1050 power supply modification

[Keneg]

Proposed Atari 1050 power supply modifications


Supply 12VDC to the Power jack. (2 or 3 amps)
Remove CR15-20.
Remover Q8.
Put jumper wires were CR18 and CR20 were.
Put jumper wire between where CR15 was and where output of Q8 was.
If the 12VDC supply is clean enough, C67 could also be eliminated.
I am not at all expert in electronics, so please share any thoughts you have, especially problems this may cause.
I realize some people might want to leave their 1050s stock, but I just want mine to work as reliably as possible. I think the voltage doubler and some of the other circuitry this would bypass increase the current draw and are sources of problems. I would put a label by the power jack noting the change.

The power circuit diagram didn't paste in. I have attached the image file below.

Edited August 10, 2018 by Keneg

[+Nezgar]

Since the 1050 operates on 5VDC primarily, and 12VDC for the motor, if you insist on modifying the power input, you're best of adapting for use of a standard PC hard drive power supply connector which supplies both voltages.

 

Look for previous threads about 'green' 1050 power. This also results in a much cooler drive, since the heat is mostly from the 5V and 12V regulators, which would be bypassed..

 

Using just 12V DC input, you don't need the 12V regulator anymore, but it would give the 7805 extra current to dissipate as heat.

 

From what I've gathered, the voltage doubler that normally takes the 9VAC to 18V doesn't work with a DC input, even if you supplied a DC input with enough over 12V.

 

I'll shut up now, and let someone more experienced in the details comment.

[Keneg]

I am hoping the difference between 9 an 12 volts to the 7805 is within its operating limits. I thought about using a PC power supply and I do have a spare, but I was looking for a more compact solution. Thanks for your input.

 

Edit: I just looked at the data sheet. I should have done that before posting. The input voltage range is 7.0 to 35, so I think that wont be an issue.

Edited August 10, 2018 by Keneg

[foft]

Adding a link to one of the green 1050 power supply upgrade options mentioned:

http://www.mathyvannisselroy.nl/Atari%201050%20goes%20green.htm

[Keneg]

Thanks for the link. That seems to still use much of the power circuit components. My idea was to get rid of most of the diodes and capacitors that fail. I have two drives imam working on that seem to draw too much power. I think the 12 volt side is where the problem resides on at least one of them. This modification would eliminate that entirely.

[Level42]

Proposed Atari 1050 power supply modifications

Supply 12VDC to the Power jack. (2 or 3 amps)

Remove CR15-20.

Remover Q8.

Put jumper wires were CR18 and CR20 were.

Put jumper wire between where CR15 was and where output of Q8 was.

....

Personally I would first do the suggested mods before supplying 12DC to he power jack.....

IF I wanted to mod my 1050s.

Edited August 10, 2018 by Level42

[_The Doctor__]

bad bad bad idea...... I've seen this done before and inevitably someone plug the 12 volt into another Atari device and kills stuff....

select on of the other mods, be forewarned some of them make noise that can be picked up by cassette and other devices....

PLEASE replace power jack with a different type of connector- one that can't be mixed up with any others!

 

I sure some has done this correctly before with no noise and a safe fail-over mode using a different jack... if not it's a project someone might take on.

 

most people just disconnect the jack and add a pc type supply at the correct point on the drive and pulling the legs on components connected to the original supply

Edited August 10, 2018 by _The Doctor__

[Kyle22]

It's fine the way it is. If you have a problem, replace the capacitors and the diodes to restore to original condition. The low power regulators are nice, and a direct replacement. Highly recommended.

Replace Components, Please don't HACK UP the drive.

[Keneg]

OK, it was just an idea. I dont really consider it hacking up the drive because it could all easily be put back to stock later.

 

What about using a PC supply with the power good pin jumpered as a troubleshooting device? Has that been done? If so, do you have to disconnect the 7805 and 7812 or can you use alligator clips to TP 13, 14, and 15? I am thinking that getting power at these points would let me determine if the power circuit is the only problem or if there are more issues.

Edited August 11, 2018 by Keneg

[Kyle22]

Ugh...

[Level42]

You're fixing a problem that is not there. You say your goal is to keep it reliable.

 

IMHO the 1050's are very reliable. I have one that was in the family since 1985. Upgraded with MegaSpeedy and works like a dream.

Edited August 11, 2018 by Level42

[Osgeld]

I am hoping the difference between 9 an 12 volts to the 7805 is within its operating limits. I thought about using a PC power supply and I do have a spare, but I was looking for a more compact solution. Thanks for your input.

 

Edit: I just looked at the data sheet. I should have done that before posting. The input voltage range is 7.0 to 35, so I think that wont be an issue.

Its more a function of current consumption generating heat than input voltage specs

 

Sure one could plop 35 volts with a 1 amp 5 volt draw on a 7805 Probally need to water cool it though

[Keneg]

OK, the consensus seems to be to fix it rather than modify it. Can anyone provide a step by step guide to troubleshooting? I am thinking to start by testing*p the diodes and capacitors until I get the correct voltages input to,the voltage regulators. Then if a regulator is bad, use the newer part to decrease heat.

[+kheller2]

OK, the consensus seems to be to fix it rather than modify it. Can anyone provide a step by step guide to troubleshooting? I am thinking to start by testing*p the diodes and capacitors until I get the correct voltages input to,the voltage regulators. Then if a regulator is bad, use the newer part to decrease heat.

Do you have a properly working unit to compare with?

[Keneg]

Do you have a properly working unit to compare with?

Yes, and I have downloaded the service manual so I know what voltages I should see. I need to get a fuse for my multimeter before I can continue.

[Keneg]

bad bad bad idea...... I've seen this done before and inevitably someone plug the 12 volt into another Atari device and kills stuff....

select on of the other mods, be forewarned some of them make noise that can be picked up by cassette and other devices....

PLEASE replace power jack with a different type of connector- one that can't be mixed up with any others!

 

I sure some has done this correctly before with no noise and a safe fail-over mode using a different jack... if not it's a project someone might take on.

 

most people just disconnect the jack and add a pc type supply at the correct point on the drive and pulling the legs on components connected to the original supply

OK, that is a good suggestion. I will do something like that if I can’t fix the issues. That might be a good temporary fix to see if the rest of the drive is working before investing too much time and money into it.