Testing Windings: Tools & Gear for Appliance Repair

[jim hardy]

A lot of scope shots posted here - I hope you don't feel too swamped.

I see you posted several while i was typing that first reply.

THANK YOU . You know engineers, it's always "More Data" .

Glad to hear speeding up the RESET decay time helped.

Sorry I'm so slow - I've learned your circuit by its signal names so had to swap back and forth to relate them to scope traces with pin numbers. But that's fine it is unambiguous.

Thanks - that's a cool device you have there.

 

[Guineafowl]

Post 45
IC2 7 is clock?
IC3-15 is RESET ?
So in post #45, RESET is yanked HIGH by Q1 turned ON and returns low well before ringdown is completed. Looks like that's when it starts counting clocks?
When Q1 turns OFF , RESET (IC3-15) 15 is clamped to -1 volt by IC3's internal diodes.

Post 46

So CH 1 is the "0" LED lit briefly? I can't quite tell whether it's aligned over first clock pulse on ch2, but RESET should light it about same time clock pulses start and it looks like that happens... .
CH2 is clock again ?

Post 44 IC2 pin6 swings only ± a diode drop, as expected. Pin 7 swings full range

Thanks, i feel a lot better now about the circuit. It makes sense . And it's clever.

I thought of you and this thread the other day. I was checking polarity of windings in an AC motor that a friend is rebuilding.
Put small amount of DC through it and verified its four poles were N-S-N-S with a Scout compass.
Found out you can overdo it and re-magnetize the compass backward so it points South...old jim

All your assumptions seem correct.

If @Tom.G agrees, I think I'll add some little decoupling caps to the TL082 as per datasheet, and build the lot up on some Veroboard.

Regarding your motor testing, I think I know of a device that might help you...

If you have a spare moment, I'd love to hear your opinion of the new gadget I bought - hand-cranked megger - thread in this forum.

 

[Tom.G]

If @Tom.G agrees, I think I'll add some little decoupling caps to the TL082 as per datasheet, and build the lot up on some Veroboard.

Go for it!

My brain was having a hard time sorting out the timing on the scope traces, many of them looked...strange?... I finally realized that the photos were of multiple traces (operating cycles) of the circuit overlapping in the photos. That's why for instance in post #45, the photo showed IC3-15 going negative before going positive; that just did not compute! I'm glad Jim and you got it sorted out. Looks like you've got a cool piece of test equipment!

I'm kind of busy this week and probably next, so will be spending limited time online. I will be checking progress here but with limited participation.

p.s. To increase sensitivity (get more counts) for poor inductors, try doubling R8. You may want to cascade another IC3 stage w/LEDs if you do that.
p.p.s. Nice call on changing C3 @jim hardy

 

[jim hardy]

Does your scope offer choice in horizontal sweep controls between ALT and CHOP ? Chop gives unambiguous timing relationship between traces whereas ALT depends on what's selected for trigger

Yes the heavy mid trace line is a giveaway it's multiple traces.

NIce Job by all here !

old jim