Any ideas on repairing a (slightly!) blown motor board ?

[Trickysystems]

Malcolm,

I just had a look in the latest handset I have and it has the values stamped on the ferrites and  an extra diode. Picture attached.

102 ferrite is 0.15 ohm at DC and 1,000 ohms @ 100MHz and 1.5A max current.

For a test, you could probably use a low ohm resistor or even short it.  As this is the interface board to the rest of the hand set, it could be tested in isolation.

Hope this helps.

Richard

[malc-c]

Thanks for the suggestion.  Does FB4 connect to the 3rd pin from the top as viewed ?  If you look at the image I posted I have a a good trace between the 4th pin form the top and pins 7&8 (+12v in from the mount) so no need for the diode.  I have also noticed U6 next to the crystal is a little charred but there are no pads or legs, so guessing its a BGA type package - but its very small ??

I've spent best part of  5hrs play with it and can't see any possible fix - even checking continuity for both Euarts on the 80 pin 18F Pic to the 6 pin connection cable header at the top of the main board doesn't ring out...  I was hoping that with some delicate soldering of some fine wire I could just take the TX/RX  directly out to the daughterboard

[malc-c]

 

unlike the ferrite bead, 3/4 of U6 remains !!

I'm also interested in what the small three wire connector does as the USB to serial chip would be used if the handset was to be used as a pass through.  The fact you could have either an EQDIR cable connected to the PICs serial port, or use the USB port suggest that the TX and RX must be linked, and that three wire could be the TX/RX and GND from the onboard USB/TTL serial chip.   Anyway, its almost 1.30am so time I retired to bed !

 

My gut feeling is that whatever vaporised the Ferrite bead may have also blown the PICs Euart and I lack the skill, tools and eyesight to remove the 80 pin package, fit a replacement and then program it !

Edited January 25 by malc-c

[Trickysystems]

Malcolm,

Just a little more snooping between my two hand controllers. The added diode in one simply is a replacement for D4, so maybe just an upgraded component for extra current? The IC that is vaporised on your controller has AJ3 as the marking and appears to be a DFN8 package. Without checking the tracks, I am uncertain of the actual type of device or the function. Note that the other hand controller I have does not have that IC present. I'll try and figure out the differences between the two circuits. Perhaps it might be possible to bypass it completely? J8 on the controllers appears to be the ICSP for the PIC. I'll check further to confirm if that is the case.

If the controller does not prove repairable, then an alternative is to remove it and put in a wireless or BT adapter in place of it to control the motors.

Richard

[malc-c]

Thanks for the images, and ID of the part U6.  Like a lot of parts in Chinese electronics those that do have labels are often non traceable.  But even then if I could find out what it is I don't have the tools to replace it.  My logic was that regardless of which port is used the TTL signals end up at one of the two USARTS on the processor, so once a suitable place was found I was going to see if adding a couple of wires directly from the pins of the handset port to the pics serial port pins.  However looking at the datasheet for the PIC18F85J10 I can see that whilst the chip is a low voltage package, the digital pins are 5.0v TTL level tolerant

[MikeAa]

So excessive current flow caused the bead to fail, therefore  something else on the board is faulty?

[malc-c]

2 hours ago, MikeAa said:

So excessive current flow caused the bead to fail, therefore  something else on the board is faulty?

That's my guess too.  Something could fail, allowing a new path for the current to flow, which then has a domino effect allowing higher voltage to reach low voltage components.

[Trickysystems]

The two controllers are very similar, with some rearrangement of components. The blown IC  is replaced by a resistor on the other board. The only SMD device in the same package, with AJ3 marking, was 3AA02/34LC02. This is a Microchip 2K I²C Serial EEPROM. If this is what the device is, I'm not sure what it is doing. Pictures attached of each controller. R18 replaces the IC on the other controller, and some other resistors are added or omitted between the two controllers. Both controllers are version 5, yet slightly different. Both have the USB connector on the hand unit.

J8 pins connect to the correct pins on the PIC to enable ICSP.

It is looking like a better option is to replace the hand controller, or use a BT or WiFi adapter. Controllers seem to be available on the second hand market from time to time.  Although my engineering past makes me want to know what went up. All ICs and transistors are encapsulated with smoke, so that is the indicator they have failed, at least that is what I was taught...

 

[malc-c]

That's very interesting.. I wonder what that small 8 pin package does.  It does seem that the same via's are all connected to one side, with the same trace running to the second from left pin on U8.  I wonder which revision came first?

