new 124ish build with problems

[toner]

fired up a 100w 124ish build. it doesn't sound right. everything works fine on it, but the volume doesn't seem that loud, and its kinda warm sounding and when i turn it way up it fizzes out. here are my voltages with seem to be ok but maybe not? power tubes not right?
V1 pin 1 186v
pin 3 1.38v
pin 6 187v
pin 8 1.38
V2 pin 1 186v
pin 3 1.52v
pin 6 196v
pin 8 1.37v
V3 pin 1 293v
pin 2 36v
pin 3/8 58v
pin6 301v
pin 7 35v
V4-7 pin 3 444
pin 4 444
pin 5 -46
pin 6 445
B+1 446v
B+2 444v
B+3 425v
B+4 288v
B+5 279v

its all 124 except i used the precision power supply 2.2/22/2.2K, and the modern rectifier/bias boards with dual 47uf caps as well as modern relay board. i ditched the 1/2 power switch too. when i biased up my first quartet of 6l6's i was at the end of the 10k pot and was at 60ma. i tried two other quartets and they biased up fine at 35ma but are near the end of the pot. maybe thats a clue whats wrong? its gotta be a power supply thing. anyone have any ideas, and thanks!!! btw, ive checked over all the values a million times and its not that, or preamp tubes.

[heisthl]

Voltages are good. Divide and conquer, test the power amp by itself.

[dogears]

Not your issue, but I noticed the V3 tube has more voltage on pin 6 than pin 1. I'd strongly suggest a balnced PI tube. Then set the trimmer to try to get 6-8 volts more on pin 1. Then listen. Then adjust the trimmer for maximum feel, sustain, harmonics, and feedback.

I have never had pin 6 have more voltage when set for best tone....

[toner]

Not your issue, but I noticed the V3 tube has more voltage on pin 6 than pin 1. I'd strongly suggest a balnced PI tube. Then set the trimmer to try to get 6-8 volts more on pin 1. Then listen. Then adjust the trimmer for maximum feel, sustain, harmonics, and feedback.

I have never had pin 6 have more voltage when set for best tone....

thanks for the tip.. i haven't messed with that too much yet but will check it out. im using a 10K pot on the PI for now since i didn't have 5K.. and just left it at 12 o'clock since when i turned it it seemed to sound worse but not make a big change. thank you!

[toner]

Voltages are good. Divide and conquer, test the power amp by itself.

thanks, well if i had an identical amp i could plug that pre into the power amp and have a way to compare.. but i don't and im not sure plugging an unknown pre into it would tell me much since i don't know what that combo is supposed to sound like. i plugged the guitar straight into the power in jack and it sounds kind of like a princeton in volume but very warm/ no high end. thank you for your help though

[toner]

there is one longshot idea i just had. im using a mercury sun 2000s OT. the color coding is exactly what is on a sun 2000s schematic. but i double checked with mercury for thier schematic for the OT, and for some reason they played musical chairs with the color coding of the secondarys. yellow goes to ground, and black is the 16ohm tap. i thought that was weird cause black is usually ground but trusted them. i don't even know what would happen if one of the taps was grounded and the ground wasn't attached to anything... thats probably not it and it wouldn't of worked at all if i had it wired up wrong.. that was just an area where i was scratching my head so i thought id put it out there
thank you!

[odourboy]

there is one longshot idea i just had. im using a mercury sun 2000s OT. the color coding is exactly what is on a sun 2000s schematic. but i double checked with mercury for thier schematic for the OT, and for some reason they played musical chairs with the color coding of the secondarys. yellow goes to ground, and black is the 16ohm tap. i thought that was weird cause black is usually ground but trusted them. i don't even know what would happen if one of the taps was grounded and the ground wasn't attached to anything... thats probably not it and it wouldn't of worked at all if i had it wired up wrong.. that was just an area where i was scratching my head so i thought id put it out there
thank you!

