SOLVED - SM Sandman Drop Target

[todler]

Hi Gents, after some assistance if possible. Not done any repairs in years and a mate has asked me to look and the Sandman Drop Target Bank on his SM. It keeps going up and down (energized all the time). This is what I have done so far

• Quick tests of transisters in back box. I assume this is still the same where you test between earth and the tab. All clear. Its Q20 for the drop target.
• Tested the relay switches while off. Relay isn't stuck on. i.e N/O is open and N/C is closed.
• Tested motor in test mode (even though its on all the time) and all switches working and activating as they should.

When you power the game on the relay is energised (light on). Tried to disable the drop target in adjustments but the motor still runs (currently now unplugged).

Any thoughts or tips on what to try next??

Cheers Tony

 

[CHRIS B PINBALLS]

If you have tested all that it may be a faulty motor try swapping it with the doc oc one

 

[todler]

Thanks for the reply Chris. We can try it but wouldn’t it be something on the control side keeping it on. If it’s energised all the time surely just swapping the motor would result in the same?
Not going back round his until later in the week so won’t be able to try until Wed/Thurs

Cheers Tony

 

[mufcmufc]

Thanks for the reply Chris. We can try it but wouldn’t it be something on the control side keeping it on. If it’s energised all the time surely just swapping the motor would result in the same?
Not going back round his until later in the week so won’t be able to try until Wed/Thurs

Cheers Tony

Swap the Sandman motor into Doc Oc first, if it works fine, you know it isn't the motor

 

[todler]

Swap the Sandman motor into Doc Oc first, if it works fine, you know it isn't the motor

Ok, will do.

 

[todler]

Ok Gents, tried/checked the following tonight.

• Plugged the Sandman motor into the drop bank supply and motor ran continuously as with the original issue. Luckily the plugs just reached so there was no need to move motors about.
• Drop Bank relay is energised all the time whereas the sand man relay is only energised when called for.

Therefore I believe it is a control issue as originally thought. Do I replace Q20 to be on the safe side or will it be something else. Like I said I have done the quick test on all the transistors and none are down to earth.

Cheers Tony

 

[todler]

Going back around my mates again tonight. Any more thoughts on what to try. Looking at the schematic these boards don't have pre-transistors as with B/W games. So anything on the board to check??
Cheers Tony

 

[todler]

Update, had another play with the SM this afternoon. Checked the transistors again, checked the output from the relevant terminals on J7 and had about 7v when it should be 0v. Then remembered someone said on B/W games to check the processing chip. Went through and pushed everything I could on the CPU board and found the ribbon cable was loose. Hey presto all up and working.
Morale is to check ALL connections on ALL the PCB's.