Starting to populate the chassis....

[dbharris]

Hi Brian,

I think you are misunderstanding the purpose of setting the bias to the most negative voltage. It is to avoid accidentally biasing the amp too hot on the first startup with power tubes. It is not a target bias point for operating the amp as a musical instrument.

Did you install the 1 ohm resistors near the power tube sockets? They connect the cathodes to ground. If so how many? In your prior pictures I thought I noticed you left the bias test point jack chassis holes empty. It helps to have them so you don't have to pull the chassis for every rebias and also makes it easier to simply insert your dmm probes into those jacks. But not necessary.

Rob Robinette designed an app to make biasing the tubes much easier, it does all of the math for you. I'd recommend you download it. You only need to take the appropriate voltage measurements (without the bulb limiter) and select the appropriate type of and number of tubes that are connected to each 1 ohm resistor. Note that as you bias the amp the B+ will change (drop) a bit with more current flowing through the power tubes.

-Dan

[BrianL]

DB
I did have the 1ohm resistors to ground, but I took them out. didn't see a reason to leave them in.
Not the only dumb thing I've done with it.
I will put them back in with some test jacks, much safer than digging around the inside of the amp.
Now the pot I'm supposed to adjust is the one on the preamp board. power coming from B+3 and mixing thru this pot out to the tubes??
Circled in red...

[timrobertson100]

Hi Brian

The bias pot is the 10k one near the power tubes.
The one in red is a trimmer that you’ll adjust at the very end to tweak the tone.

[BrianL]

OK, thanks
That's the one I was using...The 10K by the power tubes..
I asked just in case I was wrong.
BrianL

[BrianL]

Ordered test jacks from Amazon 12 pack for $9.86 6 red, 6 blk.
Should be here Thursday.
Already got 1ohm resistors, easy fix to put them back in.
Going to fix my neutral to fuse error tonight and recheck voltage readings.
Wouldn't that be something if it worked now.....
BrianL

[BrianL]

OK, I rewired the 120VAC power to the fuse, thru the fuse and to the power switch, thru the switch and then to the transformer with the wire marked 120VAC
Neutral goes straight to the transformer with the wire marked 0 volts.
Standby switch still cuts voltage to "0". I checked it with my meter...it does take a while to go to "0" though.
Longer than I thought it should., Maybe a minute or so. I thought it would be immediate, but I guess there is a lot of components to drain.
I checked all my voltages on the boards and at the tubes and it all still looks good.
Heaters are still 2.7VAC(5.4VAC) though. The tube heaters do glow....but I don't know what a good glow looks like.
I was hoping the change would solve all my issues........
I went thru my wiring again and still don't see any misplaced wires,
Hard to check continuity cause everything back reads thru the amp.
Still no sound...not reading any volts at the output jack...
I did try plugging the guitar into the "effects in" jack and still nothing. This was suggested earlier this month.
Probably one wrong wire somewhere, good thing I'm a patient guy.......
We'll get it.
Thanks for reading.
Thanks for all your help.
BrianL

[dbharris]

Brian, are you still using the light bulb limiter when measuring the heater voltage?

[timrobertson100]

After heater voltage is addressed, suggest plug in to the effect return and focus on tracing the path to the output tubes checking all component values.

Can you post new pics please?

[BrianL]

db,
No I didn't use the light bulb limiter, these are all limiter free voltages...
2.7VAC right off the two transformer wires.
Haven't put in the test jacks yet, they come tomorrow so no Bias check yet.
Tim,
17 Pictures...two posts
How do I raise the 2.7VAC without replacing the transformer?

[BrianL]

more pics

[dbharris]

Can you post better pictures of the wiring around your PT and filament transformer? It's hard to see how everything is connected.

Are you using the heater windings on your PT? Is the filament transformer for your relays only?

When posting voltages, it's helpful to state your measured line voltage, heaters, and each B+ node, in addition to plates and screens for the power tubes and plates and cathodes for the noval tubes.

-Dan

[BrianL]

db
heater wires are from the PT.
filament transformer is for the relays
pic-1 brown wire marked 120 from transformer to power switch
pic-1 twisted orange and yellow wires from standby switch to power board
pic-2 black wire marked 0 from transformer marked
pic-3 shows a bunch of wires I didn't need, I should have bought a 290FX
wires not used gray, blue, two reds
pic-4 two heater wires marked 6.3V/8A from transformer, one has a red end cause it got cut to short.
pic-4 two red/white wires marked 320VAC from transformer going to rectifier/bias board
pic-4 blue wire marked 45V going to rectifier board. I have changed the 3k9 resistor to a 47 ohm per Martin Manning to compensate for the lack of 60V
pic-4 green wire on bottom of rectifier/bias board has 450VDC and goes to power board
not shown green/yellow wire goes to ground under the ODS Relay board
not shown red/yellow wire goes to ground under rectifier/bias board
pic-5 two blk wires on relay transformer, right wire comes from power switch, left wire goes to the ground strip in the picture
pic-5 two yellow wires from 6.3v of relay transformer out, each wire is 6.3v and go to relay board
pic-5 one red wire goes back to relays
pic-5 left red wire goes to relay board reg. output I believe I get 18VDC there
pic-5 right red wire goes to relay board reg. input. I believe I get 12VDC there
better pic of red wires in next post

BrianL

[BrianL]

couple more
pic 2 shows orange and purple wires from rectifier/bias board going to bias pot 60VDC
pic 2 shows red/yellow wire to ground under rectifier/bias board
pic 2 shows black wire rectifier/bias board to ground
pic 2 shows 6l6 pin8 to ground
I really appreciate the help, couldn't have gotten this far without you guys....
If you need anything else let me know....
BrianL

[dbharris]

Thanks for the pics. Are you using an artificial center tap for the heaters? That would be 2 resistors in the range of 100 ohm to 150ohm from each side of the heater string to ground. I think I see those on v4 socket. If that is the case, lift your green/yellow wire from ground. Check voltages and if normal, clip and shrink wrap the end.

-Dan

[martin manning]

Check heater voltage with all tubes removed too. Need to find out what is dragging that down. Is that splice a really good low-resistance connection?