86206-90K00 24V-12V toyota converter (1 Viewer)

[george_tlc]

Dan has one of these old anchors that lost some of the magic smoke.

I've just repaired it after reverse engineering the schematic. Both small signal transistors were dead as well as the zener. Looks like Q702 died and caused a chain reaction that blew Q703/D702.

Anyhow, figured if anyone is ever stuck with one of these old converters and needs to repair it, it would be good to post up the info I put together.

I repaired the unit by replacing Q702 and Q703 with 2N2222A transistors with a little lead bending to get the correct E-C-B orientation. I cobbled up a zener with some lower voltage ones I had on hand (connected in series to get close to 15V for the Zener voltage). The unit runs around 13V output up to about 2A. It is fused at 3A.

This is **NOT** a DC : DC converter, so any excess voltage gets dumped as heat into the big heatsink. It is just a big linear voltage regulator. I'd suggest 2A would be the max one would want to push through it since that's already up around 30W of heat getting dissipated into the heatsink.

So, here's the schematic:

The repaired unit with some electronic grade silicone to keep the zener 'string' from rattling around when offroad:

and the re-assembled unit with power wires labeled:

cheers,
george.

 

[cruiserdan]

George did this for me laughing out loud the whole time. He was like "OK.....IF you really want it to work...".

Thanks George

 

[adspiegs]

George did this for me laughing out loud the whole time. He was like "OK.....IF you really want it to work...".

Thanks George

Dan, I came upon this from another thread about replacing a single din radio in a BJ40 and was wondering if I’m going to run into the same converter issue with my 24 volt 1993 HZJ73 as I attempt to swap out the factory radio with an aftermarket version. Attached is an image of the unit’s info sticker. Do you happen to know? Thanks!