8 flat pins is the earlier 300W version while 7 flat and one round is for the later 600w version. They had completely different controllers, but those do appear to be plug compatible. I am guessing that the change to the power supply plug was to prevent people plugging 600w heads into 300w power supplies. If you want to do it the other way around it should be fine.
I checked the earlier head and the plate on top has the serial number (5H12321) and specifically mentions using ESD (300w total) or ELH (600w total) globes. So now I have no good theory as to why the power supply plug changed.
Hi Paul,
My 500H head also has a higher serial number (5H11965), than the Ilford documented change (all units above serial number 5H11471 adapted for 2x300W lamps). It has an flat 8 pin plug, no round pin... The head
has the head baffle plates, as it should for carrying 300W lamps. It also mentions to only use 300W lamps on a sticker on the inside of the front panel of the head.
In addition, my 500S power supply, also with 8 flat pin connector, shows 400W as the maximum output on the back plate, yet connects up with the head fine, and has no problem coping with the extra load. I bought the unit second hand, however I am pretty sure no illegal modifications were made, and the unit came as it was delivered by Ilford.
I really think Ilford underrated the original 500S power supplies, and Ilford simply decided to modify the heads to allow for fitting 2x300W, while using the original stock of 400 Watt rated 500S power supplies fitted with the 8 flat pin connector until they ran out the production run, to only swap them out for the newer version afterwards.
In addition, the 7 flat, 1 round pin connectors, may be specific to the 500CPM controllers, as they function differently. If I remember it well (I don't have one), someone here on APUG mentioned the 500
CPM controllers were specifically designed for split grade printing (0/5), while my 500
C controller only has basic grade (0-5 in 1/2 grade increments) and time settings.
But correct me if I am wrong on this last point...
