Made a mistake - need advice

A

Air

New member
Was messing with my EFP III and when putting the shunt board back in miswired the B power supply and fried the 53.6 ohm resister. Smokes the resister it now measures +300 ohms but got the power off real quick. 2 questions, can I replace the resister with a 51 ohm (closest I have) and whet are the chances I messed up something else?
AS always, thx for any help. -Chuck
 
51 ohms is fine; it just sets the current into the shunt regulator.

To blow up that resistor you must have fed it way too much current, so the chances are good that something else was fried at the same time.

I see two choices:

1) you know the drill, check each transistor and LED for intact diode behavior - conducts one direction, not the other, base to emitter and base to collector for transistors. And of course measure the other resistors. I don't have a convenient test for the shunt regulator chip.

2) Spend a buck at Rat Shak for a 51 ohm resistor and give it the smoke test.
 
Thanks for your time Paul. Had to buy about a million resistors in a package for $12.95 to find a 51 ohm value. Is there any chance this problem left the Shuntboard? should I look at the other two boards? Wiil report back after getting this sorted out.
 
The shunt Board looks like the "A" Reg end of the board is supplied from the new "A" Mono power supply, with the other end of the Shunt Reg (the B end of the board)is supplied from B power supply.
If so I have something else wrong, the 53.6 ohm resister was on the A end of the shunt board, and I had the B power supply crossed?
I need to try working on my bottlehead gear at first light instead of late night after a long day.
 
Also, try not to assume we have been sensible.  :^)  The "A" end C4S feeds the "B" end shunt reg circuit, and vice versa. The wiring is easier that way, as long as you don't try to make sense of it!
 
Big relief to know, will work on it now and be back later tonight with an update. Thx so much, probably saved me hours of looking in the apple tree for the strawberries. -chuck
 
I have got everything back together. But have a problem with the resistance checks.

T12 @ 53.4K (should be 83K)
T21 @ 53.4K (83K)
T32 @ 53.4K (150K)
I have checked every wire to eat terminal and find nothing our of place.
I have checked the boards for damage and all check good (431 is Unknown)

it is odd they all read the same. Don't really want to smoke test it just yet. thought I'd ask the board first. _Chuck
 
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