MSefi.com read only forum (Jan.15,2018)

All looks good on megatune 2.25p except no RPM or O2 adjustment. RPm stim switch set to PNP, V3 jumpers per Hal/optic/EDIS. I worked the trouble shooting section; no luck.

Suggestions?

The O2 won't respond until you get an RPM signal. Are D1 and D2 jumpered out?

Yes, D1 & D2 are jumped. The diode is in place at D2 but jumped also. Q12,Q9, & Q16 are not installed.

With the RPM switch in NPN mode, do you get 5 volts at TachSelect?

5 volts at TachSelect: No, I'm useing the negitive post on the stim as a ground.

Ok. Check to be sure the optoisolator isn't shorted out.

No 5VDC at tach select. U4 is the opticislator, correct? I can't find a pin-out. Is there a link?

I think that opto is U3 on board 3. 6 pin. pinout anyone??

Matt, thanks for your help so far. I found your advice to others with the same problem :

"If you apply 12 volts to TachSelect, the voltage at TSEL should drop to zero.
If you ground TachSelect, the voltage at TSEL should go to 5 volts.

Try checking the voltage at TSEL when you ground pin 24 on the DB37, and when pin 24 is not grounded.
With pin 24 grounded, you should see 0 volts at TSEL; with pin 24 not grounded, you should see 5 volts."

Should I try this? I'm unsure of the testing for U3 without a pinout .

Kelly, thanks for the help. With the RPM switch in either postition, I get 4.96 VDC at TSEL. So one of us has a problem there.

I found U3 as you suggested. Pins 4,5,6; diode test between 6 & 4 seems fine but I'm unsuer of the symbol @ 4/5. Can you shead any light?

Nice working with you. Update me with any progress & maybe we can figure this our ourselfs.

U3 is an opto isolator. It is somewhat like a mechanical relay. If you apply the correct current to the input to light the LED, the output transistor conducts so acts like a switch. its purpose is to provide electrical isolation between two circuits.

KLattig, your circuit appears to be working OK. It may be settings; could you post a copy of your MSQ file?

Matt; I've got 0.007 VDC at techselect & 4.96VDC at TSEL (no RPM on megatune). I may have shorted something by useing a 12 Volt AC adpator.

Plus there is no stim schamtic for the stim 2.21 that I can find.

thanks

No voltage to Techselect. This is my third post trying to get help from Matt for the same issue.

You can self-test the stim (not connected to anything except 12V DC or a 9V battery) by :

1. jump DB37 pins 26 and 28 together
2. jump DB37 pins 24 and 36 together

Start with the RPM knob turned all the way to the left or counter clockwise. Put the switch on NPN. As you slowly turn the RPM knob clockwise, the IG LED should begin to blink telling you that the tach output from the stimulator is working.

wrongear wrote:No voltage to Techselect. This is my third post trying to get help from Matt for the same issue.

I am having a hard time following all your separate threads. Let's see if I can put them together in one thread.

wrongear wrote:Matt; I've got 0.007 VDC at techselect & 4.96VDC at TSEL (no RPM on megatune). I may have shorted something by useing a 12 Volt AC adpator.

Plus there is no stim schamtic for the stim 2.21 that I can find.

thanks

The 2.1 schematics are the closest.

http://www.megamanual.com/v21stim.htm

If you apply 5 volts to TachSelect, does the voltage at TSEL drop to 0?

No, it does not drop to zero; remains at 4.96

.

Ok. When you apply 5 volts to TachSelect, check the voltage at both sides of R12 and let me know what you find.

with 5 volts applied to Techselect I have .017 volts on both sides of R12.