View Full Version : Honeywell?
02-01-2006, 06:15 PM
Ran into an old boiler control system and it had a (R7503A-1018) looked to be a transformer, but can't find any reference to it???
02-01-2006, 07:09 PM
I found something with it in the diagram, looks like a 12v dc transformer.
02-02-2006, 06:32 PM
not sure that's it, but could be--could be. it is rather large and is mounted to a metal 4 switch box (vert.)If I get back there I'll put a meter on it.
02-02-2006, 07:08 PM
Thats the only refference that honeywell has to it on the web. Maybe you would have better luck calling tech support. Personally i have never heard of it, seen many boiler controllers but not anything with this r7503 converter.
02-03-2006, 05:08 PM
The R7503 was officially known as the Mod motor convertor. It took a modulating DC output control signal from a R7500/T7500 series of electronic controllers and converted it into a floating 24 volt outlet to drive a very specific line of Modutrol motors (M944B/E, M945B/C/G) and/or step controllers that had no internal balancing circuit. The R7503 had an integral transformer as you observed and also contains the balancing circuit that is absent in the motors. The R7503 monitors the feedback potentiometer in the Mod motor, compares it to where the control signal is calling for, and drives the motor accordingly.
I still have literature on this device, if you are interested. I can scan it and create a document to E-Mail, or send it Pony Express.
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