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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 .........

gallery_11296_1743_37492.jpg


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


gallery_11296_1743_38004.jpg


Reassembled back onto the testbed, I pulled the throttle back and woomph!
ohmy.gif
... 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? ......
 
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Discussion Starter · #2 ·
In a word ........... no ..
 

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Discussion Starter · #3 ·
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 ......
 

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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 ...
 

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

gallery_11296_1743_64058.jpg


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
 
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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.
 
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Discussion Starter · #14 ·
The diodes that I use are referred to as microSMP ......
 

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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.

 
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Discussion Starter · #17 ·
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.
 

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Discussion Starter · #18 ·
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.
 
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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.
 
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Discussion Starter · #22 ·
The Scalextric chips should be reasonably easy to fix as there was no fire & brimstone going on; the SP15 will depend on what and how many bits have been melted.
 

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Now that you are sitting comfortably gentle readers, I shall continue showing more photos of damaged chips .....



Obvious signs here ... destroyed NO2, stress blue wires on the right side and missing wires below the large yellow capacitor is and
directly above it, both on the outer edges of the PCB. The mark across the top diode is just a streak of glue.




Same chip, NO2 & PO3 both replaced, wires removed and added including the red & black ones. However another fault was picked up
in testing .... the blown resistor for the infra-red LED. Looking back at the previous picture shows that I missed it which is why you
should always check the functionality of the chip after repairs even in areas away from the ones you had worked in. Good job too as
this one was off The Netherlands.


Now a series of C7005s



The NO2 MOSFET (top right) had a miniscule, easy to miss pinprick hole found using a 20x microscope.




A more obviously blown NO2.



This one has a blown PO3 MOSFET. Look at the darkening around the top of the microprocessor legs. The large black blob on the bottom
right of the PO3 was the charred remains of the corner and the copper pad that it was soldered to.
 
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This chip has a displaced FB2 (Ferrite Bead). It is unlikely that heat played a part in it's southern orientation but I would have thought
that the solder might have been a bit more "manned-up".
 
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Discussion Starter · #26 ·
Hi Mike, I'll see what I can do for you .........
 

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Tricky one next, something that I have only done in practice. So tonight I went for the real thing ........




The chip remains unresponsive despite my best efforts so the only thing left is to transplant the microprocessor chip; the one with
the white stripes and 14 legs ....




the old chip has now been removed and the area cleaned up ready for the donor ........



It just needs aligning to the tracks on the PCB and soldering can commence ......




The operation was a complete success and the chip has made a full recover and is now settled into the ICP ward for further treatment .....

 

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Discussion Starter · #31 ·
It is indeed your chip .......
 

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In preparation for the forthcoming plethora of the F1 cars from the 60s, I wanted some chips that could be squeezed into tighter spaces ..

gallery_11296_1743_27386.jpg


gallery_11296_1743_35376.jpg


So I replaced them with much thinner, fast action Schottky diodes. The large silver capacitor looks so much bigger now but that
will be removed and attached to fly-leads make the board much thinner .......
smile.gif
 
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Next up is not quite a repair as much as a refurbishment of a Saloon Chip - C7006 .........#



When I get a chip like this, I would usually remove the white plug entirely and just solder the wires directly to the PCB.



A digital module plate sitting on my desk gave me a inspiration so I removed the plug from the plate and found a DPR wiring loom
in one of my spares boxes.



After a little bit of cleaning up, the iron was switched on and quickly heating up .....



Those with sharp eyes will notice that the wires on the PCB do not quite match that of the wiring loom. Here I have switched the
Green and the Yellow wires over as it was the neatest way to add the plug. The chip's internal bridging diodes will always ensure
that the correct polarity of from the track is presented to the chip correctly, so the switching of pickup wires does not matter.



The finished article. You may ask why not just add extra wire to the existing bits? The wires were just a bit too short to make the
job as easy as doing it this way .....


 
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Discussion Starter · #36 ·
Thanks ........ quite likely, I think that was for the C8186 F1 DPR chip. Do you need it re-posted?
 
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