Author Topic: Atari System 1 making LOUD speaker hum (Read 6452 times)

allroy1975 · « **on:** September 22, 2006, 02:05:41 am »

It's my Roadblasters, though I doubt it's specific to my game.

When I turn on the power all the right speaker does is HUMMMMMMM, because of it being mouted to the case it vibrates throughout the cabinet and is VERY loud. I pulled both speakers and it's definatly coming from the board that way. the speaker connected to those 2 wires will make the hum, while the other works flawlessly.

Oddly it worked fine a few months ago....

anyone know much about System 1s?

Thanks in advance
Allroy

grantspain · « **Reply #1 on:** September 22, 2006, 03:31:50 am »

do you still get the game sounds?

allroy1975 · « **Reply #2 on:** September 22, 2006, 07:51:17 am »

not out of the humming speaker. The left speaker still works fine. Music and sound are good.

grantspain · « **Reply #3 on:** September 22, 2006, 09:29:49 am »

sound board fault,either cap or amplifier chip-if one side works it proves your voltage,sound proms and wiring is o.k-all you need to do know is trace the wires through the sound board or get a schematic-at some point the sound will have a common path then split to left and right(prob amp ic) thats where to start looking for the problem

Ken Layton · « **Reply #4 on:** September 22, 2006, 11:30:02 am »

Sounds like the audio/regulator board needs rebuilding.

ChadTower · « **Reply #5 on:** September 22, 2006, 11:37:52 am »

Yep, at the very least he's getting AC ripple through it.

Rebuild the AR board and replace the big blue (power supply filter cap, giant cab about the size of a baseball).

grantspain · « **Reply #6 on:** September 22, 2006, 12:03:18 pm »

i beg to disagree with chad,if it was ac ripple you would get this on both speakers-as one speaker is working fine it rules out any power related issue and points towards the amp i/c or part of its output-for me i would be looking at the caps on the particular output line and giving special attention to the amp ic

ChadTower · « **Reply #7 on:** September 22, 2006, 12:45:07 pm »

The audio comes straight through the AR (Audio Regulator) board, which is fed directly by the power supply because it also distributes much of the power, and it's the AC ripple from a dead filter cap that usually is a leading factor in the death of the AR board.

It may not be the direct cause of the hum itself but it is probably the start of the failure chain here.

grantspain · « **Reply #8 on:** September 22, 2006, 12:57:19 pm »

why would one speaker be o.k,i'm no expert on the ar board but i'm applying standard fault finding knowledge-so i guess what your saying is that some kind of a/c surge could cause component failure on one side of the audio output

ChadTower · « **Reply #9 on:** September 22, 2006, 01:04:16 pm »

Not a surge, think more like Chinese water torture. A constant pounding of low AC current on a polarized DC component (the caps). Plus the caps are going to die anyway because that's what caps do... so one cap dies and loses its polarity/dissipation qualities, which begins to pound the next one, it happens to that one... and so on down the line until the ripple gets to something like an amp or transistor.

Eventually the chain of failure ends when it hits a component that opens on failure, like a resistor, or one of the caps opens because it physically fries.

It could easily be that one side has crapped out enough to have symptoms and the other side simply isn't as damaged yet.

EDIT: Being an Atari cab, it could also be signal noise because of a bad connector. They are notorious for degrading edge contacts and harnesses. Reseat all of the connectors involved. If that fixes the issue you'll have to renew the pins in the harness and retin the edge contacts (or replace the header pins if it is one of those). The fix you got from reseating is only temporary and will fail again soon.

Either way, it's always worth rebuilding the AR board and replacing the filter cap if you cannot vouch for it having been done already. Those caps are 20+ years old and are dead or near death.

grantspain · « **Reply #10 on:** September 22, 2006, 01:12:35 pm »

fair enough

allroy1975 · « **Reply #11 on:** September 22, 2006, 04:43:00 pm »

Quote from: ChadTower on September 22, 2006, 11:37:52 am

Yep, at the very least he's getting AC ripple through it.

Rebuild the AR board and replace the big blue (power supply filter cap, giant cab about the size of a baseball).

