Asteroids volume and audio hum

[SaminVA]

Ok here we go again. I almost hate to ask as this has been asked many times and yes I think I have read every post on this subject and still am unsure of the correct answer even if their is one.
First how loud should the sound be on Asteroids if you have the volume control turned wide open? Mine is not all that loud and has a slight hum or buzz. Back in 2001 when I first got this game running I could have swore the volume would blow you ear drums out if you turned it all the way up. Back then I had the audio hum but a new Big Blue helped lower the hum. I had this game stored in my garage for 6 or 7 years and just moved it back into the game room where I discovered I had a board problem. I sent the board off to road.runner and he repaired the board and the game works great but has a slight hum and low volume.
So I got a new big blue from Bob Roberts, the new black ones, replaced it and still have the same hum and low volume so next I replaced all the cap's on the Audio/Regulator board again with the same results, hum and low volume. So what should I try next? Replace the 2 TDA 2002 audio amps? Which brings me to my next question. I have 2 new TDA 2002 amps and the ones on my A/R board have the gray insulators between the IC and the heat sink and is mounted with nylon screws. Bob Roberts web site states the 2 TDA 2002's have no insulators and use metal screws to hold them on the metal heat sink so which is the correct way? Here is a picture of mine and a picture I found on this site of the other way.

 

[YODAinMN]

I'd like to know the answer to this as well since my AD cabaret is doing the same thing...

OBTW, I did buy that knob for the volume control via Digi-Key from the other post, it works well and saves my my fingers from pain now!

 

[SaminVA]

You would think someone would have come up with the solution by now as their are many posts with this problem. I suppose my next move would be to replace the 2 TDA 2002 audio amps.
I can live with the hum as it's really not that bad but my volume still seems low with the volume pot turned all the way up so unless the speaker is bad it must be the audio amps. I don't think it's the amp on the Asteroids board as the board was just repaired and tested. So next the speaker then the audio amps. Their has to be a fix.

 

[wolfeel]

Maybe a dumb question, but did you try a different AR board in the game to see if perhaps it is not the AR board but the speaker or wires? Probably a long shot but at least you could rule those parts out that way. Hope you fix it!

 

[SaminVA]

Maybe a dumb question, but did you try a different AR board in the game to see if perhaps it is not the AR board but the speaker or wires? Probably a long shot but at least you could rule those parts out that way. Hope you fix it!

I don't have another AR board to try but if I did I would have to rebuild it also. I think first I'll connect a known good speaker directly to the AR board which will bypass the volume pot and wires going to the speaker and if the audio amps are good the sound should blast wide open. If it's the same volume then the speaker and wires should be good and the problem has to be the audio amps or the connections back to the main board.

 

[dezbaz]

Hi Sam

I have an asteroids converted to LL, but the harness is made from an Asteroids, I had all them symptoms

The volume on these is set up like a voltage divider.

Sometimes in games there is just a pot in series with the speaker, but in old ataris the speaker is in parallel with the volume pot (putting it simply).

Therefore it is possible for a burnt volume pot to cause some unusual problems. IE high volume even, If you need to get another pot, they are 50 ohms, 25 watt, wire wound. I got 2 x 25 ohm pots on the net as 50 ohm was not available cheaply

Secondly, is it a new speaker? An old speaker could be the cause, if you replace it make sure it is an 8 ohm speaker

Thirdly, the grill could be vibrating too, loosen it off or push on the grille and see if you can reduce the sound

Other than that, it could be that the speaker wires are running in the same harness as the fluorescent light wires. Try separating them from each other or shielding the speaker wires (this would mean the spkr wires need to be replaced and the shielding goes to GND
Try disconnecting (IE unplugging) the fluoro lead from the power brick and see if hum goes away

Good luck, please let us know how that goes

 

[SaminVA]

Hi Sam

I have an asteroids converted to LL, but the harness is made from an Asteroids, I had all them symptoms

The volume on these is set up like a voltage divider.

Sometimes in games there is just a pot in series with the speaker, but in old ataris the speaker is in parallel with the volume pot (putting it simply).

