Joust - need some advice

meauxmeaux

New member
Joined
Aug 6, 2006
Messages
101
Reaction score
1
Location
Kingwood, Texas
I'm working on an Upright Joust.

Fuse 3 on the Power Supply Board keeps blowing. It's a 4-Amp Fuse.
Anyone have some advice (with this game) on what I should be tracking down to fix it?
 
I know the very first machine I was able to fix was a Defender and it kept blowing fuses and it turned out to be that one of the ribbon cables was reverse. Not sure if thats whats going on with yours or not, but you can check the ribbon cables. I forgot what the inside of the joust looks like, but I think it is pretty much the same as the Defender.
 
My Joust had a switcher in it when I got it. The power supply board has a big burned section. Everyone said to leave the switcher beacuse the power supplies suck. You may need to rebuild the power supply or adapt for a switcher. I would go through all of the connections first though. Also try powering on just the power supply and see if the fuse dies without everything attached to try and narrow down the location of the problem.
 
Status

Okay, I disconnected the 4 molex connectors attached to the board.

Reconnected them to see which one blows the fuse.

The fuse is being blown by the connector that goes directly to the transformer assembly.
 
Fuse 3 goes to the +12VDC regulated power and the +27VDC unregulated.

The +27 VDC is used for the solenoids in the coin door that work the coin accept mechanism. This is the easiest to test for. Try pulling the 6 pin coin door power plug (4J3) and powering up. If the fuse doesn't pop then it is likely that it is the coin acceptor solenoids. If you are not accepting coins (i.e. it's on free play) you can disconnect these solenoids.

If the fuse still pops, try pulling the main power output cable (4P2) and power it up. If the fuse doesn't pop, measure the voltages, particularly the +12VDC regulated and the +27VDC.

The +12VDC regulated goes to 1 place, the MPU board where it is used to power the MPU board. If it still pops the fuse, there are several possibilites:
- the SCR (Q2) could be bad
- the 2B3055 transister (on the heat sink) could be bad
- the zener diode ZR2 could be bad
- voltage regulator IC1 could be bad
- the bridge rectifier BR2 could be bad

You probably need to replace or rebuild the power supply board.

Try to narrow down the subsystem that is causing the problem.

You probably do not want to convert to a switcher as they periodically cause CMOS RAM corruption issues in Williams boards.

If you don't feel like rebuilding the power supply board yourself, I do have replacements for $30 + shipping or I will rebuild your PS board for $20 + return shipping. PM me for details.

ken
 
Okay, I disconnected the 4 molex connectors attached to the board.

Reconnected them to see which one blows the fuse.

The fuse is being blown by the connector that goes directly to the transformer assembly.

See previous post. It sounds like there is a short on the power supply board itself. It needs to be replaced or rebuilt.

A switcher is not a good idea with Williams boards because of the way the CMOS protection circuit is designed. The 68xx processors are notorious for writing randomly to memory as they are powering down, including the CMOS memory. There is a circuit that watches the +12VDC unregulated line and when the power goes off thsi voltage goes to zero very quickly. This trips the CMOS protection circuit. Meanwhile the large capacitor contiues to provide +5V power to the board for a few milliseconds. Switchers don't have that reserve capacity on the +5VDC line. It goes down at the same time as the +12VDC line does. This does not allow the CMOS protection circuit to kick in fast enough to save potential random writes into CMOS. Hence the threads about "My CMOS keep getting trashed".

ken
 
No luck yet

Ken, I disconnected the coin door molex, no difference (blew again.)

I've narrowed it down to the line coming from the Transformer.

There is a 15 pin connected the transformer to the Power Supply Board. It looks like it has had problems in the past. Pins 1,2,3,4,5,6 have been removed from the connector, and soldered directly to the power supply board.

The wires from Pins 8, 9, 10, 11, 12, 13, 14 & 15 go directly to the transformer. It only blows when this connector is attached to the board.

I have no problem replacing the Power Supply Board (and I can run by your house anytime to buy one of yours)...but is there something in the Transformer that keeps causing it to blow? How would I fix that?


Thanks,

Rob
 
No. The transformer is up line from the fuse. There has to be a short in the power supply board. If it was the transformer, you would be blowing the fuse on the power brick.

Pins 1 & 2 + pin 6 = 21.4VAC input 2.
Pins 3 & 4 + pin 5 = 21.4VAC input 3.

These two 21.4VAC inputs power the +5 VDC and the +12 and -12 VDC unregulated power. These do not appear to be a problem, but they need to be put back into the connector and the header on the PS board needs to be fixed.

Pins 8 & 9 power the +12VDC circuit and this is the one fused by fuse 3 (the one that blows on you).

If you bring the whole power brick by (and it sounds like you will have to since it is soldered on) I can unsolder the wires and put them back into the connector so you can use a new PS board. Please bring the big heat sink as well, as it could be the 2N3055 causing the problems.

I have a rebuilt and tested PS board available.

ken
 
The 15-pin connector is broken in half. The half that holds the "resoldered" pins is gone.

I would certainly appreciate that type of help that you are offering.

Send me a private message to let me know when I can come buy the part (and get help with resoldering the wires).

I REALY appreciate the help, Ken!



Rob
 
See previous post. It sounds like there is a short on the power supply board itself. It needs to be replaced or rebuilt.

