Another GK500B modulator question

[wa2dtw]

Happy New Year everyone!
Am trying to get a GK500B modulator into working order.   The previous owner made a modification that I cannot understand:
On the schematic, the 811A's are in push-pull, with the center tap of the filament transformer going directly to ground.   However, the previous owner added a 5K resistor between the center tap and ground.   Can anyone figure out why he might have done that? 

Thanks and 73
Steve WA2DTW

[WD5JKO]

Steve,

  That 5K will drop enough voltage to turn off the 811's with reverse bias. Look for other mods such as a relay to short out the 5K. Maybe the prior owner decided to keep the modulator HV on, and key the cathode bias resistor with a relay?

Jim
WD5JKO

[W2PFY]

Check to see if it has the original plate transformer. It may have been replaced with a higher voltage one. Jim, comments would also apply if that were the case. The original owner may have been running it at higher voltage where bias may have been applied to the modulators and he may also have put in a circuit where the modulation meter is remotely viewed.   

[wa2dtw]

Many thanks, Jim and Terry.
Yes, there is a relay in the circuit.
And yes, the original plate transformer was apparently replaced by a higher voltage transformer.
Am trying to figure out whether I should leave it in the circuit, or to find some other way to drop the plate voltage.


73
Steve WA2DTW