Tweed Tremolux build 5G9, need some help !

[Daver]

Second stage? Do you mean the second tube as in the phase inverter? Crackling is almost always a poor connection but could be a bad resistor or cap. Even then it's usually a bad connection internally to the component. You'll need to touch up all the solder joints on the tube socket and board. You can try pushing the wires around and pushing on the components on the board and see if you can make it crackle. Then you've found the problem.
Dave

[tweedmarmot]

Yes, second tube is what i was meaning...

Now the crackling noises are solve. That was, as you said and tubeswell said, a bad solder joint on a ground...

it sound really good, but the tremolo is not working ... !? I use the same fender foot switch that I use for my other tremolux..

[tubeswell]

it sound really good, but the tremolo is not working ... !? I use the same fender foot switch that I use for my other tremolux..

Check that you have all the resistors and caps required in the LFO RC circuit and that you have them wired up properly. Its a common mistake to miss or miswire one of the wires on the back of the board

[tweedmarmot]

Hi guys, taking the voltages on the trem 12ax7, I now have
1-240
2- 0!?
3- 1,7
6- 362
7- 240
8- 241

I guess it's not "normal" that the grid 2 is at 0V.. is it ?

Again, thanks you for the great help !

Stephane

[tweedmarmot]

Ok first, lets get some voltages since I have work a lot on it..

from left to right

6V6
3- 349
4- 362
5- -22,2
6- 365

6V6
3- 350
4- 362
5- -22,2
6- 365

trem 12ax7
1- 240
2- 0
3- 1,7
6- 362
7- 240
8- 241

phase inverter 12ax7
1- 204
2- 169
3- 26,4
6- 139
7- 17,5
8- 26,4

12ax7
1- 157
2- 0
3- 2,4
6- 151
7- 0
8- 2,4

That looks better but still no trem ... !?

I have double check caps and resistors and they look ok .. I dont want to unscrew the board and take it out until I have no more choice ..

Any ideas ?

Thanks !

Stephane

[tubeswell]

trem 12ax7
1- 240
2- 0
3- 1,7
6- 362
7- 240
8- 241



That looks better but still no trem ... !?

I have double check caps and resistors and they look ok .. I dont want to unscrew the board and take it out until I have no more choice ..

Any ideas ?

Thanks !

Stephane

Those voltage all look in the ballpark. So you have a wiring error. With the amp off and unplugged, get out your R-meter and look for DC connections where they should be* in the trem oscillator and CF stage.

* i.e.: LFO plate to .03uF, .03uf-.01uF junction to speed pot input, speed pot output to 1M, 1M-.01uF junction to LFO grid, etc etc. Get the picture?

[Daver]

You had some trouble early on with the bias arrangement. Since this is a bias vary Trem type, could there be something wired incorrectly there?

[tweedmarmot]

Hey !

That 220k resistor connected to pin 8 of the trem tube, measure 240k is it ok ? ( i figure that +/- 20% is ok ???)

And that capacitor ,03 pF is it ok if it's a 333k ? (from sozo)...

again, thank you for all the help.

Stephane

[tubeswell]

"333" is 'E-series' code for 33nF (33,000pF, .03uF), which is 'correct' there. The plate resistor is okay at 240k. I'm picking its a wiring error. Have you checked for dc-continuity with your R-meter?

[tweedmarmot]

Well, the tell the truth, I am just trying to figure out how the tremolo work on the 5G9..

And I am also trying to figure some acronyms like CF (cathode follower) and LFO plate and trying to see what they look like in the layout and schematic...

[tubeswell]

The LFO stage is an inverting stage (so the plate signal is 'naturally' 180 degrees out of phase with the grid). The RC network of resistors between the plate and the grid of the LFO puts the signal a further 180 degrees out of phase. When you hook up the plate to the grid the stage self oscillates, and you tap into that 'trem wiggle' at the LFO plate, where the grid to the CF stage is connected (NB: the CF stage is just an ordinary CF buffer stage, and its purpose is to drive the 6V6 grids with a good supply of wiggle current, but the CF doesn't do the oscillating - that part is done by the LFO stage).

Now if the LFO grid and the plate are not connected via (the RC network of) the three (.03, .01 .01) caps and the two 1M resistors and the 2MRA pot, then it won't oscillate. So the first thing to check is that you have all the wires where they should be to form this RC network. It goes: plate to 0.3uF (with 2M pot to ground), then .01uF (with 1M to the cathode), then .01uF (with 1M to ground) to the grid. You also have to have the 220k plate resistor connected between the plate and the High Tension (HT) supply, and a 1k5 cathode resistor (bypassed with 22uF) connected between the cathode and the ground for it to work (and of course, the heater's filament has to be supplied with 6.3VAC). That's the LFO stage. Also check that you haven't accidentally grounded the RC network to the trem footswitch jack's ground lug. It needs to be going to the jack's tip lug for the trem to work. When that connection is switched to ground, as intended through the footswitch, it kills the oscillator)

The CF buffer is direct-coupled to the LFO plate (LFO plate to CF grid) and the CF plate is directly connected to the HT supply. The CF cathode is connected to the 220k cathode load resistor, and the cathode of the CF stage is connected to a coupling cap which is connected (via a 1M dropper resistor) to the depth pot input lug. The depth pot wiper goes to the 2 x 220k grid load resistors for the 6V6s, and the depth pot ground lug goes to the (-ve VDC) bias supply. As LFO plate is directly coupled to the CF grid then the CF grid follows the LFO plate's trem wiggle up and down, and so then does the CF cathode. This trem wiggle is moderated through the 1m and the 250k depth pot (which is basically a resistive divider) that controls the strength of the trem wiggle that is sent to the 6V6 grids.

[tweedmarmot]

You also have to have the 220k plate resistor connected between the plate and the High Tension (HT) supply, and a 1k5 cathode resistor (bypassed with 22uF) connected between the cathode and the ground for it to work (and of course, the heater's filament has to be supplied with 6.3VAC).

22uF !? I have a 25 uF there .. ( as on the schematic ) is it ok ?

[tweedmarmot]

Am I suppose to have any voltage that goes from where the .03 uF and the .01 uF of the LFO to the 2M speed pot input lug ? because i have about 0,01 moving to 0,02 ..

[tweedmarmot]

one more thing, when turn on the tremolo with the foot switch, I can see the 6v6 grid oscillating from -24,5 to -25,3 and getting slowy stable at -24,8.....

[tubeswell]

test the caps in the RC network for DC leakage.