[soundguy937]

Got to step 7 with my latest kit and the voltage between tp1 & tp2 keeps jumping up and down by hundredths of vdc. I did let the tube warm for at least 15 mins before testing. What would cause the voltage to flutter? Is it possible it is the tube?

Thanks

P.S. I got the U6 part for the stereo right kit today, Thanks a million

[soundguy937]

UPDATE: my DMM keeps fluttering between 1-4vdc in small to large increments between tp1 & tp2. All the other prior tests seems to be working correctly. 

[JPK]

Try without any input signal.
Was the DMM stable when you measured the V+ voltage?
Remove U4 and measure the voltage on TP1 and TP2 against 0V.
Is the voltage accross TP1 and TP2 more stable?

[soundguy937]

looks like I am stable at the v+ although I am now noticing its reading negative instead of positive 15.6vdc, V- reads 15.5vdc positive vs. the setup saying it should be negative.

V+= -15.6vdc
V-= 25.5vdc

with U4 removed
TP1 to 0V= 32.3vdc
TP2 to 0V= 28.4vdc
TP1 to TP2= maybe slightly more stable, but still jumps around from a few hundredths to a couple tenth of a percent of voltage +-

[JPK]

V+= -15.6vdc
V-= 25.5vdc
Do you put the black probe on 0V?
Check your DMM batteries and check your lunchbox voltages.
Voltage variations between TP1 and TP2 are normal. They should stabilize once thermal equilibrium is reached.

[soundguy937]

okay now with black probe on 0V I'm reading :

V1= 15.68vdc
V2= -15.65vdc

all my tests between TP1 & TP2 have been after at least 15-25min of warming up.

TP1 & TP2 after 30min and U4 still removed varies between +-1 to 2 hundredths of a VDC. 

With U4 replaced shortly after shut down of last test and waiting another 30min I am seeing my DMM with fresh batteries jump around again not stabilizing between 0.00 to +-0.05 VDC. Unfortunately it takes twice as long to mostly stabilize than what I seen in my first kit and the setup recommendation waiting time. Is this to be expected?

[JPK]

Can you change the tube with the one from the other unit and check if it stabilizes better?

[soundguy937]

Unfortunately it does not appear a tube swap made a difference in stabilizing the voltage.

[JPK]

Check that the input transformer is in the correct orientation.
Check that TR1 and TR2 have the correct value.
Check that R3 to R10 have the correct value.
Check that the voltage on B+ is stable.
Check the input transformer coils resistance (in circuit, input pot on max): 

• 2-4 : 37 ohms
• 3-5 : 37 ohms
• 7-9 : 100 ohms
• 8-10 : 100 ohms

Check the input resistance (between XLR pins 2&3, input pot on max): 4.6k

[soundguy937]

Input transformer is in correct orientation.

TR1=202 2k
TR2=102 1k

B+ stable at 45.5VDC

R3= 3k3
R4= 3k3  
R5= 10k 
R6= 10k  
R7= 10k  
R8= 470R 
R9= 10k  
R10= 10k  

input transformer values (input on max)

2-4= 37.2 ohms
3-5= 37 ohms
7-9=100.1 ohms
8-10= 99.1 ohms

input resistance pins 2&3= 4.61 k ohms

everything mostly checks out excepts input transformer 8-10 being 99.1ohms. 

[JPK]

All OK.
Check again the tube heater (step 4 of the setup guide).
I am sorry, I am short of ideas. Do you want to sent it to us for a check at the lab?

[soundguy937]

I will try to test the Tube heater test tonight or early tomorrow. At this point I am strongly considering sending it in as I cannot see what I may have done wrong. I have built many diy kits from microphoneparts.com and diyre.com and have had little to no issues. Your kits seems pretty strait forward and I was able to do the builds with very little frustrations lol.