MEP-803A, AUX fuel pump won't work

The -24 TM?

fa35jsf said:

Fuel pump module. It is the little box on the right lower side of the unit, looking at the fuel tank. Try unplugging it and jumpering pins 1&3. If aux pump turns on, then it’s the transistor inside that burned up.

Technically this part is considered a consumable and non-repairable part. But it is actually very easy to fix. You just need to purchase a mje800G transistor and solder it in.


Sent from my iPhone using Tapatalk

Click to expand...

Looks like mje800G transistors are getting hard to find. Mauser says they are in end of life. Any substitutes known?

jmenende said:

Looks like mje800G transistors are getting hard to find. Mauser says they are in end of life. Any substitutes known?

Click to expand...

There you go

Has anyone tried any of the direct replacements for the MJE800G if so which one? I need to order one asap.

I did the search based of characteristics and one come close however its all over my head.

Mouser #: 512-KSE800STU
Mfr. #: KSE800STU

Thanks!

I use the BD681G components when I repair them.

---> DigiKey BD681G

I ordered a few KSE800STU from Mouser and did the repair today and It worked like a charm. I put some thermal paste between it and the heatsink only because i had some laying around. I dont know if its necessary or if it works for this application.

Does anyone know why this transistor fails? or why this is a wear item?

I have an extra one or two, if someone needs one ill mail you one snail mail for free, let me know.


KSE800STU

Mouser Link

Here is some pics.

@bosko Congratulations on getting the repair done! That is great.

Personally, I think components die of some combination of random chance, age, overheating, and / or overloading (current or voltage or power). I see lots of components specified at close to operating voltages, and currents close to the load. To me, for semiconductors, that is penny wise and pound foolish in my experience.

If a component fails catastrophically on me I tend to go several fold higher in specifications (V/A). It is not worth my time to do a repair more than once, although in theory that may be kicking the can down the circuit so to speak. I can't think of a time that I have had to go back to a board for the next component on the circuit for repair.

YMMV.

All the best,

2Pbfeet

Great write up Bosko! Thanks

@bosko

this is a typical failure due to overheating because the heatsink paste has dried out and the heat is no longer transferred properly from the device to the attached heatsink.
Any electrical apparatus operated in high ambient temperatures will suffer this fate at one point or another.
The remedy is to check the heatsink paste every 5 years or so and renew

peapvp said:

@bosko

this is a typical failure due to overheating because the heatsink paste has dried out and the heat is no longer transferred properly from the device to the attached heatsink.
Any electrical apparatus operated in high ambient temperatures will suffer this fate at one point or another.
The remedy is to check the heatsink paste every 5 years or so and renew

View attachment 939489

Click to expand...

@peapvp If it is a known issue, why not switch to heatsink tape, or a heatsink clip, or a larger, less loaded component that doesn't require the heat sink, to keep the component in its thermal performance zone? Renewing heat sink material every so often seems like extra work at a minimum, but what do I know?

All the best,

2Pbfeet

2Pbfeet said:

@peapvp If it is a known issue, why not switch to heatsink tape, or a heatsink clip, or a larger, less loaded component that doesn't require the heat sink, to keep the component in its thermal performance zone? Renewing heat sink material every so often seems like extra work at a minimum, but what do I know?

All the best,

2Pbfeet

Click to expand...

This all depends, over sized component would work, if there is enough room. More often then not, larger Bi Polar Transistors require larger Base currents, so the preceding driver stage may have to be up sized as well.
Heatsink tape will work too, but also dries out. Nature of the beast. Direct mounting by either screw or clip will diminish heat transfer without paste or tape.

@peapvp I defer to your deep real world field experience, but for me tapes, (silicone, silver, copper, or graphite) have worked well and have remained stable in the devices that I have worked with.

All the best,

2Pbfeet