Did I Kill the DC Regulated Power Supply?

[Diablo]

I'm trying to put together an adjustable DC voltage regulator to supply the field coil on a Jensen F12N. I'm using a Hammond isolation transformer that puts out 80VAC input to the AudioWind Electronics-Salon Model SP-4 regulator. The field coil resistance is 680 ohms and I only want to put up to 100V DC, so I don't smoke the coil. During testing, I connected a 1K ohm-25W resistor to the output to test the regulator. It was working perfectly, and could be adjusted from 5-100V. I disconnected the 1k ohm load resistor, and again tried to measure the DC output. I was measuring 5 volts and as I turned the pot up the voltage increased, and then I heard a snap. Now I can only get a max of 7.5 volts output with the 1K ohm load resistor. I don't see any obvious signs of heat damage, but I'm certain I fried something. Are these regulators not designed to work if there is an infinite resistance across the output? Any guesses as to which component I killed, or how to test it? I've attached the specs on the regulator below:
Thanks.....

http://www.audiowind.com/pdf/sp-4.pdf

[Jazz P Bass]

The 'snap' sounds like the TL783 regulator went.

Easy enough to check.
Start at the bridge rectifier.
If Vin matches the Vac input & the TL783 output doesn't change, then the TL is bad.

The only item of interest that I see on the TL datasheet is that there is a minimum current requirement on the output. 15 ma's.

http://www.ti.com/lit/ds/symlink/tl783.pdf

[g1]

The only item of interest that I see on the TL datasheet is that there is a minimum current requirement on the output. 15 ma's.

I saw that too, but due to the poor English I couldn't figure out if that was just a requirement to get proper regulation?

[Diablo]

Thanks gentlemen. I was also wondering about the 15mA minimum. I was thinking that maybe the voltage climbed too high - above 125V - without a current load. On the schematic, there is a 22K ohm load resistor across the outputs, but I guess it didn't help enough to keep me from frying the regulator. I checked Vin to the regulator, and it has 125VDC, so I must have fried TL783CKC. I'll order some from Mouser and hopefully I'll be back in business.