(Topic ID: 211291)

Two Bits Dash 35 Build


By JT-Pinball

2 years ago



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  • 29 posts
  • 8 Pinsiders participating
  • Latest reply 2 years ago by JT-Pinball
  • Topic is favorited by 3 Pinsiders

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    #1 2 years ago

    Was looking thru the forum for anyone who has built a Two Bits Dash 35 board? I did not see where anyone has posed anything in the past about these boards except a few post where some were for sale. So I figured that I would document my progress here as I build this thing out. I got the board for 50 bucks and I already have most of the parts. I ordered the chips and missing parts I needed that maybe cost another 30 bucks. So here goes. I started out by installing the sockets for the CPU, PIAs, and U2 and U6, then the switches. I got the rest of the sockets for all the other chip sockets seated and soldered in last night. Next up will be to build out the Valid Power Detector circuits. That way I can check that I have good voltage before moving on. More pics when I have that done later today.

    #2 2 years ago

    Watching like a hawk. Post lots of pics please.
    -Mike

    #3 2 years ago

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    #4 2 years ago

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    #5 2 years ago

    I bought a couple of those to build up. I started the same you have, sockets and DIP switches first...not completed one yet as they are for when I am slow and have nothing else to do. So far not slow around here. I will be watching in interest as well.

    #6 2 years ago

    I built out half a dozen of them 5-6 years ago.. all at the same time! Not something I'm proud of lol. I think it worked out to be $90 or so per board in materials.. and then a lot of time. Good weekend project for someone that likes to DIY though. Get that warm and fuzzy when you fire it up and it works

    #7 2 years ago

    Well got most of the Valid Power Detector in. Wound up putting a couple capacitors in other circuits just because it was convenient because I had them out. I’ll try to post pics later. My build sheet calls for a 2K 1/2 watt resistor at R113 and R16. I only have 2.2k 1/2 watt so ordered 2k 1/2 watt. My schematic are from Xenon and they do not show 1/2 watt there. Got 2 k 1/4 watt. Got a few parts board and few working MPU sitting here and they all have 1/4 watt. This some upgrade or just the build sheet I have?

    #8 2 years ago
    Quoted from JT-Pinball:

    Well got most of the Valid Power Detector in. Wound up putting a couple capacitors in other circuits just because it was convenient because I had them out. I’ll try to post pics later. My build sheet calls for a 2K 1/2 watt resistor at R113 and R16. I only have 2.2k 1/2 watt so ordered 2k 1/2 watt. My schematic are from Xenon and they do not show 1/2 watt there. Got 2 k 1/4 watt. Got a few parts board and few working MPU sitting here and they all have 1/4 watt. This some upgrade or just the build sheet I have?

    2.2K 1/2W for both R113 and R16 is fine. You want even values for a 50% divide. 2.2K will be close enough, but less precise and bonus of using less energy.

    you want half watt resistors because at 2K the resistors would be using about 0.22w which is too close to a 1/4w rating. If the resistors do start to burn open they can go in a way that ends up killing u14 with over voltage.

    For ease and speed of assembly it works best for me to stuff parts smallest to biggest and them in steps by component type. Stuff all the caps then solder them. Stuff all the resistors then solder them. Then the diodes, etc...

    #9 2 years ago
    Quoted from barakandl:

    you want half watt resistors because at 2K the resistors would be using about 0.22w which is too close to a 1/4w rating.

    Great info, glad we have experienced techs watching this build to point stuff out.
    -Mike

    #10 2 years ago
    Quoted from barakandl:

    2.2K 1/2W for both R113 and R16 is fine. You want even values for a 50% divide. 2.2K will be close enough, but less precise and bonus of using less energy.
    you want half watt resistors because at 2K the resistors would be using about 0.22w which is too close to a 1/4w rating. If the resistors do start to burn open they can go in a way that ends up killing u14 with over voltage.
    For ease and speed of assembly it works best for me to stuff parts smallest to biggest and them in steps by component type. Stuff all the caps then solder them. Stuff all the resistors then solder them. Then the diodes, etc...

