I have compared the pictures with both the stereo VU and the mono PPM/VU meters that I have. Both boardsets are the same, except for 1 resistor, and of course the Eeprom (or something similar) that is used. The yellow sticker on the Eeprom shows you whether its stereo VU or mono PPM/VU. I can see the resistor though, it tells me that the meter shown in the picture is mono.
But it could be that the mono meters are made in different scale readings..... Could it be these are specially made for a readout of RFI ?!? What does the sticker say ?
Anyway, I have digged up a few meters already, and I only need 4, not 8. So I will pass on these (sorry for your time).
But to help you a bit with the sale :
I think I have a schematic of the 85470 interface card of the meters somewhere.
If not, I'll draw one and post it here (it's a simple PCB with a just a few components). This card drives up to 8 meters. It needs -24v, -18, +18 and +5v (+5V is not really necessary).
With this board, Intensity can be adjusted with a simple pot. PPM/VU mode can be switched with a simple STDP switch, and you can also switch between normal PPM and fast PPM modes.
I use a seperate switching module for it with a few extra switchoptions and extra inputs. (SL544 meter switcher)
I also have the calibration and pinout documents of all 5K meters in digital format. Phase (SL575), mono PPM/VU (SL574), and Stereo VU (SL578). Schematics ?.... maybe in paperformat, maybe not.
Oh, just a sidenote, the lamps in the used 5K meters are usually dead. Without the lamps, the meters don't show anything. I replaced them with leds in mine.