joetechbob
Member
Hi all!
I picked up a non-working (but clean) Asteroids off of a regional auction site. Before I purchased the machine I was able to go take a non-thorough look at it and found that when turned on it made a loud buzzing noise, had both P1 and P2 buttons lit solid and no video (but had neck glow on the monitor--spot check light was on though). Looking online I saw others had hit a similar issue before and it sounded like it tended to be a low 5V line going into the game PCB.
When I got the game home, I did some basic diagnostics and did find that the 5V rail on the game PCB was low (around 4.5 volts). I then adjusted the regulator to give around 4.95 to 5 volts on the power rails (and Vcc legs on spot checked ICs). After resetting the game I continued to get the buzzing sound and solid P1/P2 lights. My next course of action was the following:
1) Pull all of the socketed chips, cleaned the pins and re-seated the chips.
2) Clean the edge connector with a pencil eraser
3) Looked for obviously bad solder joints--found a couple and ran jumper wires.
After doing this I fired the game back up and I was still getting the same issue. I then checked the RESET pin on the 6502A and found that it was low. I tried connecting the watch dog disable loop to ground, but that didn't seem to affect the state of RESET.
[Note: I have a digital multimeter with a basic frequency counter built in that is supposed to support measuring up to 10MHz signals.]
Next--after testing RESET--I checked the 6MHz tap and had my multimeter show around 4.8MHz. Testing the other divisions I saw 2.4MHz and 1.2MHz (can't test the 12MHz as my meter won't go that high). This was a bit of a concern, but I took it with a grain of salt as I am using a $100 multimeter to take this measurement. However, when I got to B4 I saw that the 3kHz and 12kHz pins were just outputting complete garbage (according to my multimeter)...I was reading anything from 45kHz to 75kHz on one pin, for example.
I double checked and re-checked power throughout and everything looked good. Long story short, I have a local collector friend who has a non-working Asteroids Deluxe board that he let me borrow. When I hook up that board I see almost the exact same measurements on the clock circuit, RESET is low, and the symptoms are more or less the same (makes a buzzing sound...P1/P2 lights are a different pin out on Deluxe so I didn't verify those).
I was hoping that the LS393 at B4 (counter) was going to be bad on my board (and thus causing the bad 3kHz and 12kHz), but what are the odds that someone else's board gives the same measurement/behavior?!? Is that a high failure chip/circuit? It seems almost like my power supply *is* bad (despite the solid 5V I'm getting). Perhaps it's noisy and I need to replace the main filter cap (big blue)? Has anyone else seen this before?
I picked up a non-working (but clean) Asteroids off of a regional auction site. Before I purchased the machine I was able to go take a non-thorough look at it and found that when turned on it made a loud buzzing noise, had both P1 and P2 buttons lit solid and no video (but had neck glow on the monitor--spot check light was on though). Looking online I saw others had hit a similar issue before and it sounded like it tended to be a low 5V line going into the game PCB.
When I got the game home, I did some basic diagnostics and did find that the 5V rail on the game PCB was low (around 4.5 volts). I then adjusted the regulator to give around 4.95 to 5 volts on the power rails (and Vcc legs on spot checked ICs). After resetting the game I continued to get the buzzing sound and solid P1/P2 lights. My next course of action was the following:
1) Pull all of the socketed chips, cleaned the pins and re-seated the chips.
2) Clean the edge connector with a pencil eraser
3) Looked for obviously bad solder joints--found a couple and ran jumper wires.
After doing this I fired the game back up and I was still getting the same issue. I then checked the RESET pin on the 6502A and found that it was low. I tried connecting the watch dog disable loop to ground, but that didn't seem to affect the state of RESET.
[Note: I have a digital multimeter with a basic frequency counter built in that is supposed to support measuring up to 10MHz signals.]
Next--after testing RESET--I checked the 6MHz tap and had my multimeter show around 4.8MHz. Testing the other divisions I saw 2.4MHz and 1.2MHz (can't test the 12MHz as my meter won't go that high). This was a bit of a concern, but I took it with a grain of salt as I am using a $100 multimeter to take this measurement. However, when I got to B4 I saw that the 3kHz and 12kHz pins were just outputting complete garbage (according to my multimeter)...I was reading anything from 45kHz to 75kHz on one pin, for example.
I double checked and re-checked power throughout and everything looked good. Long story short, I have a local collector friend who has a non-working Asteroids Deluxe board that he let me borrow. When I hook up that board I see almost the exact same measurements on the clock circuit, RESET is low, and the symptoms are more or less the same (makes a buzzing sound...P1/P2 lights are a different pin out on Deluxe so I didn't verify those).
I was hoping that the LS393 at B4 (counter) was going to be bad on my board (and thus causing the bad 3kHz and 12kHz), but what are the odds that someone else's board gives the same measurement/behavior?!? Is that a high failure chip/circuit? It seems almost like my power supply *is* bad (despite the solid 5V I'm getting). Perhaps it's noisy and I need to replace the main filter cap (big blue)? Has anyone else seen this before?
