KenLayton
In Memoriam
I don't see why it wouldn't work.
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Please post all monitor technical topics in the Technical - Videogames - Monitors section, not in the General Help section.
Taito Power Supply schematic needed....
- Thread starter modessitt
- Start date
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modessitt
Volunteer: Encyclopedia Submission Moderator
Well, if that isn't a ringing endorsement, I've never heard one. I think I'll give it a shot......tomorrow......
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modessitt
Volunteer: Encyclopedia Submission Moderator
Well, I tried it - and it didn't work - or didn't work as I wanted.
Isolating that circuit affected the other power voltages (no +12 anymore), so I used the switcher for all the voltage outputs (with -5 connected to the -12) and the board does not come up.
I'm thinking the problem is with the RESET coming from IC3. I have good +5 to it, but the reset line is a steady +4.45. I'm wondering if the problem is with the signal coming from the circuit above where the TILT signal is?
At one point I did have the scores at top and the Taito line at bottom, but no attract and couldn't add a credit or start a game. After cycling the power I continue to get a blocky pattern image on the screen.
Any other bright ideas? Is there a way to generate a RESET signal? Or maybe I can just direct connect the +5 to the board and not even use/need a reset signal?
Isolating that circuit affected the other power voltages (no +12 anymore), so I used the switcher for all the voltage outputs (with -5 connected to the -12) and the board does not come up.
I'm thinking the problem is with the RESET coming from IC3. I have good +5 to it, but the reset line is a steady +4.45. I'm wondering if the problem is with the signal coming from the circuit above where the TILT signal is?
At one point I did have the scores at top and the Taito line at bottom, but no attract and couldn't add a credit or start a game. After cycling the power I continue to get a blocky pattern image on the screen.
Any other bright ideas? Is there a way to generate a RESET signal? Or maybe I can just direct connect the +5 to the board and not even use/need a reset signal?
ThurworAlpha
New member
Hey,
Sounds like pin 2 of IC3 is never going high. A momentary low at pin 2 will cause a high output pulse on pin 3 of around 500 - 100 mSec, if the values I read are correct. They are using the half-wave recifier at the 'tilt' signal to cause pin 2 to go low until the +5 Volts is good. With a switcher in there... the 'tilt' pulse might not be working. mainly because it comes on too fast.
There are several ways to make a POR (Power On Reset). The simplest is a transistor switch like most Atari games. The venerable 555 like they used on this game works great too.
I believe my Stratovox does not use the 'tilt' signal. If this is the case on your game I would try to use the existing 555. I have not tried this but....
1). Remove the resistor from IC3 pin 2 to ground. (I cannot read the reference designator on the schematic)
2). Change R59 to 10K Ohms. (longer delay, just in case, may not need to do this one)
3). Remove D22 to disable the 'tilt'. (or if your game uses this line, leave D22 and cut the trace from D22 to pin 2 of IC3 and place the previously removed resistor (the one I cannot read) from D22 Anode to ground.
That oughta give you a low pulse on IC3 pin 2 which should trigger the original high ouput pulse on pin 3.
Let me know if you try it!
We CAN make this work... all it takes is time, and effort!
Maybe I should draw up a universal reset circuit for those of you who like switchers, or haven't got the time to troubleshoot every ancient power supply that acts-up.
Kenneth
Sounds like pin 2 of IC3 is never going high. A momentary low at pin 2 will cause a high output pulse on pin 3 of around 500 - 100 mSec, if the values I read are correct. They are using the half-wave recifier at the 'tilt' signal to cause pin 2 to go low until the +5 Volts is good. With a switcher in there... the 'tilt' pulse might not be working. mainly because it comes on too fast.
There are several ways to make a POR (Power On Reset). The simplest is a transistor switch like most Atari games. The venerable 555 like they used on this game works great too.
I believe my Stratovox does not use the 'tilt' signal. If this is the case on your game I would try to use the existing 555. I have not tried this but....
1). Remove the resistor from IC3 pin 2 to ground. (I cannot read the reference designator on the schematic)
2). Change R59 to 10K Ohms. (longer delay, just in case, may not need to do this one)
3). Remove D22 to disable the 'tilt'. (or if your game uses this line, leave D22 and cut the trace from D22 to pin 2 of IC3 and place the previously removed resistor (the one I cannot read) from D22 Anode to ground.
That oughta give you a low pulse on IC3 pin 2 which should trigger the original high ouput pulse on pin 3.
Let me know if you try it!
We CAN make this work... all it takes is time, and effort!
Maybe I should draw up a universal reset circuit for those of you who like switchers, or haven't got the time to troubleshoot every ancient power supply that acts-up.
Kenneth
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modessitt
Volunteer: Encyclopedia Submission Moderator
Hmm, interesting concept. I'll give it a shot. Maybe tomorrow....
I am following this thread... I have a very similar issue and I would like to use a switcher, rather than continuing to troubleshoot the old one. Please keep posting your progress !
