Solid State Regulator Reliability?

[lardawge]

Hey Matt, that is very interesting. Almost looks like it’s the same person who built these.

Wouldn’t the regulator be the determining factor on 6v vs 12v?

Do you know how to test each component? I would love to figure out what burnt out.

Part numbers are going to be hard. The diode looks like it is partially rubbed off. See pics.

How is the diode attached on the bottom? Is it bolted to a heat sync or something that can dissipate heat?

_________________
11/2/54 L227 Strato Silver Ragtop - Soon to be L41 Black - Build Thread
1/7/55 L275 Light Beige

[qwerty]

The regulator ceramic gizmo is a 12V alternator part that has been modified by sawing off some unused part so it fits in the regulator can. Similar to this one:

https://store.alternatorparts.com/d691-regulator-19si-20si-alternators.aspx
There is a 6V version too.
https://store.alternatorparts.com/search.aspx?find=d10se6
That’s the only difference between the converted 6V and 12V electronic regulators like these that are on the market.

When the generator is outputting max current it goes through the diode to the battery B+. Schottky power diodes have a forward voltage drop of 0.5V
at current levels of 40 amps. So with the lights on or with the battery low and needing a big charge, the diode has to dissipate 0.5 x 40=20 watts. Insufficient heat sinking of the diode, and being inside a can and bolted to a hot engine means the diode overheats and fails (or gets so hot that the soldered connection melts).


The diode can be checked with an ohmmeter.
I’ll check the diode specs if I can find the part number.

[Matthew Tolbert]

Lardawge yes even the epoxy used to mount the new regulator, the brand of the capacitor and varistor used and the section cut off of it are the same. My diode doesn’t have any numbers left so not sure about it. Yes the regulator would be the determining factor I just would not have thought there would be a 6 volt version like that but QWERTY proved that thought wrong, but that’s why I wanted to see the part number so I could look up it’s specs. Cool to know these exist though.

As far as testing goes like QWERTY said you can check the diode and capacitor with a ohm meter. The capacitor and varistor wouldn't keep it from charging they are there as a filter to smooth out the DC output. mine had both broken loose once after my initial issue and it still charged fine. I found it when I opened it for inspection. As for the diode there is a anode and cathode, for that diode the anode is where the wire is attached and the cathode is the canister/mounting stud. Disconnect the diode from the circuit, set your meter to ohms or better yet if it has a diode test capability use that and put the red lead on the anode and the black on the cathode and you should get a small value then switch the leads and it should read OL. If that’s the case the diode should be fine and the regulator would be suspect or other connections that could have came loose. As far as testing the regulator I’m not sure of a way to test it so can’t help there. My diode looks to be mounted just like yours from what I can see so no heat sink. I’ve tried to think of a way to add one but with the limited space makes it difficult.
_________________
Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S

[lardawge]

Thanks both for the information! Do either of you know what the specs would need to be for the diode? I see a few different ones on Amazon so not sure. If you have a source, that would be great.

I am wondering if mounting it to a piece of aluminum vs a thin piece of steel would help a bit with the heat. Once I get specs on the diode, I can confirm if that or the regulator is fried and start experimenting.

In the meantime, I am going to reach out to Don and let him know what I discovered. Would love to hear his thoughts on how it would ever be possible to dissipate the heat.

The other thing that might be a good idea is to cut a few slots on the backside of the regulator housing so that the heat has somewhere to go.
_________________
11/2/54 L227 Strato Silver Ragtop - Soon to be L41 Black - Build Thread
1/7/55 L275 Light Beige

[Ovally]

[Matthew Tolbert]

I do not know what the specs are for the diodes that were used. My understanding is you can use a lot larger one than needed if cost and space are not a factor. So I bought some 600v 80amp ones off eBay for around $3 each. I went off price because they are the same size as the ones we have now. Those numbers are the max they can handle before failure. Here’s the eBay link.

https://www.ebay.com/itm/261311028051?mkcid=16&...media=COPY
_________________
Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S

[lardawge]

[Ovally]

You can place the diode with heat sink further away, then you need 2 longer wires but that was not necessary in my case.

