• Please review our updated Terms and Rules here

North Star Horizon power

I would be inclined to replace all of the tantalum capacitors and both ‘L’ voltage regulators.

With the components removed (and the desoldering tidied up) check there are no short circuits between the incoming +/- 15V rails and 0V/GND. If this is correct, power up and make sure your ‘raw’ supplies are Ok at this stage.

Also, check there are no short circuits from the output of each of the ‘L’ voltage regulators and 0V/GND. You might want to consider doing this before powering up (above).

Solder the ‘input’ tantalum bead capacitors in place and test again.

I would now remove the 1488 and 1489 RS232 drivers next and install the two ‘L’ voltage regulators and test again. You should now observe stabilised +/- 12V on the output of the regulators.

Solder the ‘output’ tantalum bead capacitors in place and test again.

Install the 1488 and 1489 and test again.

Basically, proceed slowly and in an ordered manner.

Good luck...

Dave
 
I got the 7812s, 7xL12s and C3 removed. C1 had already been replaced, so I’m sure it’s good. I also pulled the 1488s and 1489s

When I measured the resistance this time I got:

+8v to ground: 99.6 ohms
+16v to ground: 165.4 ohms
-16v to ground: 165.3 ohms

Removing the 78L12 pulled a ground trace off the board, so I’ll need to fix that before going any further

6F4FEA5E-E73C-4A51-9194-9F7C6D3BF935.jpeg
 
The resistance readings look good now.

Shame about the track though - but it looks like an easy fix.

Dave
 
Since the regulator you were trying to desolder was the dead one, I would have suggested 'snipping' the three leads of the regulator and then desoldering each individual lead that was left behind one at a time.

You know for next time...

Dave
 
Since I got one of those engineer suckers I have had a much easier time desoldering things, the silicone nozzle allows a seal around the leg and the tip of the iron. Pain in the arse to clear the tool but I can remove things far cleaner than before (never had any real success with wick)
 
Gary C said:
Since I got one of those engineer suckers I have had a much easier time desoldering things, the silicone nozzle allows a seal around the leg and the tip of the iron. Pain in the arse to clear the tool but I can remove things far cleaner than before (never had any real success with wick)
Click to expand...
Yeah, I picked up one of those, a spring-loaded one, a month or two ago. It does help
 
daver2 said:
That’s two heatsinks you have ordered then :)?

Dave
Click to expand...
Hmm. Not sure how I did that. Anyway, one heat sink came with the Horizon kit, the other I got when I added the second disk drive. Must've found something at Radio Shack or some such place. I think it was all they had, so I made it fit by brute force. Part of it I broke off to use as a heat sink for a 7805 regulator. Getting parts was not easy back in the 20th century, especially if you lived far from a major urban center
 
You must log in or register to reply here.
Back
Top