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Re: [T3] Voltage Regulator

On 20 Jun 2005 at 11:10, James Montebello wrote:

> Ultimately, it's usually cheaper and easier to just buy another VR. 

I completely agree. I've never been able to rejuvenate a bad one, but I suspect 
I could if I replaced that resistor, polished the contacts, and then readjusted 
the whole thing. It's a LOT of work

I modify the Bosch mechanical VRs that I sell. I add a diode that should make 
them last considerably longer. I really don't know how much longer they might 
last this way, because I've not yet worn one out.

> Better yet, buy a modern solid-state VR that uses electronics to
> control the current flow.  These will last a lot longer than the
> mechanical units. 

Should be true, but I'm working with a 412 customer right now to get him a good 
VR for his early alternator system. This system originally came with a 
mechanical relay VR, but he bought a solid state aftermarket VR from JC 
Whitney. Both his old VR and the brand new one regulated at 13V. The transistor 
in the old one was leaky, so I've now replaced it to see if this changes 
anything. I'm afraid that this design dissipates too much power in that 
transistor, which then overheats and damages itself. It's a linear regulator, 
rather than a PWM (pulse width modulation) approach, so it has to run hot. This 
was is quite simple, but I'm not impressed with its performance so far.

It's another work in progress....
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

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