Zwreck help!!!!

[jlprry]

Hey

First time posting, but long time lurker. Love this forum and have learned more from it than any other resource i could find..thanks!!!

My issue is with the Zwreck I have built (pics attached). I am getting very, very low volume out of it, maybe an 1/8 of what it should put out, if not less! Also the very little sound I do get is weak and muffled, with very little highs, and practically no gain. As I turn the volume up there is a low frequency hum as well.

Now I should say that the iron I using is recycled iron, so it is not exact spec for sure, but I have tested them and I should be at least getting a reasonable amount of sound. I have even tried different OT's with the same result. Basically the amp sounds choked, like something is impeding it.
Here are the voltages I have. Note that the pt is about 330-0-330.

v1:
pin1-296
pin3-2.5

v2:
pin1-263
pin2-166
pin3-166
pin6-166
pin8-1

v3:
pin1-253
pin2-38.5
pin3-56.5
pin6-246
pin7-36
pin8-57

v4,v5:
pin3-10
pin7-335
pin9-342

v6,v7:
pin3-10
pin7-337
pin9-343

I realize that my screens are higher than my plates, but I wouldn't think that that would cause my problem, but maybe! Also note that I had originally put in a 1MEG audio pot in place of the 500ka for the volume, but swapped it for a 500ka I found (a smaller one) which made no difference at all.

Hopefully I don't sound like a totally noob, and there just something obvious that I am missing. either way any help would be greatly appreciated!
Thanks
Jody

[Phil_S]

Voltages indicate an obvious error on V2. Can you post or direct us to the schematic you are using. If there is a layout, that's helpful, too. There are often many variations on a design and it helps a great deal to be sure what needs to be verified.

Also, if the B+ (plate supply) rail is typical, it is unlikely it was meant to deliver 296V to V1, then 263 to V2. This is usually the other way around. Let's see the schematic you're working with, please.

[jlprry]

Thanks for the reply!


I don't have a schematic or layout per se. I am basing the dropping string on the info from this thread:

https://tubeamparchive.com/viewtopic.ph ... k&start=75

specificlly about how the dropping string is paralleled from the screen supply node, which as I understand it would make the plate on v1 higher than the plate on v2, but i could be wrong!!

Here is a pic of the actually zwreck I was basing mine on.

Thanks
Jody

[Fischerman]

I think you have pin 1 of V1 connected to the wrong end of the 220k plate resistor. That explains the too high voltage on pins 1 and 3 of that tube (and the 'almost' no sound).

[jlprry]

WOW!!! That is why I love this place!!! Thanks you very much...I totally missed that! It just goes to show sometimes you need a fresh set of eyes! I will fix that tonight and let you know the result.

Thanks again
Jody

[Fischerman]

WOW!!! That is why I love this place!!! Thanks you very much...I totally missed that! It just goes to show sometimes you need a fresh set of eyes! I will fix that tonight and let you know the result.

Thanks again
Jody

We all do it, sometimes that's all we need, fresh eyes. I'm about to build one of these myself so I may need the favor returned! I predict you'll be playing a lot of guitar tonight.

[jlprry]

Yeah I do it all the time, but ususally I pick up on it! I hope your prediction comes true!!! Hopefully your Zwreck goes smoother than mine. Thanks again!!!

[M Fowler]

You have to pay attention to how the B+5; B+4; and B+3 are wired.

B5 black wire to B2 cap
B4 brown wire to B3 cap
V2 orange wire to B4 cap


Mark

[DR.Z]

I'm a little late to the party, but it seems Jody was in good hands that sus'd out his problem, excellent.

DR.Z

[Cliff Schecht]

Good looking build, minus the missing grommets on the transformers. I see the heatshrink around the protruding wires but still not as safe as fat rubber surrounding the sharp corners..

[jlprry]

You have to pay attention to how the B+5; B+4; and B+3 are wired.

B5 black wire to B2 cap
B4 brown wire to B3 cap
V2 orange wire to B4 cap


Mark

Thanks Mark! I will double check that tonight. I am pretty sure I have it right, but I am not 100%, so thanks

Jody

[jlprry]

I'm a little late to the party, but it seems Jody was in good hands that sus'd out his problem, excellent.

DR.Z

Thanks for even taking a look Z. It is cool that you come on here and help us hacks out! You are the man!!!

Jody

[jlprry]

Good looking build, minus the missing grommets on the transformers. I see the heatshrink around the protruding wires but still not as safe as fat rubber surrounding the sharp corners..

Thanks Cliff! Hopefully it will be up and running by tonight!

As for the grommets, I actually have grommets for all the trannie holes, you just can't see them...

Thanks
Jody

[Cliff Schecht]

Cool, I obviously couldn't tell but it's one of those things that can cause problems down the road if you leave them out and move the amp around a lot.

[jlprry]

Success!!!! Switched the wire going to v1 pin 1 (thanks again Fischerman!!) fired it up and...wow!!! This amp rocks!! Another great design Dr Z (and of cousre Mr. Fischer!!!).

Thanks evreyone for all the help.

Jody