fraggle

Put me down for one. I'm tired of rebuilding or swapping questionable units.

pcar928fan

^^^^^^
Don't say that!!! I just got a used one from 928 International... I think I better cross my fingers and hope it lasts till we get some sort of (I hope affordable) replacement!

dr bob

Tangent: Folks, make darn sure your fans aren't dragging. The factory piece is more than capable if the loads from the fans aren't excessive. Clean motors with new bearings is a huge part of the solution. Think of the final stages failure as a symptom, dragging motors as the problem. I'm all in on a more reliable module from John, probably two in my case so I can have another working spare JIC. But the fans are where I'll be putting the most effort.

GregBBRD

Dr. Bob:

My experience would indicate that these fan amplifiers are not nearly as reliable as you think they are....and now that they are getting older, they all seem to be on their "last legs".

A fairly large percentage of these units have the little peened over pot metal "transistor retaining" nubs broken off, which means the transistors no longer make contact with the heat sink.

You can do almost anything you want, with the fans, but if the transistors loose the ability to transfer their heat, I'd guess it is going to be "over" pretty darn quick.

dr bob

Damn, Greg. I had one reliable data point. Right up until it failed on one channel, the one that coincides with the dragging fan. I'm on the list of interested replacement unit buyers. I'll fix one that I have, drop one of the new modules into another, and continue to drive on the on the replacement I'd socked away until it fails. Obviously I had plenty of faith in the original, but still CYA'd with a working spare when the opportunity presented itself.

The dragging fan will get bearings, as will the other one.

jleidel

All, lots of progress on the boards. We have a full parts list, multiple source vendors and a sample board design. We're finalizing the circuit through a Spice model. A few questions:

- What is the current requirement for the fans? We need this to verify our model.
- We have yet to find a suitable replacement for the connector head. If we can't find one, then we have two options:
1) setup a refurb system where you send us your dead units and we use your existing connector and housing. we replace the board with a new unit and solder on your existing header
2) we build a completely new unit with a complementary header. We also ship a "pigtail" which you splice into the existing harness. This requires more work from the owner, but removes _all_ of the old components.

Technically speaking, we can probably do both options given enough time in doing the board layout. However, I'd like to see which option is more popular.

soontobered84

John,
WTH is a "spice" model? Isn't that some sort of look good girl singing group?

Maybe one of the more electron enlightened crowd could chime in on the current requirement. I do
believe that each fan uses a 30 amp fuse, though.

Either way you do it would be okay with me since I and people like me have extras. The "core"method would hurt the folk that do not have an extra and also the onesy's that will occur after the intial rush but contact you when their controller fails, but it would probably be the most economical and I guess, aesthetically pleasing (since it will look like original)

dr bob

John--

I'll plug in my cute little H-F ammeter thingy in the morning. Says it will handle up to 30A. Good test for it.

John Speake

There will be a much larger initial surge current than the steady state amps.

Simulate a large inductive load in your Spice model. Get your boys to measure the inductance of the fan windings.

jleidel

Ha! "Spice" is a computer modeling tool for electronic circuits. It simulates the function of a given circuit based upon different input. It allows us to verify that the circuit is truly correct before taping out and having one built.

fraggle

Yes do not neglect the inductive load in the model!! I prefer the new unit to direct plug into the same spot as the old one, I'll send a core. I even have a spare.

G8RB8

I'll play, depending on the cost, but I can't advance the core. Can there be a core charge and return type deal?

fraggle

Once this gets up and running I'll donate my spare as a "core in stock"..

jleidel

G8RB8, I believe we can get this setup. Shouldn't be a problem.

fraggle, thanks for the donation! This will be greatly appreciated. We also have a few others floating around the DFW group.

dr bob

Days later...

Fan reads about 17 Amps steady load, inrush/surge was less than 20 Amps.

Unplugged both fuses so the controller would see a fault when testing just one, and force high speed. AC running to get the fans on. Middle speed is about 10 Amps running.