A switcher is not a good idea with Williams boards because of the way the CMOS protection circuit is designed. The 68xx processors are notorious for writing randomly to memory as they are powering down, including the CMOS memory. There is a circuit that watches the +12VDC unregulated line and when the power goes off thsi voltage goes to zero very quickly. This trips the CMOS protection circuit. Meanwhile the large capacitor contiues to provide +5V power to the board for a few milliseconds. Switchers don't have that reserve capacity on the +5VDC line. It goes down at the same time as the +12VDC line does. This does not allow the CMOS protection circuit to kick in fast enough to save potential random writes into CMOS. Hence the threads about "My CMOS keep getting trashed".

ken

Thanks for the info Ken. I will add rebuilding my power board to my to do list. That will also free up the switcher for another project. ;)
 
The 15-pin connector is broken in half. The half that holds the "resoldered" pins is gone.

Not really unusual. I have had 4 or 5 like that. It is an operator on-site hack. The pins probably overheated and melted the connector and the op just took a clipper to the melted part of the connector and 5 minutes of soldering and it was back up and running. Looks like SH*T but it was running and sucking quarters. It is a testament to these sorts of hacks that 20 years later they are still working.

I would certainly appreciate that type of help that you are offering.

Send me a private message to let me know when I can come buy the part (and get help with resoldering the wires).

I REALY appreciate the help, Ken!


Rob

Not a problem.

PM sent.

ken
 
Update: Rob stopped by and we fixed the connectors from his stepdown transformer, swapped his PS board & heat sink assembly for known good ones.

His boards were a glorious riot of hacks. The AC power connector as previously documented was split. From the charring it looked like the connectors overheated and melted through the nylon. So the hack was to wire the 22.6 VAC lines to a 6 pin connector and the mating connector wired directly to the back of the PS board to the 1, 3 & 5 pins on 4J1.

The bridge rectifier had been unmounted and was on 4 wires stretching out about a foot. It was probably bolted to the metal plate to use it as a heat sink. This is an old pinball hack from the earliest days of SS pins.

The third major hack was pins 1,2 & 3 that go to the 2N6057 transistor on the heat sink were disconnected and attached via a 3 pin connector and some extra wire to the back side of the board to the correct pins.

None of those 3 hacks were the reason the PS didn't work. BR2 had fried or capacitor C14 had gone bad and had taken BR2 out. This took out IC1 the voltage regulator.

Step 1: I removed the extraneous wires from the PS board
Step 2: Added a new molex connector to the wires on the heat sink transistors
Step 3: Replaced the 15 pin AC input header
Step 4: Remounted a BR1 on the PS board
Step 5: Powered it up and blew fuse 3
Step 6: Traced the 12V circuit looking for shorts and found a hairline crack in BR1
Step 7: Found a burned mark at the base of C14 where it overlapped the AC line going to BR2.
Step 8: Replaced BR2 & C14. No fuse popped, but voltage was only 3.3V.
Step 9: Replaced IC1 and retested.

Success. Regulated voltages: +5.01, -5.01 & +12.13.

An interesting repair. I have never seen a bridge rectifier crack like that.

Hopefully Rob will chime in and let us know if that fixed everything and got his Joust back up and running.

ken
 
I've seen the bridge rectifier hack in pins. This was the first time on a video game power supply. The other two hacks were probably just on-site work arounds to fried connectors. I have to say though as the supply of unmodified but non-working power supply boards dries up the wierdo hacks are starting to be more and more popular.

ken
 
In the last month or so, I have repaired 3 power supplies that have had wires soldered directly to them from the power brick. I have another one of those gems sitting on my to be repaired shelf too. Actually had to breakdown and buy some more .156 headers today. I am also seeing a lot of 3502's with tabs being soldered off the board instead of using 3502's with wire legs. I have one where some assclown used 1N4004's to make both BR1 and BR2. Will have to post pics of that gem.
 
I am also seeing a lot of 3502's with tabs being soldered off the board instead of using 3502's with wire legs. I have one where some assclown used 1N4004's to make both BR1 and BR2. Will have to post pics of that gem.

Yep, got some of both of those. My current favorite is the one with a PCB screw down block replacing the transistor header.

I can see why some shops have a "no hacked boards" policy.

ken
 
Well, Ken is a GOD! Swapped the board and heatsink...and used his precious time to restore the transformer wiring back to it's original set-up.

THANK YOU, KEN!!!!

Got home and hooked it back up. Power works...no more blown fuses.

The game does not work. Unfortunately, it will be Saturday before I get a chance to figure out what's wrong. Offhand, there is not input to the screen (just static), and no sound. I CAN get a sound by depressing the diagnostic button on the sound board....but that's it.
 
Is there any indication coming up on the little 7 segment LED on the ROM board? Usually there will be three numbers that flash when there is an error:
1 - X - Y is a RAM error at chip Y on row X
2 - 0 - Y is a ROM error at ROM chip Y
3 - 0 - 0 is a CMOS RAM error

A solid 0 indicates that the boards passed the Power On Self Test (POST).

If you are still having trouble next weekend, call me and I can swing by and see what's going on.

I was really hoping for a happy ending here, maybe it is just something simple.

ken
 
Actually, nothing is coming up on those LEDS.

Before the power supply board fix, it was flashing 1 3 1

I was hoping for a quick fix too. But, considering how the supply board was hacked..I imagine there's some other ones I need to look for in the other boards.
 
Possibly, but most ops would swap a bad board out rather than try to hack it.

More likely when the bridge went out it sent a voltage spike down the line and something blew. The sound board takes its voltage from the 12 V unregulated so that is prbably why that was unaffected.

Let me know. I can bring a working Joust boardset over and we can figure out what isn't working.

ken
 
Back
Top Bottom