be a hold over, partly, from my original issue):
one channel is softer than the other.  In this case it follows the tube.  Whichever socket I put the suspect tube into, that channel is about 2 sweetest whispers clicks below the other side.

Any ideas?  

I did not check the pins of my 12AU7 tubes as you described to me in an earlier post.  I can do that.  I'm burnt out for tonight ... just glad to be listening, even with the SW pots at different settings.

Thanks Again,
Mike

[Frank Breech]

It could be fatigue, but I 'think' the channels are evening out, level-wise.  Is is possible that it could take a while for one channel to get warmed up or something to output the same as the other channel?

They are still a bit far off, but better than before.  When I attenuate each all the way, but the CD player is still going, I can hear the music through one channel (the louder one) a bit, but cannot hear it at all through the other (softer) channel.

Mike

[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