Dynaco ST70 power supply transformer short problem - HELP!!

[Jcricket]

LIGHTBULB!!!!!!!!!!!!!!!!!
Great idea, vacuum tube on top of solid state.

Sometimes the obvious is the best. I will try this !!!!!


Mark

 

[Pio1980]

LIGHTBULB!!!!!!!!!!!!!!!!!
Great idea, vacuum tube on top of solid state.

Sometimes the obvious is the best. I will try this !!!!!


Mark

Credit due.
https://audiokarma.org/forums/index...120-wont-hold-bias.657410/page-2#post-8760949

 

[gadget73]

those diodes do nothing to reduce the current flow through the tube, so they are not a magic solution to all rectifier ills.

 

[Pio1980]

those diodes do nothing to reduce the current flow through the tube, so they are not a magic solution to all rectifier ills.

No but the bridging jumper does double the current capacity of whatever 5AR4 is in the socket by paralleling the halves, rather than duty cycling them singly without the diodes and bridge jump.
D.G. explains it well in the link.
https://audiokarma.org/forums/index...120-wont-hold-bias.657410/page-2#post-8760949

 

[gadget73]

missed the jumper, yeah that will help. The usual method still uses the plates individually.

 

[Pio1980]

Have you tried retensioning the socket pin clips, checked solder joints?
Fwiw, the pin clips in the Dyna octal sockets can be interchanged if broken.

 

[Jcricket]

I still suspect a possible socket problem, with a bad\no contact to one rectifier anode.
If it is a Dynakit, they came with two screw & nut fixed front accessory sockets that can serve as replacements for defective/ charred chassis tube sockets.

I think I have a few nos sockets for this unit in my collection. I'll check and replace if I find any suspicious elements.

Sounds like you may be running half wave rectification on that amp with one side of the HV gone...

Sorry for the delay in responding to you. You hit it on the head. This is exactly what happens after the rectifier tube has run for several hours. One side goes kablooie