A little help please [resolved]

[Karl5150]

I thought I'd start a new topic to attract attention. I finished the build and ran the resistance checks and all was well until #45.
It should be 0 Ohms, but it reads like the other side, varying readings up into the mega ohms.
I re-flowed both 45L and 45U
Bad cap?
Thanks for any help on this.

 

[howardnair]

Karl. I have the first version but if that is a resistor across the electrolytic it looks broken

 

[Karl5150]

Thanks for looking, it is a bad phone picture, just to show proper location and orientation. 45U is on the right end of the strip, striped side of the electrolytic, nothing else attaches to 45U. All the other electrolytic caps read 0 in the striped side.
Still puzzled

 

[Paul Joppa]

It appears to me that T45 and T42 might read high or low depending on which meter terminal is grounded.

 

[Karl5150]

Paul, thanks for the reply. I tried 2 meters, both terminal alignments but 45U always acts like the unstriped side of any of the electrolytic caps. Still stumped.

 

[Paul Birkeland]

45 and 42 are connected, and will not measure 0 Ohms.  This is an error in the manual.

-PB

 

[Karl5150]

Thanks Paul. I will proceed with the V checks.

 

[Karl5150]

I went ahead with the power-up and voltage checks. All tubes and LEDs glow, no sparks, no smoke & no odd smells (from the amp anyway)
Three voltages came up way off:

#4-  Manual: 0V                Actual: up and down, max observed 58V
#7-  Manual: 170-230V      Actual: up and down, max observed 290V
#17- Manual: 0V                Actual: up and down, max observed 48V

 

[Paul Joppa]

If you observed this by conecting the meter, then turning on the amp, then turning it off to change the meter connection, and repeating this sequence, these are reasonable numbers - but what the manual reflects is the steady state voltage after the turn-on transient, which you have not provided.

If on the other hand you left the amp on for all the voltage checks, and the steady-state includes fluctuation of these maximum magnitudes without ever settling on a steady value, then there are some severe problems.

Please let us know how you made these measurements.

 

[Karl5150]

Paul,
The voltage checks were all made with the same auto range meter (Klein MM200) with the common clipped to the safety ground tab. The numbers reported were recorded after running through all the voltage checks and determining they were the only anomalies, the amp being powered on for several minutes.
I went through the resistance checks again and all AOK (the issue with #45 being solved earlier) I will do another step by step visual check with manual to see if I missed something the first couple times through.
Again, thanks for the quick feedback.

 

[Paul Birkeland]

#4-  Manual: 0V                Actual: up and down, max observed 58V
#17- Manual: 0V                Actual: up and down, max observed 48V

Are you 100% sure about this?  There's a 249K resistor between 4 and 5. 4 is grounded, and the 249K resistor is supposed to hold 4 to ground.  Are you seeing some mild fluctuations that might be 58mV? (or 48mV?)

#7-  Manual: 170-230V      Actual: up and down, max observed 290V

That may settle after the amp has been run for a while.  If you want to check, swap the 12AT7's and that voltage should move over to T14.

-PB

 

[Karl5150]

I went through the manual again, step by step visually confirming all locations/connections. I even ran the transformer output checks again: As with the resistance checks, all good.
After work I will check Vs on #s 4 & 17 to make sure I didn't misread the meter.
As for #7, I must be, in some small way, catching on a bit because my plan was, as you suggest, to swap tubes, since #14 reads a steady 191V.
Again, thank you guys for the support.

 

[octavian]

Hi Karl,

I just finished mine last night and all of the voltages checked out, so I suspect it's not an error in the manual, if that helps!

 

[Karl5150]

Octavian, you got 0 Ohms on #45?

 

[Karl5150]

My bad. I see you said voltages. Thanks

 

[octavian]

I had the same readings as you as far as resistances went, so 45 is an error. I found one more error which I'll bring up when I get home tonight and can check out my resistances sheet. Somewhere in the 30s if I remember right. Something that's a star should be 0 as it's on the ground bus.

 

[Strikkflypilot]

VERY good looking build, Karl!

 

[Karl5150]

Thanks, looking fwd to getting the V #s good and giving a listen.
Man is Octavian's workspace clean and uncluttered, I'm betting the finished product reflects that attention.

 

[octavian]

Hah! I totally didn't push all of the junk to the other side of the table so it would be out of the shot!

 

[Karl5150]

Thanks everyone, call this one solved. The only problem was with my ability to read a meter. (Oh yea, the little m means mili...)
The driver tube must have liked being reseated cause now I'm getting about 215 out of one and the other is still at 190.
Hooked up and playing on the bench. Just a little scratchiness (not related to any controls) the kind that immediately starts to cook out. Gonna just let it run for a while.
I guess I have to clean up the bench so I can put some clear coat on the base.
Thanks again