Question for boB

[cschlessman]

Hi boB, I picked up (for free) 3 Trace SW4024's 2 were connected to batteries backwards and one works but cooling fans do not come on. Could you give me some advice on what to look for and if they are possibly repairable before I rip them apart in my blind ignorance.

Thanks fro any help you could give.

Chuck

[boB]

I would think that being connected backwards would NOT hurt the fans without hurting a LOT more than just them !

When one of these inverters are connected backwards, the intrinsic diodes in the FETs will conduct, allowing
just a couple off volts negative across things which would then hopefully just trip the circuit breaker or
blow the fuse.  The fans run off of the auxiliary power supply which won't normally be hurt by those couple
voltage or reverse.  So, I'm not quite sure what's up there.   Those fans are 12V nominal so you might
connect their RED wire to +12V and the BLACK wire of the fan to gnd and see if the fans themselves
are bad or the circuitry around them is bad.

Might be something I'm not remembering right about the fan circuitry there.

boB

[Halfcrazy]

My guess is those fans are dead from natural causes? Where you the owner of them before they where hooked up backwards? Did the fans work then?

[cschlessman]

The fans are not working on one, It works except for the fans and it was not hooked up backwards. I replaced it for a neighbor when it kept shutting down with a fan error.
The other 2 were connected by a guy who didn't understand + and -. I replaced them for him and he gave them to me. To quote him " when I turned them on lots of sparks and they stopped working. Hmm, I said I would take them if he didn't want them and he gave them to me. I haven't opened them up yet. Just though I would ask if specific things went bad when reverse connected.

Thanks
Chuck

[tecnodave]

Chuck,

If they are in that condition.  "Sparked and stopped working"   you have nothing to lose in looking......what goes is the FET 's field effect transistors and it is usually obvious....heavily smoked...lids blown off etc. This kind of damage will be apparent and not too hard to fix but what is not known is there damage in the control circuits as well?

The FET's  make some heat so are always mounted on heat sinks of some fashion. There will be groups of them maybe 32 or so but different on different. Models

Take a look at the FET banks before you pour money in there.......a lot of time a good close physical examination will show the damage,

David

[cschlessman]

tecnodave, thanks for the info. So apart they come

Thanks again
Chuck

[TomW]

what goes is the FET 's field effect transistors and it is usually obvious....heavily smoked...lids blown off etc.

That is why I refer to them as "Fire Emitting Transistors"

Tom

[boB]

That is why I refer to them as "Fire Emitting Transistors"

Tom

LOVE IT  !!!!!