What strikes me is that major manufactures of graphics cards make active schematics and component ids available, but try and get the same from Synta... you have more chance of finding fairy dust !

Anyway, this handset will sit in the draw until someone else ends up cracking a screen or something that can be fixed by swapping parts over. 

 

[Carbon Brush]

Late into the discussion, and only a couple of photos to look at. But maybe relevant.

Circuit designers sometimes omit over voltage suppression/protection components.
Either they don't think about them, or a bean counter somewhere argues about bill of materials cost and the designer tries to save 10p.
Then in the real world it is realised there are more failures than expected. If not warranty claims, they are loss of company image/status when they get known for unreliable product.
Oh - maybe overvoltage or reverse voltage protection is a good idea after all.

The 'extra' diode mentioned by @Trickysystems may be a 1N5401 (3A rated) diodes in series with the supply. Providing reverse voltage protection.
The tiny 8 pin device U6  could well be a zener protection network. These are made by several companies and find their way onto USB ports.
They would help on logic level RS232 ports.

HTH, David.
 

[malc-c]

David, thanks for the info... I wonder how many designers have gone back to the accountant and said "told you so" after such practices are employed.  

[Trickysystems]

Of the two controllers I have, the earlier one has the AJ3 IC (U6) and the later one just has a resistor, at least based on when they were purchased, but the actual controller delivered may just be a question of stock on hand at the time.

The controller without the tiny IC 6 has R8 omitted, R10 installed (150K), and a new position, R18  (100K) installed.

Having a closer look at the circuit, PIC pin 6 (RG1/TX2/CK2) connects to  pin 5 (2A) of U8 (74HCT2G125), so is an input. The output of U8 then goes via R18, which is a pull up resistor, to a through hole where small IC U6 would be mounted on the other controller. The other output from U8 (1Y) appears on another through hole next to it. As this appears to be a multi layer board, it is very hard to identify where the tracks actually end up.

This could mean that the PIC is OK, and also U8. Repairing the issues on the daughter board may allow the main board to power up. The outputs from the burnt U6 would need to be identified and direct connected, so possibly fixing the controller?

As for the extra diode soldered to one of my controllers, it simply replaces D4 and so is not extra, just heavier duty.

Richard

[malc-c]

Richard,

I did consider a direct connection to the pins of the RJ45 socket, but with an 80 pin package, and not knowing if the firmware is written to use com port 1 or 2 (or should that be com port 0 and 1?) and the fact that I don't have anything thin enough to solder I shelved that.  But now you have done your best to trace out the path, at least to points where the solder mask can be scrapped back to expose the tracks and enable a ware to be soldered might give me something to work with. - Many thanks

 

[mimmo]

On 23/01/2024 at 00:15, malc-c said:

Just to clarify the port on an EQ6 / NEQ6 that has a D9 port does not run the serial lines at true serial voltages.  The TX and RX lines are TTL level, 0 to 5v.  The problem is that next to the data lines there is +12v and GND so what you have probably done is basically shoved 12v across the data lines and blown the EUART port of both PIC micro controllers.

The only way to fix this is to follow the steps in this thread to program two new 16F886 microcontrollers, desolder the existing ones, being carful not to lift any pads and damage the tracks, and then solder the newly programmed microcontrollers in their place.  Prior to Christmas I could have sold you a mainboard that already had the repair undertaken as I had several spares due to other members kindly donating blown boards to me after they had already gone out and purchased a new replacement control board.  However I no longer have any as they have all gone.

The other problem is that as you are in Italy the cost of shipping the faulty board for repair will be expensive as it needs to be insured and tracked.  Due to issues I've had with sending replacement micro controllers  and a control board outside of the UK I can only take in boards for members based in the UK mainland.

Replacing the microcontrollers isn't that difficult, but unless you have or can find someone with a PIC programmer who can program them for you it's pointless to try.   The HEX code for an EQ6 has been attached (assuming the forum software allows that).  

If a repair is not possible then the only alternative is to replace the old board with a new one.  If you do choose that option, then please consider donating the faulty board to the exchange program and send it to me by the cheapest postal service (no need to send it insured or tracked as its faulty anyway, should it get lost in transit).

EQ6-NCP.hex 46.5 kB · 4 downloads

Hi Malc I found some pic programmers for a few euros 15/20 euros, are they safe or better left alone.
Thank you

[Trickysystems]

On the subject of programmers, the PIC programmers I use are pictured. The K150 needs the config file updated to program 16F886 PICs. The PICKit 3 works better for me although the required sockets need to be purchased. There are PICKit 3.5 devices advertised on the Internet, but these weren't designed by Microchip. I'd stick with PICKit 3 and use the standalone software available free from Microchip.

