UberTuber

[EBK]

T2 is a bit high but not too worrisome. T1 is a problem though. I start by increasing the plate resistor on that one from 100k to 150k. You could lower T2 by increasing its resistor to 120k. Your V+ and heater are spot on so it's just wrangling those plates in.

Hmm...   
I made the changes to 150k and 120k.

Now I get:

V+: 17.97V
T1: 14.39V (down from 15.28V)
T2: 13.68V (up from 13.07V)
T3: 11.59V
T4: 6.32V

[madbean]

Well I don't know how your voltage could have gone up, haha. That is strange indeed. Can we see a pic of the top of the board, please? Let's see if we can figure out what's going on here.

[EBK]

Well I don't know how your voltage could have gone up, haha. That is strange indeed. Can we see a pic of the top of the board, please? Let's see if we can figure out what's going on here.

Is this the top?


This pic was taken before I swapped the resistors.  Also, there is a piece of foam tape insulating the toggle from the back of the daughter board (in case that isn't clear).

[madbean]

Insofar as I can tell, that looks right. Except maybe R4 which does not appear to be 22k but I can't quite make out all the color bands (not sure if the 1st band is blue, or black but it should be red, red, black, red, brown).
The tube you got from smallbear, is it the 6111 or 6021?
I probably should have suggested socketing those two plate resistors but instead made an educated guess as to what would bring it into proper bias.

[EBK]

Insofar as I can tell, that looks right. Except maybe R4 which does not appear to be 22k but I can't quite make out all the color bands (not sure if the 1st band is blue, or black but it should be red, red, black, red, brown).

I'll check that one out when I get home.

The tube you got from smallbear, is it the 6111 or 6021?

It's the 6111.  Thomson brand, if I recall correctly.

I probably should have suggested socketing those two plate resistors but instead made an educated guess as to what would bring it into proper bias.

I'll probably will socket them before making any further changes. 

[EBK]

Just checked my R4.  It is 22k (21.98k measured).  Weird shadow plus thin paint sure did make that look incorrect in the other pic.  Here is a closer view (which only looks a little better):



It is interesting that the T2 voltage went up with the higher plate resistor.  Apparently, that resistor changed the current quite a bit.  I suppose I could fuss with the cathode resistors.  Maybe I should just try another tube....

[BryGuy]

Don't know if this helps but I just measured my voltages TP2 seems to change with the position of the drive pot. Assuming that's normal? I also have a Thomson brand tube from Small Bear, 6111 printed on the glass. Everything does seem to be working, CUT & SAT pots included. Both subtle effects but they are there.

VC 18.34
TP1 14.54
TP2 (DRIVE @ 0) 13.08
TP2 (DRIVE @ MAX) 14.85
TP3 11.47
TP4 6.54

Like I said everything seems to be working and it sounds pretty good. Just unsure if plate voltages being high could cause a problem down the road? Like shortened tube life or something?

[madbean]

That actually is a good point. The Drive knob probably does change the input bias a bit going into the second triode which would explain small differences in voltage readings. I'll need to take a look at mine to verify but it seems to be the likely explanation.

I am a bit more concerned about the higher plate voltages some people are having. Like I said, I've built the UT at least 2-3 times and with different tubes and my results have been consistent. And, I've built different variations of this circuit with a 6021 and got similar results, IIRC. So, it does seem like the best thing to do is suggest people socket R5 and R8 to allows for fine adjustments. There is still a range of plate voltages that should work but I would really prefer people to get consistent results with what the build doc lists.

I will be placing another order for boards next month so I will go ahead and change those resistors to trimmers. I'm kind of kicking myself now for not doing that. But, the first time you do a new type of project there's always a bit of a learning curve.

[EBK]

I'm in the process of adding sockets for R5 and R8. 

[EBK]

Don't know if this helps but I just measured my voltages TP2 seems to change with the position of the drive pot.

That probably explains my increasing T2 voltage.  I more or less centered the controls for my measurements by rough feel (no knob indicators).

[EBK]

Threw in some 180k resistors.
T1: 14.05V
T2: 11.30V

Should I just keep jacking that plate 1 resistor higher and higher?

220k:
T1: 13.57V

[madbean]

Threw in some 180k resistors.
T1: 14.05V
T2: 11.30V

Should I just keep jacking that plate 1 resistor higher and higher?

220k:
T1: 13.57V

Definitely close enough. How is it sounding with the new plate voltages?

[EBK]

Definitely close enough. How is it sounding with the new plate voltages?

I'll report in tomorrow on how it sounds.
I actually haven't listened to it since I clipped the original resistors out. 

[EBK]

Ok, I've listened to it again.  It is definitely much more gritty and crunchy now.  I kind of feel that it is cutting too much high end though, even with the cut control at its minimum.  With cut maxed, it is very dull sounding.  I may try lower those plate resistors a tad to see if I like it a bit better.  The saturation control is still barely noticeable.

[madbean]

Man, I'm sorry this is giving such trouble. The Sat knob should be very, very noticeable.

I will probably go ahead an order one of the 6111 from smallbear and compare it to mine. I still have the box of ones I bought from CE Distribution but I simply haven't had time to test each one. But, if I can pull out a good one I'll send it to you if we can't get your build sorted.