Thursday, June 9, 2011

hacked fliptronics 2 board on a fish tales

Been repairing a Fish Tales.

The powerdriver board was very badly repaired.. don't have pictures available now, they're still on my phone and I have to upload them to my pc (don't have a smartphone...)

All bridge rectifiers had been replaced in the past, but the soldering was done very badly. 3 different types of rectifiers were installed (some with fast-on lugs, some with wires, ..)

Using an incorrect type of bridge isn't a problem on itself. The problem was the bad soldering to keep them in place. Only the thick traces were actually connected to the bridge. And not all of them, some pins have traces at both the top and bottom of the pcb, and sometimes only 1 side was soldered. Some traces were burnt around the pin hole.
There are also a few very small traces going to the bridges, and they didn't make continuity.

One of the capacitors was also loose. Just replaced it and made sure it was soldered well (making continuity on both sides of the board).

I had so much fun desoldering everything, replacing the bridges and trying to figure out how every trace should be connected. :-/

It seems the repair person had read Clays guides as there were some jumper wires in the back added (not all of them like Clay recommends). Unfortunately one jumper was totally wrong !

The previous repair person probably made a mistake and switched the numbers of 2 connectors around.. it had to go to J104 pin 1 and went to J101 pin 4 (or something like that, going from memory here). Anyway, this gave a big short, and the bridge was dead.. this probably made one large trace on the board just disintegrate.

After all my work the powerdriver board was done, this pinball machine booted fine.
All leds on the powerdriver board lit up, the cpu got its voltages, ..
All coil worked, switches also, .. I was happy to see there were no playfield issues. At this point I had expected to have found some stuck on transistors and burnt coils too..

The only thing wrong with this pinball machine was that the flippers did not work.

Power was present on the flipper coils, connecting the middle lug of the flipper coil to ground activated the flipper... the flipper buttons themselves registered fine in switch test.. so problem was on the fliptronics 2 board.

Removed the board and then I saw this:

aaah.. so nice. A totally burnt away trace. It was enough for me not to try and repair this on location (it was getting late) but to take the board back home.

Now I've inspected this more closely, I notice this burnt trace isn't a problem anymore. On the back it has been jumpered with a wire. I do wonder what happened to this machine, as there was 1 trace burnt on the powerdriver board and also this one on the fliptronics board. These are pretty thick traces, to have them completely disintegrate like this you need quite some voltage hooked up wrong..

Anyway, the board didn't work even with the jumper.. so inspecting it further I noticed the row of burnt resistors ! R13 to R20 (the whole horizontal row of resistors below the 8 transistors - click on the image to see a larger version) are all brown and broken. They're burnt in the middle, probably acted like fuses..

Don't know what happened to this fliptronics board (I assume too many voltage) but I'm afraid the board will not work after just replacing these 56ohm resistors..

When I look at the schematics these resistors are somewhere in the middle between a lot of other components (like all the transistors). If they were the first thing in the schematics near a connector, they could have acted like fuses and protected the rest of the circuit.
But now they're in the middle of the circuit.. so I'm pretty sure that other small components (like the 8 smallest transistor, possible the ic's also) are damaged too.

Don't know yet if I'm going to put time into this board and try to repair it, or just get a new one..


  1. If the 56 ohm resistors are burnt inline, I'm not sure that means all the other components are fried.

    I calculate that as they are 1/4W resistors, they only need about 67mA to reach full rated heat dissipation...
    P (Watts) = I*I*R
    so I*I = P/R = .25W / 56 Ohms
    I = .0668 A or 67mA

    I figure they would start to cook like that around 70mA, so not much current. You say they acted as fuses, do they all read as open? Maybe more components are damaged, but that current is unlikely to have killed the power transistors.

    The main thing that's worrying here is that all those resistors are fried and they are in separate series circuits. To me, it points to 50v being input on the 5v rail and shorting to ground through those burnt resistors. If that's true, then all the ICs will also be toast and the board is probably uneconomical to repair. Testing a the 8 x 2n4401 and a few of the ICs would tell more.

    Regards, -Richard

  2. Hi Richard,

    Thanks for your feedback.

    Yes the 8 resistors are totally burnt, all read as open.

    Probably not every part on the board is damaged (the larger transistors with metal tabs I measured and they seem ok).

    I have my doubts about the smallest transistors (black body, without metal tab), they didn't give identical readings like those of a working fliptronics board, but maybe measuring them in circuit with the burnt resistors had something to do with that.

    Don't know if I want to put time in replacing the resistors+small transistors, to only then find out that it still doesn't work and I need to replace all the ics too..

    Or maybe it'll works now, but some other components (resistors/diodes) are maybe a bit damaged and will fail in a few weeks/months..

    Next week I have some time and will take another look at this board.