(Topic ID: 112877)

Fixing Bally S & T, Stern SB-300 and VSU-100


By jonbatson

4 years ago



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    #1 4 years ago

    Bally S & T, Stern VSU 100 Vocalizer and Stern SB300 Sounds

    There isn’t much information on these various boards and what there is available is either from Bally original documentation or from various hobbyists. No information I’ve managed to find on the net is especially recent (not surprising) and all (no doubt from necessity) would seem to be based quite naturally on single board testing.

    But before going any further it would be remiss of me not to mention specifically the detail provided by Clive Jones on the S & T http://www.pinrepair.com/bally/squawk.htm and for the Stern SB300 you can go to http://www.pinball4you.ch/okaegi/rep_soundsb300.html. This later can be found on a number of sites – but no where can I find a name to attribute to it. What there is points towards www.pinball4you.ch and someone with the handle okaegi. It would be nice to find a name to properly tie the work to.

    And finally to Bob Sokol of Two Bit Score Inc. Who provided the following detail on the SB300 via http://www.twobits.com/ballytesterbook/ballytesterbook.html

    I have nothing but praise for the above who, via the detail they provide, have enabled me to fix many boards over my 30 years as a pin addict. With my electronics background have repaired 100s of machines and this is has been helped by details like that provided by the above – and also from Bally and the other manufacturers manuals and schematics. And a very sincere thanks to all.
    And in these 30+ years I have never before had anything particularly useful to add to what is already available on the net. But now maybe I do have some useful detail to add.

    This is not a tutorial – just a few notes and comments to add to what is already provided. Where I hope this is useful is where it is focused on a period a few weeks fixing ten Bally S & T boards, eleven Stern SM300 Sound Boards and three Stern Vocalisers. My comments that follow then are based on what I found in making a number of focused repairs on a particular board type over a short time. Some of my findings came as a bit of a surprise.

    So read on and make your comments. If it's useful then maybe someone can make it more easily available.

    Bally S & T

    There are various references to the Bally boot up sequence and the number of flashes.

    General Comment

    1. On no occasion running various game software did I ever see “the fists flash” or flicker. Maybe I’m blind?
    2. All references to the boot up stipulate 5 flashes. This is true on some software, but not on others. Certainly the addition of the 5 x EE straps and the installation of the U12 (AY3-8912 Sound Generator) adds at least another flash to the sequence.
    3. SW1 is not a reliable way of starting the voice check additional test. Nothing wrong with the test – just that SW1 does not have (anti bounce) so the test often has to be started again by a total Power OFF Reset. This is confirmation of what has already been suggested by other authors.
    4. The two parts of the board are the Sounds and the Speech (The Squawk and the Talk). The SW1 Self Check tests the speech held in memory, but only tests very briefly the Sound generation. Hit SW1 and the first and last half second of what you hear are the Sounds and the rest is the speech. You will often hear more of the Sounds when the machine finishes it’s own power on process.

    Testing Process

    1. Swap as many IC’s as you can with good ones. Standard elimination process.
    2. How many flashes? If it does them all and you don’t have any volume, then try touching the components around U14. The power is not sufficient to harm you – not even a tingle. But if the TDA2002 Power Amplifier is working you should get at least a loud hum. Or if you are lucky you might, like me in NZ, pick up a local radio station. If not the TDA 2002 is almost certainly the problem.
    3. Get the hum? Yes – but still no Sounds or Speech. Try changing U14 and then maybe U13.
    4. Try changing out the capacitors? Especially C29 and C43. They are closest to the Power Amplifier heat sink and so most prone to drying out.

    My Faults

    The following is what I found as I worked through the failures. Please note that some boards had more than one failure – difficult to see why two (or more) seeming unrelated problems should happen on the same board. Except that is until you see where the boards came from, commercial machines, often operating alone, S & T goes down, the rest of the machine still running and taking money. How long do you run it like that before taking it off-line?

