Another Asteroids Loud Hum Post

rknucklez

rknucklez

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I went back and searched previous posts and found a lot of posts on Asteroids and its knack for developing a loud hum. I had a perfect working Asteroids up until this evening.
I turned my Atari vector row on, and good ol' Asteroids was dead.
For a long time now, I have had a working board that has faint sounds and an earsplitting loud hum. Now that I need it, I am embarking on figuring out how to fix it.

I know the problem is in the pcb because my old board had no hum when it worked.


10:30 pm - The first thing I am going to try is replacing the audio pre amp..

I will keep you guys posted...

feel free to add any input

~RK
 
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rknucklez said:
10:30 pm - The first thing I am going to try is replacing the audio pre amp..

I will keep you guys posted...

feel free to add any input

~RK
Click to expand...

1:00 am - Ok, so for the sake of archiving I will post my glorious results;

I found an electronic schematic of the Asteroids audio here;
http://arcarc.xmission.com/PDF_Arcade_Atari_Kee/Asteroids/

After a lot of squinting I was able to pinpoint the onboard amplifier to be
a LM324N located at P11.

I carefully removed both LM324N 's
one from my pcb with the deafening hum
and the other from the pcb that died tonight (but had flawless sound)

I soldered in a 14 pin socket, plunked in the ic, and fired her up.

Quiet as a mouse, slowly raised the volume pot and thump thump thump


wooohooot!

hopefully this post will help out someone with the same problem in the future.

I intend to one day get my ass in gear and keep repair logs on my arcade's site
but alaas I am lazy when it comes to web site shite..

I am off to bed
 
My Asteroids starting making an insanely loud buzzing/humming noise last month. I replaced the LM324N @ P11 and the noise is completely gone.

Thanks Richie!
 
New member to the LM324N club. I replaced it and cleared my hum as well. It also restored missing thruster and somewhat restored missing shooting sounds. Instead of a high pitched pew, pew, pew my ship and both saucers have a low pitched bzzt, bzzt, bzzt while shooting. Everthing else sounds great including the saucer "siren" sound.

I took a LM324N off a parts board but do not know if the parts board had working sound, so perhaps I should just order a new one and a socket.
 
FWIW, the LM324 is better replaced by the TL084. Pin compatible and not prone to crossover noise and weird failures like the LM324.
 
WindDrake said:
FWIW, the LM324 is better replaced by the TL084. Pin compatible and not prone to crossover noise and weird failures like the LM324.
Click to expand...

Good info to know, thanks!

mkillewald said:
Instead of a high pitched pew, pew, pew my ship and both saucers have a low pitched bzzt, bzzt, bzzt while shooting. Everthing else sounds great including the saucer "siren" sound.
Click to expand...

For future reference, I fixed the ship fire and saucer fire sounds by replacing a 4016B @ M10 (rev 5 board)
 
rknucklez said:
Quiet as a mouse, slowly raised the volume pot and thump thump thump


wooohooot!

hopefully this post will help out someone with the same problem in the future.
Click to expand...

Nice!

rknucklez said:
I intend to one day get my ass in gear and keep repair logs on my arcade's site
but alaas I am lazy when it comes to web site shite..

I am off to bed
Click to expand...

or...... you could sign up here:

http://www.arcaderestoration.com/ContributorSignup.aspx

and add your repair logs there... has all the tools already.

Then people can search for them here:

http://www.arcaderestoration.com/FindRepairLogs.aspx
 
WindDrake said:
FWIW, the LM324 is better replaced by the TL084. Pin compatible and not prone to crossover noise and weird failures like the LM324.
Click to expand...

Whooa, slow down there a little with the op-amp substitutions.

Just cause the pinouts match doesn't mean the op-amp is a good sub.

LM324 is good for Vcc+/- up to 32V. But the TL084 is only good up to +/- 18V. This would be somewhat academic except that asteroids powers them with +22 (and GND for Vcc-).

The LM324 is specifically designed to operate on a single-sided supply (as it does in ast). The TL084 is designed for a bipolar supply. It'll work single-sided, but may have issues if the input goes within 3v of Vcc-. An LM324 in a single-sided application, with a properly biased input, should never see a zero-crossover.
 
DarrenF said:
Whooa, slow down there a little with the op-amp substitutions.

Just cause the pinouts match doesn't mean the op-amp is a good sub.

LM324 is good for Vcc+/- up to 32V. But the TL084 is only good up to +/- 18V. This would be somewhat academic except that asteroids powers them with +22 (and GND for Vcc-).

The LM324 is specifically designed to operate on a single-sided supply (as it does in ast). The TL084 is designed for a bipolar supply. It'll work single-sided, but may have issues if the input goes within 3v of Vcc-. An LM324 in a single-sided application, with a properly biased input, should never see a zero-crossover.
Click to expand...

I actually had to go dig up datasheets to argue my point, because I momentarily freaked out and thought I had it wrong. Damn you for scaring me! :D

Datasheets:
LM324
TL084
TI Single-Sided Op Amp Design Document

Simply put, our maximum supply voltage for a TL084 running single-sided is 36v, or 18v running split supply.

