Help wiring power transformer Transformer

[Enzo]

I agree that -113v of bias is enough to have the power tubes in cutoff, and then power off kills that bias and so allows sound to emerge as the B+ fades.

Fix the -113v bias.

[nosaj]

I agree that -113v of bias is enough to have the power tubes in cutoff, and then power off kills that bias and so allows sound to emerge as the B+ fades.

Fix the -113v bias.

Good deal at least I'm retaining some of the stuff that gets thrown at me.
nosaj

[Leo_Gnardo]

Fix the -113v bias.

Deafinitely! With the Hammond PT, you must be picking a little current off one of the arms of the hi voltage secondary. That current passes thru a resistor, then a single rectifier, then it's filtered by a 10 uF cap. What's the value of that resistor? The Ceria schemo shows 27K but its PT has a separate 100V bias winding. The Marshall schemo shows 150K, that's probably more like what you should have Willie. In any case have a peek at that & let us know what it is, OK?

[GroundskeeperWillie]

cool

[GroundskeeperWillie]

If it's the resistor connected to the diodes it's a 56k , the Ceri layout shows 220k & yes in the Marshall schematic shows 150k

[GroundskeeperWillie]

I don't have a 150k ,I do have 220k resistors

[Leo_Gnardo]

I don't have a 150k ,I do have 220k resistors

Good I've seen both 150K & 220K values in that position, & sometimes I've used 180K or paralleled another resistor with 220K to get the bias supply into a useful range. So let's try 220K, for now leave output tubes out of their sockets. With the 220K in place, fire up and see what range of bias voltage you can dial in with the bias adjust control. 2 last things, remind us what output tubes you'll be using? And do you have 1 ohm current sensing resistors between chassis ground and output tube socket pins 1 & 8?

[GroundskeeperWillie]

I got the 220k in place & with the Apex matched JJ el34's & yes I got SOUND!!!!! ...

[GroundskeeperWillie]

yES i have the 1 ohm resistors soldered in but I get no reading DC ,is that a miliamp or volts setting .off pin 5 of the power tubes i'm in the -40 range

[Leo_Gnardo]

yES i have the 1 ohm resistors soldered in but I get no reading DC ,is that a miliamp or volts setting .off pin 5 of the power tubes i'm in the -40 range

YAY! Progress at last. And the bias voltage on pins 5 is about where we want it. What you'll read on those 1 ohm resistors is MILLIvolts. Each millivolt corresponds to 1 milliamp of bias current in each EL34. This measurement is done with no signal passing thru the amp. Somewhere around 35 millivolts would be ideal, you should be able to adjust that with the bias pot.

[GroundskeeperWillie]

Ok got her done ,35 millivots .Awesome i know it's still a ways to get this completely ready to go like the that depth control is causing a motor boating effect unless in's turned down & then i think it's restricting the tone so I may remove it till i get the amp straightened out .
Guys thanks a Million for all the help ,Such knowledge is here on this forum ..I know where to go when I need help ...Thanks

[nosaj]

Ok got her done ,35 millivots .Awesome i know it's still a ways to get this completely ready to go like the that depth control is causing a motor boating effect unless in's turned down & then i think it's restricting the tone so I may remove it till i get the amp straightened out .
Guys thanks a Million for all the help ,Such knowledge is here on this forum ..I know where to go when I need help ...Thanks

Good job, thanks for sticking it out.

nosaj

[GroundskeeperWillie]

Here's a question
Tomorrow I will solder in the cliff jacks for the 4,8,& 16 ohm speaker configuration as there is no impedance switch & as the depth control is connected to the negative feedback how do I go about adding it to all 3 impedance jacks & don't some use a resistor or cap ....the .0047 uf cap is already on the resonance control

[Leo_Gnardo]

Here's a question
Tomorrow I will solder in the cliff jacks for the 4,8,& 16 ohm speaker configuration as there is no impedance switch & as the depth control is connected to the negative feedback how do I go about adding it to all 3 impedance jacks & don't some use a resistor or cap ....the .0047 uf cap is already on the resonance control

No need to have neg. feedback from any other than the one output tap shown. If you connect a speaker to a different output jack than the one with the NFB lead attached, there's still signal voltage present on the tap with NFB, it will get where it's supposed to go no worries.

Been a long day. I'm delighted you made some progress especially in recent hours. Gonna conk out & dream of chocolate bunnies.

[GroundskeeperWillie]

I fixed the oscillation problem by swapping the primarys of the OT
Whats so special about the Apex matched power tubes from CE Dist , one of my el34's reads 30ma & the other one reads 38ma .Don't consider that matched .