    1 Substitution of ICs found at least half the faults. Partly this was due to flaky IC holders – especially U1 and U11. It also highlighted a comment from the net about the physical strength and resilience of the U8 TMS5200. Its legs do rot out (two cases) and the damage to the holder that this causes also needs to be checked.
    2 Using the above substitution technique found one faulty U1 6808MPU, one faulty U11 6821 and one faulty U6 6810.
    3 R9 & C51. If your speech does not contain the correct resonance. Either it sounds too fast and high pitched or too slow and low – one or the other of these two RC components is likely to be the cause – probably the capacitor (two cases).
    4 Bad capacitors. Three cases – C43 (twice) and C29. The only other capacitor I had to replace was C1 (one case). While a few had already been replaced, I found no need to change the lot in one go. I don’t have a problem with the technique – just that I personally enjoy finding out the actual cause of the problem (if I can) rather than a generic one fits all approach.
    5 Sound and Speech Volume controls. These pots are notorious – but in my experience – while most of them were a little flaky – a quick twiddle cleared the dust and debris on the tracks, so one fault cleared but none replaced.
    6 The other faults involved a bad Power Amplifier and a U17 Address Decode IC.

    Still No Help?

    If you are still down and you if you haven’t got access to an Oscilloscope then it’s a question of poke and hope or find someone to fix it for you. This board, with its mix of analogue and digital techniques, is not easy. The most effective method of fault finding is the substitution method and comparing one board operating the same software with another identical version.
    I appreciate most hobbyists don’t have that luxury.

    Stern SB300 Sounds

    No flashes or any other help. Just power the machine up and listen.

    General Comment

    1. To properly test the board is ok you need to set the machine in self test, run the solenoid self test and wait until the later part when you should hear two distinct beeps, then four bursts of noise gradually increasing in volume and then (if you have the Vocaliser) you will hear a number of game related speech segments. Then the solenoid test starts all over again.
    2. Unlike the Bally S & T there is no separate and distinct boot up self test for this board. Actually I find this an advantage because (unlike the Bally) this board should beep each time the MPU goes through its seven flash power up boot.
    3. This board only generated sounds. Any speech your machine may have is generated by a separate board – the Vocaliser. The Vocaliser has its output fed back to the SB300 at J3 – pin 5 and then via a hard wired connection on the rear of the board to the junction of R24, R25, R30, R23 and C14. This is where the three potential sound types all come together before output via U4 and then U1 to the speaker. Not particularly elegant – but effective and reliable.

    Testing Process

    1. Standard IC swap elimination process, but not so effective in this case as there is only one IC in a holder. The U18 6840.
    2. Did you get the beeps? If you have a Vocaliser fitted – do you get the voice? If the Sound Output stages are ok and you have the Vocaliser you might get speech and no sounds.
    3. If still nothing at all and you don’t have any volume, then try touching the components around U4. If you get a hum (or radio even) try further back around U7. The power is not sufficient to harm you – not even a tingle. But if the TDA2002 Power Amplifier is working you should get at least a loud hum. Same IC as the Bally S & T.
    4. You might try changing capacitors – it is recommended. But none of my faults would have benefited from doing this and with eleven boards as a reference base I can’t honestly recommend it. However, I should add that three of my boards have in the past had some or all capacitors changed so I guess the jury is still out..

    My Faults

    The following is what I found as I worked through the failures. Please note that some boards had more than one failure – difficult to see why two (or more) seeming unrelated problems should happen on the same board. Except that is until you see where the boards came from, commercial machines, often operating alone, Sounds or voice or both goes down, the rest of the machine still running and taking money. How long do you run it like that before taking it off-line?

    1. Substitution of ICs was useful and did find two U18s.
    2 It also found a couple of U18 IC Holders with broken connections internally.
    3 All control of this board comes from the MPU Board via the Ribbon Cables. These are relatively unreliable so check them for continuity first and then check they make contact at each end reliably.
    4 By far and away the single biggest fault item was the MC14516B at U12. Not always the same symptoms, wrong sounds, no sounds, distorted sounds –but each fault in the end a single failure of U12. Five boards out of eleven.
    5 Bad capacitors. Two cases – C15 (twice), C 16, and C14. These were the only ones I needed to replace. And each of these two boards needed U4 & U& replaced, so I reckon someone had connected something to the external volume control and caused a ripple of failures.
    6 Other faults involved two bad U1 Power Amplifiers and a whole series of address and control signal decoder issues involving U16 & U17 together with their control of the U8 flip flops. See also * later.
    7 And finally I did have to replace a single Quad Latch at U14.

    Still No Help?

    If you are still down and you if you haven’t got access to an Oscilloscope then it’s a question of poke and hope or find someone to fix it for you. This board, with its mix of analogue and digital techniques, is not easy. The single most effective method of fault finding is to replace U12. But this only worked in under half the cases so it is not recommended as a “cure all”.