Mod,
I see 2 5.1v and a 7.5v zener on that power supply. If those are bad then your voltage may be out of whack.
Also, I see a couple of electrolytic caps... one right to the right side of T3 and one on the right side of T4. Replace those.
Next would be to check the components providing the feedback loop. If those are out of whack (Op Amp at the bottom over to T4 and related components) then your output will be out of whack.
For a reset signal you need something that will keep the reset pin low for 100 to 200ms (or longer) after the CPU has been powered up THEN go high and stay high for it to run. You can do this by using a resistor and a cap. Many game boards have done that.
Or, you can use a reset chip like MB3771 off an old board to handle the power on reset.
RJ
I see 2 5.1v and a 7.5v zener on that power supply. If those are bad then your voltage may be out of whack.
Also, I see a couple of electrolytic caps... one right to the right side of T3 and one on the right side of T4. Replace those.
Next would be to check the components providing the feedback loop. If those are out of whack (Op Amp at the bottom over to T4 and related components) then your output will be out of whack.
For a reset signal you need something that will keep the reset pin low for 100 to 200ms (or longer) after the CPU has been powered up THEN go high and stay high for it to run. You can do this by using a resistor and a cap. Many game boards have done that.
Or, you can use a reset chip like MB3771 off an old board to handle the power on reset.
RJ
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modessitt
Volunteer: Encyclopedia Submission Moderator
i will be getting back to this soon. I have already run all the power to the PCB from the switcher, and am not using the PS for anything other than to generate the reset, so I'll probably be trying the instructions above. Once I get a chance to do so, I'll report back as to whether it worked - or ask for more help...
The reset is just ground isn't it?
ThurworAlpha
New member
In this instance, at pin 1 of the power supply (or pin 10 of my boardset) the reset pulse is high(5V-ish) and normal operation is low (gnd). So you would want a high(5V) on the reset line for 100 to 1000mSec after the power supply comes up to full voltage, then return low for game play. (it is inverted on the boards before it goes to the processor)
Kenneth
Kenneth
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modessitt
Volunteer: Encyclopedia Submission Moderator
Update: I tried this tonight. I wasn't sure which resistor you were talking about in step 1, as there was a cap off of it to ground, and a resistor between it and the Tilt ouput, so I removed the one to the Tilt output. Did the other steps as you said and the game is now coming up. There is a field of gray when it boots, but then about 2 seconds later it comes up with a good picture and good gameplay. So THANKS!
On to the next problem. I have only a humming noise that fluctuates slightly instead of sound. Before I picked the game up, they told me it would make a loud humming noise when it was turned on, but that it would go away after about 10 minutes. I am running all the voltage from a switcher, and have the -5 connected to the -12 line, as that should be enough for the sound to work.
I guess I'm just wondering if the sound problem is power related, or whether I should try recapping the sound section of the board...
ThurworAlpha
New member
Taito Reset
Cool!
Sorry I didn't get back sooner. Glad it worked!
There is a smudged/missing trace, on the schematic from the junction of R59 and the resistor I could not read to IC3 pin 2. (looks like maybe R60) Obviously it was not critical. (might give you a start screen sooner if it was disconnected...but it works so who cares)
Hum is usually capacitor related... could be on the input to the amplifier or, more often, output. As usual check/replace any electrolytics.
Let us know what happens.
Cool!
Sorry I didn't get back sooner. Glad it worked!
There is a smudged/missing trace, on the schematic from the junction of R59 and the resistor I could not read to IC3 pin 2. (looks like maybe R60) Obviously it was not critical. (might give you a start screen sooner if it was disconnected...but it works so who cares)
Hum is usually capacitor related... could be on the input to the amplifier or, more often, output. As usual check/replace any electrolytics.
Let us know what happens.
Mod-
Am I reading this correctly - you're powering the machine with a new switcher, and are using the original board with the changes only to generate the reset signal for startup?
If so, would this work if my board is not putting out a valid +5 (specifically if F5 is not present)?
Am I reading this correctly - you're powering the machine with a new switcher, and are using the original board with the changes only to generate the reset signal for startup?
If so, would this work if my board is not putting out a valid +5 (specifically if F5 is not present)?
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modessitt
Volunteer: Encyclopedia Submission Moderator
I did do it that way. I removed a bunch of parts from the original power supply (basically isolating the area where I made the lines) then attached a new switcher to it in order to make a Reset signal to start the board. it worked, but I found that the game would lock up if left on for a long time. Turning it off and back on would make it work again. Eventually I tracked down a known-working original PS board and put that back in...
Known working boards seem rather rare. Did you find it locally, on here, or some other source you'd recommend?
Did you find another -5SA board, or do other variants of the board work for these games?
tks
Did you find another -5SA board, or do other variants of the board work for these games?
tks
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modessitt
Volunteer: Encyclopedia Submission Moderator
Well, I might be parting a trimline SI out soon. I'll keep you posted...
