Dot Matrix Circuit Board Components; can they be fixed?

DeLoreanRide

New member
Joined
May 14, 2007
Messages
165
Reaction score
0
Location
West Chester, Ohio
Dot Matrix Circuit Board Components; can they be fixed?

I had a problem where my dot matrix screen went out on my Jurassic Park pinball. I went through the power supply and ended up needing to replace a transistor, 2 diodes, and a capacitor.

When I powered on, there was just some static on the DMD. When I took it apart I found the smoking gun, literally:

DSC_0437.jpg

DSC_0439.jpg

DSC_0442.jpg


R4 is clearly shot as you can see and transistor it goes into (Q2) is now shorted on one side so I believe those are the two that need replaced. I'm not sure if this is a random incident or whether it's all connected or what. I'd like to think this began back when the power supply components went out and are not a product of the circuit board replacement parts. I used exact parts ordered from digikey so I'm pretty confident.

R4 I believe is a 2K ohm resistor and Q2 is a transistor of unknown values. Is it possible to replace/fix things like this? Where can I find circuit board components like this? Digikey? I'm not really sure where to start.

Thanks everyone!
 
They're called SMD (Surface mount device) components. You need a 2K ohm SMD resistor, but I'm sure wattage comes into play there to determine the size.

Q2 - good luck on that one. Hopefully you have a decent parts list for that DMD board. I know the standard DE schematics are the suck. No parts lists either.
 
Take a look at the resistor size chart I attached. It will help narrow down your choice for the smoked resistor. As far as wattages the following may apply - the 0603 (1/16 watt); the 0805 (1/10 watt); the 1206 (1/8 watt). These are typical values but can be different. There are a couple of other sizes commonly found; 0402 - 1.0 mm x 0.5 mm (0.04" x 0.02") and 0201 - 0.6 mm x 0.3 mm (0.02" x 0.01") and wattages for those tend to be lower. Hopefully with this you can get a replacement.

The transistor looks to be a SOT-23 package (3 mm x 1.75 mm x 1.3 mm) and according to the schematic is a PNP. You may be able to get by with a generic equivalent. However, I think Shardian is right, good luck on finding the right Q2.
 

Attachments

  • SMD Resistor size chart.jpg
    SMD Resistor size chart.jpg
    20.3 KB · Views: 12
Does anyone have any idea how to find the values of the transistor? (Q2) I have no idea how to replace it without that information.
 
Is there no notation somewhere else on that drawing designating the ratings for Q2? Maybe a note that reads something like 'All transistors value XXX'?
 
Yeah, I downloaded the manual and I can't find anything either. Maybe you should try to contact the manufacturer of the board? I have had luck in the past contacting original equipment manufacturers directly when I have tech questions.
 
Does anyone have any idea how to find the values of the transistor? (Q2) I have no idea how to replace it without that information.

I downloaded your photo of the board and tweaked it a bit with Photoshop. I can barely make out some lettering on the transistor itself. Is it possible for you to take a closer picture of the same area (Q1, Q2)? I may be able to give you some options if you can capture a better pic.

Looking at the rest of the schematic you show it has Q2's collector going to U6 pin 1. U6 is nothing more than a hex inverter. Therefore Q2 is going to be there to act as a buffer (keeps noise transients out) to the input of the inverter. A generic PNP would work here as long as the voltage specs are in the right range.

Obviously, the best course of action is to get the "real" part number for Q2. Barring that, anything else will be nothing more than a "band-aid". It will work but not like it was designed to do.
 
The writing on Q2 reads: 2L >

No idea what that means. Also do you believe that U6 would be damaged as well? I'm not really sure how to test for that.
 
Last edited:
The writing on Q2 reads: 2L >

No idea what that means. Also do you believe that U6 would be damaged as well? I'm not really sure how to test for that.


Hmmm, 2L not much to go on there but will try.


Although it is possible for U6 to have taken a hit, I would also consider U3 as having played a part in the failure of R4. As I said earlier, U6 is nothing more than an inverter. Pin 1 is the input of the first inverter with Pin 2 being the output of the first inverter (the sequence continues around the chip with the exception of pins 7 & 14). If you have access to a logic probe you could apply a pulse to pin 1 and check pin 2 for an inverted signal to test it. However, that chip is fairly inexpensive (less than $2.00). If it were me I'd just replace it only because it may have suffered a latent failure (a failure that may show up in the future).
 
I've got a shopping cart at Digikey with the resistors I need and the hex inverters I need. Without figuring out what the voltage is on the transistor though I'm still up $hit creek :-(
 
those header pins look a little rough especially the ones marked Vsn and Vrw. take a little sandpaper to them and reflow the solder if they need it. check the pins too inside the connector.

maybe Q2 got hot and the lettering isnt legible. do any of the others have the same numbers with better lettering for verification?

i cant believe there isnt a parts list to tell you what they are. hate that.
 
those header pins look a little rough especially the ones marked Vsn and Vrw. take a little sandpaper to them and reflow the solder if they need it. check the pins too inside the connector.

maybe Q2 got hot and the lettering isnt legible. do any of the others have the same numbers with better lettering for verification?

i cant believe there isnt a parts list to tell you what they are. hate that.

I think that's just the way the flash is hitting it. The pins leading to the connector going to the power supply board are very clean.

that's all the transistors say. Fortunately in Florida on http://www.villagebbs.com/forum/index.php/topic,4745.0.html

Someone posted:
2L is a Motorola (or ON Semiconductors) MMBT5401. It's a 2N5401 pnp transistor rated at 150V in a SOT-23 package.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MMBT5401LT1GOSCT-ND
 
i cant believe there isnt a parts list to tell you what they are. hate that.

That's my number one hater complaint on Data East. NONE of the boards in a Data East pin have parts lists! I can only assume this was done to encourage users to send all of their repair work back to Data East/Sega.
 
That's my number one hater complaint on Data East. NONE of the boards in a Data East pin have parts lists! I can only assume this was done to encourage users to send all of their repair work back to Data East/Sega.

Yea but this is a Vishay board. I dont know if Data East is really to blame since it's the same board thats in williams and balley games as well. Blame Vishay!
 
Back
Top Bottom