    Thanks barakandl. I figured on putting in half watt no matter what just wasn’t sure what being 10% over on the resistance would do to the voltage at the zero cross. Or if it would matter. Bally used to run this stuff right to the edge of tolerance. Wonder if that was engineered in for service?

    Makes sense on the parts. I was costing myself a lot of time going back and forth between parts bags.

    #11 2 years ago
    Quoted from acebathound:

    I built out half a dozen of them 5-6 years ago.. all at the same time! Not something I'm proud of lol. I think it worked out to be $90 or so per board in materials.. and then a lot of time. Good weekend project for someone that likes to DIY though. Get that warm and fuzzy when you fire it up and it works

    Yes. I have maybe 4 hours in this. Some of it is buying parts. Phone died before I got last pic tonight. But made some progress.

    #12 2 years ago

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    #13 2 years ago

    Phone died before I could take last pic. I have 90% of the resistor soldered in. Few stragglers on resistors and caps then finish off the Diodes for the switches.

    #14 2 years ago

    @ barakandl , When building a board like this for example, is there any side effects or problems with the idea of using 1/2 watt resistors where it would call for 1/4 watt?
    Keeping the same resistance value of course.
    -Mike

    #15 2 years ago
    Quoted from Grizlyrig:

    @ barakandl , When building a board like this for example, is there any side effects or problems with the idea of using 1/2 watt resistors where it would call for 1/4 watt?
    Keeping the same resistance value of course.
    -Mike

    The resistor might not physically fit. Higher power rating is usually larger in size.

    power ratings on a resistor is a maximum. They work up to that power rating before they self destruct.

    If both resistors are 2000 ohm the resistor divide is 50/50 so there will be about 21v across each 2000 ohm resistor.

    (V²) / R = Power (watts)

    (21²) / 2000 = 0.2205W

    a "quarter watt" resistor =0.25W.

    Seems best to overshoot resistors power ratings by at least 50% to avoid it burning over time. It is common to see R16 and R113 burned on the bally MPU. No other 1/4w resistor on the bally MPU needs upgrading.

    The 82ohm 2W resistor can be eliminated by using NVRAM and jumpering CR5 and CR7. That sucker burns up too. I would use at least a 3w resistor there. 5w gets a little tight.

    Knowing the that 12v unreg supply commonly reads as high as 16v...

    (16²) / 82 = 3.12W

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    #16 2 years ago

    Thank you for a clear explanation and the diagram.
    -Mike

    #17 2 years ago

    How you doing? Any new progress and pics?
    -Mike

    #18 2 years ago

    Haven’t had much time to work on the -35. Been busy with the day job and putting in working on a Flight 2000 project. I took barakandl suggestion and stoped trying to install circuits and just stuffed each component as it came up on the build sheet. Here are some more pictures of where it stands.

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    1 week later
    #19 2 years ago

    Had some time to get this finished over the last few days. I was missing a few other resistors, some that I waited on. In the end think I harvested a few off a parts board to finish up. I still need to order the switch for 33. The ones that fit the old Stern MPU -100 that I have from GPE don't fit this board. Here are some more pictures of the board thru completion.

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    #20 2 years ago

    So I boot the board up on the bench prior to setting up in a game. I get no flashes on the LED. Are you kidding! Pulled U11, U10, U6 and U2. Put the Leon in U6 and ran out all Address and Data lines. All good! Have rhythm on test LED. Still not main LED on board. Checked the LED, its bad! guess that explains why we have no flashes. Replaced the LED. Now it is flashing in sync with the test. Installed U10 and U11. Checked all Input and output lines. All good. Reloaded U6 and U2. Board boots to 6 flashes on bench. Time to install in a game!