Therefore it is possible for a burnt volume pot to cause some unusual problems. IE high volume even, If you need to get another pot, they are 50 ohms, 25 watt, wire wound. I got 2 x 25 ohm pots on the net as 50 ohm was not available cheaply

Secondly, is it a new speaker? An old speaker could be the cause, if you replace it make sure it is an 8 ohm speaker

Thirdly, the grill could be vibrating too, loosen it off or push on the grille and see if you can reduce the sound

Other than that, it could be that the speaker wires are running in the same harness as the fluorescent light wires. Try separating them from each other or shielding the speaker wires (this would mean the spkr wires need to be replaced and the shielding goes to GND
Try disconnecting (IE unplugging) the fluoro lead from the power brick and see if hum goes away

Good luck, please let us know how that goes

It's the original speaker and volume pot, the wire wound type. The volume control works though the full range it's just not very loud in the full position. Their is a hum but it's really not that loud but it is a 60 cycle AC type hum. It could be the speaker so tomorrow I'll try a known good one. I forgot I have my friends Lunar Lander cabinet out in my garage so I can barrow his AR board and try that. I suppose I could put my asteroids board in the LL cabinet just to test the sound but I am not sure if the pin out is close enough. I'll have to look up the pin outs on LL and asteroids to see if it's possible. I was also looking at the schematics for the AR board and it shows 2 transistors Q4 and Q6 both 2n3904 between the audio input from the asteroids board and the 2 TDA 2002 audio amps but I don't see them anywhere on my board. Makes me wonder if I have the correct AR board or maybe I am looking at the wrong schematics.

 

[wolfeel]

Makes me wonder if I have the correct AR board or maybe I am looking at the wrong schematics.

It should be the AR board that looks like it is cut in half (just the left side).

 

[SaminVA]

It should be the AR board that looks like it is cut in half (just the left side).

Well that's what I have but I found a picture of another one that has the 2 -2n3904 transistors so which is the correct one? Could this be part of the problem as to why my volume is low because I don't have the AR board with the pre amp transistors Q4 and Q6 ?

 

[wolfeel]

Looks like the one that is in mine. I have had two other ones and they were the same board as in your picture. I am guessing you have the correct board. You can always look in the manual and see what the picture looks like just to double check..

 

[SaminVA]

Ok after looking at Elektron Forge's Atari Regulator/Audio Application Guide
http://www.elektronforge.com/AudioRegs.htm
Which has pictures of the boards it appears Asteroids AR board should have the 2 transistors and Asteroids Deluxe doesn't have the transistors. So it appears I have an Asteroids Deluxe AR board which I believe is why my volume is low.
On the guide for Asteroids and Asteroids Deluxe it says see note #1 which states
1.The "dash" numbers on Regulator/Audio and Regulator/Audio I boards are not marked, so it is not obvious which is which since they both have the same basic part number (A034485). An easy way to tell the difference between the -01 and the -03 is to check the pair of large capacitors near the SPKR 1 and SPKR 2 test points. If the value of the caps is 1000uF, then the board is a -01 (Asteroids). If the value of the caps is 3300uF, then the board is a -03 (Asteroids Deluxe). They are *almost* interchangeable - the sound will be slightly garbled but everything else will be OK.
I think what this means if you use the asteroids AR board in AD then the sound is distorted because it's over amplified because of the 2 extra transistors.
Dose that make sense?
So I have the wrong AR board which works just has lower volume. Now I'll have to look in the Lunar lander and hope it has the one I need to test my theory.

 

[road.runner]

I can confirm the top photo is Asteroids and the bottom one is Asteroids Deluxe. Note the 4 pin connector (audio out) is different on the boards. Asteroids has a 4pin row where Asteroids Deluxe has a 2x2 connector.

 

[wolfeel]

I can confirm the top photo is Asteroids and the bottom one is Asteroids Deluxe. Note the 4 pin connector (audio out) is different on the boards. Asteroids has a 4pin row where Asteroids Deluxe has a 2x2 connector.

Yep..............

 

[ggames]

I'm not sure this is the same hum, but I just got done working on an asteroids that had a hum to it. Game played fine. Picture looked good. Turned out that the reg board was sending out 4.61 volt. Slowly turning up to 5 volt slowly reduced the hum to nothing.

 

[dezbaz]

It's the original speaker and volume pot, the wire wound type. The volume control works though the full range it's just not very loud in the full position. Their is a hum but it's really not that loud but it is a 60 cycle AC type hum. It could be the speaker so tomorrow I'll try a known good one. I forgot I have my friends Lunar Lander cabinet out in my garage so I can barrow his AR board and try that. I suppose I could put my asteroids board in the LL cabinet just to test the sound but I am not sure if the pin out is close enough. I'll have to look up the pin outs on LL and asteroids to see if it's possible. I was also looking at the schematics for the AR board and it shows 2 transistors Q4 and Q6 both 2n3904 between the audio input from the asteroids board and the 2 TDA 2002 audio amps but I don't see them anywhere on my board. Makes me wonder if I have the correct AR board or maybe I am looking at the wrong schematics.

