A Look Inside the GM 10si/12si Voltage Regulator

For those of you who would like to repair your voltage regulator if you have the parts handy.
All parts:
MJD44H11 Transistor which allows the current to flow through the field winding.
6.2V (E4) zener
(2) transistors : K2F & K2X (PNP & NPN) equivalent to : 2n2907a & 2n4401
(2) capacitor chips
1n4005, 1n4006 or 1n4007 diode.
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[@111000100101001]

Thank You very much for offering this info to the diy folks like myself:)

[@electronicsNmore]

Glad to help! Be sure to rate thumbs up, subscribe, and look over my extensive video playlists below for many other videos of interest to you. Taking one minute to share a link to my channel with others on social networking sites would be greatly appreciated. Thanks! kzbin.infoplaylists

[@HomeBrewAudioNut]

I had the same problems. Output voltage and regulation: Laughable. In all fairness the regulator I had was from a knock-off of an SI-12 Alternator and was blasting out anywhere from 15 to 17 volts into a fully charged battery. I can tell you there's way better available in making your own regulators from op amps, PWM or linear voltage regulator IC's, or even more sturdy components. Think of the alternator as nothing more than a transformer controlled by the current into the rotor.

[@geojor]

very good, thanks ...

[@abousamah1967]

Very nice explnation Can we use it externaly for other alternator

[@INTERNA9]

THANX

[@Oldcomputer]

cool vid. Would be neat to see inside the regular old 4pin delco hei module.

[@electronicsNmore]

Unfortunately I don't have one on hand. Glad you enjoyed the video! I have a lot of excellent videos on my channel that cover many different subjects, so be sure to check out my extensive video playlists for other videos of interest to you, rate thumbs up, and share my channel with others. Thank You

[@marktheunitedstatescitezen185]

Have you thought how to get this alternator A GM 10 SI B.B low turn Charging High Amp to get to charge “ 48 v “ can it be done ?

[@sterlynali6679]

so did you get true with the repair ?

[@electronicsNmore]

Yes, left them out. They go to the bases of the transistors. They rarely go.

[@zx8401ztv]

You may have some etched resistors on that pcb, it must have limiting resistors. Dont want you to fail the repair :-)

[@lukesandbichler556]

Where are the resistors that determine voltage set point? What would be the easiest way to raise the voltage set point on this regulator?

[@luciendebeer5574]

If the 2 wires on the outside of the regular are changed the other way around and the alternator stays at 12 volt- doesn"t charge is the regulator broken or the alternator diode?

[@electronicsNmore]

Test the diodes and connection with the brushes first, if they're OK, then replace the regulator.

[@fabio40]

Is this the same regulator found in the 27si? It looks the same.

[@electronicsNmore]

Yes. :-) Be sure to check out my extensive video playlists for other great videos of interest to you, rate thumbs up, and share. Thank You

[@jimrojas62]

If I replace the zener to 12v, will that give me 24v charging?

[@electronicsNmore]

I would think that doubling the zener voltage used in that regulator would double the charging voltage.

[@jimrojas62]

@@electronicsNmore Thanks.

[@jonathangilbert9092]

I'd like a follow up video of this because I think I have a fried regulator and don't know how to test it.

[@electronicsNmore]

Very easy to test, with the engine running you should see a stable 14 - 14.5VDC output at the battery if it's close to full charge. If you don't, buy a new regulator. They aren't expensive.

[@jonathangilbert9092]

Hi electronicsNmore, thanks for the response, but I have to add something here. I checked the battery body ground and it had too much resistance on the one test, and was only showing 7 volts instead of what should be 12.6 battery voltage through the grounding point to the body, probably due to the resistance. Because the regulator grounds to the body through the lamp side path, the regulator wasn't sensing a rising ground charge, so I don't think it was shutting off the field voltage, which keeps rising as a result of positive voltage being pushed out through the B+ post. I don't ever see a ceiling voltage cut-off occur at the B+ or the field feed. 14.5 volts pushing through the regulator probably welded the transistor contacts together or something. From your video, it looks like I could use a multimeter on the legs of the big PNP transistor to verify that that isn't the case. Am I understanding this correctly? Do you know what a voltage check on the running alternator between a good ground and the grounding leg of the regulator should show me, so I know what to look for? Is that a good test, or should I run the test with a lightbulb type load in series with the meter leads? Thanks in advance.

[@jonathangilbert9092]

Hello again electronicsNmore, I wanted to follow up with what I finally figured out. It wasn't the alternators. I was able to re-install my original and right now it seems to be fine. I cleaned up the body ground and verified body voltage and battery voltage grounds. Even after doing that, the alternator on the vehicle was still way overcharging, but before I started the engine, I verified regulator through lamp to whatever ground I found on the engine was 9.6 ohms. That I suppose is what is supposed to differentiate between battery to ground and field to ground for step up charging purposes. Even though I thought I was out of the woods, when testing at that running engine, I was still disappointed to find too much voltage being blasted out of the B+ terminal. I thought that the transistor was burned up. The next day, I checked the fuses. I had 2, 20 amp fuses which were open, neither of which indicate anything to do with a charging circuit. One is listed for blower, which had been out for a wwk, and the other was for choke heater, of which I have no idea how long it had been out. I replaced them, and was not surprised to find the blower now working. What surprised me now was that in the key "on" self check position, the red charge light was now on, something it hadn't done with any of the alternators, and also, when I started the engine, the charge light went out so that was a big (HoRaY). I went ahead and swapped my original alternator back in, and as of a day later, it seems to be fine. I forgo and didn't carry tools with me if I had had a problem. So thanks for being a listening ear, and encouraging a people like me to fix a problem.

[@ZaheerKhan-jt6ve]

Can you please give me the internal schematic of this regulator.

[@BYENZER]

YES!! That would be excellent!

[@jimh712]

👍👍👍

[@electronicsNmore]

Glad you enjoyed my video! I have many excellent videos on my channel, so be sure to look over my extensive video playlists for other videos of interest to you, rate thumbs up, and most importantly share my channel with others. Thank you

[@humbertotorres2650]

Finally reverse engineer the 12si , 27si voltage regulator i have... How do i upload my pictures and schematic

[@electronicsNmore]

Send images to [e-mail] if you want them added to the video description area. I'll make sure you're credited. Thanks

[@blackbird309]

Would I be able to get access to this? I don't feel like paying 100+ for an alternator I can fix myself, or 25$ for a part I don't actually need. Thanks!