Converted Peavey Deuce issues

[Leo_Gnardo]

Sorry Leo, I should have mentioned that it was a rubber handled screwdriver with a metal shaft. No buzz on V1. When I get home today I will further troubleshoot.

We're trying to work it back from the power stage as mark enger suggests. So - it's screwdriver tip to your output tubes' pins 5, then drive tube V3 pin 2 & 7.

ALSO what's the bias voltage, screen grids & plates on your outputs. Not that it would result in strange noises you describe but if the output tubes are "choked off" by too much bias voltage = too little bias current, we're not going to hear any pop or buzz on the field tests we're suggesting.

[beasleybodyshop]

Ok gents, here is what i have:

im getting pops/noises on all tubes.

voltages:

V4

(GND) (3.11AC) (430v) (304v) (-37v) (303) (3.10AV) (GND)

V5

(GND) (3.11AC) (430v) (305v) (-37v) (304) (3.11AC) (GND)

pins 4 and six looks lower than spec. could this be why its not working?

EDIT:

I have also checked the 68K resistor to ground, my continuity shows no connection, so its not touching ground.

also, Im getting maybe .2 volts on the outer and middle lugs of the volume pots, it jumps around when i move them up and down.

[mark enger]

Are you sure your input jack are wired right? and are they grounded, v4 v5
seem suspect not sure on that though mark

[Leo_Gnardo]

Ok gents, here is what i have:

im getting pops/noises on all tubes.

voltages:

V4

(GND) (3.11AC) (430v) (304v) (-37v) (303) (3.10AV) (GND)

V5

(GND) (3.11AC) (430v) (305v) (-37v) (304) (3.11AC) (GND)

pins 4 and six looks lower than spec. could this be why its not working?

EDIT:

I have also checked the 68K resistor to ground, my continuity shows no connection, so its not touching ground.

also, Im getting maybe .2 volts on the outer and middle lugs of the volume pots, it jumps around when i move them up and down.

Yes those pin 4 screen grid voltages are looking mighty low AND so are the bias voltages on pins 5, besides why is any voltage showing up on pins 6? Let's see what you have in the power surprise, I expect a way big resistor between the main B+ and second HV node to explain those low SG voltages. When you do fix those SG voltages you'll also have to up the bias to compensate, because -37 V won't be enough for sure. All your hi voltage readings to the pre tubes will also increase. Please remind us - those outputs are 6L6 or EL34? I plumb forgot..

.2V on the volumes, somehow there's DC leakage to them. Does this go away when fully turned down? If it remains on the "hot" tab of the pot, it's coming from the stage driving the pot. That would first point to a leaky cap on the plate of the driving tube, or leakage through contamination on the circuit board - unlikely because it's new.

If both hot and wiper go to zero, it's coming from the stage following the pot. All your caps are new and presumed good, the only suspect left is the tube V2 or its circuit. Volumes down and a meter to the grid pin 2 of V2 will tell you if the tube's turning out the dodgy voltage. All the rest of the preamp readings look OK if a little low in the high voltages. Again, this will increase as you get the 2nd HV node up to where it oughta be.

Still don't see why squeeks & squeals might come out of the pre. With DC on the volume controls - yes that would make scratch & pop noises as you move them, and that will go away when the DC does.

[martin manning]

Is the screen (power tube pin 6's) connected to the right filter cap? Also, stand the 5k6 grid stoppers (pin 5's) on end to get them and the lead feeding them up and away from other leads.

Leo, the screen grid resistors are using pin 6 for a tie point.

[Leo_Gnardo]

Leo, the screen grid resistors are using pin 6 for a tie point.

I figured that was the case but did see slightly lower V reported on pins 6. I'll take it as a small measurement error then.

[beasleybodyshop]

I have required all the wires coming off the input jacks. No change there.

When I get home from work today I will check the pot voltages and track down the big resistor dropping the screen grids. I was considering maybe shooting a short video to show what kinds of sounds I was getting. I would occasionally get weird sustained squealing when I was testing preamp pins.

[Leo_Gnardo]

I would occasionally get weird sustained squealing when I was testing preamp pins.

To be expected especially on grids.

[beasleybodyshop]

Progress has been made!

I have double checked all my grounds including the ones off the power tube sockets.....both of the grounds were questionable. After resoldering, input jack one on channel one started working! SG voltages are now around 420v. However none of the other jacks/channels work yet.

