[GregK]

An F1 DPR chip arrived on my doorstep to be fixed. It looked perfectly OK but would not run when connected to a chassis and tested on a powerbase. After a check of the components, I found that three of the four diodes were not working at all so I replaced them with 1A Schottkys .........

All still looking OK ....... time to test my handy work .......

Reassembled back onto the testbed, I pulled the throttle back and woomph!

... very bright flames & tons of acrid smoke.

As you can see, the dual MOSFETs, top left, has decided to expire. It is a dual MOSFET bereft of any magical smoke, it is an ex-MOSFET.
I wonder if Farnell can help me out in the morning? ......

 

[GregK]

In a word ........... no ..

 

[GregK]

This the result after removing the debris with my hot-air re-worker .........

Even if Farnell's did have some in stock, there is nothing left to solder the legs to ......

 

[Ade]

Hi
Funny I thought I saw it move

 

[Geoff997]

I have had one chip suffer damage, which removed the solder pads. So just followed the circuit diagram and used kynar jumper wires to connect to the next component. Worked just fine!

 

[RikoRocket]

I've done similar on a Pit-Pro that someone smoked, not on a chip though...

 

[GregK]

Thanks Geoff ....... the pin outs for this IC are .....

..... and it's dimensions are ......

I don't think that I could have trimmed the tape fine enough as the tracks were miniscule .....

Other chips are reasonably straight forward to fix using the kynmar tape, but the F1 DPR ones are very small indeed ...

 

[Rick Sirrom]

Flip!
Good going Greg = You must have the eyes of a hawk

.
We'de be Digitally'Lost without you Chip'Repair knowledge.

I put 1 of your Stage#1 chips into an *Old'Motor'SCX* & fitted a 10z pinion =
Running Super Smooth & Responsive

.
Cheers m8~ R ....................

 

[GregK]

This was a much easier chip to fix .......

All it needed was the diodes replacing so I replaced the 1A ones with 2A Schottkys ... the one on the left is the one that was fixed

 

[injectorman]

Hi Greg.
Looks good. What I find to clean up solder pads and pin holes and compressed air. Get the solder hot then blast. Works really well. I have a tiny battery powered soldering iron with a super small sharp tip. Oh and the magnifying glass of course.

Rick

 

[sealevel]

Are those surface mount Schottkys you are using? What size are they...SS24?
Cheers!

 

[GregK]

Sorry ....... I don't know what an SS24 is.

Another F1 chip ......

I've marked the damage on this side where NO2 should be. The transistors (A8Es) on the left have been removed as well, just in case
there is further, unseen damage.

On the other side, FB1 has literally melted in half. This ferrite-bead leads to the +ve motor wire which happens to be the black wire.

 

[sealevel]

When I did a search for Schottky's on eBay, I found they had numbers stamped on them.
Here is a link to a Schottky listing:
50 pcs Toshiba Schottky diodes
Cheers!

 

[GregK]

The diodes that I use are referred to as microSMP ......

 

[GregK]

Next up are a couple of SP15 repairs ......

The dual MOSFET chip has melted and released it's quota of smoke and vapours ....

Sometimes, the evidence for the chips failure is not always quite so easy ...

The larger arrow shows a degree of discolouration on the solder pad of a diode. A further clue to the problem is highlighted
by the smaller arrow, is an adjacent solder has turned orange from a normal silver. These features are caused by
excessive heat ....... note: the wires for the braid pickups have been removed for clarity.

 

[sealevel]

QUOTE (GregK @ 9 Nov 2014, 03:49) <{POST_SNAPBACK}>The diodes that I use are referred to as microSMP ......

Thanks, GregK.
From what I have read, the microSMP is a specific packaging size from Vishay:
"Vishay's Schottky rectifiers and TVS devices feature minature MicroSMP package with a space-saving 2.5 mm by 1.3 mm footprint." - digikey

At least that will give us some reference as to the size of the Schottky diodes.
Thanks again.

Cheers!

 

[GregK]

Size is no problem just measure the item in question with some vernier callipers. Then it is a simple Google for the package size which is usually quoted as imperial as opposed to metric sizes.

 

[GregK]

Sometimes there is more than one fault ........

The damage to the NO2 MOSFET is quite obvious and not unexpected but what about PO3, the MOSFET that controls braking?
If you look carefully, you will see a split running down through the surface marking. Only replacing NO2 would correct the power
to the track part but when you test it you would probably find that the motor would run continuously. Often the damage to
these MOSFETs can be a miniscule pin-prick mark on the surface and sometimes there are no visible signs at all.

 

[docdoom]

So what goes on theses chips when u have short in the motor? have at least 5 chips that dont work because it took me two trys before I found that the motor was bad or the wire was touching the metal part of the motor. two dprs, two salons and a slot it 15 chip. nothing sucks more than pulingl a new chip out the package. installing in the car and poof nothing

. waiting to hear back from gmyers2442 to see if he still repairing chips.

 

[GregK]

It rather depends on what you are trying to install the chip in ....... can you give me details of the motors that have caused you grief?

I have heard that Greg has gone awol .....

....... I might be able to help you though.