Starting to populate the chassis....

[BrianL]

Db
V4 has a 120R resistor to ground from the each heater wire,
Do all the tubes need this?
I will lift the green and yellow wire and try it.

Martin
Voltage was 2.7vac from the start, even before I spliced the wire.
I will check voltage with all tubes removed.
Thanks guys
BrianL

[BrianL]

Ok, I removed the green and yellow wire and have 2.7vac stil

Removed all the tubes and still have 2.7vac

Have my voltmeter set at ACV 200 it reads 2.7
If I put it to ACV 750 it reads 3.0
I figured the lower checking reading would be more accurate cause it’s closer to what I’m looking for.

I have 117 vac wall current , checked with my voltmeter.
BrianL

[dbharris]

Keep the green/yellow wire floating from ground. It does not matter where I'm the heater string those resistors are.placed,.but you only need one per side how you have it.

What was your B+ without tubes?

[BrianL]

DB
I heat shrunk the end of the green/yellow wire and tucked it away with all the other transformer wires I'm not using.
B+ is 446VDC with or without tubes.
446VDC runs across the bottom 7 points of the power board with or without tubes
Got my test jacks today , going to put them tonite
BrianL

Got my jacks in and wired:
1ohm resistor from pin 8 to ground, wire from pin 8 to jack.
repeat four times,
add ground jack...'
put tubes into amp, turn it on...and off of standby
set voltmeter to DCV 200M
put black probe in ground jack and check red jacks one at a time:

tube 4 .5M
tube 5 .7M
tube 6 .7M
tube 7 .5M
Are these close enough? They're supposed to be a matched set...

checked voltage on pin 3
tube 4 445VDC
tube 5 445VDC
tube 6 445VDC
tube 7 445VDC

Go to bias calculator page on "Tube Depot's" website:
Type in tube type, 6L6GC
type in voltage 445VDC
comes up with this page below
set bias to 70% which was 47.19
I could only set to 47. or 48. ,I went for 48.
It's actually a minus number -48.
rechecked pin 3 voltages and they are now 437VDC.

Did I do this right????
Thanks,
BrianL

[timrobertson100]

You’re adjusting the bias until you read around 47mV across your 1ohm resistors? Sounds correct.

The b+ will change a bit as you adjust bias. It’s an iterative process.

What the bias voltage from the potentiometer is (-48V or whatever) isn’t so important.

Tubes vary, plus your 1ohm resistors will also all be slightly different so the readings are close approximations.

[BrianL]

Hi everybody, I left kind of unexpectedly back in Sept. 2024. My 22 year old daughter was schedualed for surgery, we knew this was coming for a couple of years, she was born with a malfunctioning heart and went in to have a valve replaced. Long story short...she died three times on the operating table and they ended up putting in a pacemaker and she died again after that, one of the wires came off. 14hr surgery but she did live thank God.....She's doing fine right now but we still worry everyday...I want to cry for her every time I look at her for all the stuff she's had to go through in her life. Things are finally starting to settle down....

Now down to business, I'm gonna make this amp work sooner or later....
If anybody remembers my transformer will not give me 6volts to power the heaters, I get like 5.7.
So tonite I unsoldered the transformer and took it out of the chassis in case it was grounding somehow. I plugged it into a 120 cord and checked voltages.(I have 117 vac house current)
across the red /white wires I get a constant 645vac. I'm using that to power the amp
across the green heater wires I get something funny....it's not a constant reading, it starts at 3.9vac goes up to 7.8vac then goes back down to 3.9vac, goes up, goes down. it's pulsating up and down. That can't be normal??? It's averaging about 5.8vac, not enough for tube heating.....so I'm looking at getting a 290FX form Tube Depot if I need a new one.

As always any and all help is appreciated.
Brian

[martin manning]

Good to hear your daughter is on the mend. Best of luck to her.

Good strategy in pulling the PT and testing on the bench. The fluctuating heater voltage is weird. Never heard of that. If you can confirm your meter is working correctly, I'd go for the 290FX.

[BrianL]

Martin, thnx for the daughter wishes.

That's my plan then, if the current transformer is acting weird, to go with the 290FX.
B4 I stopped posting I was trying to follow the signal through the amp to find a bad connection or loose solder joint, voltages seem to stop when I got halfway across the preamp board
so I'm gonna start my search there....

Is the transformer supposed to ground itself through the chassis mounting or anything like that?

Thnx, Brian

Yeah, I thought it was weird too, I could watch the meter count up, then count down, then count up, then count down, yet across the 320 wires I had a good solid reading, I don't think it's the meter,
I do have another meter so Ill redo my tests with it....

[martin manning]

I could watch the meter count up, then count down, then count up, then count down, yet across the 320 wires I had a good solid reading, I don't think it's the meter,
I do have another meter so Ill redo my tests with it....

The stable reading at higher voltage is reassuring, but checking with another meter is a good idea. Sometimes weird things happen if the batteries are low, so that's something else to check.

[BrianL]

So I took the preamp board off the chassis to do continuity checks to find where I'm losing it, I've been watching amplifier assembly videos on you tube and seeing assembly order and dressings
and voltage checks and I'm actually learning stuff and why it makes a difference. I've decided my internal wiring looks like crap and is very hard to follow and is very sloppy and icky. So, I did what any good fabricator/assembler would do, I completly gutted it and I'm starting over ......again......

I've got front and back faceplates that I bought b4 I bought Amplified Nation chassis that I'm gonna build the controls on and then transfer to the chassis, that will give me more room to work and be neater with my work.
Also gonna move the "FET" board and the third relay board farther towards the back on the side of the chassis, there's a lot more room for it.
Brian

So I'm gonna ask all of my stupid questions all over again!!!!!!
Just kidding, I've got 14 plus pages of info from you guys to search through.
Thanks for being so helpful and patient with me as I struggle through this.

[dbharris]

Glad to hear your daughter is doing better.

If you are moving the FET board to the back of the chassis, you may want to run shielded wire for the input and output connections to the FET jack.

-Dan

[BrianL]

Not a bad idea, sounds like a must do, anything to help control signals and hums and stuff...

Brian

[BrianL]

Bought a soldering station today, Weller WE 1010, $115.00 from Amazon, bought extra tips to go with it too. That should help with my soldering, much better than the $15.00 unit from Menards.....
It has a slim handle, small diameter heating stem and digital display, also came with a stand and sponge.
I look forward to using it.

So what temperature do you guys use to solder ground wires to the back of potentiometers, I've always had trouble with that, it always took forever to get hot and solder, usually didn't stick and I always worried about burning up the inside....
Thnx, Brian

[Jake Kershaw]

Hey Brian,

After looking at your build pics, I noticed your screen grid resistors are 470k! (yellow-purple-yellow). It would probably be a good idea to check them and lower them to 470R or 1k, depending on the power tubes you're using. Good luck on your build!

[BrianL]

Old picture, what I have now says 470R on it. Sorry for the old pic...

Brian