K, there are two of them, should I replace both?

ChadTower · « **Reply #12 on:** September 22, 2006, 09:46:19 pm »

I like the numbers. Just in case someone didn't count.

I would replace both. Any cap of that age is pretty much doubled over its life expectancy by now.

allroy1975 · « **Reply #13 on:** September 22, 2006, 11:04:08 pm »

christ.....

I numbered them in case you wanted to say "no, just replace #1" or 2..whatever..

I'm glad you got a chuckle out of it and thanks for the help!

allroy1975 · « **Reply #14 on:** September 26, 2006, 09:32:54 am »

Order placed with Mr. Roberts! w00t!

man I'm excited.

This is kinda fun!

cw · « **Reply #15 on:** September 28, 2006, 09:45:42 am »

Kinda?

allroy1975 · « **Reply #16 on:** September 28, 2006, 11:00:40 am »

Quote from: cw on September 28, 2006, 09:45:42 am

Kinda?

Okay, it's REALLY fun.

Bob says to expect the stuff today.

ChadTower · « **Reply #17 on:** September 28, 2006, 11:12:15 am »

Bob is a good guy. Hard to find these days.

allroy1975 · « **Reply #18 on:** October 02, 2006, 07:31:06 pm »

w00t! bob got my payement the same day I got my stuff! Thank god! I would have felt like a real jerk if the PO lost my check.

anyway, how do I remove the 2 transistors in the middle of the heat sinc?

I swear I feel dumber every minute

ChadTower · « **Reply #19 on:** October 02, 2006, 07:33:40 pm »

Remove the heat sink. The transistors are screwed in.

allroy1975 · « **Reply #20 on:** October 02, 2006, 07:35:48 pm »

thanks for the quick responce, but it appears to be bolted on at the top and bottom....

ChadTower · « **Reply #21 on:** October 02, 2006, 08:25:06 pm »

It wasn't always attached. Figure out how it went in and it will come out.

allroy1975 · « **Reply #22 on:** October 02, 2006, 10:53:54 pm »

replaced everything...still humming!!!!

ChadTower · « **Reply #23 on:** October 03, 2006, 07:51:31 am »

You rebuilt the AR board, replaced the filter caps, retinned the edge connectors, and repinned the harnesses, in 2.5 hours?

Wow.

fredster · « **Reply #24 on:** October 03, 2006, 12:14:24 pm »

Look up on the board itself and trace the audio circuit back. It might be one of the caps on the board in the pre-amp part of it.

If not, then it has to be a chip in the audio circuit itself, but it's usually a cap that does that. The caps filter the noise out.

Speaking of which, there's a square filter capacitor next to the power supply isnt there? That can cause a hum or distortion if it isn't working I believe.

ChadTower · « **Reply #25 on:** October 03, 2006, 12:19:57 pm »

I'd have to see a pic but I've never seen a square cap. If it's square right next to the filter cap then it's probably a bridge rectifier.

allroy1975 · « **Reply #26 on:** October 03, 2006, 12:20:55 pm »

Quote from: ChadTower on October 03, 2006, 07:51:31 am

You rebuilt the AR board, replaced the filter caps, retinned the edge connectors, and repinned the harnesses, in 2.5 hours?

Wow.

you're assuming that I hadn't started working on this until I posted the question about the 2 transistors in the middle of the heat sinc.

I wish there was some sort of applicable saying about assuming I could post..but nothing comes to mind.

Seriously you've been helpful to this point..but this post wasn't much help. Seemed more like "you're lying and you didn't do anything".

also..thanks Fredster.

ChadTower · « **Reply #27 on:** October 03, 2006, 12:24:47 pm »

Not really, but sure, if you want to believe that. Some guys are fast. I'm not, takes me forever to work on my games. I tend to marvel at the guys who do it quickly.

I think I'll just bow out here, good luck with the game.

allroy1975 · « **Reply #28 on:** October 03, 2006, 12:30:47 pm »

Quote from: ChadTower on October 03, 2006, 12:24:47 pm

Not really, but sure, if you want to believe that. Some guys are fast. I'm not, takes me forever to work on my games. I tend to marvel at the guys who do it quickly.