Also when i turn up the presence control, i get a high pitched squealing.

Channel 2 volume pot is the one that keeps squealing/scratchy. I resoldered all my connections on V2, but it still makes funny noises. When i get home today i am going to re-do all my input jack connections.

[Leo_Gnardo]

Also when i turn up the presence control, i get a high pitched squealing.

Channel 2 volume pot is the one that keeps squealing/scratchy. I resoldered all my connections on V2, but it still makes funny noises. When i get home today i am going to re-do all my input jack connections.

Progress - is good to hear! What was pushing those SG's down'? You have re set bias voltage I hope.

Pres. control - well we still aren't sure which way is up with the OT polarity, so re swap the plate wires & see if it stops squeeking or not.

If ch 2 volume is crackly due to DC and ch 1 is not, then the DC is likely NOT being back fed from V2's grid. Here's my logic - the wipers of Vol1 & Vol2 are joined by a pair of resistors (mixer) and off to V2 grid. If there was DC developed on V2 grid it would show up on both volume controls. It isn't so the problem is elsewhere. Leaky cap from the Vol 2 preamp is now the suspect.

Onward & upward!

[beasleybodyshop]

Leo, is the preamp for volume 2 one half of V1? I will try swapping around OT wires tonight, but let me get something straight:

One side of the OT has the red/white/blue wires for the power tubes and the one connection on the board. I think I checked they were 3.6K ohms each. Are these supposed to be interchangeable? Every time I've switched them around nothing different happens.

[Leo_Gnardo]

Leo, is the preamp for volume 2 one half of V1? I will try swapping around OT wires tonight, but let me get something straight:

One side of the OT has the red/white/blue wires for the power tubes and the one connection on the board. I think I checked they were 3.6K ohms each. Are these supposed to be interchangeable? Every time I've switched them around nothing different happens.

If you built it in the standard way, yes each pre is one triode of V1.

Now let's jump to the output. There's a - hopefully negative - feedback loop. IF inadvertently, there's a positive loop, then it's much easier to set the output circuit into oscillation. The frequency could be anything, a low freq pup pup pup pup pup, a midrange howl, a hi frequency squeal. You said dialing up the presence led to a squeal. Within 5 minutes, swapping the wires on the plates, you'll either get rid of that squeal, or you'll hear something even worse. Let's hope the swappage sorts things out. BTW the first two tubes won't make any diff in this because the FB loop is to the drive tube V3. So, swap & report, better or worse. Without test equipment this is the field fix method.

Not being familiar with the color coding of your OT wires, just make sure it's the center tap you have connected to the B+. Should measure more or less equal ohms from CT to each plate wire. 3600 ohms must be the AC impedance. When you measure DC resistance it could be as little as 1/100 that much.

If it turns out you didn't have the CT to B+ don't worry, just set it right. I've made that misteak too. Put "DOH!" smiley face here... I'm sure others have as well.

[Reeltarded]

Earlier you swapped the OT primaries I think I remember.

^^^^^^ Leo is right. It's backwards and if you swap them back you'll have an amp.

[beasleybodyshop]

Here is the spec sheet for my transformer:

http://www.classictone.net/40-18025.pdf

What does the dot by the blue wire indicate? Negative? Ground?

I done went and re-did all them lead dresses last night 'till the early morn So hopefully I've completely eliminated that as an issue.

[Leo_Gnardo]

Here is the spec sheet for my transformer:

http://www.classictone.net/40-18025.pdf

OK, according to their print, white is the center tap.

Note - many have been fooled, thinking red is CT as it often is. Including me. But not always. (Fender's color code always sticks in my head. Marshall just "has to be different.") And a check with ohm meter will always confirm which wire is the CT. Sometimes - rarely - there's an error.

3600 ohm AC impedance across the whole winding.

What does the dot by the blue wire indicate? Negative? Ground?

I done went and re-did all them lead dresses last night 'till the early morn So hopefully I've completely eliminated that as an issue.

Dot indicates direction of winding. So you can predict polarity of output.

If you're still having squeek with presence turned way up, and swapping OT primary polarity isn't getting anywhere, you might try running the FB from different taps on the OT's secondary. Whichever gives you stable operation, is good. BTW with no FB you should have no oscillation problems but also will have no presence control. Removing the FB connection will bump up your gain a bit too. If you can't get the presence to behave no matter what, you might consider letting the output run without the FB loop, wide open Texas style yee-hah!