Atari 720 (Working on the Repro harness now)

Dokert

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First off this is NOT a for sale thread, and no list of buyers will be taken here.

Two different members have loaned me 720 harnesses to use as templates. Oddly enough both of them are hacked and trashed pretty closely the same. Just about every 720 harness that I have seen looks like one of these two or worse.

The main problem seems to be the "Switching / Linear" power supply. It has sense lines just like an Atari A/R II, but it doesn't have a R29 or R30 to burn up when it fails. Instead this bad boy burns up the ground side of the power headers on the video board and the cpu board.

The fix for most people is to just slap on some new connectors and call it a day. Others are a little more desperate and solder the power wires directly to the video board and the cpu board. The "Correct" fix would be to replace the burnt connectors AND the burnt headers.

CPU BOARD

100_5504.jpg

100_5506.jpg

VIDEO BOARD

100_5505.jpg

100_5509.jpg

Current Status with this Repro Harness.... Roughly, halfway done with the prototype.

I could really use a measurement for the speaker wires to the Audio II Board from the speakers.

:001_sdrool:
 
Mine isn't hacked, but I'm not removing it from the game. If you need ANY measurements or pics, send me a PM and I'll get em.
 
thanks for the update Dok..
on the boardset i sent you did you notice any issues with the headers?

where would i get and what part number/name would be a replacement header for each board?

also, if these ground connections are not properly working, would the boardsets still light up red and show a 5 volt reading, but the game not work?

if you cant get the measurements let me know and i can go and try to measure mine for the speaker wires...
i am guessing it is about 3-4 feet...it goes from the audio board which sits under the control panel, through back, behind the monitor and up into the "boom-box"
 
thanks for the update Dok..
on the boardset i sent you did you notice any issues with the headers?

where would i get and what part number/name would be a replacement header for each board?

also, if these ground connections are not properly working, would the boardsets still light up red and show a 5 volt reading, but the game not work?

if you cant get the measurements let me know and i can go and try to measure mine for the speaker wires...
i am guessing it is about 3-4 feet...it goes from the audio board which sits under the control panel, through back, behind the monitor and up into the "boom-box"

Bob Roberts sells .156 and .1 Molex headers, among others.
 
thanks for the update Dok..
on the boardset i sent you did you notice any issues with the headers?

Yes, the headers J13 & J20 are burnt

where would i get and what part number/name would be a replacement header for each board?

Bob Roberts has them, Mouser, Riptor, GPE, etc.

also, if these ground connections are not properly working, would the boardsets still light up red and show a 5 volt reading, but the game not work?

Not to the best of my knowledge

if you cant get the measurements let me know and i can go and try to measure mine for the speaker wires...
i am guessing it is about 3-4 feet...it goes from the audio board which sits under the control panel, through back, behind the monitor and up into the "boom-box"

Yes, I need the measurement please. Right speaker to the Audio II board and Left speaker to the Audio II board.

Does everything that you sent me work?

:)
 
i looked at my machine today.. the speaker cables from the audio board to the boombox are approx 60" each (this is with some slack on each).

as far as i know all the boards i sent you were working, did you notice otherwise?

thanks.
 
i looked at my machine today.. the speaker cables from the audio board to the boombox are approx 60" each (this is with some slack on each).

as far as i know all the boards i sent you were working, did you notice otherwise?

thanks.

Have not tested them as of yet. Nailing down the last few wires here in a few minutes.
 
Hey guys,

Sounds like I'm pretty much in the same boat as you guys. I'm trying to stabilize my 720 and have had some conversation with Dokert regarding this. I looked up J13 and J20 in the schematics and found the following. From my understanding both are.156. I purchased the following from Great Planes Electronics (http://www.greatplainselectronics.com).


I chose Molex vs. Keltron due to higher heat capacity.

Connectors:
- http://www.greatplainselectronics.com/category-86.asp
- 09-50-8061 (6 pin)
- 09-50-8091 (9 pin)

Headers:
- http://www.greatplainselectronics.com/Category-79.asp
- 26-48-1245 (trim to length)


Crimp contacts:
- http://www.greatplainselectronics.com/Category-80.asp
- 45570-3050 (13 Amps)
- 08-52-0113 (7 Amp)

Hopefully I'm not too far off when it comes to picking the right parts. I'm kinda excited to get started on this. I must say I'm NOT exited about doing solder work on my 720!
 
Dokert,

Would you mind posting a picture of a burnt out J13 or J20 header? When I look at my 720, the header itself looks good, the connector looks slightly browned and in my case, overall shabby.

Perhaps the burnt out part of the header is on the other side of the board that we cannot see unless we un-mount the board entirely? The pics you posted look like the connectors are totally fried, but from what I can see, the headers look clean.
 
