Air Hockey Table Scoreboard help

[Karl V]

I picked up a Classic Sport Air Hockey table and the scoreboard isn't working. When I first got it the E & D segments were not working nor the speaker. I replaced the speaker with on from another unit and trying to figure out the segments from an old thread from another site, I replaced the transistors for those 2 segments. Now all the segments seem to light up some what dimly and the E, D G segments seems to always stay lit, but not full on bright. I noticed 1 or 2 other transistors getting really hot until I unplug the speaker. I couldn't read anything on the old speaker and I had an 8ohm 2 watt speaker from another electrical item so I tried that and that is causing the other transistor(s) to get hot. Also the countdown is fast, it actually takes about 6 seconds to count down 10 seconds on the display. After about 1-2 minutes, the G segment starts to flicker a bit, but it is definitely hard to read the scores. Any help would be greatly appreciated. I tried removing those 2 transistors again and then the whole board got wacky, only the right zero would light up for both home and visitor.

You can see when 10 minutes is selected, you can't read 10 minutes, when 20 is selected, that reads ok, and when 30 is selected, again, you can't read it. The one picture has the timer running and I scored one puck on the home side and you can see it doesn't show a 1.

Thanks,
Karl

 

[Karl V]

I was just checking, and when I was checking power on the circuit board the other night, I was getting 13.5 volts on 2 pins. I just happened to look at the power adapter that came with the air hockey table tonight and I see it's output is supposed to be 7.5VDC. I am getting 14.3VDC out of it. I ordered a replacement one from Amazon and "should" get it by tomorrow. I am hoping that is the problem, that I am getting too much voltage and that is causing the malfunction. I just hope I didn't damage anything.

 

[Karl V]

So the replacement power adapter came in and I am still having the same issues. Even the clock runs fast, takes about 6 seconds to count down 10 seconds on the clock.

 

[Martaine2005]

The same issues?.
What’s the voltage from the new adapter?.
Voltage on the 2 pins you measured previously?.
I notice that the missing segments do work, so LEDs are ok.
All the components on the board can be checked quite quickly with your meter except the ‘blob ic boards’.
Those are the main brains which are probably a common board and can be purchased from China.

Martin

 

[Karl V]

Martin,
I am getting 7.83 VDC out of the adapter and on the 2 pins on the PCB.
The same issues I am having is that the segments are not working properly. for example, when I power it up, everything lights up as a self test, granted segment G flickers and then when the clock should show 30:00, segments E & F stays lit and D is dim, for the 3. For the 0's D is dim also, D should be bright for both of those. When I go to 20:00 minutes, for the 2, F stays on and D is dim, nothing changes with the 0's. Then I go to 10:00 and F & E are bright and D is dim.

Also after a minute or 2 of switching it all on, the G segment will start to flicker for a minute or two and then stop for a while and then repeats.

I am thinking something is overheating on the board causing that and whether that is from the old power adapter outting out too much voltage? I did check the 5002 voltage regulator and it is stepping the voltage down to 5 volts. I thought maybe that would have fried with the excessive voltage.

I did check for voltages at the transistors and I get the following for each segment:
G-->E 6.0V B 6.6-6.7V C 7.6V
F-->E 6.8V B 6.9-7.0V C 7.6V
E-->E 6.2V B 6.7-6.8V C 7.6V
D-->E 4.7V B 5.2-5.3V C 7.6V
C-->E 6.3V B 7.0-7.1V C 7.6V
B-->E 6.9V B 7.0-7.1V C 7.6V
A-->E 6.6V B 7.4-7.5V C 7.6V

So obviously I see a low voltage with Segment D, but I do not know what controls that and how to fix that,

Thanks for your help!
Karl

 

[Martaine2005]

I would guess that the board with a black blob (controller) is damaged.
These sometimes have part numbers printed on them and should be available to buy a replacement.

Can you trace each output from the ‘blob controller’ board to the transistors?. You could try injecting voltage at the outputs to check everything downstream.
That board would be my suspect.

Martin

 

[Karl V]

I will give that a try. I tried entering the number I see printed on the pcb, but doesn't come up with anything.

 

[Martaine2005]

Also have a read of this. It may fix yours. It appears to be the same board as yours.

Martin

 

[Karl V]

Yes, that is where I started and following those directions. That's why I went ofter a couple of the transistors right away. It was weird, when I tested them on the board, I showed two open transistors for the two segments not working originally. Once I removed them and tested them again they were working. I still went ahead and replaced them and then these issues started.