Hi Max ... so happy I found you. I was reading here at this old posting about Johnson Fitness power board and I need some help if you can.
Link : https://forum.allaboutcircuits.com/...ol-board-johnson-fitness-jdyf02l-revg.110355/
At first I thought my UC3842 was cooked ... it has a very odd crater like mark on it but removed and built test circuit and is fine ... bought a new one anyway. What I found next is Q6 (beside Q7) is cooked ... so would you happen to know what those part numbers are ? Closest I can see on the smd marking (A6 for Q7) is it's a N chan mosfet ... but who knows. The marking on Q6 is completely gone and Q7 has BBH and A6 on it. It was described in that post that these two Q6 and Q7 are a set of push pull transistors ... I also removed Q7 to test it and it doesn't read like a mosfet should ... could use yer help there master.

Journey11

 

You also mentioned you may have some schematics for some of these brds mine happens to be JDYF02L Rev f but I saw that the g rev is nearly identical as I'm sure others are very similar as well.

 

Johnson Fitness JDYF02L REVg



References:
https://forum.allaboutcircuits.com/...ol-board-johnson-fitness-jdyf02l-revg.110355/
https://forum.allaboutcircuits.com/...johnson-fitness-jdyf02l-revg-repaired.176273/

 

You also mentioned you may have some schematics for some of these brds mine happens to be JDYF02L Rev f but I saw that the g rev is nearly identical as I'm sure others are very similar as well.

I only have info on the MC-60, MC2100 versions, unfortunately.

 

Hi again Max,
Last week when I found this forum and this thread ...
https://forum.allaboutcircuits.com/...ol-board-johnson-fitness-jdyf02l-revg.110355/
I remember finding a post from someone who had done a block diagram like schematic where he traced the pwm signal from the Q4 FET to Q6, Q7 .. back thru U8 and U7 ... to opto then to U2 .... I cannot find it there anymore. I thout I saved it but cannot find.
Maybe you saved a copy ? Repost if U can.
Barring that ... I need to confirm the Q6 and Q7 placements or rather which is the PNP and NPN ?
From memory of that partial schematic I found and when I removed them that Q7 is the PNP (BBH) part abd Q6 is NPN (BCH)
Is this correct ?