Restoring a 90's JTM30 to original

[bluezmax]

Hi 18 Watters !

So I bought this 90's JTM 30 head which actually was a JTM30 combo that got converted to a head using a JTM60 head shell.
It's relatively unmolested but the volume is extremely low. Upon inspection, I can see the previous owner modded the drive channel by adding a couple of resistors to 2 of the clipping diodes to make it asymmetrical (which I think I will keep as is...).
I've already ordered a cap to replace the blown out C108 which will probably help the volume issue.
But next to C108 I noticed that R107 (which on the schem is a 4.7Kohm) seemed to have been replaced with a 39KOhm and a 120Kohm resistor in parallel which would result in 29.43 Kohms. Which seems like a massive difference. I'm waiting on the new cap to install it and test voltages but I'm assuming these resistors were replaced in order to lower the bias which would then affect the overall volume if biased too cold.
It currently has some russian 6n3c-e in there but just to be sure, I ordered a matched duet of Sovtek 5881/6L6GCW tubes that I will pop in after checking the voltages.
What voltages should I be seeing at the power tubes ?
What would you set the bias at if I have to change those resistors to achieve the correct bias ? And how would you achieve it (what combination of resistors or single resistor would you pick?) ?

Thanks,
BlueZMax

[bluezmax]

So here's a little more data to work with. This is with the 6N3C-E tubes that shipped with the amp. I do have new Sovtek 5881/6L6WGC tubes to throw in there.

​Plate voltages:
V4 = 460V
V5 = 456V

Plate/cathode current:
V4 = 15.2mA
V5 = 14.9mA

Calculated dissipation:
V4 = 7W / 34.1%
V5 = 6.8W / 33.1 %

Which explains why the amp is so quiet....
What would you guys do next ?
Replace the 29K Ohm resistor with a lower value somewhere in between the 4.7K Ohm from the schematic and maybe 15K Ohm ?
What value would you try first ? I have a full assortment of 1/2W and 1W resistors to experiment with....

Thanks in advance !
BluezMax