Stout TMB with Blues JR. Iron

[jasonvilla]

I'm making a Stout TMB from a Blues JR Power and Output transformer. So far I just have the power section hooked up. The power transformer doesn't have any center taps. So Im using two 100ohm resistors to ground for the heaters and 4 1N4007 diodes to make a full wave rectifier for B+. When I turn the power on, it works, but Im only seeing 243vdc at the end of the rectifier and the heaters are reading 7.3vac. Is something wrong or do I need to hook up the first filter cap to see a higher voltage reading?? Thank you for any help.

[sluckey]

do I need to hook up the first filter cap to see a higher voltage reading??

yes

[jasonvilla]

do I need to hook up the first filter cap to see a higher voltage reading??

yes

Thank you

[PRR]

No cap: 0.9
With cap: 1.4

So for 270VAC:
No cap: 243VDC (huge ripple!)
With cap: 378VDC

[Willabe]

......and the heaters are reading 7.3vac.

No tubes in, unloaded?

The heater voltage will drop with the tubes in.

[jasonvilla]

No cap: 0.9
With cap: 1.4

So for 270VAC:
No cap: 243VDC (huge ripple!)
With cap: 378VDC

Thank you! That's helpful, everything looks right so far.

Does anyone know if there is a more traditional board layout for the Stout TMB? Where the tubes are below the board and controls above? Thank you

[sluckey]

Hoffman's layout will work very well for what you want.

[jasonvilla]

This is what I came up with... I hope everything is going where it's supposed to! :)

[jasonvilla]

I just realized the Hoffman Stout layout diagram shows a 120k feedback resistor but the schematic shows lists an 82k. Does anyone know the correct value. I'm pretty sure I have an 82k in there now. Thanks!

[sluckey]

I would use the 82K. Only Hoffman knows for sure. Send him a pm so he can correct the docs.

[jasonvilla]

I would use the 82K. Only Hoffman knows for sure. Send him a pm so he can correct the docs.

Thank you sir.
It works great. All the voltages are about 20-30 lower than the schematic states. Im going to swap out the 10k dropping resistor for a 5k to try to bring V1 and V2 up a bit. I am also going to reduce the bypass cap on the power tubes as it's a bit too dark right now.

Oh and the heater voltage is still high- 7.03VAC

[EL34]

I just realized the Hoffman Stout layout diagram shows a 120k feedback resistor but the schematic shows lists an 82k. Does anyone know the correct value. I'm pretty sure I have an 82k in there now. Thanks!

The schematic shows a 82K feedback resistor
https://el34world.com/Hoffman/files/Hoffman_Stout.pdf

Not sure where the 120k feedback came from?
Copy and paste error probably


I uploaded New PDF's for Stout and Stout TMB

You may have to clear your image cache in chrome if it does not download the new files

[jasonvilla]

Thank you


I added 2 1N5408 diodes in reverse parallel on one side of the heater supply and that reduced the voltage to exactly 6.3vac. So Im happy about that.
I've gone down the rabbit hole with this amp (surprise surprise). Blues Jr transformers were NOT a good choice. I kind of understand why the Blues Jr circuit has so much going on. But Im getting there :)