Fun Projects Voltage Regulator repair question

[Chris Bamford]

Yesterday I was setting the null point on my '24 Speedster, out of the car and using a 12-vt battery (per Ron Patterson).

Sadly, it never crossed my mind to remove the Fun Projects VR prior to this procedure. BZZZT!! and then all the factory smoke billowed out of the case. Oops.

Plan B was to convert the fried VR into a diode cutout until I got a replacement, then keep the diode unit as a spare. Upon opening the FP BR case I found that only one component seemed to have overheated. It is the rectangular gizmo circled in the photos below and is connected to the generator terminal.

So, maybe there is a path back to health for this unit. Can anyone identify this component and suggest an appropriate specification? There are no ID markings that I could see. There is a well-stocked electronic component vendor in our city and if this is all that's wrong I might be able to replace it successfully.

Thanks in advance.

[TRDxB2]

Email our Assistant Admin he makes new ones
Assistant WebSite Admin
1921 Model T Touring, 1930 Model A Roadster
Voltage Regulators, Starter & Generator Repair
www.modeltregulators.com
www.modeltstarters.com

[John E. Guitar]

I'm sure there's a circuit diagram floating around on the web...

[Moxie26]

Consult your WellStocked component supplier for replacement part, possibility of him fixing it for you.

[Chris Bamford]

Thanks everyone for the replies, and to John G in particular for that link. I have a better understanding now, think I know what is needed, and emailed our Asst Admin for further clarification.

Time to go T-ing in the sunshine!

[John E. Guitar]

You're welcome!

[AdminJeff]

Chris,
you fried the MOSFET! The rest of it should be fine. This is a common problem with these units, mine inclucded.

If you're interested, here's a link to the circuit diagram of the FP Voltage Regulator. Pretty basic design using PWM. Ours design is quite different but just as effective. Unfortunately the FP regulator became unavailable when Fun Projects was sold to Birdhaven. One of the critical parts became unobtainum.

https://www.cool386.com/regulator/regulator.html

I also sent you an email. I can send you a new N-Channel MOSFET (no charge) or you can send me your regulator and I'll fix it for you.

To help prevent this in the future, ALL my new VR's now include this little warning, right up front. Remove it at your own risk!
If you want one of these stickers to put on your FP regulator, let me know - Im happy to send you one, no charge.
.

1000 Cutout can tops just arrived a couple of days ago - the last piece of the massive puzzle. I'll been having VR assembly parties for days now. Mass quantities available everywhere soon!

Jeff

[Chris Bamford]

Jeff, that is great news. Thank you kindly. I will send a PM shortly.

Congrats on getting the big volume of VRs underway!

[Mikey1968]

Jeff,
May I make a suggestion?....on your next batch of warning stickers, provide your contact info stating something like for service and details, contact blah blah. Might get you even more business. I know if my FP VR fried and I put that sticker on, a quick look would show me where to get help.
Cheers,
Mike

[SurfCityGene]

Now That's the kind of vendor service we're talking about Jeff!!
You know you can a trust a product when you read comments like Jeff posted! Thanks

[AdminJeff]

Jeff,
May I make a suggestion?....on your next batch of warning stickers, provide your contact info stating something like for service and details,

I’m working on that! A round sticker on the bottom.

If you pop the top off, all my contact info is on the circuit board.

The new tops fit so well that I’ve decided to stop spot welding the tops on and just put a slight bend in it in 2 spots. This also means it will be user adjustable (there are pros and cons to this). If someone needs to raise or lower the charge voltage, it is now possible.

Jeff

[Chris Bamford]

And it's fixed... Woo-Hoo! Thank you Admin Jeff!

The fried component was a MOSFET (metal-oxide-semiconductor field-effect transistor), basically a switching device, connected to the generator terminal. Jeff says this is the most likely failure with these VRs and that reminded me that John Reagan had described a common failure condition that preserved all but one replaceable component. And here we are.

These MOSFETS are apparently dirt cheap in quantity—Jeff offered to mail me one no-charge—but I sourced mine locally for CDN$10.50 full retail OTC. Swapping it into the VR was straightforward and I took the extra step of affixing the cover onto the base with a couple of itty-bitty screws. Another Jeff suggestion. Originally there were two small spot welds holding things together.

I used a good working mechanical cutout while setting the charge rate and installed the repaired VR once everything was adjusted properly. Max charge rate is now 5-6 amps, which should be plenty. My speedster is an easy-starter so the battery tops back up quickly and the LED headlamps don't pull the ammeter into the negative.

[AdminJeff]

Chris,
Absolutely PERFECT job!!! You can get them on Amazon in a 10 pack for about $8. I order them in 500 quantities, so my cost is much better:)

And yes, the MOSFET is the component that fails most frequently. Most of the time it gets blown when folks connect the generator tab to the battery tab to test if the generator is working. You can do this all day long with a Cutout. You CANNOT do this with a Voltage Regulator. If you do that, the MOSFET self destructs and shorts the generator output to ground. Permanently. Thus requiring the fix that Chris just finished.

On a side note, I got the Model A version (positive ground) of the regulator in the mail to 2 folks who offered to test them. Results of that will be forthcoming. It works in my 1930 original(ish) Roadster, but will it work in their cars???

Jeff