Q*bert Trouble

titanfan

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Have a little trouble with my cussing friend today. He will not go to the diagonal bottom right. All other directions are perfect. I have checked for continuity from the CP all the way to the board. Is there an input chip or something there?

Thanks,
Dustyn
 
Have a little trouble with my cussing friend today. He will not go to the diagonal bottom right. All other directions are perfect. I have checked for continuity from the CP all the way to the board. Is there an input chip or something there?

Did you check that the switch is making good contact that and it's not just a dirty contact at the switch side ? Do a continuity test between the switch contacts by moving the joystick to engage the switch.

- James
 
Yep I checked it all as far as wiring is concerned. I even took the bare wire of the ground and the button and touched them together in test mode and got nothing.
 
Yep I checked it all as far as wiring is concerned. I even took the bare wire of the ground and the button and touched them together in test mode and got nothing.

A corroded button would just be too easy a fix ;)

Put a multi-meter on the wiring to the input lead and check it's pulled to to 5v, if it's not pulled to 5v check SIP2 on the game board for physical damage, like being cracked, that seems kinda unlikely tho'. as the other stick inputs are working.

Then it could be as easy as replacing IC B14, a 74LS240, on the CPU board. If you've got a logic probe, with the machine powered stick it on pin 8 of B14 and move the stick do down-right, you should see it go to low. If that's all good and seeing as the other joystick directions are working replace B14.

- James
 
After much delay. I have finally replaced B14. This did not fix the problem. There is no change. Does anyone have any ideas on where to look next?
 
Was this resolved??

Dustyn - did you ever get this resolved? If so what fixed it?

My Q-Bert started doing the exact same thing - will not go SE (diagonal down/right).

It's NOT the switch - under the control panel where the 4 switches are - if I jump them (so not using the joystick controller) Q-Bert moves in the 3 directions - but not down right, so its not the switch. I'm in the process at trying to jump it right at the board to see if its the wiring/connectors.

Funny thing - while trouble shooting, all of a sudden it started working. I put it back together, played a few games - perfect. Job done. The next day, turned it on, didn't work. Also - when it works - it always works(played about 5 games straight without 1 hiccup), and when it doesn't work, it never works - so I don't think its a contact issue, as I know some have suggested.

Anyone have any ideas?? (keep in mind I know nothing when it comes to repairing these things!!)

Chris
 
Quick update - I **THINK** my Q-Bert issue was the connector at the board - I cleaned it real good, jumped it there, and worked fine. Hooked everything back up, and all worked fine.

The real test will be how it holds up for the next few days.

Now that I have Q-Bert pulled out & open, I'm back to trying to solve the knocker issue (it has never worked on mine).

Never knew how tempermental Q-Bert is!!

Chris
 
Update 2 - no dice. :(

Fired up Q-Bert today and he's back to not going down/right. I check out continuity from the switch to the board (back end of the connector on the board), and there is current.

Now I am a total loss what to look for.

Can anyone help me?

Thanks in advance...

Chris
 
now thats down right annoying eh ? (pun intended :D)

have u got a copy of the qbert manual with schematics ?
1. print the schematics and stick them together so you have a full page schematic to trace. dow the same with the wiring diagram. these will help follow the following descriptions.

the down right switch is pin 19 on the PCB card edge.

have you checked that the earthing of the switch is also good ? i ask that as vibration coould be enough to stop it working if you have a dry joint (or a crack in a joint of the trace into the buffer IC).

pin 19 is IP40, which connects to B14 via R16.
when down right stops working there are a couple of tests you can do
1. check that R16 is not broken or open circuit or high resistance - with qb turned off, test continuity/resistance - it should be 470 ohms. if open circuit, rpelace or tack a 470 ohm or similar value resistor across r16 and retest.
2. check SIP 2 - that there is continuity/resistance between the JS side of r16 and pin 1 of the sip2 package - it should read 1k. if it is open circuit, you could temporarily tack a 1k resistor between r16 JS side and +5v. see if that makes a diff. look at the board layout to find SIP2
3. check the capacitor c16 (.1uF ) - lift or cut the leg and tack a .1uF monobloc or green cap or ceramic cap and retest.

4. if none of the above make a diff, need to look closely at B14. with QB turned on,
- short the downright switch with some clip leads (card edge pin 19).
- and short down left switch with some clip leads (card edge pin 20).

then test the voltages at IC B14 (74ls240) that buffers the switches.
- downright input is pin 8 of B14, and
- down left imput is pin 13 of B14

then test the voltages on the other side of B14 for each of Down left ande down right. as B14 is an inverting buffer, then with the js switch shorted to ground, the corresponding output pin should be logic HIGH or >2.x volts.
-downright output is pin 12 of b14
- downleft output is pin 7 of b14

if u are not getting a logic high for pin 12 the replace B14. ditto for pin 7.

hopefiully that should fix your issues with downright. dont forget if u haved lifted legs or cut legs, replace or resolder the appropriate component too.
 
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the knocker - the 2n6044 darlington transistors apparently go bad. i hav eone to fix myself, just waiting on parts and time to go visit. they are q1-4 at the top of the PCB.

having said that, do the follong first:
- checkj the knocker fuse.
- check the knocker coil for continuity and trhe knocker assembly harness and conne3ctors for continuity.
- check the diode across the knocker (IN4004) for correct operation (may be open circuit or shorted too).
- check the harness for continuity form the fuse to the Qx output
- check the resistor R32 on the 2n6044 base
- check of someone has cross wired one of the resistors to another one of Q1-4 - that would indicate a failed tranny, and as q4 and pmaybe q3 were spare they may have cheated and hacked the spare into circuit!

the 2n6044 trannies are cheap to buy - 1-2 dollars at most. replace all 4
also check and maybe replace the associated resistors r31-34, and caps c31-34
also check the header connectors on the PCB and filter boards for those outputs.

failing that the 74ls377 ic (A8) maybe dud.
 
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Thanks Andy!!!

For Q-Bert going down/right, I have moved/opened up another thread here - check out Arcade Repair 101 - I think i'm close, but I'm missing something simple! Just need a little guidance....

As for the knocker - I fixed it!! Bad 2n6044 transistor. For the time, I borrowerd the one from Q4. I'll make a permanent fix when I get a new one. Can I get one locally (Radio Shack, Frys, etc..) or only online.

Thanks again - Can't wait to get Qbert back into action!

Chris
 
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