Ampeg SVT CL screen voltages on different schematics

[tubeswell]

So having (spent several weeks on my life I won't get back and having) resurrected a dead one of these amps, I'm about to button it up and call it fixed. On the one I have fixed, the screen voltages are all about 390-ish and the plates are running about 670-ish as measured with my bias probe.

I'm mildly concerned about the screen voltage being on the high side (JJ6550s), but it appears (correct me if I'm wrong) that the amp was designed to run the screens at 380V. Or is that 345V?

Take a look at the two sets of schematics (output tube board shows 345V screen node, and sheet 4 of the Power Amp schematic shows 380V going to the screens) and feel free to opine about this discrepancy.

[Enzo]

As I read the schematic, I see 345v on the screens, but on the power amp circuit, I see the 380v supply used by the 12AU7 drivers. I don't spot a 380v on the screen reference, if I missed it, point it out.

[tubeswell]

Sheet 1 of the attachment is a scheme of the complete layout. It shows J18* on the main board going to J13** on the output tube board @ 380V. This is the screen connection between the two boards (brown wire). It was hooked up like this when I first disassembled the amp.

* the same J18 which is indicated at 380V on the schematic in Sheet 4 of the Power Amp (SVT-2 Pro) file. (THis is the same junction from which the 380V supply is taken for the 12AU7 CFs buffering the PI from the output tubes).

** the same J13 which is indicated on the Output Tube bd schematic as being at 345V. (Were these drawn by two different contractors? Did somebody at the factory forget to provide another R/C filter dropper between the 380V on the main board and the '345V' at J13 on the output tube board?)

[Enzo]

Or it is a drawing error.