My 124# is up and running!!!!! A few issues?

[rogb]

These are voltages from UHOP's #183 build. This is the ballpark you need to shoot for. These are the voltages I have pretty close on my 50w #102 build. If you aren't getting near them something is connected wrong or a component is the wrong value or failed.

Recheck your parts and wiring to the layout, do it again and again till you find the fault.


No load B+: 479V
Loaded B+: 462V
Screens: 456V
B+3: 436V
B+4: 321V
B+5: 313V

OD
Pin 1: 214.5V
Pin 6: 207.5V

CL
Pin 1: 200.9V
Pin 6: 189.2V

PI
Pin 1: 295V
Pin 6: 300V

Bias Voltage: -41.2V

[rogb]

Are those cloth covered wires your filament wires? Man that is not going to do on a 124 build, they need to be tightly twisted and up in the air away from any signal parts.

If that is the standard, then don't take offence, do what TM said, rip it up and start again, using Ultra Hooked on Phonix 183 build pics as a guide. If you are 50% as good then you will have a fine quiet and working amp

I would say mines is 50% there in comparison and it is a really good sounding quiet build.
(Build thread following soon...)

[martin manning]

I suspect there is a wiring error around V2 and V3. I don't understand the latest set of voltages with the pin numbers are listed as 4, 5, and 6.

I suggest rewiring the pots, going back to the nominal 22k dropping resistor and getting a complete set of voltage measurements:

Power supply nodes 1-5,

V1 and V2 pins 1, 2, 3, and 6, 7, 8,

V3 pins 1, 3, and 6, 8, and voltage at the bottom of the 820 ohm bias resistor (you can't measure the pin 2 and 7 grids on the phase inverter directly because your meter will upset the operating point).

On the power tubes get voltages at pins 1, 3, 4, and 5.

[echo44]

Thanks everyone I was 1/2 sleep last night when measuring voltages
(i know not a good idea)

1) don't think I want to scrap the amp and start over the clean channel sounds amazing, I have no hum and no pops on the clean channel!
Plus with the knobs reversed, when they are on zero the volume is the loudest so when my bandmates complain I am too loud I can say "it can't go any lower its on zero .

2) Ok I think "Bcook" user found my problem. with the amp off the cathodes on V2 are measuring 150K they are supposed to be at 1.5k correct
this means I used the wrong resistors.

3) here are my voltage measurements taken at 7:00 AM wide awake(haven't changed the v2 cathode resistors yet)

V1 1= 190, 2= .002, 3=1.2, 6=194, 7=0, 8=1.2

V2 1 =273, 2= .001, 3= 3.6, 6=194, 7=.001, 8=3.6

V3 1=300, 2=34, 3=53, 6=303, 7=33, 8=53

And One 6l6 V4 (the rest have the same values give or take a volt)
V4 1= -45, 3=438, 4=436, 5=-45, 6=439 8=04

B+ Voltages:
B1= 440, B2= 440, B3=430, B4=278, B5= 270

As a rookie I can't thank everyone enough, I have learned so much here on these forums. I have read a few books, however the knowledge I have gained here and in trying to build this amp is the real deal !!!
I will post pictures of the entire amp a little later.

[echo44]

Bingo!!!!!!!!!!!!!!!!!!!!!!!!
It was the cathode resistor on V2!!!!!! Thanks to everyone again!!!
I had them at 150k instead of 1.5k changed them out this morning
Now the OD channel works, the voltages on V1 and V2 dropped so I took out the 44k that I was using in the power supply and put back the original 22k
and now all my voltages are better with the power supply being original. I understand( I think) why the cathode resistor in V2 being wrong affects the plate voltage of V2 but why does it also affect the voltage on V1?

Ok and now the dumbest question ever.
What I learned from this experience as I was messing around with trying
to lower the voltage as I increased the resistor value the voltage on the plates dropped but here is where I get confused with the basic physics.
V=IR so as you increase the R doesn't V have to increase if I stays the same?

[martin manning]

With the large value Rk's you had both triodes in V2 in cut-off, so you were missing half of the current draw down-stream of the 22k. Therefore you got half of the voltage drop, and that's why doubling the resistance brought V1's voltages in line.

Get a new set of voltages for review.

[echo44]

New voltages with resistors on cathode v2 corrected

b1=440 b2=440 b3=424, b4=304, b5= 296

V1 1=207, 2=0, 3=1.3, 6=211, 7=0, 8=1.3

V2 1=207, 2=0, 3=1.4, 6=213, 7=0, 8=1.4

V3 1=300, 2=001, 3=53, 6=301, 7=33, 8=53

[rogb]

Well done , you found the fault, wrong value component, so easily done, ask me how I know

You might be able to drop v1 by rolling tubes through it, can easily be 10v difference between them, I have just done the same thing in my build and now I have a good balance of voltages.

New voltages with resistors on cathode v2 corrected

b1=440 b2=440 b3=424, b4=304, b5= 296

V1 1=207, 2=0, 3=1.3, 6=211, 7=0, 8=1.3

V2 1=207, 2=0, 3=1.4, 6=213, 7=0, 8=1.4

V3 1=300, 2=001, 3=53, 6=301, 7=33, 8=53

[martin manning]

To be clear, do you have the 150k and ?k voltage divider on the FET board hooked up?

Pin 2 on V3 is wrong, it should look like pin 7, and as I said above you can't measure pin 2 or pin 7 directly (so they are both wrong ;^).

If the FET supply is wired in, I'd say you are about 20V high at V1's plates, so you can try increasing the 22k.

[rogb]

To be clear, do you have the 150k and ?k voltage divider on the FET board hooked up?

Pin 2 on V3 is wrong, it should look like pin 7, and as I said above you can't measure pin 2 or pin 7 directly (so they are both wrong ;^).

If the FET supply is wired in, I'd say you are about 20V high at V1's plates, so you can try increasing the 22k.

What Martin said, on my first D style build, I didn't have an FET and forgot to ground the FET sub tail resistor so my voltages were high till the guys here put me right

If your FET isn't in circuit and loading, volts will be high.

[echo44]

Ok i will double check the FET board and
where do you measure the voltage on the bias pot?

[echo44]

new voltages I put a 27k instead of a 22k

V1 1=195, 2=0 3=1.2 6=198, 7=0 8=1.2

V2 1=195 , 2=0, 3= 1.3, 6=201, 7=0 , 8=1.2

V3 1=295, 3=1.3 6=298, 8=52

[martin manning]

V3 pin 3 is not right, or at least you are not measuring it correctly. It should be exactly the same as pin 8 since they are tied together.

Don't worry about the bias voltage, just set the idle current to your liking, 30-40mA.

[echo44]

yes i measured them wrong they are the same at 53
should i drop the voltage more? i do not have higher than a 27k 2 watt
but i could add a 2.2k in series to the 27k to get closer to 190 or is
195 close enough?

[martin manning]

195 is ok for now, play it a bit and try swapping tubes to see what happens.