bias taps on rectifier

[gary sanders]

My bias winding on my 124 ODS clone shorted out and I had seen on older amps used a tap off the rectifier instead of a winding just for the bias.heres a pdf on it,whats the pros and cons of using this type of bias?

[Bob-I]

I don't know of any pro or cons, other than perhaps you need to drop less voltage when you have a bias winding so less heat dissipation, but that's minor.

Are you sure the bias winding is shorted and not open? I wouldn't run an xformer with a shorted winding as there will be current flow. Ohm it out and make sure it's open/safe before you do this.

[FYL]

whats the pros and cons of using this type of bias?

The series Rs turn the circuit into high-Z, with much higher time constants and a spongy/slow voltage response. Safety is also quite poor with this kind of circuit : any wiper or pot problem leads to no bias, runaway power tubes and a dead OT.

[tubeswell]

Why not just tap it off one side of the HT secondary with a voltage divider? (like so many fender amps)

[Structo]

I know it's not what you want to hear but I would replace the PT.

$78 plus shipping here.

http://shop.amppartsdirect.com/Vintage- ... -18004.htm

[gary sanders]

I know it's not what you want to hear but I would replace the PT.

$78 plus shipping here.

http://shop.amppartsdirect.com/Vintage- ... -18004.htm

I think Id be better of to do that.Thats a really good price.Think I will go ahead and get a choke and reverb driver while Im there and save some shipping.

[gary sanders]

Ohm it out and make sure it's open/safe before you do this.

Could you explain how to do this?Do you mean just check the leads for short/continuity?