    *If you do have a scope you might be interested in the following.

    I had some serious difficulties with faulting the chip at U12. Using my scope (my ever reliable and excellent Tektronics 2445A) it really looked like the control lines to the chip were no being set. If you have the diagram you can see a chip train of approx. half a dozen gates all intended to provide (eventually) a one shot start of the up / down counter at U12.

    During this period I changed out a number of U16 and U17 ICs that looked to be causing the disconnection. In all but one case these replacements were not the problem. Unfortunately it was the first one I replaced which proved effective, so I wrongly replaced a few more before I realised my mistake.

    I never did get the scope to trigger successfully on this one shot (probably because I found the following tip so useful, that I didn’t need to look any further for an elegant solution).

    So my tip is: If you want to see if the flip flops at U8 work – set you scope on their outputs and with the machine on and not in test, try shorting out pins 9 and 10 on U16. You should see U12 pin oscillate. If that’s ok then you can go further back in the decode train and try shorting out U16 pins 5 &4. Be careful though – any further back and you are going to be working on lines that directly connect back to the main MPU Address and Control lines and you can easily cause the machine to reset or worse.

    And the end result of all this were faulty U12’s

    Stern VSU100 Vocaliser

    No flashes or any other help. Just power the machine up and listen.

    General Comment

    1 To properly test the board is ok you need to set the machine in self test, run the solenoid self test and wait until the later part when you should hear two distinct beeps, then four bursts of noise gradually increasing in volume and then (if you have the Vocaliser) you will hear a number of game related speech segments. Then the solenoid test starts all over again.
    2 You will only hear speech from this board either in game play or during the Solenoid Self Test.
    3 All control of this board is from the main MPU to Lamp Driver lines that are intercepted at J1 and J2.
    4 This board only generated Speech. The Vocaliser has its output fed back to the SB300 at J3 – pin 5 and then via a hard wired connection on the rear of the board to the junction of R24, R25, R30, R23 and C14. This is where the three potential sound types all come together in the Sound Board before being merged with the speech and then output via U4 and then U1 to the speaker. Not particularly elegant – but effective and reliable.

    Testing Process

    1. Swap as many IC’s as you can with good ones. Standard elimination process, but not so effective in this case as there are only two or maybe ICs in a holder. U9 and U10 are the two ROM / EPROMs and U8 the S14001A at U8..
    2. Did you get the beeps? If you have a Vocaliser fitted – do you get the voice? If the Sound Output stages are ok and you have the Vocaliser you might easily get sounds and no speech.
    3. If still nothing at all and you don’t have any speech, then try touching the components around U7. If you get a faint hum depending on the volume you have set on the Sound Board. Do you have the Sound Board strap in place?

    My Faults

    The following is what I found as I worked through the failures. Please note that some boards had more than one failure – difficult to see why two (or more) seeming unrelated problems should happen on the same board. Except that is until you see where the boards came from, commercial machines, often operating alone, Sounds or voice or both goes down, the rest of the machine still running and taking money. How long do you run it like that before taking it off-line?
    And please note that I only have three faulty boards to consider and your fault may very well bare no relation to what I found

    1. Substitution of ICs was useful and did find two faulty U8s. These are difficult to source and expensive. However, I can heartedly recommend one location – Kevin Keinert at http://www.gameroomrepair.com/
    2. The only other fault I found revolved around the software available off the net. One of my machines (a Catacomb) failed the speech and while the actual fault was the EPROM failing – getting a replacement to work was a little more of a problem. Basically I found some of the net sourced software simply wouldn’t run and I’m still trying to find out why.

    Still No Help?

    If you are still down and you if you haven’t got access to an Oscilloscope then it’s a question of poke and hope or find someone to fix it for you. This board, with its mix of analogue and digital techniques, is not easy. The most effective method of fault finding is the substitution method and comparing one board operating the same software with another identical version.

    I also feel that a reliable method of reprogramming EPROMs would be useful. I have two programmers and a combination of the older and very slow machine able to program 2532, 2716 and 2732 EPROMs to be invaluable. My newer machine with all it’s plethora of capabilities (like all its current ilk) can’t manage 2532s – so the old one still has its place.

    I appreciate most hobbyists don’t have that luxury.

    Jon Batson (19/12/14)

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