Sounds like you have this sorted, so it's a great thread as a future reference

By the way LL and asteroids pinouts are close enough to put an LL into an asteroids cab

You can't coin up though unless you use a jumper wire to the coin pin

The vectors all work then etc just no game play

 

[SaminVA]

I can confirm the top photo is Asteroids and the bottom one is Asteroids Deluxe. Note the 4 pin connector (audio out) is different on the boards. Asteroids has a 4pin row where Asteroids Deluxe has a 2x2 connector.

Yea someone must have modified the one I have by adding the 4 pin inline plug for the speaker. Top picture is the one currently in my game and the bottom one I found in a open box in my garage and was dirty as heck. It cleaned up real good but haven't tested it yet but I am sure it could use a rebuild and new Molex plugs as they look corroded. I did look in the LL cabinet and it has one I can use to test with but I got side tracked today as I got my Eliminator sound board for my Multi SEGA and I had to test it to see if it was a working board and it was so now I have everything for my new Vector Labs multisega but that will be another thread.

Thanks Dez for the info about testing Asteroids in a LL cabinet, good to know, just like Asteroids and Asteroids Deluxe.

 

[wolfeel]

Yea someone must have modified the one I have by adding the 4 pin inline plug for the speaker.

I also have one just like that. I wonder if it was factory built?

 

[SaminVA]

Fixed my Asteroids Hum

Well today I finally got rid of my HUM and I have plenty of volume.
Ok lets recap my problem. My Asteroids had a bad hum in the speaker and low volume with the volume control turned all the way up.
I replaced the Big Blue and no change
I checked all my grounds including the main board edge connector. All grounds checked out good.
Rebuilt Audio regulator board with no change but I noticed my A/R board was really the board for Asteroids Deluxe.
Found the correct A/R board for Asteroids, rebuilt it and now I had more volume but the hum was also louder.
Thought the 2 transistors on this board (2n3904) were pre amps but I was wrong. Turns out they are part of the audio disable circuit,like a mute switch, which is not even used in Asteroids.
Checked the audio inputs 1 and 2 at the board edge connector and found one input was amplifying audio fine but the other was barely amplifying anything so I figured one of the Amps must be bad.
Replaced both of the TDA 2002 audio amps and I now have a loud volume with almost no hum to speak of.
Turns out the 2 TDA 2002 amps are in a push pull configuration and with one of the amps bad it was causing the output to be unbalanced which was causing the hum.
So my fix was to replace the bad audio amp and my hum problem was solved and I have plenty of volume.

 

[dezbaz]

Well today I finally got rid of my HUM and I have plenty of volume.
Ok lets recap my problem. My Asteroids had a bad hum in the speaker and low volume with the volume control turned all the way up.
I replaced the Big Blue and no change
I checked all my grounds including the main board edge connector. All grounds checked out good.
Rebuilt Audio regulator board with no change but I noticed my A/R board was really the board for Asteroids Deluxe.
Found the correct A/R board for Asteroids, rebuilt it and now I had more volume but the hum was also louder.
Thought the 2 transistors on this board (2n3904) were pre amps but I was wrong. Turns out they are part of the audio disable circuit,like a mute switch, which is not even used in Asteroids.
Checked the audio inputs 1 and 2 at the board edge connector and found one input was amplifying audio fine but the other was barely amplifying anything so I figured one of the Amps must be bad.
Replaced both of the TDA 2002 audio amps and I now have a loud volume with almost no hum to speak of.
Turns out the 2 TDA 2002 amps are in a push pull configuration and with one of the amps bad it was causing the output to be unbalanced which was causing the hum.
So my fix was to replace the bad audio amp and my hum problem was solved and I have plenty of volume.

Nice work

Well done!

 

[kevlarunderwear]

rip off

Maybe a dumb question, but did you try a different AR board in the game to see if perhaps it is not the AR board but the speaker or wires? Probably a long shot but at least you could rule those parts out that way. Hope you fix it!

rip off is a great game, used to play it at the jersey shore as a kid