Converted Peavey Deuce issues

[beasleybodyshop]

Hello everyone! Awhile back I started converting a Peavey Deuce combo into a JMP 50 watt: https://tubeamparchive.com/viewtopic.ph ... ight=peavy

Now I have gotten everything wired in, I'm running into a problem:

When I power the amp up and switch it off standby, I am getting no sound whatsoever from either channel - no hiss, no hum. When I move the volume pot on channel 2 I get weird, insanely loud screeching noises. Whenever I power off the amp, after a second or two after i kill the switch it makes this crazy "growling" noise and then shuts off. photos are attached. Any help would be appreciated.

PS - I have already swapped tubes around, and double checked with known working pre/power tubes.

I have reflowed all the solder joints on the tube sockets.

Preamp pin voltages:

V1 (170V) (signal) ( .74V ) ( 3.25 ) ( 3.25 ) (160.5V) (signal) (2.4) (3.24)

V2 (146V) (sig) (1V) (3.24) (3.24) (269V) (146V) (148V) (3.24)

V3 (210v) (sig) (35.4v) (3.24) (3.24) (206v) (sig) (35.5v) (3.24)

Thoughts?

[Leo_Gnardo]

When I move the volume pot on channel 2 I get weird, insanely loud screeching noises.

Thoughts?

Cool! A Ted Nugent solo and you don't even have to plug in!

But seriously now, the preamp voltages all look sensible. So far so good.

Still, let's do this section by section. Power amp first. I'd remove V1 & V2, and buzz test the power amp by touching the grid of v3 with a metal probe (with insulated handle) or screwdriver tip. The grid, that is, driven from the previous tube, dunno if that's pin 2 or 7. Should get you a nice healthy buzz from the speakers. Might not be very loud but should be audible. Try that, then we'll see what next.

Also what test equipment is available? You have a DVM I'm sure, how about scope, signal generator?

No chance of miswiring to the input jacks? I've run across hot/ground swaps, heck done that myself.

[M Fowler]

Swap the OT wires to the power tube sockets around, NFB causing this issue.

[beasleybodyshop]

Thanks for the responses guys. Here is what I have done:

I have swapped the blue and red wires around on the OT to the tube sockets. Still squeals.

I have pulled V1 and V2 preamp tubes, and powered it up, took it off standby. turned up both volumes, touched V3 grid (pins 2 and 7) with a plastic screwdriver, no noise.

Leo, all i have is my DVM, no signal generator or scope

also i double checked the input jacks, it is wired as per the metro amp layout.

[M Fowler]

Recheck all wiring for correctness based on build manual and layout on last page.

I would make sure you wired that standby switch correctly.

[Structo]

Do you have that bridge rectifier grounded?

Touch your voltmeter probe to the V1 plates, Pins 1 & 6.

Same on V2, you should get some pops from the speaker.

If not then the tubes are not passing signal.

[beasleybodyshop]

Do you have that bridge rectifier grounded?

Does the negative lug need to go to ground? According to the layout on the Metroamp instructions there is no wire going to that lug.

and when i touch the pins on V1 and V2, do i need to pull the tubes first or leave them in?

[M Fowler]

They are only using two of the four diodes in that bridge diode block so no negative is connected. You have it wired correctly.

[cbass]

Is there any voltage at the volume pot?

[cbass]

Is there any voltage at the volume pot?

[Leo_Gnardo]

I have pulled V1 and V2 preamp tubes, and powered it up, took it off standby. turned up both volumes, touched V3 grid (pins 2 and 7) with a plastic screwdriver, no noise.

Plastic handle (to keep you out of shock land), metal blade. An all-plastic tweaker-driver won't do for this.

Volumes won't make any diff here because you're applying your test signal (buzz) after the pre stages and pre tubes are out anyway, just output drive tube is in.

- - - - -

If you do get a buzz test positive with V3 in place, then plug in V2 & do the same touching pin 2. Since this is the EQ drive, your EQ positions will make a difference in the buzz tone. Might start with 'em all the way down so you don't startle yourself.

Lets see how that goes.

[beasleybodyshop]

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.

And thanks for all the help guys. Your one in a million.

[cbass]

Do you have that bridge rectifier grounded?

Does the negative lug need to go to ground? According to the layout on the Metroamp instructions there is no wire going to that lug.

and when i touch the pins on V1 and V2, do i need to pull the tubes first or leave them in?

You need to have the tubes in to check for "pops" and to get meaningful voltages Like Leo said start with V3 then put in V2 and then V1

[cbass]

damn DP

[mark enger]

Start with a pop test on powertubes, probing powertube sockets should produce a pop, then work your way back from v3 to v2 to v1 they all should pop but powertubes have to first, also your grounded input wires could be causing you trouble check the backside of the 68k R and see if they read to ground they should'nt, and i can't see if your input jacks them self are grounded, everything look pretty good im sure you'll get it if your allowed post the layout mark