(Topic ID: 195681)

MB Drac Motor not working


By lpnsocal

2 years ago



Topic Stats

  • 13 posts
  • 6 Pinsiders participating
  • Latest reply 2 years ago by lpnsocal
  • Topic is favorited by 2 Pinsiders

You

Linked Games

#1 2 years ago

Story begins like so many..., There I was looking to give my machine a little love so I decided to strip and clean/tune up PF. Whereupon reassembly something doesn't work, Damn Drac and his trac! During Drac test, it says," motor is running." but it's not. I checked all the fuses(good), despite there being 12v regulated all the way to the motor board. But during the test, there is no voltage leaving the board to the motor( checked at pins and motor.) I think there are 2 solenoids that control the direction of the motor causing Drac to move about, tho I'm not sure if that plays into this(There is good continuity for these wires back to the driver board.) Additionally, the proximity board with the 5 optos all show working on the switch edge test. Tho I get an error for a couple of them not working one of which is the home opto. I assume continuity is fine back to CPU because of the sw edge test. I even rebuilt the gearbox having read about the bound up grease that plagues these older machines, obviously it didn't fix my issue but it'll be good for another 10+ years. I also checked the diodes on both boards because I know how. They're all fine.

I've checked the forums and nothing fits my issue, Anybody have a fresh angle?

#2 2 years ago

Update: I was able to test motor using leads from drop target motor board and it does work. I double checked the switch edge test to see if any multiple switches were indicating when one was tested, no multiples. Tested all components(in board) on the trac proximity board w 5 optos, everything was within parameters. I also tested all wires back to CPU for good continuity.

#3 2 years ago

Update: Swapped motor control board #A-16120-1 from another machine and bingo, problem solved. ...., sorta. I still have to figure which component(s) failed and replace. I think for $10 I can replace everything or spend $100 for a whole new board(but where's the fun in that?).

#4 2 years ago
Quoted from lpnsocal:

Update: Swapped motor control board #A-16120-1 from another machine and bingo, problem solved. ...., sorta. I still have to figure which component(s) failed and replace. I think for $10 I can replace everything or spend $100 for a whole new board(but where's the fun in that?).

Funny how topics about pinball get little to no response, but if you post about Mcdonalds being too slow or a post asking if you're a cigar smoker, will get you hundreds of responses.

#5 2 years ago

Seems like he did just fine figuring it out on his own.

#6 2 years ago

Well I do appreciate the additional posts, and agree it's hard to glamorize this mundane subject, especially when it's kind of off the beaten path. I was pleasantly surprised to find a replacement board for sale at Marco but I guess that means it apparently fails enough for someone to make it!

And whereas I did narrow it down to the correct controller board, I have not figured out how to narrow it down further on the board itself( although resisters and diodes are easy to test.) I'm hoping that Ed at Great Plains can narrow it down a bit, though I think I can replace every component on the board 2x for $10, and fine tune my soldering skills. The new board is still the last resort.

#8 2 years ago

Aside from the obvious things like dry jointed pins, damaged tracks etc it really can only be an optocoupler or H-bridge driver IC that is faulty.

The optos are easy to find and inexpensive - the IC is harder to find and will probably cost about $12~18 but if the optos don't fix your problem the IC almost certainly will.

Don't try to save the parts on the board, cut the legs and remove each pin, one by one. This way you will avoid PCB damage.

Remember, the PCB has the value NOT the suspect parts you are replacing.

#9 2 years ago

dudah

Thanks for the post, I read your documentation/link and found it very insightful as well as helpful. Eventually, I hope to be able to test boards as in depth as you. Additionally, I guess knowing which games had this board would have made it easier to find repair posts. I now know of three.

homepin

Quoted from Homepin:Aside from the obvious things like dry jointed pins, damaged tracks etc it really can only be an optocoupler or H-bridge driver IC that is faulty.

The optos are easy to find and inexpensive - the IC is harder to find and will probably cost about $12~18 but if the optos don't fix your problem the IC almost certainly will.

Don't try to save the parts on the board, cut the legs and remove each pin, one by one. This way you will avoid PCB damage.

Remember, the PCB has the value NOT the suspect parts you are replacing.

Thanks for the post. There are no obvious "tells" on this board, in fact all components look like they could be original. I only say that because of the solder flows on the back are wonderfully consistent and un molested. Since I would be ordering parts online from Great Plains, I tend to over order and have extras while avoiding the next unnecessary shipping charge. All the parts, you mentioned are part of my blind order(including the expensive IC 3A DMOS Bridge Drive). I will add C3 to the mix, as I can't imagine more life in that 20 year old cap.

Upon receipt I will replace in the order you've instructed and test in machine, tho C3 will be replaced regardless. Thanks for the reminder on clipping the legs, that is invaluable!

#10 2 years ago
Quoted from rx3:

or a post asking if you're a cigar smoker

Er, Ipnsocal....Are you a cigar smoker?

#11 2 years ago

You would think as a bourbon drinker I should be, but I've tried, and and decided to leave that vice to others. (assuming you are speaking in the most literal sense )

3 weeks later
#13 2 years ago

Final Update: After a couple weeks I finally was able to break out the parts box from Great Plains with effectively every board component ordered(just in case) with extras for the future. First, I decided to go with replacing the Opto isolators(U1, U2) along with the IC DMOS bridge drive(U4) in the first guess repair. Test failed so in the 2nd guess repair I replaced/socketed IC 74LS32(U3). Test failed again so I re-re-checked all the resistors, diodes and capacitors and only a little 1uf cap ( C1) measured way off, so I removed it. It tested fine off the board. So even with the 5v LED lit I figured to replace 100mfd cap(C3), 5v regulator 7805(Q1) and decided to put the removed 1uf cap back in despite having bought new ones(silly move on my part as they are like 5 cents apiece.) 3rd test was the charm and the board is functioning as it should for about 1/3 the cost of a new one and I have a bunch of extra new parts to add to my growing inventory.

Thanks again for everybody's helpful advice!

Promoted items from the Pinside Marketplace
$ 14.00
Electronics
Yorktown Parts and Equip

Hey there! Got a moment?

Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside