Dead Stunt Cycle : now working but has constant audio noise

Check / replace all the electrolytic capacitors in the sound generation section. I tried to merge the two sections of the schematic and note the suspect caps.

If you were to pick one, I would replace C25 (Base of Q13, 10 uF, 25V) first - as it is part of the White Noise generator and can wreak havoc on virtually anything downstream. On my board, this was the cap that was causing the most trouble related to sounds.

It could even be one of these caps that is shorted and pulling down your +5V.


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Check / replace all the electrolytic capacitors in the sound generation section. I tried to merge the two sections of the schematic and note the suspect caps.

If you were to pick one, I would replace C25 (Base of Q13, 10 uF, 25V) first - as it is part of the White Noise generator and can wreak havoc on virtually anything downstream. On my board, this was the cap that was causing the most trouble related to sounds.

It could even be one of these caps that is shorted and pulling down your +5V.


View attachment 856196
I will check orientation I put in a cap kit from arcade parts and repair, replacing all electrolytic caps. My next thought are some of the disc caps might be shorting, or leaking voltage. I am going to make a recording of the audio I am getting with all capacitors connected.
 
New things I have tried.

For voltage and video I interference I replaced all 0.10uf disk capacitors for modern ceramic and that seems to have helped the video tho there is still some wiggling at the top in the posted video it seems to be a little better now.

Replacing these capacitors resulted in a positive outcome tho I still have power problems.

Power is being provided by a transformer obtained from eBay. 115/230 VAC primary 16 VCT 0.8 A secondary 50/60 Hz


The voltage regulator was also replaced with one sold as new purchased off eBay. LM309K STEEL National Semiconductor 5V 1A Positive Voltage Regulator IC TO-3. From. Reputable seller 99.9% rating.

Still only getting 3.5V.
Pulled LM309 checking voltage at Diodes. 7.5VAC on each leg of the 2 diodes. Diodes floating I get about 7VDC on each leg and when combined with 4ohm resistor in circuit but no LM309 I get about 8VDC. When I put the LM 309 in circuit I get 5.35VDC on the input of the LM309 and 3.5VDC on the output.

I am still obviously having some kind of intermittent problem with the cycle reseting on the bottom and the cycle is consistently below the bottom track except when it resets high like captured on the video. The reseting on bottom and riding low on the buss track happen enough to be annoying.

So looking for the game problems I put the comparator on pretty much every chip on the board, even the ones I do not think it works very reliably, if at all, on for testing. There were a couple that lights flashed so the chips came out and tested good. There were a couple E1 & E2 that lights flashed intermittently and when pulled tested bad n my old B&K IC tester so I replaced them. I looked at the signals on the outputs on new chips nd it all looked the same and comparator reacted same. Later I pulled a 7450 and B&K said not in library, that's when I remembered the ALL11 tests ICs as well as programing ROMS. So I pulled up the 7450 and it was in library and it checked out good. So I decided to test the other chips the 74194 from E1 & E2 and they test good n the ALL11.

Not sure what to think about the 194's or the 50's I do know I have chips test bad in B&K and when replaced the board works in past and some chips test Good in my little Chinese tester and are not any good. I usually count on the B&K, and this is the first time testing chips with ALL11 Programer. Anyhow I still have problems. Still have sound issues.

Sound problems. Tested and or replaced everything except Mica capacitors. Power supplied by 25vct transformer and voltages are what is expected. 18VDC, -5VDC. I am using an MPSA06 as suggested earlier and it is in circuit as the schematic dictates.


 

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Aha! That's a replacement transformer! (Just saw the photos). And I don't think it's beefy enough…0.8 amps just ain't gonna cut it!

Try this:
Pull the diodes to isolate the regulator from the transformer. Apply 8 VDC (from your bench supply) to the filter cap that feeds the regulator. Then measure the +5V rail and tell us the voltage on that rail and how much current the bench supply is providing.

Fix the the power supply first. Or at least verify it. Nothing else matters really until you do that.
 
Aha! That's a replacement transformer! (Just saw the photos). And I don't think it's beefy enough…0.8 amps just ain't gonna cut it!

Try this:
Pull the diodes to isolate the regulator from the transformer. Apply 8 VDC (from your bench supply) to the filter cap that feeds the regulator. Then measure the +5V rail and tell us the voltage on that rail and how much current the bench supply is providing.

Fix the the power supply first. Or at least verify it. Nothing else matters really until you do that.
I will do this, thank you for the reply. Did not think to try this.
 
I have taken power advise and powered the voltage regulator by removing rectifier diodes and putting 8v 2.5amps at the filter capacitor as suggested and found that my original regulator LM309 was bad and the new one works fine. My transformer I was only powering half the primary and when I got bot sides working I still was under powered outputting 6vdc into regulator which bumped it up to 4vdc, still too low. I need a new transformer.

I found on cap that was backward on the motor sound but I had motor sound. Not sure what it did being reversed but it made no difference getting rid of the rank sound.
Check / replace all the electrolytic capacitors in the sound generation section. I tried to merge the two sections of the schematic and note the suspect caps.


 

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Lastly I started with the comparator again and everything was basically the same until I get to the 74107@K4. I was getting steady lights on outputs. So I started probing that and the counters going into it and thought they were off until I listed the outputs in order and they all looked good except the 256V. They seem to be the same as what is going in and not half. I figure I will pull this chip as it seems to be off.IMG_1045.png
 
Lastly I started with the comparator again and everything was basically the same until I get to the 74107@K4. I was getting steady lights on outputs. So I started probing that and the counters going into it and thought they were off until I listed the outputs in order and they all looked good except the 256V. They seem to be the same as what is going in and not half. I figure I will pull this chip as it seems to be off.View attachment 857879

The vertical counter resets before the terminal count. So 128V and 256V have the same frequency ~= 60 Hz. But they have very different duty cycles. 128V is (nearly) 50% duty. But 256V is only high for 4 scan lines out of 262 => 1.5% duty. Check the waveforms with your scope. I think it's working fine.

I have taken power advise and powered the voltage regulator by removing rectifier diodes and putting 8v 2.5amps at the filter capacitor as suggested and found that my original regulator LM309 was bad and the new one works fine. My transformer I was only powering half the primary and when I got bot sides working I still was under powered outputting 6vdc into regulator which bumped it up to 4vdc, still too low. I need a new transformer.

As I suspected...the transformer is undersized. I'm glad you were able to verify the new LM309 is working. You probably need something like 1.5 amps from the transformer...it's hard to guess because each leg is only providing current for 10 or 20% of the time. The current will peak at 10 amps or more.
I wouldn't go less than 16.5V, 2A for the transformer.

Hand wavy approximation: Assume the unregulated DC supply is 11V and the load is 2.5 amps. So you need to deliver about 28 watts. Add 20% for safety margin. So pick a 16.5 VAC transformer with a VA rating of 33 watts or more. (That's how I got the 16.5V, 2A rating above.)
 
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The vertical counter resets before the terminal count. So 128V and 256V have the same frequency ~= 60 Hz. But they have very different duty cycles. 128V is (nearly) 50% duty. But 256V is only high for 4 scan lines out of 262 => 1.5% duty. Check the waveforms with your scope. I think it's working fine.

Biased on the advise I checked the chip in question with the oscilloscope and compared input to output and found that this is what you are talking about. Both channels clock at 60hz. When I looked a second time I saw that I had already pulled this chip as it probably gave the same comparator error before and well I AM STARTING TO DO THINGS TWICE apparently.

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Well while looking at this chip on the horizontal my signals looked like this.
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I started to wonder if these signals are "dirty" enough to cause erratic intermittent problems and make my cycle ride low on the last "road". So I looked at the other signals and this is what the bad ones looked like the others looked clean and solid. Something should be off as the bike clearly is riding below the road.
 

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Your xxxH and xxxV counters look correct. Those are fixed counters and shouldn't be changing. HOWEVER, what you should see on every one one them is a series of 50/50 pulses with the exception of the last low or high which may be shortened due to the counter resetting before it's terminal count. These are the sync counters. They generate the horizontal and vertical sync signals and graphical elements with fixed positions. For the cycle position you need to be looking at the decoders for the motion counters.

I don't have schematics handy, but it's probably a pair of slipping counters to create the smooth cycle movement. Look elsewhere for more counters with something like Hxxx and Vxxx on the outputs. You can also start at the throttle pot and follow that to a 555 or 566 (or similar variable oscillator) that generates the clock pulses for the horizontal motion counter. Then follow that signal to the horizontal motion counters. And from there you should be able to find the vertical motion counters.
 
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