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Hi I've just finished my first 18 TMB build thanks to help from this board, many thanks for that.

Are my V2 numbers on the low side?

V2- pin1 149
pin3 0.94
pin6 265
pin8 150

my guide gives pins 1 and 8 nearer 180

the rest of my numbers appear to be within spec, any ideas?

Cheers

Ya that is a little low.. What do you have at the + end of the 16uf cap adjacent to V2?
Stew
OOps never mind I see 265..hmmm... Hows voltages on V1? Is that 100k across the tube socket (v2) correct? Not damaged ect.
Stew

101k across the V2

V1 numbers

pin1 149
pin3 0.99
pin6 147
pin8 0.95

V3

pin1 207
pin2 54
pin3 79
pin6 208
pin7 53
pin8 79

V4 & V5

pin3 12.8
pin7 354
pin9 336

V6

Pin1 310
pin3 367
pin7 310


cheers

Hmm ..OK..check the V on pin 7 of v2. And the 8.2K resistor near the powersupply end of the board.
Stew

The V on V2 pin7 is 149 and the 8.2k power end is reading 8.08k

cheers

dave

Very interesting
Could you check the 3 tMB pots and make sure there's no dc on any of the contacts.

The TMB pots check out ok, no DC

cheers

dave

The 100k on the plate of V2 (pin1) is indeed a 100K?

Yeah it measures 101k,

time for a cup of tea n some biscuits

cheers

dave

Have you tried swaping tubes and see it the problem follows?

Yes I tried it but the problem stays on the number 2

cheers

Dave

Well I'm grasping at straws here.. .but are all your grounds connected to that copper buss and is that buss connected to the chassis near the i/p jacks. It's almost like everything is correct except that the measurement rederences are offset
Unless phil or stephen can chime in you might have to upload some good clear photos of the board/tube sockets.
Stew

OK, I think the ground at the cap connected to pin 8 is not grounded properly. resolder. test with continuity meter. This is why you have high voltages on pin 8. that is throwing the rest of that triode off kilter too.

_________________
Stephen
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Ok, I've resoldered all the grounds, checked the bus bar & star points, checked the continuity all good, the low voltages are still there.
V2 - Pin 8 & pin1 still only showing 150, and only 0.94 on pin3

cheers

dave

Just a quicky....what's your filament voltages?
Also can you check the Rs on both cathodes of V2 pins 3 & 8.

6.7 across them all for the heaters

For the resitamce on the cathodes do I measure across 3 & 8?

cheers

No ..cathode to ground (power off of couse).. Just trying to figure out if that 1.5 v you have vs the proper 0.9-1.0v is caused by an incorrect cathode resistor.

If that checks out power her back up and check for DC on the grid (pin 2 V2).

I think I should have 1.5v but I've only got 0.94 on pin 3

resistance on pin 3 is 863 & pin 8 is 58k

I'm not seeing any DC on pin 2, to be clear pin2 power on to ground?

Dave