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Discussion Starter · #321 ·
continuing on with the C7006 .....

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Everything back in place ........

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A more sensible length for the wiring loom .....

Just need the lockdown to go away whence I can get out and find a Post Office to return them ......... :)
 

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Discussion Starter · #322 ·
Another sad old C8515, Rev F:

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Quite a bit of damage to this one .... the nylon socket has been removed to facilitate soldering iron access ....

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This MOSFET has slightly more than a hairline crack ....

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The arrow on the left highlights heat damage along the copper track to the capacitor; the others point to further damage ....
 

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Another day ...... another bag of chips arrived .....
smile.png


These, however, were not for repair but for upgrading. The owner wanted the diodes uprated from 1A heat wasting silicon ones to fast switching 3A Schottky

ones with the extra va-va-Voom .....
dribble.gif


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Here is a standard C8515 DPR chip. The plastic cover of the JST header (socket) has been removed to facilitate the wielding of a hot iron ....

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The four silicon diodes have now been removed and the PCB has been cleaned up ready for the next step ....

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The new turbo nutter-barstud diodes are now in place and the JST header is replaced ready for the rigours of some hard racing ....

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The smooth running of a chip is always checked before I change anything. That way, I know it is my fault if it doesn't work afterwards. This one didn't run, upon closer examination, one of the onboard ferrite beads was found to be damaged causing a break in the circuit ....
 

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Discussion Starter · #324 ·
Yet another couple of Rev H C8515s ploped onto my doormat ....

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The usual suspects were quite apparent ....
 

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Discussion Starter · #325 ·
Another day, another pile of chips ....... :)

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This batch was quite interesting in that it was mostly comprised of DPR Rev-H chips ......

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The blowhole that allowed all of the magic smoke to escape from ....

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This one has de-soldered a MOSFET all by itself. The small scorch mark reveals that it was an act of self-immolation ....

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Both MOSFETs have gone to silicon heaven. The chances of fixing it is roughly 70/30 as it will depend on the extent of the copper track remaining ....

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This one is definitely an ex-chip as the copper track and some of the components have been vapourised ....
 

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Jeez! What on earth caused that on Rev-H chips?
ohmy.png
 

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As yet, I have not heard a convincing explanation, but what I do know that of the 1068 chips that I have repaired is that not one of them has come back with the same problem.

As digital chips, and this includes those of all manufacturers, are being built with smaller surface mounted components the amount of damage suffered by nearby components is often catastrophic when the chip does blow.
 
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Discussion Starter · #328 ·
Another day ....... another chip to fix and this one was did not exhibit any intentions of being fixed quietly or quickly .....
dribble.gif


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The fire damage seen beneath the ferrite bead FB1 happened as I hooked it up for testing. A bright glow and acrid smoke alerted me to further problems elsewhere on the chip.

More investigations to follow .......
innocent.gif
 

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Discussion Starter · #330 ·
Thanks Ade ..... very interesting find .... :thumbsup:
 

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Discussion Starter · #331 ·
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Sadly, this little feller did not pull through. Despite all of the peripheral components checking out as OK, the main µ-processor was identified as the culprit. The final test was to see if there was any output that would drive the infrared LED ........ was negative.
 
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The damage caused to this C7005 chip was entirely due to soldering. The chip was tested when the Ferrite Man was made up and everything worked well. The trouble came when the chip was fitted into a car. During this process, the bare wires managed to touch so when the car was placed upon the track for a run ........ a cloud of smoke and the whiff of sulphur filled the room.

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Discussion Starter · #334 ·
Putting the smoke back in is the easy part ......... the sulphurous odour not so .... :)
 

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Another milestone passed .......... 700th chip re-flashed with InCar-Pro ....
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Another day, another first ....... "Could you quieten down a Rev H chip, please?"

After a bit more probing, I found out that the member didn't like how "twitchy" his new chip was, particularly at low speed, compared to his older Rev Gs. The answer was to change the diodes for the older silicone ones of the original DPR chips.

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The four Schottky diodes have been removed and the solder pads cleaned up. The DPR socket was gently levered off to provide room for the soldering iron ....

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Et voila ....... old-school silicon replacements ....
 

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Discussion Starter · #338 ·
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Yet another missing onboard ferrite bead .....

Damage to FB1 is becoming more common these days. Quite why is beyond my pay scale but it might be worth Scalextric having a look at this.

Oh hang on ....... that would mean me fixing fewer chips ...
ohmy.png
. Perhaps it's best to leave sleeping dogs lie .....
unsure.png
 

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Discussion Starter · #339 ·
It seems that the Covid-19 lockdown is still keeping slot car racers indoors as I have received another pile of chips for fixing ........

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Thankfully, not a Rev F in sight ....... :banana:
 

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Discussion Starter · #340 ·
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You first have to remove the carrier plate of the C8515 to inspect and repair it. Slicing through the top of the four supporting pillars is all that is needed. The N-channel MOSFET, which controls the motor, is the usual suspect and true to form it has blown as shown by the arrow ....

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Sometimes you get the P-Channel MOSFET which controls braking, blow. Here we have both that have released their magic smoke and sulphurous odour. This type of damage rarely occurs ....

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Rarer still is damage to a switching transistor marked as TR3 and TR4. In this case TR3 had gone. Both of them were replaced as was the two MOSFETs as a precaution ....
 

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