Regards.
_________________
VW Bug Oval 1953
VW Bug 1200 D motor
Porsche 911S MFI 1970
Mazda 929 Hardtop 1977
Mercedes SLC 180 Roadster 2018

[Matthew Tolbert]

Yes you could mount it and heat sink remotely. Just follow the large red wire on the regulator that goes down to the starter and take it off at the starter and put it on the anode side and add a wire from the cathode side back to the starter. It all could be mounted right by the starter. Just make sure it’s all isolated from ground. Of course you also have to connect the wire inside the regulator where the diode was mounted. The diodes only purpose is to prevent the battery from draining while the engine is off.
_________________
Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S

[lardawge]

Hey Matt, can you give me an ohm reading on a good diode?
_________________
11/2/54 L227 Strato Silver Ragtop - Soon to be L41 Black - Build Thread
1/7/55 L275 Light Beige

[Matthew Tolbert]

I’ll try to get one later this evening I’m at work right now. The more I think about it the more I’m liking the remote diode idea. It gets it away from the engine heat, you can mount it on a nice heat sink and less stuff inside the original regulator. If I have any more issues with mine I may go this route.
_________________
Matthew Tolbert
1958 ragtop
1961 doublecab
1965 Notchback S

[qwerty]

Here are readings from a good diode

[qwerty]

Here is a reading of the MOV. About 6K ohms.

[qwerty]

Here’s a schematic of the conversion.
The ceramic block has Field, D+ and Ground connections.
51 is B+ to battery/starter/fusebox
61 is really D+ and goes to red generator light in speedo.

Overall it looks like they disassemble the core regulator, then plate the metal pieces and paint the can. Then reassemble with the phenolic separators and sometime plastic isolated rivets to get the connections they want. Wired connections seem to be amateurish and some components are not well mounted for vibration effects. And the diode as stated before has insufficient heatsinking.

[qwerty]

Here’s my failed 6V photos

[Ovally]

[qwerty]

Electromechanical regulators have four functions:

Voltage regulation (by varying the Field current)

Battery cut-out (disconnects the generator Armature or D+ from the battery 51 B+ when the generator output is too low). This occurs when RPM is too low or engine is off. Keeps the generator from draining the battery under these conditions.

Overvoltage protection (cuts field current if generator exceeds voltage limit)

Overcurrent protection (cuts field current or forces cut-out condition if the electrical load due to headlights/starter/dead battery current draws exceed the generator current output limits.

With this style of electronic regulator conversion, voltage regulation is performed by the ceramic module and cut-out function is performed by the blocking diode. It is possible that the ceramic module could implement overvoltage protection, but it cannot provide overcurrent protection function as the ceramic module has no ability to measure the current between the generator output D+ and 51 B+. This is a major shortcoming of this design.

So say you have a ‘dead’ 6V battery and you jumpstart the car. Once it is running and the jumper cables are removed, the generator/regulator could be trying to supply 50+ amps while trying to charge up the battery. With no overcurrent protection….poof goes the diode or if it doesn’t blow open, it overheats and melts the wires to it or the generator armature winding/soldering.

[Ovally]

[aa390392]

[Zwitterkafer]

Some thoughts:

If the wire inside the regulator came that close to burning, what about the B+ harness wire connected to the regulator? Is it still fine, or maybe a little cooked under the insulation?

Fusing the regulator B+ terminal is interesting....have extra fuses in the car. So long as the ignition switch (and therefore the coil) always sees power. Best to have some kind of indicator that the fuse has blown, otherwise in daytime it may be possible to keep driving too long from the battery alone.

The engine compartment is not a good place for that 10uF 25V electrolytic capacitor, which will eventually dry out from the heat and fail. Power film capacitors have a better heat rating.

If the diode approach is at all viable, maybe it could be mounted to a CPU fan heatsink.
_________________
"Criticism comes easier than Craftsmanship"
- Zeuxius, 400 BC