5902 design problems

[UR12]

Have you tried a different tube ? Is this the bread boarded version or the PI in the amp. Check your 470k resistors and make sure they measure the same.

[Disabled_shredder]

this is the bread boarded version with the 6112 tube. i will try adding a pot to direct voltage offset to one side or the other? is that wise? also i will try with a 6111. i realized quite a few things in breadboarding this phase inverter over what i was doing with swapping out components on the turret board. i feel like this one is working its just not balanced well. i hope the photos i gave are accurate enough or allow you to see well enough what i am doing so what confusion i cause in my writing (i horribly relay my thoughts, its in part from adhd and all the concussions i got in the army) can be cleared up. i do not think it is the tube or necessarily the past attempts as much as it might have been me not grounding my scope, ignorantly looking in the wrong places etc. im not sure about the 470k resistors you are talking about i used 100k on the plates one megs from cathode to grid and 1k cathode with a pot dialed to 39k as the tail with a 1k from the pot to ground. i did however adjust the pot some to see what would happen and other than dumping it completely to ground i saw no real difference. i think i will use a 22 or 24k as thats the value i have on hand and do not have any 39k resistors, i do have 47k if you think that would suffice and not be too large of a tail resistor. but good thing is that i got a clean signal on the output and a nice inverted signal as well. now to just balance them. maybe make one of the plate resistors 120-150k or am i thinking about this wrong again?

[UR12]

The two 470k I'm talking about are the two 470k resistors after the coupling caps going to the grids of the power tubes. They act as a load to the triodes in the phase inverter and provide a reference to ground for the power tube grids. If they don't measure the same or the wrong value was accidentally used, For example, if one was a 470k and the other 47k this would imbalance the two out of phase signals. Also make sure you don't have the 1k and 39k swapped around as the 39k resistor is developing the signal to feed the grid of the second triode. Changing the value of the 39 k may help to balance the two outputs

[Disabled_shredder]

Dana right now I do not have 470ks hooked up after the coupling cap it's just the phase inverter o have nothing past the coupling caps so I can see the wave but when I had the power section hooked up I had 220k resistors going to the control grids.

[Disabled_shredder]

So without adding the power amp tubes/section to the pi I have adjusted the plate resistor of the inverted side to a lower value also I tried a 47k 22-24-18k and all seem just just change the voltage but doesn't bring the inverted side closer to even. I am going to go ahead and build the values of the pi that I have into the turret board and try adding the power amp section and see what happens. I hope that it will balance the pi. I have been using 470r for the screen grid but I'm gonna try 1k 1.5 and 2.2k and maybe bigger and see how it reacts

[Disabled_shredder]

ok so i have the phase inverter connected to the power amp section tubes in from the liverpool pi values just for reference i ran 220k resistors through 1.5k to the control grid. i am using 1.5k screen grid resistors and have cathodes tied directly to ground. a ground that is shared with the output jack ground i might add. i am getting absolutely no output. i am using lugs 3 and 6 of my hammond 125c output transformer. i have on the plates i have 163.3 and 161.7 respectively and on the screens i have 162.8 and 162.4 respectively both have a negative bias of 30.1. i have a perfect waveform on the pi and i scoped the plates and have a nice signal as well. the problem i have is i have no signal on the output. could it be a phase issue with the transformer? could the secondary be bad? i know im getting signal to the primary of the transformer so what gives? i already have a request in with ce to get me a confirmation to send the transformer back to hammond. i hope im missing something. also i am hooked up to lugs 3 and 6 and from there to the hot signal and my ground is hooked to the chassis. shouldnt there be a negative from the secondary of the transformer? please let me know about this last one cause i feel like there should be a negative from the secondary. thanks again to everyone who has helped with getting this power section going. im glad i have it working like a top i just dont know why im not getting a signal at the speaker connection.

jake

[Disabled_shredder]

well gents, i have a beautiful waveform on my output. i made my last ignorant error and had both lugs 3 and 6 to hot. i moved lug 3 to ground and off she went. i have a beautiful waveform on the scope from output if i ever saw one. i will post a pic in the am. tomorrow when my son is not sleeping in the next room im going to hook it up to some speakers and give it a listen. then i will figure placement of components and tubes drill and mount then off to the races for preamp!!!!!!!! it took a week to get the power amp built but thats good, gives me more time to fool with the preamp and decide what i like and what sounds the best. thanks again guys for all the help. im sure ill be back on this thread with preamp questions.

[dayn]

I am in the design stages of another lil amp that uses the AC30 as a starting point with a pentode front end using a 6205 or 5840.

Just noticed this, can't wait to hear more!

[katopan]

So glad you found the problem. Looking forward to hearing about the rest of it coming together.

[Disabled_shredder]

it is coming along very nice although i had to put it down for a bit because of a move. a problem i had when i let it go to the side was that i couldnt get output in triode mode. i am running 4.61k screen resistors and im tying that directly to the plate. ive got another thread going for that issue but im just breadboarding preamps and auditioning them until i get the perfect one. im in the middle of testing at least on paper a laney gh50l preamp as the basis for the 2 channel and tone stack but im adjusting the tone stack and other aspects to best suite an 8 string guitar tuned to a flat

[JazzGuitarGimp]

im adjusting the tone stack and other aspects to best suite an 8 string guitar tuned to a flat

Fun!

[Disabled_shredder]

ya not really i breadboarded 2 pre amps so far. both times the tone stack was faulty in some way because i was getting signal until the ts and then it was gone.