Tweedle Dee weak output

[philbard]

Hey gang,
Built my first Tweedle Dee, using the Tweedle D Mod schematic from the files section, with the cascade switch added. It appears to be working but the output to the speaker is very weak. I can barely hear the guitar when the channel and master volumes are cranked to 8. First of all, here are my voltages:

Tweedle Dee Voltages
12AX7A, 6V6GC, GZ34

1 2 3 4 5 6 7 8 9
V1 164 1.34 177 1.18
V2 218 1.43 301 3.34 7.6
V3 27 373 351 25mv 25mv 27
V4 27 375 351 16mv 16mv 27

Injecting a 100mv 1K Hz signal to the input jack with the channel and master volumes at noon I'm getting 2v after the coupling cap off V1 and 1.7v out of the phase inverter to the power tube screens. Speaker jack tip to ground is 0v, not sure if this is the issue or that its an incorrect way to measure output.

From what I can hear, the character of the signal reflects the design of the amp, gain channel gives me overdrive early on, clean is pretty clean til the volume is ramped up, the cascade switch behaves as it should.

Any thoughts? Gut shot attached...

Cheers,

Tweedle Dee Final.jpg

[philbard]

Arg, blew the voltage list. Here's a jpg...

Voltages.jpg

[sluckey]

V2 pin 6, 7, and 8 voltages are way messed up. What is the value of the plate resistor indicated?

[philbard]

V2 pin 6, 7, and 8 voltages are way messed up. What is the value of the plate resistor indicated?

109K, and the neighbor is 98K.

[philbard]

Also, forgot to post the power supply voltages:

B+1 384v
B+2 352v
B+3 317v
B+4 298v

[sluckey]

109K? That's fine. But I expected to see Brown-brown-black-orange. I can't see that in your pic. What colors do you have, top to bottom?

Also, what resistance do you measure from V2 pin 8 to ground (probe directly on the tube socket pin)?

[pompeiisneaks]

I don't see the connection to ground between the V2a and the ground side of the Inst Vol pot... maybe moot since I think I see that going to the buss bar, but it's just something worth looking into. There also are a couple jumpers that are not visible due to likely being underneath your board, but in the layout it shows a jumper between the 56k and the 33k on top of hte board... I'm guessing yours is underneath... just confirming, otherwise there's no ground reference for the second half and might cause the problems Sluckey noted with voltages being off for V2b

Also it appears to me that your cathode resistor for V1b is upside down. I don't think that would cause the issue, but it means you've got an error there for sure... (i.e. the ground connection is in the middle of those two 25uf/25VDC caps and you've got the + connected on the one on the side closest to the instrument/pot panel. )

Might just want to triple check that all grounds are as expected, and that the jumpers under board are where they're expected to be etc.

~Phil

[philbard]

109K? That's fine. But I expected to see Brown-brown-black-orange. I can't see that in your pic. What colors do you have, top to bottom?

Also, what resistance do you measure from V2 pin 8 to ground (probe directly on the tube socket pin)?

It's hard to see from the gut shot, here is a close up of one. It is indeed Brown Brown Black Orange. Resistance V2 pin 8 to ground is 98K.

110K.jpg

[philbard]

I don't see the connection to ground between the V2a and the ground side of the Inst Vol pot... maybe moot since I think I see that going to the buss bar, but it's just something worth looking into. There also are a couple jumpers that are not visible due to likely being underneath your board, but in the layout it shows a jumper between the 56k and the 33k on top of hte board... I'm guessing yours is underneath... just confirming, otherwise there's no ground reference for the second half and might cause the problems Sluckey noted with voltages being off for V2b

Also it appears to me that your cathode resistor for V1b is upside down. I don't think that would cause the issue, but it means you've got an error there for sure... (i.e. the ground connection is in the middle of those two 25uf/25VDC caps and you've got the + connected on the one on the side closest to the instrument/pot panel. )

Might just want to triple check that all grounds are as expected, and that the jumpers under board are where they're expected to be etc.

~Phil

The 2 gain pots and the Master Volume pot are grounded to the bus bar. The jumper between 56K and 33K is indeed under the board and there is continuity, just checked.

Bingo on the V1b Cap! It only arrived late yesterday and I was tired when I put it in. Will reverse and try again! Thanks for the sharp eye....

[philbard]

I don't see the connection to ground between the V2a and the ground side of the Inst Vol pot... maybe moot since I think I see that going to the buss bar, but it's just something worth looking into. There also are a couple jumpers that are not visible due to likely being underneath your board, but in the layout it shows a jumper between the 56k and the 33k on top of hte board... I'm guessing yours is underneath... just confirming, otherwise there's no ground reference for the second half and might cause the problems Sluckey noted with voltages being off for V2b

Also it appears to me that your cathode resistor for V1b is upside down. I don't think that would cause the issue, but it means you've got an error there for sure... (i.e. the ground connection is in the middle of those two 25uf/25VDC caps and you've got the + connected on the one on the side closest to the instrument/pot panel. )

Might just want to triple check that all grounds are as expected, and that the jumpers under board are where they're expected to be etc.

~Phil

Phil,

Correcting the reversed cap has the amp working now, THANKS! The V2 voltage to pin 5 is still way too high, though, so will have to do some more sleuthing....

[ijedouglas]

The V2 voltage to pin 5 is still way too high, though, so will have to do some more sleuthing....

Heater voltage? Pin 5?

You may also want to check and potentially swap out that cathode cap.

[philbard]

The V2 voltage to pin 5 is still way too high, though, so will have to do some more sleuthing....

Heater voltage? Pin 5?

You may also want to check and potentially swap out that cathode cap.

Heater is 3.12v Pin 5 to ground, where it should be I believe. Yeah the cap could have been damaged perhaps

[philbard]

Here is the layout I worked from, cobbled together from the Dumble File copy, RobRob's and also Fred's modified TD. I ended up putting the power switch on the back and may add a Standby.

Tweedle Dee Deluxe Bard.jpg

[fred.violleau]

Hey Phil, congrats on your build!

Side note my coupling cap on V1A is .005 if instead of 0.02uf, and Marcus put this on a switch so he could have the 0.02 for single coils and the .005 for humbuckers.

Cheers!

Fred

[philbard]

Hey Phil, congrats on your build!

Side note my coupling cap on V1A is .005 if instead of 0.02uf, and Marcus put this on a switch so he could have the 0.02 for single coils and the .005 for humbuckers.

Cheers!

Fred

Thanks Fred, I learned quite a bit from your build threads and also from the videos you put up. My build is a little heavy in the bass with buckers, sounds really good with single coils, so the switchable cap option might be a nice addition as I play with both types of pickups. The bigger bass does sound good at home volume levels but I suppose could be too much for a gig.

Still don't have a faceplate for it but wanted to wait until I was sure of the positions for the controls.

IMG_7535.jpg