Does anyone out there have a schematic for this unit? Fixed a couple of problems with this unit already, but I am having a problem with the high voltage spiking at initial power on and then bleeding off over a 2-3 second period down to 0 volts.

Thanks,
Al

Hi,
What vintage? it sounds primarily like a capacitor shorting out, but could also be a rectifier problem if it uses a gas rectifier or gas regulator (loss of primary vacuum).

:
:Does anyone out there have a schematic for this unit? Fixed a couple of problems with this unit already, but I am having a problem with the high voltage spiking at initial power on and then bleeding off over a 2-3 second period down to 0 volts.
:
:Thanks,
:Al

Hi John, I think this unit comes in around the mid to late 60's. It uses (2) VR150 regualtor tubes that check out ok on a Hickok 539B. I found 4 faulty caps , replaced 1 and have the other 3 on order. The caps are .05uf on both regulator tubes and one other one. It seems like the HV is coming up before the Vregs do perhaps? Thanks for the reply! I think finding a schematic on this is going to be very difficult.

Regards,
Al

:Hi,
:What vintage? it sounds primarily like a capacitor shorting out, but could also be a rectifier problem if it uses a gas rectifier or gas regulator (loss of primary vacuum).
:
:
:
::
::Does anyone out there have a schematic for this unit? Fixed a couple of problems with this unit already, but I am having a problem with the high voltage spiking at initial power on and then bleeding off over a 2-3 second period down to 0 volts.
::
::Thanks,
::Al

Hi,
Are any of the old larger value filter caps in the circuit? Sometimes these can test okay because most cap testers/checkers use a much a lower voltage, and you might see the voltage rising to the point of breakover inside the caps. Personally, I do not trust any of those old can caps and would suspect those right away. Forget about "reforming" the oxide insulating layer in these caps.

If this is the case, the VR150's should be glowing very brightly if they are before the caps (normally they are only dim to moderately lit in use.)

Once the caps have all been replaced, check for misrouted wires (actually bent terminals and bare leads of components), and check the wires wherever they cross an edge, or corner of the chassis/subchassis, especially feedthroughs.

:Hi John, I think this unit comes in around the mid to late 60's. It uses (2) VR150 regualtor tubes that check out ok on a Hickok 539B. I found 4 faulty caps , replaced 1 and have the other 3 on order. The caps are .05uf on both regulator tubes and one other one. It seems like the HV is coming up before the Vregs do perhaps? Thanks for the reply! I think finding a schematic on this is going to be very difficult.
:
:Regards,
:Al
:
:
::Hi,
::What vintage? it sounds primarily like a capacitor shorting out, but could also be a rectifier problem if it uses a gas rectifier or gas regulator (loss of primary vacuum).
::
::
::
:::
:::Does anyone out there have a schematic for this unit? Fixed a couple of problems with this unit already, but I am having a problem with the high voltage spiking at initial power on and then bleeding off over a 2-3 second period down to 0 volts.
:::
:::Thanks,
:::Al

Thanks John! I will check into the vr tubes and how they glow at turn-on. You may be on to something here. Will also consider filter cap replacement.

Regards,
Al

:Hi,
:Are any of the old larger value filter caps in the circuit? Sometimes these can test okay because most cap testers/checkers use a much a lower voltage, and you might see the voltage rising to the point of breakover inside the caps. Personally, I do not trust any of those old can caps and would suspect those right away. Forget about "reforming" the oxide insulating layer in these caps.
:
:If this is the case, the VR150's should be glowing very brightly if they are before the caps (normally they are only dim to moderately lit in use.)
:
:Once the caps have all been replaced, check for misrouted wires (actually bent terminals and bare leads of components), and check the wires wherever they cross an edge, or corner of the chassis/subchassis, especially feedthroughs.
:
:
:
:
:
:
::Hi John, I think this unit comes in around the mid to late 60's. It uses (2) VR150 regualtor tubes that check out ok on a Hickok 539B. I found 4 faulty caps , replaced 1 and have the other 3 on order. The caps are .05uf on both regulator tubes and one other one. It seems like the HV is coming up before the Vregs do perhaps? Thanks for the reply! I think finding a schematic on this is going to be very difficult.
::
::Regards,
::Al
::
::
:::Hi,
:::What vintage? it sounds primarily like a capacitor shorting out, but could also be a rectifier problem if it uses a gas rectifier or gas regulator (loss of primary vacuum).
:::
:::
:::
::::
::::Does anyone out there have a schematic for this unit? Fixed a couple of problems with this unit already, but I am having a problem with the high voltage spiking at initial power on and then bleeding off over a 2-3 second period down to 0 volts.
::::
::::Thanks,
::::Al