Atari 720 problem?

[redcoats]

I hope this is the right forum to post this in? Hey guys I have a question for anyone out there that knows how to work on real arcade machines, not mame machines. I have a 720 cabinet in my house that is acting all wacky.

First let me explain a goof up that I encountered. I bought this 720 machine off of a buddy for 50 bucks and he didn't know what was wrong with it, so when I get it home I power it up and nothing, no sound, no picture, nothing? So it sits for a few months because I didn't have the money to fix it. So one day I decide I'm gonna try it again, so I plug it in, turn it on, and bam! now the picture is there but no sound? Why it worked this time is beyond me.

So I have it powered up and working everything but sound. So I started fiddling around with some of the wires to try and get the sound to work and I ended up hooking up something wrond and saw smoke come from somewhere in the audio amp area, so I figured I fried the sound amp? But I still have video but now I can't add credits and I can't start a game. Since I couldn't add credits I set it on free play and now I can start the game but as soon as it begins it ends up resetting back to attract mode?

That's not all though(I know long post, sorry) because I figured I had fried the audio board I was looking on ebay and found a guy that sold me his complete 720 but I didn't want the whole thing so I had him part it out to me. He basically sent me everything but the cabinet. All of his items were in better shape then mine so I swapped the majority of the parts out. This is what I changed out, The wiring harness, except the transformer and transformer wires, the power supply, the PCB's, the audio amplifier, the wiring to the joystick and buttons. The only original wiring I left in it was the transformer wiring and the coin door wiring?

So after changing all those parts out including the PCB's the game is still doing the same thing? I'm baffled. The game just looks like it keeps resetting, not shutting off but just kicking me back to the first screen you see when you power it up. If there is anybody that knows how to fix this problem please help me out

Sorry for such a long post but i wanted to get everything out there so there was no confusion. Thanks alot for any help given.

[SirPeale]

Two suggestions:

1) you're messing around with the wiring, and you already caused something to smoke.  Stop playing with it until you know better what you're doing, before you make it worse.

2) Try on the KLOV forums.  There are a few 720 afficianados on there.  Perhaps one of them can help.

[Rocky]

You are not going to fix it by "lucking" into something. Just messing with wires is not the thing to do.

Basic Trouble shooting begins with:
1. Visual inspection
- broken wires
- unhooked wires
2. Voltage checks
- DMM is needed

These things will tell you (or others who have worked on them) what to do next.

If you swapped out the main components with the same problem, it sounds to me like it's either wiring or a power supply issue.

Please either read and proceed slowly or get someone who knows what they are doing.

[redcoats]

Well I see where you guys are coming from but the good news is, I didn't fry the boards. I got it to work. Apparently the transformer went bad so I switched it just now and what do you know, it works. I didn't want you guys to think I was just pulling wires and plugging them just anywhere. I just made a mistake when I was hooking up the audio board and out came smoke. I learned my lesson after that. The only problem I'm having now is getting the monitor adjusted correctly. I'll post some pictures in the monitor forum for that. Thanks for the help and sorry to post a thread when it really didn't need to be posted.

[Rocky]

I'm glad you got it working.

[redcoats]

I'm glad you got it working.

[dek]

Resident KLOV 720 afficianado

You got a deal for 50 bucks. Want to sell any extra parts you have left over>?

[redcoats]

Well I have a new problem. The audio board I have has a bad volume pot in it. There is only two settings, off and full blast. Since I wouldn't know how to go about removing and replacing the volume pot, is there a way I could just leave the speakers at full volume and add a volume control inline with the speakers? Anyone ever done something like this? If I knew how to remove the volume pot I could replace it but I have no idea since it is 6 prongs ino the audio board. How do i go about removing it? I can't use a soldering iron because you can only heat up one prong at a time? Anyone have any ideas? I figured the inline volume was my best bet since the volume does work, it is just full blast? Anyway throw me a bone here people.

[dirt]

an inline pot should work.


dirt

[redcoats]

Well the inline pot didn't work the way I needed it to. I figure I will fix the other audio amp in the mean time since it has a good working volume pot on it. Anyome here work on circuit boards, PCB's and what not? On my non-working audio amp board I have a chip on it that is called TDA2030 it is the amp chip, anyone know where to find this chip so I can replace it? I'll post a picture:

[paigeoliver]

Try searching google for (wait for it), TDA2030.

There are 10 pages of results. Take your pick.

[redcoats]

Try searching google for (wait for it), TDA2030.

There are 10 pages of results. Take your pick.

Well I did that the only problem is they seem to be different?

[redcoats]

This is the only page I found where you can buy one and I'm not quite sure if it is right?

http://www.ampslab.com/trans_tda2030.htm

[APFelon]

It's a transistor, not a chip. (I know that it seems like a petty semantics issue, but folks might not know what you are talking about if you call it a chip).

And that one you linked looked about right... a five legged transistor, just like yours. And hey, it's only two bucks. If it isn't the right one, search your couch cushions to make up the difference.

APf

[dabone]

Actually it is a chip.


Crosses to the NTE1380.


The NTE1380 is a monolithic integrated circuit in a 5-Lead TO220 type package intended for use as an audio class AB amplifier. Typically, it provides 14W output power (THD = 0.5%) at a supply voltage of

[APFelon]

I love learning new things, thanks. I would have gone to my grave insisting that it was a transistor.

APf

[redcoats]

Actually it is a chip.


Crosses to the NTE1380.


The NTE1380 is a monolithic integrated circuit in a 5-Lead TO220 type package intended for use as an audio class AB amplifier. Typically, it provides 14W output power (THD = 0.5%) at a supply voltage of

[dabone]

The chip you listed is right. But if they don't have stock, the nte replacement I listed is available in alot more places.


Later,
dabone

[redcoats]

The chip you listed is right. But if they don't have stock, the nte replacement I listed is available in alot more places.


Later,
dabone

Oh ok. Thanks for your help.