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    #21 2 years ago

    Yes I realized that C81 was missing. I installed it prior to testing the board. Seems I have one last issue. I got board installed in a game. Hot Hand in this instance. I had a Bally -35 in the game so I set the new board up the same way. Game boots and enters attract. Plays fine except the score and credit displays all roll. Didn't do it before so I know it is not the displays. All data on displays is correct. I am guessing this is an issue with blanking or zero cross? Guess I will have to run a few more test. Anyone thoughts?

    #22 2 years ago
    Quoted from JT-Pinball:

    Yes I realized that C81 was missing. I installed it prior to testing the board. Seems I have one last issue. I got board installed in a game. Hot Hand in this instance. I had a Bally -35 in the game so I set the new board up the same way. Game boots and enters attract. Plays fine except the score and credit displays all roll. Didn't do it before so I know it is not the displays. All data on displays is correct. I am guessing this is an issue with blanking or zero cross? Guess I will have to run a few more test. Anyone thoughts?

    The 555 timer circuit creates a display interrupt pulse around 320-360hz. That pulse tells the CPU to update the displays. You can check that signal with a frequency count feature on a DMM. It is labeled as "DISPLAY INTERRUPT" on the schematics, goes to a PIA port.

    Rolling displays is usually a power supply issue. Last time I saw it a lead of the 230v filter cap had broke loose.

    #23 2 years ago

    This is great to watch! Overall, how many hours do you think it took you?

    #24 2 years ago
    Quoted from barakandl:

    The 555 timer circuit creates a display interrupt pulse around 320-360hz. That pulse tells the CPU to update the displays. You can check that signal with a frequency count feature on a DMM. It is labeled as "DISPLAY INTERRUPT" on the schematics, goes to a PIA port.
    Rolling displays is usually a power supply issue. Last time I saw it a lead of the 230v filter cap had broke loose.

    Thanks Andrew! I will check the power output on the SDB. This SDB has new caps and a new HV section. I have U12 P3 going to U11 P40. Looks like good place to start for frequency. I will pull the schematics for the 555 to be sure.

    #25 2 years ago
    Quoted from NJGecko:

    This is great to watch! Overall, how many hours do you think it took you?

    Maybe 8. I really didn't track it out. It took me a hour maybe to go thru and order parts. Probably 5 to 6 to assemble and 1 to 2 now in testing, troubleshooting, and scavenging a few parts from other boards. I could build 4 at the same time, now and probably not have more than 4 to 5 hours in each. To bad there is no market to build them out! lol.

    #26 2 years ago

    I did this a few years ago basically to see if I could. Seemed like a fun challenge. I grew up with Heathkit kits for learning the basics and this was maybe a couple steps farther. Not fiscally sound but still entertaining. I have Alltek MPUs in all my Bally machines now so I use it as part of my wire harness making jig.

    Shawn

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    #27 2 years ago
    Quoted from Mk1Mod0:

    I did this a few years ago basically to see if I could. Seemed like a fun challenge. I grew up with Heathkit kits for learning the basics and this was maybe a couple steps farther. Not fiscally sound but still entertaining. I have Alltek MPUs in all my Bally machines now so I use it as part of my wire harness making jig.
    Shawn

    I haven’t had the chance to get this working 100%. This weekend I will get it finished. I like it because now I have fully socketed board. Make it easy to test any chips that I may have that are suspect.

    #28 2 years ago

    One of these came installed on my SBM. I didn’t know this was a kit. It’s been working fine. Twobits is a good company from my experience. Sent them a few Bally boards for repair and had them back in a few days.

    #29 2 years ago
    Quoted from Bricarus:

    One of these came installed on my SBM. I didn’t know this was a kit. It’s been working fine. Twobits is a good company from my experience. Sent them a few Bally boards for repair and had them back in a few days.

    I thought Two Bits sold them assembled back in the day. Maybe they all started as a kit and they just assembled some of them. I know they sold a module for fixing testing them back in the day.

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