I think I'll just bow out here, good luck with the game.

oh c'mon dude, don't be like that. I was really appreciating the FACT that you were helping me. Seriously. That post just rubbed me the wrong way. Please take into account how frustrated I am with this. Like..when I bought the machine..it was working, and I've had nothing but trouble with it. So most of my frustration is with the machine and I'm sorry if I seemed to take it out on you.

If it wasn't meant personally, I'm sorry I took it personally. Incidentally I probably would have posted the previous night (Sunday) if I hadn't burned the hell out of myself with the soldering iron in the middle of it. So...no, I'm not fast, I'm clumsy and in the middle of doing it the first night I burned myself and didn't get to it again til the next night.

grantspain · « **Reply #29 on:** October 03, 2006, 01:12:51 pm »

so this buzzing,is it over the sound or instead of the sound?

allroy1975 · « **Reply #30 on:** October 03, 2006, 01:14:29 pm »

it's instead of the sound. no sound comes out of the right speaker. The sound from the left speaker has a very slight hum to it, but it's nothing I would imagine is out of the ordinary.

grantspain · « **Reply #31 on:** October 03, 2006, 01:46:04 pm »

look towards your amp chip(like i said earlier),if you had a chip pinout you could lift legs and swap outputs from left to right,that would certainly show you area of problem
the a/r board,does it get a stereo input from the game board or does it get mono then use the amp i/c to create stereo

fredster · « **Reply #32 on:** October 03, 2006, 03:06:33 pm »

It's the RF filter in the can next to the AC cord inlet on the inside.

I don't know if the old atari's have one. I can't remember if there is one in the asteroids I have or it's those big blues that do that in there.

grantspain · « **Reply #33 on:** October 03, 2006, 03:18:36 pm »

Quote from: fredster on October 03, 2006, 03:06:33 pm

It's the RF filter in the can next to the AC cord inlet on the inside.

I don't know if the old atari's have one. I can't remember if there is one in the asteroids I have or it's those big blues that do that in there.

i don't get the logic in that diagnosis,why would an a/c filter affect a sound output,and if it did then both would be affected not just one channel-so if your amp at home starts buzzing on one channel its down to the a/c,i am sorry i can't see it myself-but i would love you to prove me wrong

fredster · « **Reply #34 on:** October 03, 2006, 04:28:48 pm »

The capacitor takes out any static radio frequencies. Humming is almost always a filter capacitor. Either it's on the amplification circuit or in the actual sound generating circuit somewhere.

The RF capacitor I'm talking about is shown here

Without one of those I had a supergun make radio freqencies. I knew that because my remote controls went nuts when a game was in it. Put one in line, and that went away.

The filter capacitors should take that out. In this case, we have to have a stereo system here because only one channel is bad. Has to be a capacitor somewhere.

He replaced the filters on the bottom, in the AR board, he traced the wires, etc.

Only thing left is any caps on the board that look loose or that filter capacitor.

If that isn't it, then it has to be a pre-amp transistor. But that usually does more buzzing and volume thingies than humming.

allroy1975 · « **Reply #35 on:** October 09, 2006, 07:49:48 pm »

what are the odds that I'm just too ---smurfing--- stupid for this hobby? every time I touch this machine it gets worse. I'm having power supply problems now. I suspect the Bridge Rectifier, but I'm not smart enough (even with Bob's page on Bridge rectifiers) to know for sure that it's hooked up right. and I sure as hell can't read the schematics I've got.

This stuff seems like it should be pretty straight forward, I've done board repairs before...I've deceided I can solder. I can get electricity to flow from point a to point b. I simply have no idea how it move through components. I'm frustrated and angry and confused.

grantspain · « **Reply #36 on:** October 10, 2006, 03:06:30 pm »

what supply problems,first thing to learn is how each component works eg a diode lets voltage one way only-a bridge rectifier is 4 diodes that turn a/c voltage to d/c so therefore it easy to read a bridge because one side is(for arguments sake)18v a/c the output side is 18v d/c


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