Ugly distortion with tube amp when you play

[g1]

All voltages on both sides of V1 are suspect. Look at V2, all the same component values on the side being used. Those are your rough target voltages for each side of V1. The B+ goes through an extra dropper for V1, so they may be a little lower, but should be something close.

[The Dude]

Agreed, yes, there is definitely a problem at V1. Check all the wiring, component values, etc. Being a freshly built kit and not a normal repair, there could be any number of problems there. Look at the circuit as if you were building it from scratch and verify that all is correct.

[Ampzone]

So I replaced the OT with a Marshall style 50w OT. It was a touch stronger sounding? but it still is clipping when you played chord solidly or picked a note with any real bite it got nasty and choked off sounding. So maybe we can rule out the OT. Can we assume the PT is ok? I see solid heater voltage throughout.


If so now back to the preamp section. I may have to lift this whole board up to see what gives underneath. Back to it in the AM.

[Ampzone]

I noted that V1 has its grid tied (pins 2-6). So it does not match the schematic G1 found exactly. Looking at his source the closest I can find to this build is:
http://hiwatt.org/Schematics/DR_Pre2InputSAP.pdf

I am in the process of removing the board so I can see whats tied together, I'm hoping its some wiring issue or cold solder joint.

I ruled out a bad OT but should the PT be suspect?

[Jazz P Bass]

Fix V1.
Not too sure why you are jumping around.
Now you suspect the PT?
Troubleshoot the problem.

[Ampzone]

At this point I suspect anything, maybe not the OT now I am trying to get up under the board to see what is around V1, I was just noting there is jumper between pin 2-6 on V1.

[g1]

Please redo your V1 readings and post them.

Check that pins 3 and 8 are going to the right places and their resistors are correct value, according to the most recent schematic you posted in post #64.

[eschertron]

I am trying to get up under the board to see what is around V1, I was just noting there is jumper between pin 2-6 on V1.

How many input jacks are there on this amp? If pins 2 and 6 are tied together, sounds like there aught to be only 2 input jacks, and maybe a matchless style input section. The schem in post #64 definitely WON'T have the grids tied. Hope that helps in finding the right print!

[Ampzone]

How many input jacks are there on this amp? If pins 2 and 6 are tied together, sounds like there aught to be only 2 input jacks, and maybe a matchless style input section. The schem in post #64 definitely WON'T have the grids tied. Hope that helps in finding the right print!

Correct only two inputs.

[Ampzone]

Please redo your V1 readings and post them.

Check that pins 3 and 8 are going to the right places and their resistors are correct value, according to the most recent schematic you posted in post #64.

I will check directly, at the moment I am trying to lift the board up to see what is going where, so I have some leads unsoldered. So far I can say the pins on V1 2 & 6 are linked.

[g1]

The schematic in post #64 does have 1 & 6 connected. Maybe that is where the error is.
You are going to have to draw up a schematic of how V1 is currently wired in that amp.
Either way, it does not match any of the ceriatone kits. Can you find out from the owner what exactly it's supposed to be? And which layout the builder used?

[eschertron]

The schematic in post #64 does have 1 & 6 connected. Maybe that is where the error is.
You are going to have to draw up a schematic of how V1 is currently wired in that amp.
Either way, it does not match any of the ceriatone kits. Can you find out from the owner what exactly it's supposed to be? And which layout the builder used?

OK. I see now. Not only do I lose count after 5 (fingers, y'know) but there's a typo on that drawing. If pin 7 on your amp's first tube connects to the inputs and pin 6 goes to pin 2 then it is similar to the schem in post #64 with the two triodes swapped (and valve correctly numbered!). In any case, +1 to drawing out what is there exactly so I don't have to guess and make a fool of myself any more (than usual).

[Ampzone]

The schematic in post #64 does have 1 & 6 connected. Maybe that is where the error is.
You are going to have to draw up a schematic of how V1 is currently wired in that amp.
Either way, it does not match any of the ceriatone kits. Can you find out from the owner what exactly it's supposed to be? And which layout the builder used?

I did, apparently it was/is some Ceritone parts (spelling) and not a whole kit. It started out to be a Dr103 amp with more gain and did not work.

[The Dude]

Regardless of that, the builder must have used some kind of scheme to build the thing? You don't just go blindly soldering parts together without something mapped out.............or, in this case, maybe you do?

[g1]

Some good pictures of the V1 area would be a great help.