100 watt power tap suggestions

[dcribbs1412]

wondering if this might work for a conversion build.
Peavey Heritage VTX solid state to a clean 100 watt tube
Having trouble figuring out the bias and voltages.
thread is here https://tubeamparchive.com/viewtopic.ph ... 7&start=30
power supply from Peavey schem
my idea for the bias
any suggestions/advise is greatly appreciated

Darin

[tictac]

Do this...

[tubelectron]

Hi,

Starting from the HV and using a cap or a resistor in serie to drop the voltage to the suitable value and rectify it, that works. I always used a serie resistor instead of a capacitor, finding it more "controllable and safe".

You will have to tweak the values, but you can start with a 56K resistor, an 1n4007, a 100µF 200V filter cap to GND, a 10K LIN bias pot connected to GND via a 10K resistor. It should cover the -35 to -65V range on a 100W amp (680VAC CT HV transformer, like Twin-Reverb).

A+!

[dcribbs1412]

Do this...

thanks tt and tubelectron
you saying like this?
(bias pot has a 15k to ground)
top pic is the way I have it now...not working correctly.

Darin

[tubelectron]

dcribbs1412,

Here is the system I use for years :

[img:800:657]http://img4.hostingpics.net/pics/361677biasing.gif[/img]

A+!

[dcribbs1412]

dcribbs1412,

Here is the system I use for years :

[img:800:657]http://img4.hostingpics.net/pics/361677biasing.gif[/img]

A+!

Thanks
I don't have any 1n5408's...can I sub in 1n4005's or 7's ?

[M Fowler]

What kind of PT are you using a Fender type or Marshall type?

For Fender I would make the SS board and bias board like those shown in Dumble section.

If Marshall then you have it as shown, full wave bridge like the Plexi layout

[dcribbs1412]

What kind of PT are you using a Fender type or Marshall type?

For Fender I would make the SS board and bias board like those shown in Dumble section.

If Marshall then you have it as shown, full wave bridge like the Plexi layout

Hi Mark
it's Peavey 100watt donor iron.
Made a little headway(removed the .01 1KV caps from bias and changed to a 56k ...I have sound now but the voltages are real low 250V on pin 3 and 6 of the 6l6's biased at 30-32ma...

Darin

[ToneMerc]

Darin, did you verify that you are truly using the high tap of the PT secondary?

TM

[dcribbs1412]

Darin, did you verify that you are truly using the high tap of the PT secondary?

TM

good question TM...and would make sense but I'm not sure...looking at the Peavey schem
I'm using the 2 red taps(bottom not marked red) and the R/Y as the CT.
would this be correct?

Edit: after looking closer it looks like the HV CT connects to the filter caps
instead of ground? Wondering if this would up my voltage?
any suggestions/advise is appreciated

Darin

[tubelectron]

I don't have any 1n5408's...can I sub in 1n4005's or 7's ?

1N5408 are 1KV / 3A, 1N4007 are 1KV / 1A... It should work, but I like the rectifier diodes to be (sometimes way) bigger than needed, for reliability.

A+!

[dcribbs1412]

I don't have any 1n5408's...can I sub in 1n4005's or 7's ?

1N5408 are 1KV / 3A, 1N4007 are 1KV / 1A... It should work, but I like the rectifier diodes to be (sometimes way) bigger than needed, for reliability.

A+!

I understand. I will use the 4007's to get it running and change when I order next.

[LOUDthud]

dcribbs1412, Are you are using the Peavey transformer like the first schematic you posted? The circuit with the Hi/Low settings as part of the standby switch? That transformer will only give you about 250V in the Center Tap Full Wave circuit. The secondary is something like 175-0-175. You will need to use the capacitor coupled circuit for bias if you want a 500V B+ and a bias supply from that winding.

With this type arrangement you should connect the cap to the yellow striped red wire so that you get the same bias voltage in Hi and Low power mode (unless the fuse blows).

[dcribbs1412]

dcribbs1412, Are you are using the Peavey transformer like the first schematic you posted? The circuit with the Hi/Low settings as part of the standby switch? That transformer will only give you about 250V in the Center Tap Full Wave circuit. The secondary is something like 175-0-175. You will need to use the capacitor coupled circuit for bias if you want a 500V B+ and a bias supply from that winding.

With this type arrangement you should connect the cap to the yellow striped red wire so that you get the same bias voltage in Hi and Low power mode (unless the fuse blows).

Hi LOUDthud
Yes, using the Peavey from a heritage vtx...not using the switchable lo/hi
voltage just wanting the 500V sec. which I have now...
problem is the bias is not cooperating...way more than I need
jumps to like over 100ma when I hit the standby switch.Not sure about that. Also I'm kinda concerned about having 520V on my first 22uf 450V cap. I'm thinking I have to rebuild my power board..not sure I have it right. Here's a pic Bias goes...220K>4007>100/100v cap>bias pot with 56K to ground...


Darin

[LOUDthud]

As I said in my previous post, you need the cap coupled bias supply because of the full wave bridge.