Atari 1050 help

[Cretedriver75]

I have an atari 1050 drive that will do nothing. i tested the psu and its good. It had 3 bad caps the bigger ones 4700uf 25 v and 3500uf 35v. Replaced them. Tested the 7805 voltage reg i get good voltage in and nothing coming out. the test pin 13 has nothing on it also. I am at a loss on what do do next. Any help would be appricated. I did replace the 7805 with the same result.

[+Nezgar]

I'm not saying I know, but it sounds familiar to a recent thread about a similar issue on the 12V side, culprit was a bad capacitor:

http://atariage.com/forums/topic/273958-atari-1050-12vdc-internal-power-supply/?p=3930100

[Cretedriver75]

It does seem odly fimilar. Guess I'll go and start re checking caps. And go from there.

[1050]

Could be a chip in backwards or any other means to

short the 5 Volt system to ground. How was the 12

volt side?

[Cretedriver75]

11 volt was good.

[_The Doctor__]

11? noooooo 12 yessssssss

[1050]

11 might be fine when the 5 volt side has a dead

short to ground like this, there isn't enough current

left over to pump up the 13 volt in to the 7812 VR

to make it do higher than 11 as the VR needs an

overage of 2 volts minimum.

 

What I would do next is pull all socketed chips to

see if the 5 volts return. If so then it's one of the

chips that were removed so replace them one at a time

until the guilty party stands out like a sore thumb

and then replace him.

 

Still no 5 volts then we have the possible non-socketed

chips and/or filter caps hung onto the 5 volt rail to

be checked as best as possible. One way to 'see' the

bad chips at this point might be to spray them with

alcohol mist and see if any stand out as to drying off

much faster than the others do. Flashjazzcat does this

to find bad ram and it's a brilliant option since we

can see much better than smell high temp chips.

 

Whatever it is that is dumping all the 5 volt supply to

ground is getting warm while it does it. Not hot enough

for smoke but still noticeably warmer than normal. Even

a shorted cap should show it.

 

[_The Doctor__]

I use a sparkle marker on bad chips to make sure I don't do what FJC just did...

It's seemingly almost always RAM, MMU, then support chip, followed by freddie in that order..

then you move on the OS and CPU as a toss up, followed by the other Large scale chips.

 

wrong power supply, ram freddie mmu in that order follow the rest of the blurb from there.

 

@ FJC, have you tried a knee/shin chair? I had to use one after a back injury.. they work wonders but get a bit of adjustment time do hop in and out of them quickly.

It helps big time.

 

https://www.google.com/search?client=firefox-b-1-ab&tbm=isch&sa=1&ei=ji58WvCTNJGV5wKf-7KADg&q=best+knee%2Fshin+chair&oq=best+knee%2Fshin+chair&gs_l=psy-ab.3...34134.39812.0.40861.10.10.0.0.0.0.143.897.7j3.10.0....0...1c.1.64.psy-ab..0.3.254...0i13k1j0i8i7i30k1j0i13i30k1j0i24k1.0.cRfQ6TXPQRU

Edited February 8, 2018 by _The Doctor__

[Level42]

I use a sparkle marker on bad chips to make sure I don't do what FJC just did...

 

I always completely bend in pin 1.

[Cretedriver75]

After Some testing. Caps that were reading good are now reading bad. Decided to just shotgun the caps on the whole board. Waiting on Mouser now. Will update post after i recap the board. I guess 40 year old caps need replaced lol.

[thorfdbg]

While at it, also check the diodes in the voltage doubler circuit. They burn out easily - as they are a bit too weak for the current the motor draws.

[Cretedriver75]

Replaced all the caps in the drive board and the drive now shows power light and spins a disk. Iam at work so wont be able to test it until tonight. I have high hopes though.

[Cretedriver75]

It works perfectly.

[Cretedriver75]

It works perfectly.

[_The Doctor__]

Glad we could help. I am always super happy when it all works out! You've made my day!

[Cretedriver75]

I am super happy it worked out also. I feel like i have a fantastic new piece for my collection.

[+Nezgar]

Awesome work! I still love loading software from real disks, and I love that game Trains! With the work you've done on the board it should be good for a good long time now, probably longer than the disks.