Yikes! All manner of crap could be going on if that were the case. At minimum, your global NFB tap would likely be providing positive feedback (which is often a source of strange behaviour in a new build anyway)

[toner]

there is one longshot idea i just had. im using a mercury sun 2000s OT. the color coding is exactly what is on a sun 2000s schematic. but i double checked with mercury for thier schematic for the OT, and for some reason they played musical chairs with the color coding of the secondarys. yellow goes to ground, and black is the 16ohm tap. i thought that was weird cause black is usually ground but trusted them. i don't even know what would happen if one of the taps was grounded and the ground wasn't attached to anything... thats probably not it and it wouldn't of worked at all if i had it wired up wrong.. that was just an area where i was scratching my head so i thought id put it out there
thank you!

Yikes! All manner of crap could be going on if that were the case. At minimum, your global NFB tap would likely be providing positive feedback (which is often a source of strange behaviour in a new build anyway)

hmmm... well, everything works and sounds "ok".. but its low volume (for a 100w) and not good "tone" as id expect. i wonder if i should look into this further. the other thing that had my scratching my head was that mercurys 50w version of this trannie has the correct color codes as id expect, which is the same as the sun 100w schematic. but when i talked to mercury they assured me that the sun schematic colors were wrong, and that on thier 100w trannie yellow goes to ground. maybe someone who's used this trannie can chime in. or maybe theres an easy way to measure it in circuit? thanks again for your input

[talbany]

I had the same thing on a N sensor 100 w OPT Brown is common and black is 4 ohm.. Same thing with this Merc tran,,
You can check it in circuit (unplug everything) start at where you think is common or find the 2 that has the highest resistance and pick one..go to 200 ohm setting on the meter Your 16 ohm should be the highest around 2. the 8 ohm tap should read a bit lower 1. and the 4 ohm around .8.. Your results will very but you get the idea... Good Luck


Tony VVT

[heisthl]

The 100 watt Mercury's I use have Black as ground.

[toner]

another thought. when i first fired it up, i had the OT primary leads the way i i thought they were supposed to go (backwards from mercury schematic). what i heard wasn't the normal oscillations i expect when they are backwards. it was a crazy loud bzzzzzzzzzz like when you ground the tip of a plugged in guitar cable or something like that. not a good sound/sign a jump out of your chair "oh shit, hit the power switch as fast as possible" kinda sound. but since i had it backwards according to the mercury schematic i reversed them and the amp works and the crazy loud buzz was cured. and thats where im at with it. everything works fine but not as loud and clean as i would think. and sounds too warm to me when i was expecting somewhat brite

[heisthl]

I think you're going to find something stupid like an output coupling cap not connected or a wrong value somewhere.

[toner]

I had the same thing on a N sensor 100 w OPT Brown is common and black is 4 ohm.. Same thing with this Merc tran,,
You can check it in circuit (unplug everything) start at where you think is common or find the 2 that has the highest resistance and pick one..go to 200 ohm setting on the meter Your 16 ohm should be the highest around 2. the 8 ohm tap should read a bit lower 1. and the 4 ohm around .8.. Your results will very but you get the idea... Good Luck


Tony VVT

thank you tony... well i measured to the 3 taps in reference to ground and got
4ohm .3
8 ohm .4
16ohm .6
im not sure if thats close enough, and the readings seemed to fluctuate on my digital meter, but never got over an ohm. i wasn't sure what you meant by looking for common since its attached to ground right now. (i could losen the jack so its not attached to ground i guess?) thanks for your help!

[talbany]

Common/ground same thing.. With respect to OPT it's usually referred to common but whatever.. If your starting @ ground and working your way through the winds they should up in resistance like you have it...If you had the ground reversed to yellow/Black whatever it would go opposite.. So sounds like you have it wired correctly.. Generally with that low an ohm reading will be slightly different meter to meter and transformer to transformer but they all slightly increase in resistance as you go up the wind is what your looking for... no need to disconnect the jacks from the chassis.. I meant unplug any speaker cables....I would use the 4 ohm tap for NFB... If your using a higher tap would explain the clamped highs.. Good Luck!!


Tony