Arcade repair 101 - can someone explain this to me?

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Arcade repair 101 - can someone explain this to me?

OK, so I am trying to solve my Q-bert issue - he refuses to go down/right.

So after spending many hours trying to troubleshoot/solve the problem, this is what I have learned:

- under the control panel, if I jump the contacts going into the 4 switches, Q-bert moves in the appropriate direction that I am jumping - except down/right. This tells me, that it is not the switch. Am I right?

- the 2 wires going to the switch (for down/right) are the solid white (common for all 4 switches and P1/P2 button) and the black/orange wire (for down/right) I follow these wires all the way to the back door of the unit where it connects to the connector board.

- if I use my meter and test connectivity for both wires - from the connectors under the control panel all the way to the board on the back door - both are good. That tells me the wire is good, with no shorts. Am I right?

- now, for the the kicker - if I jump the same 2 wires (solid white & black/orange) from the back door board connector board- Q-bert moves down/right just fine!

What am I missing here?? Basically when I jump the wires under the control panel - nothing, but when I jump it at the connector board in the back, all is fine (same wires!!).

Can someone please shine the light for me???

By the way, this is my first time ever working on an arcade. As I took a break from this issue, I looked into why the knocker wasn't working (never has for the 2 years of owning the machine). After doing my research, I jumped the Q2 transistor to use the Q4 one, and I got the knocker working! Now if I can just play the #^@% game!

Please tell me what I'm missing here!

Chris
 
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is there a butt splice in the wire or a connector between the board and the control panel?
if the wire goes directly from the pcb to the switches, i'm not sure what's wrong...if the wire has been spliced together or goes into a connector, there may be a bad connection
 
You could disconnect a set of the working wires from a working switch to the non-working set to see if it works. If the control moves the correct direction then it would make it a bad switching action.
 
When you jumper the wires on the back, are you sure they're the same ones, and not the ones on the other side of the filter board? The filter board is notorious for bad solder joints. If you haven't resoldered that board already, I'd do that... if it doesn't fix this problem, it'll save you headaches down the road.

DogP
 
Thanks for the quick replies guys - I appreciate it.

from mudhens1:
is there a butt splice in the wire or a connector between the board and the control panel?

There are not cuts/breaks/splices in the wires between the board and the control panel, but there is one connector about 1/2 between. But my meter test for continuity shows all is good.


from DogP:
When you jumper the wires on the back, are you sure they're the same ones, and not the ones on the other side of the filter board?

yeah - first I'm making sure they are the same wire by color, then I test for continuity by putting one probe on the control panel end, the other probe on the filter board end. I get a beep. (plus I have it all written down - I'm sure I'm working with the right wires) I did this for all 7 wires (7 wires are coming from the control panel to the filter board).

Now, on the filter board, I am testing the back side (oppposite side of the where the connectors are). That way I can keep the control panel connected, and jump the wires (solder points) at the same time.

I am having my wife (bless her heart putting up with all this!) stand in front of Qbert - I jump the wires in back, Qbert jumps, I have her move the control, no jump. But I try to jump from under the control panel, and still no jump.

I know Im missing something easy/stupid....

thanks

Chris
 
Check the connector that the wire is crimped into. Also reflow the pins on the filter board. They usually have problems.
 
reposted from prev thread.

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

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

on the schematic, down right switch is IP40, pin 19, which connects to IC B14 via R16.

provided your wiring is good from the earth point on one side of the DR switch to the filter board pcb trace, when down right stops working there are a couple of other 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.

dont forget to replace or resolder the appropriate components too.
 
.... if I jump the same 2 wires (solid white & black/orange) from the back door board connector board- Q-bert moves down/right just fine!

What am I missing here?? Basically when I jump the wires under the control panel - nothing, but when I jump it at the connector board in the back, all is fine (same wires!!).
....

could be the connection into the idc (insulation displacement) connector :
- test the downright (DR) connections wire at the top of the IDC connector(s) where the DR and common wires go in to the IDC(s)

if DR doesnt work there, but works at the solder traces on the back of the filter boardm then may be as simple as
- (per mr gorf) reflow solder on the header pin for DR
- clean the header pin for the DR wire (may be corroded)
- clean the mating socket in the IDC connector (tiny bit of sandpaper, file or scraper ?) - or get a bit of wire same size and rough it up with file cross ways then rub it up/dwn in the socket to clean the connector
- (per mr gorf) repunch the wire into the idc connector (pull it out and repunch it back in at a new position on the wire making sure you push the wire home - then test in the end of the wire to the metal of the idc connector for that wire)

if u still dont get reliable connectivity u may have to replace the idc connector(s)
 
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Did anyone ever find a solution to this? Mine just started having the same issue and i am trying to find out exactly what the problem is...
 
My vote is cracked solder on the filter board or bad connection at one of the IDC connectors. These are the first things to check on any qbert with problems.
 
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