Ahh, thanks.

Interesting a WH5 runs better than a WH6. I think I’ll be the first person to run a 135W SOX on a WH7.

I personally prefer to run my fluorescent and HID lamps at full power whenever possible.

I agree, I think a WH7 should work, but I’ll have to verify with a multi meter if I get it. I’ve heard of WH8s actually overdriving 135W SOXes if wired certain ways such as using more than two output wires.

Alright, I just ordered the Workhorse 7 off Amazon.
 

When you take your measurements, make sure that the lamp runs at 165v 950mA.

It's difficult to measure lamp current with a high-frequency workhorse ballast. A good method was described by GLOBE COLLECTOR in this thread. Unfortunately he deleted his description in his gallery which was here, and alas, I never tried it.

But since I have numerous 135w/180w magnetic ballasts, where a clamp meter works quite fine for arc current measurement, I exploit light-meters to measure the light output of the same setup. I first run a 135watt lamp with the magnetic ballast, check for the current, then meticulously measure the light. I simply swap out the magnetic ballast for the HF electronic ballast (keeping everything else the same, including items far from the setup) and measure the light output again. Notice that I largely ignore the lamp current. But I try to do it "safely", first using one red wire (plus the yellow on the other socket side) then two reds wired together, then three, etc. Did this with a few WH5s & WH6s, but not with a WH7 yet. When I get one myself, I'd start with one red, going up to 4 reds together and check the light output.

The WH5 & WH6 are safe for a 135w SOX lamp with all 4 reds together - lamps are under-driven. The WH6 heats up a little after 1 hour on a 135w SOX since this runs at maximum trying to light it. The 90w lamp is also fine using either a WH5 (3 reds, but underdriven) or WH6 with (4 red wires, nearly correct output). I'll attempt to post some info over the winter. I also acquired a SOX-E 66w lamp which might work even better with the WH5 or WH6.

As they're advertised, the workhorse ballasts are quite "adaptable". I used a WH3 ballast with a number of used & new 26w SOX-E lamps. It appears that a WH3 will overdrive some used lamps by about 25% (more light), however in less than 5 minutes the WH3 pulls back. The output settles down to what I get with a 35/55w magnetic ballast. I'll be repeating these tests as I recently got a Tridonic OMBX26 magnetic ballast specifically to measure the light output of 26w SOX-E lamps.

Thanks for the info.

When the WH7 ballast arrives (which should be Friday) I’ll try one red wire and one yellow going to the lamp, if the lamp doesn’t warm up satisfactorily then I’ll pair two reds and see if it improves, and so on.

-UPDATE-

The ballast has arrived. It has 2X reds, 2X yellows, 2X blues, and the black & white input wires.

That one is made for 2 lamp CFL and/or fluorescent. Not sure how to wire a sox lamp with it. At least you can try up to 2 of the red and one of the yellow. Not sure if you can connect the reds & blues together.

Well, I can confirm you can safely operate a 135W SOX on a Fulham Workhorse 7 ballast using 1X red paired with 1X yellow. I’ll definitely try using 2X reds plus the 1X yellow which I believe will deliver better performance. The lamp seemed to warm up decent but definitely I think it can do better. In conclusion, a WH8 is probably a better option, but the WH7 is a viable alternative option.
 

Any updates using this type of WH7 ballast (2red + 2blue + 1yel)? Is your 135w lamp lit with it? Tried 2red+1blue with one yellow yet?

Not yet, but I’ll try to do it soon when I’m off work.