Heathkit AA100 151 some repair direction needed

[kaplang]

Trying to get a Heathkit AA151 back to operational. It has no output at all.. When it is powered on all the tubes light but after a few seconds of being turned on the GZ34 rectifier tube arcs and the amp meter I have in line with the power cord and variac shows greater then a 2 amp draw. This only happens for a for a split second and then it settles down to a 1 amp draw and then it starts all over again. Rectifier tub arcs and then greater then a 2 amp draw. I have tested the tube and it tests good. I also had another tube to try and it shows the same problem. I don't think my problem is the tube. I need some direction at where to start looking.

Any help here will be greatly appreciated.

George

 

[tcdriver]

What you describe could be caused by a shorted or very leaky power supply capacitor. Test all the power supply capacitors for leakage and value. Do not continue to arc your rectifier tubes, they will certainly be damaged.

 

[gadget73]

yeah, bad filter caps sound pretty likely to me as well.

 

[kaplang]

Will test and see.
Thanks

 

[shelly_d]

If they are as old as the rest of the unit, I would go ahead and replace all the power supply caps. If one is going bad, and it looks like that is what is happening, then the others could be end of life as well.

 

[kaplang]

Had some equivalent PS caps. Bypassed the can caps and put them in place on the bottom. This has solved the arcing of the rectifier tube and the high amp draw. The amp is now delivering output but it's still not right. Input using the MAG inputs gives oscillation when the volume goes up above 1/3 of the volume control.
I will be getting some replacement can caps from Hayseed Hamfest.

 

[gadget73]

could be another capacitor in there someplace. Oscillation is sometimes caused by poor power supply decoupling (aka bad filter caps) but it could also just be something it does if the inputs are open.