The latest programmer is the PICKit 4, but for our purposes, the PICKit 3 will work and is cheaper. Make sure it has the logo.

[malc-c]

On 27/01/2024 at 18:21, mimmo said:

Hi Malc I found some pic programmers for a few euros 15/20 euros, are they safe or better left alone.
Thank you

Without any details it's impossible to say.  The 16F886 has been around for some time so should be supported by most programmers.  I use the PicKIT2 (now superseded by the PicKIT3 and PicKIT4 ).  You will also need an adapter to hold the 28pin SOIC package.  This is my setup I use to program them, the clam socket and PCB was kindly sent to me a couple of years ago from a fellow SGL member.  

 

Prior to that I was using a 28 pin SOIC breakout board and a sprung clothes peg 

 

 

Edited January 28 by malc-c

[mimmo]

On 29/1/2024 at 00:12, malc-c said:

Senza dettagli è impossibile dirlo. Il 16F886 è in circolazione da un po' di tempo, quindi dovrebbe essere supportato dalla maggior parte dei programmatori. Utilizzo PicKIT2 (ora sostituito da PicKIT3 e PicKIT4). Avrai anche bisogno di un adattatore per contenere il pacchetto SOIC a 28 pin. Questa è la configurazione che utilizzo per programmarli, il socket a conchiglia e il PCB mi sono stati gentilmente inviati un paio di anni fa da un altro membro della SGL.  

 

Prima utilizzavo una scheda breakout SOIC a 28 pin e una molletta da bucato 

 

 

Ok thanks

[mimmo]

On 23/1/2024 at 00:15, malc-c said:

Giusto per chiarire che la porta su un EQ6/NEQ6 che ha una porta D9 non fa funzionare le linee seriali a tensioni seriali reali. Le linee TX e RX sono di livello TTL, da 0 a 5v. Il problema è che accanto alle linee dati ci sono +12v e GND, quindi quello che probabilmente hai fatto è stato sostanzialmente inserire 12v attraverso le linee dati e far saltare la porta EUART di entrambi i microcontrollori PIC.

L'unico modo per risolvere questo problema è seguire i passaggi di questo thread per programmare due nuovi microcontrollori 16F886, dissaldare quelli esistenti, facendo attenzione a non sollevare alcun pad e danneggiare le piste, e quindi saldare i microcontrollori appena programmati al loro posto. Prima di Natale avrei potuto venderti una scheda madre che era già stata riparata poiché avevo diversi pezzi di ricambio perché altri membri mi hanno gentilmente donato schede bruciate dopo che erano già usciti e avevano acquistato una nuova scheda di controllo sostitutiva. Comunque non ne ho più perché se ne sono andati tutti.

L'altro problema è che, essendo in Italia, il costo di spedizione della scheda difettosa per la riparazione sarà elevato in quanto deve essere assicurato e tracciato. A causa dei problemi che ho avuto con l'invio di microcontrollori sostitutivi e di una scheda di controllo al di fuori del Regno Unito, posso accogliere solo schede per membri con sede nel Regno Unito continentale.

Sostituire i microcontrollori non è così difficile, ma a meno che tu non abbia o trovi qualcuno con un programmatore PIC che possa programmarli per te è inutile provarci. È stato allegato il codice HEX per un EQ6 (supponendo che il software del forum lo consenta).  

Se la riparazione non è possibile, l'unica alternativa è sostituire la vecchia scheda con una nuova. Se scegli questa opzione, considera la possibilità di donare la scheda difettosa al programma di scambio e inviarmela tramite il servizio postale più economico (non è necessario inviarla assicurata o tracciata poiché è comunque difettosa, nel caso in cui si perdesse durante il trasporto).

EQ6-NCP.hex 46,5KB · 6 download

Hi Malc, I've started checking the components of my eq6 board again. I found that the Skothy D1 diode gives 390 mV in one direction and 0 in the other.
instead the skothy diode d2 gives 0 both in one direction and the other, so it should be skipped, right?.
the diodes are SK34A smd. Can I possibly replace it with a traditional one?

[malc-c]

I would still replace it with a Schottky barrier rectifier diode that has the same 40v, 3A forward current (70A peak) rating.  It doesn't need to be a surface mount component, a normal radial through hold package will do so long as you can solder to the pads where the diode is mounted