Old S-32-P vs Feeder Gas Control Board

[Ron B]

So, my gas quit working and I pulled the control card out. It has power in at the card leads but none on the leads out to the solenoid. It is a #091746 miller part which is of course is discontinued. I've looked all over the web plus called a few repair places with no luck. Does anybody have one of these boards or know of a retrofit that might replace this one?
Thanks,
Ron

[jjohn76]

Hi Ron, I sent you a PM. That is an old feeder... which is good from my standpoint. The operator manual for it has everything you need to repair the board. Post some photos or the top and bottom side so we can look for failed transistors or signs of corrosion/failure.
Jon

[jjohn76]

Ron, here are some things to check to see what you want to do with the S-32P.
FIrst check for continuity across fuse F50. If it's blown, replace and continue checking below because something else caused it to go.

Q51 - this is the mosfet used to energize the solenoid in your gas valve. It switches on and off very quickly, like a buck converter. It's duty cycle (on vs off time) is based on the voltage across your power leads, which are what you measured going in to the card. It basically keeps the voltage across your gas valve solenoid at around 15V. Check resistance across the drain to source - use pin 1 on your gas valve connector and either side of R60, let us know if it doesn't read open circuit or very high resistance

Q50 is used as a linear power supply that provides 15V from the input voltage. Check resistance from the positive terminal of C50 (cathode of D50, or the collector pin on Q50) to the emitter of Q50 (pins 12, 13, or 15) on U50. If it doesn't read high resistance, there could be a problem.

U50 is a SG3524 PWM controller, which basically sets the duty cycle for Q51 to keep the voltage across the gas valve at around 15V. Check resistance across U50 pins 12/13/15 and U50 pins 11/14. The / means that those pins are connected on the board.

If you don't want to mess with it, you may be able to take it to some electronics repair place in your area. Print out the circuit diagram, parts listing, and board photo from the manual.

Hope this helps,
Jon

[Ron B]

Thanks Jon. I'll look at it again when the snow stops. I'm a retired welder turned hobbyist so it's not a pressing matter. I believe what happened was, I use the feeder on a Dynasty 280 with cv and forgot to switch the power lead and pumped hi frequency into it. That's when I found the gas wouldn't turn on. My goof.
Ron

[Bushytails]

If you fed it HF and only lost the gas control, count yourself lucky!

I think I see the real problem here. You have a dynasty 280 with CV. I'll take it and trade you a dynasty 300DX instead. Since it doesn't have CV, you won't be tempted to connect the feeder to it, so you won't have this problem again.

[jjohn76]

HF'll do it... Check across diode D50 too. With HF, that might have been the path of least resistance...

[Ron B]

I might consider that bushytails. NOT!