Dag-nabbit....my new build is a complete TURD

[Dunkmop]

Try replacing/checking the PI bridging cap.

I had a mare of a job finding this when my amp intermittently cut out from normal big tone to the thin lifeless tone you talk of. I did all the voltages, etc.; until i literally started the last resort of swapping components, and thus found this as the problem.

Could be a quick try. Seems this fault is probably an easy fix, but hard to find.

[neikeel]

I really think a voltage chart of all your valve pins would be useful now, particularly if you have George chipping in

[lifer]

Yes, we have strict upload attachment quotas, necessarily so for security purposes. All images should be hosted elsewhere (photobucket etc) and linked to here.

george

cool--- wasn't sure if it was my ancient computer! lol

[lifer]

I really think a voltage chart of all your valve pins would be useful now, particularly if you have George chipping in

copy that......i'll get a full reading. be back

[lifer]

Try replacing/checking the PI bridging cap.

I had a mare of a job finding this when my amp intermittently cut out from normal big tone to the thin lifeless tone you talk of. I did all the voltages, etc.; until i literally started the last resort of swapping components, and thus found this as the problem.

Could be a quick try. Seems this fault is probably an easy fix, but hard to find.

amazing....i replaced the ol' lemco "dogbone" with a standard silver mica cap. Small improvement! still not right.....but definately much better.

it's gotta be another crummy component on the board somewhere. i'm 99% everything is wired correctly. none of the pots are scratchy....so i dont believe any of the coupling caps are leaking DC. what a bummer man.

All i could get to this w/e. i'm going to post my voltages. oh--- the MV is a kenny fisher one. 1meg audio pot. simple but i think it sounds good. works for me anyway. lol

[lifer]

ok....i took some readings. i think i have a problem at V3, pin 7. Take a looksy---

V1-- pin1: 134 pin3: 1 pin6: 184 pin8 1-2

V2-- pin1: 146 pin3: 1 pin6: 257 pin7: 147 pin8: 147

V3: pin1: 195 pin3: 35 pin6: 188 pin7: 23 pin8: 35

power tubes... plates at 438v screens 435 bias -41

So, V3 pin 7 is "signal, right? But i'm reading 23 vdc? and now, one of my speaker jacks has a loud hum...if i plug into it. other works fine.

UGH!!!!! lol

[neikeel]

Those voltages are not far off.

20v or so on pin 2 and 7 of the PI are not unusual.

The hum is more of a concern (is it grounded properly.

Just to get it working suggest you remove the MV for the moment.

[Tazin]

Your voltages are very similar to one of my amps...Mine are as follows:

V1-- pin1: 136.2 pin3: 0.82 pin6: 130.5 pin8: 0.81

V2-- pin1: 143.3 pin3: 0.96 pin6: 256 pin7: 143.3 pin8: 149.8

V3: pin1: 200 pin3: 34.2 pin6: 187 pin7: NA pin8: 34.2

power tubes... plates at 438v screens 432 bias -29.9

My V1 pins #6 & #8 differ since I have the 820R/0.68uF setup rather than a 2K7/0.68uF arrangement.

[lifer]

Those voltages are not far off.

20v or so on pin 2 and 7 of the PI are not unusual.

The hum is more of a concern (is it grounded properly.

Just to get it working suggest you remove the MV for the moment.

oops....yeah, your exactly right neikeel, thank you. i confused myself, when looking at my schematic, as usual---- LOL yeah...V3 pin7, is DC cathode voltage.....with AC riding along with it.

damn....not sure what to do. the hum just "started" last night when i plugged 'er in. not sure where that came from. oi vey.......

i might just go commando on it....swap out one component at a time. Stupid amplifiers. hahaha

[lifer]

Your voltages are very similar to one of my amps...Mine are as follows:

V1-- pin1: 136.2 pin3: 0.82 pin6: 130.5 pin8: 0.81

V2-- pin1: 143.3 pin3: 0.96 pin6: 256 pin7: 143.3 pin8: 149.8

V3: pin1: 200 pin3: 34.2 pin6: 187 pin7: NA pin8: 34.2

power tubes... plates at 438v screens 432 bias -29.9

My V1 pins #6 & #8 differ since I have the 820R/0.68uF setup rather than a 2K7/0.68uF arrangement.

TAZIN-- copy that, thank you for checking buddy. sigh.....i'll just keep on checkin stuff, i guess.

how's it sound with that cathode set up? gotta be more "gain" right? i never tried that one myself. i know some folks will drop the resisitor to 2k or 1.5....but then use a larger capacitor. like 2uf....or larger.

[Tazin]

Yeah, there is a bit gain with the 820R/250uF & 820R/0.68uF split cathode arrangement on V1 so you have to keep the Bass turned down when you crank up the volume.

I suggest you follow Neikeel's advise regarding troubleshooting since he knows his stuff.

[lifer]

Yeah, there is a bit gain with the 820R/250uF & 820R/0.68uF split cathode arrangement on V1 so you have to keep the Bass turned down when you crank up the volume.

I suggest you follow Neikeel's advise regarding troubleshooting since he knows his stuff.

copy that- i might have to try it out. see what it's like.

well....good news, i believe i nailed down the problem. the humming output jack, turned out to be a blessing.

i decided to remove the Cliffs....and wire up a open 1/4" jack...for testing. i don't have any spare cliff's on hand. as i'm removing them.....turns out the "common" lead from the OT did not have a real solid ground at the jack. it broke loose as i was fumbling around with the jacks!

put in the phone jack....and the problem seems to be remedied. woot-woot! time to punish the amp by making it scream for mercy!!!! hahahaa

thanks for helpin out guys. i appreciate you takin the time!

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