Dokert,

Would you mind posting a picture of a burnt out J13 or J20 header? When I look at my 720, the header itself looks good, the connector looks slightly browned and in my case, overall shabby.

Perhaps the burnt out part of the header is on the other side of the board that we cannot see unless we un-mount the board entirely? The pics you posted look like the connectors are totally fried, but from what I can see, the headers look clean.

Your headers are burnt, post pics of them and I will see if I can circle the bad pins for you.
 
i'd love to see these pictures as well pointing out the burnt pins...thanks for all the help dokert.

did you notice any problems with the boardset i sent you? as far as i knew it was working, but you told me you saw the bad headers on it.
 
i'd love to see these pictures as well pointing out the burnt pins...thanks for all the help dokert.

did you notice any problems with the boardset i sent you? as far as i knew it was working, but you told me you saw the bad headers on it.

You should be able to look at either the header pins on a board or the connector pins inside of a connector housing. If the pins have a shiny (silver) plating, as most will be, they are doing the job. You'll probably see some ground or power pins that are either tarnished, darkened, black at worst. Those must be replaced. You must replace the header pin strip on the circuit board and the crimp on pins for the wiring/connector. It's time consuming, but not difficult.
 
Dokert,

Would you mind posting a picture of a burnt out J13 or J20 header? When I look at my 720, the header itself looks good, the connector looks slightly browned and in my case, overall shabby.

Perhaps the burnt out part of the header is on the other side of the board that we cannot see unless we un-mount the board entirely? The pics you posted look like the connectors are totally fried, but from what I can see, the headers look clean.

i'd love to see these pictures as well pointing out the burnt pins...thanks for all the help dokert.

did you notice any problems with the boardset i sent you? as far as i knew it was working, but you told me you saw the bad headers on it.

Ok here are pics of burnt headers. J13 is far worse than J20. Look very closely and you will see the blackened pins.

J20

100_5516.jpg100_5515.jpg

J13
100_5514.jpg100_5513.jpg
 
wow, thanks for posting that, i would have never noticed.
so, when a pin shows that blackening, it probably wont work anymore? the silver still looked shiney and thats why i figured it was ok..

do the audio 2 boards in 720 ever suffer from this, i think there is a ground on the same circuit that goes to them as well, correct?

thanks again. you guys rock.
 
No, the Audio II board is not on the sense circuit. It has one ground that goes to the power brick and a ground that goes to J13 pin 10 daisy chained to J15.
 
wow, thanks for posting that, i would have never noticed.
so, when a pin shows that blackening, it probably wont work anymore? the silver still looked shiney and thats why i figured it was ok..

do the audio 2 boards in 720 ever suffer from this, i think there is a ground on the same circuit that goes to them as well, correct?

thanks again. you guys rock.

This is a great article that will answer most of your questions. Although it's on a pinball site, same thing really-

http://www.pinrepair.com/connect/
 
This is a great article that will answer most of your questions. Although it's on a pinball site, same thing really-

http://www.pinrepair.com/connect/

Excellent example, one of these days I will have to bookmark that page.


The 720 harness prototype is done, with the exception of the speaker cable. I have two speaker cable measurements and they are about 3 1/2 feet apart. I really need another speaker cable measurement, if someone could please provide from the speakers to the speaker header on the Audio II board.

All that is left to do is to test the harness, but before I can do that I will have to make a few test jigs. Got to get power to everything, and get hooked up to a monitor. (damn med res game)
 
Excellent example, one of these days I will have to bookmark that page.


The 720 harness prototype is done, with the exception of the speaker cable. I have two speaker cable measurements and they are about 3 1/2 feet apart. I really need another speaker cable measurement, if someone could please provide from the speakers to the speaker header on the Audio II board.

All that is left to do is to test the harness, but before I can do that I will have to make a few test jigs. Got to get power to everything, and get hooked up to a monitor. (damn med res game)

You'll get that measurement tonight or tomorrow from me. I'll take a pic too.
 
You'll get that measurement tonight or tomorrow from me. I'll take a pic too.

Thanks Brother! I didn't expect to be this far yet, but the Wife has been pushing me. She likes it when I make interesting stuff.

These harnesses are a bitch to make, and use a bunch of oddball connectors. The Wife has already said that she may limit the run to 10. Right now, it all depends on what my partner in crime (Timberterror) thinks about it. We will be including replacement headers for J13 & J20 with this harness.
 
Thanks Brother! I didn't expect to be this far yet, but the Wife has been pushing me. She likes it when I make interesting stuff.

These harnesses are a bitch to make, and use a bunch of oddball connectors. The Wife has already said that she may limit the run to 10. Right now, it all depends on what my partner in crime (Timberterror) thinks about it. We will be including replacement headers for J13 & J20 with this harness.

I'll try to get a measurement for you as well. I have another cab here with a surprisingly nice looking harness.
 
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