By comparison, the LM324 is good to 32v single, or 16v split.

The Op Amps themselves have very similar, nearly identical characteristics, hence the common substitution. So sorry Darren but the TL084 is a very robust, practical replacement for the LM324.

FWIW I've had the noise burst at zero demonstrated to me on the LM324. I used to work with one of the two guys that designed AirPhone's in-flight seatback phones, and the LM324's nearly caused them to lose out on their first contract thanks to that noise burst. Funny if frustrating story (same story that taught me Digital scopes lie to you.) :)
 
WindDrake said:
I actually had to go dig up datasheets to argue my point, because I momentarily freaked out and thought I had it wrong. Damn you for scaring me! :D

Datasheets:
LM324
TL084
TI Single-Sided Op Amp Design Document

Simply put, our maximum supply voltage for a TL084 running single-sided is 36v, or 18v running split supply.

By comparison, the LM324 is good to 32v single, or 16v split.

The Op Amps themselves have very similar, nearly identical characteristics, hence the common substitution. So sorry Darren but the TL084 is a very robust, practical replacement for the LM324.

FWIW I've had the noise burst at zero demonstrated to me on the LM324. I used to work with one of the two guys that designed AirPhone's in-flight seatback phones, and the LM324's nearly caused them to lose out on their first contract thanks to that noise burst. Funny if frustrating story (same story that taught me Digital scopes lie to you.) :)
Click to expand...
GTE I presume?
 
Before GTE bought it, yeah. My buddy worked in Special Projects. He went to In-Flite Phone once GTE ousted Jack (and he followed not long after).
 
WindDrake said:
I actually had to go dig up datasheets to argue my point, because I momentarily freaked out and thought I had it wrong. Damn you for scaring me! :D

Datasheets:
LM324
TL084
TI Single-Sided Op Amp Design Document

Simply put, our maximum supply voltage for a TL084 running single-sided is 36v, or 18v running split supply.

By comparison, the LM324 is good to 32v single, or 16v split.

The Op Amps themselves have very similar, nearly identical characteristics, hence the common substitution. So sorry Darren but the TL084 is a very robust, practical replacement for the LM324.
Click to expand...

OK, I was wrong about the supply voltage thing. Misread the TL084 datasheet. Voltages are with respect to the midpoint of Vcc(+) and Vcc(-).

However, the TL084 is designed and intended for a split supply. Take a look at the datasheet you linked. Almost every spec test condition and graph is for +/-15V, and those that aren't are for +/-10 or +/-5. I couldn't find anything in the datasheet about a single-sided supply application.

The LM324 is specifically designed to operate from a single-side supply. From the LM324 datasheet you linked: "...designed to operate from a single supply..."

Finally, the Design Document you linked is very interesting. However, it's talking about the TLC07X and TLC08X (quoting the abstract: "New op amps, such as the TLC247X, TLC07X, and TLC08X have excellent single-supply parameters"). The "C" parts are different from the regular TL07x and TL08x. In fact, the document details some of the sortcommings of the "old generation" parts such as the TL07x (see Figure 7 and associated text on p5).
 
Last edited:
DarrenF said:
OK, I was wrong about the supply voltage thing. Misread the TL084 datasheet. Voltages are with respect to the midpoint of Vcc(+) and Vcc(-).
Click to expand...

No worries.

However, the TL084 is designed and intended for a split supply. Take a look at the datasheet you linked. Almost every spec test condition and graph is for +/-15V, and those that aren't are for +/-10 or +/-5. I couldn't find anything in the datasheet about a single-sided supply application.

The LM324 is specifically designed to operate from a single-side supply. From the LM324 datasheet you linked: "...designed to operate from a single supply..."
Click to expand...

Not sure how much I agree here so I'll agree to disagree, as there are a ton of designs out there using TL084's single sided (Atari SAII Audio Board schem's come to mind fwiw).

Finally, the Design Document you linked is very interesting. However, it's talking about the TLC07X and TLC08X (quoting the abstract: "New op amps, such as the TLC247X, TLC07X, and TLC08X have excellent single-supply parameters"). The "C" parts are different from the regular TL07x and TL08x. In fact, the document details some of the sortcommings of the "old generation" parts such as the TL07x (see Figure 7 and associated text on p5).
Click to expand...

Good catch, my skimming wasn't quite up to the task there.

Quick googling shows the TL074 as a low-noise upgrade to the TL084. If Asteroids wasn't all beeps and boops, it might we worth looking into. :D

Anyhow, YMMV here as the TL084 requires minimum 7v input supply to operate or it's outputs suddenly go high, so in certain analog (likely non-audio) implementations this may not work for you. For audio, I don't ever see anybody having a problem unless it's in low-voltage setup, then you'd be better off using something like an MC33079.

As always, thanks for bringing this up Darren. There were some considerations I didn't think of before, Re; TL084 vs. LM324. Granted, now I'm just going to recommend the MC33079 in those cases. :)
 
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