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#1 25-10-2010 16:01:13

Istar
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NewBrain Resurrection

Hi everybody!

Back in '82 (pretty sure) my parents bought the family our first computer - a NewBrain AD. We spent many hours working with it, since it had a dual role as the main computer in Dads' business, as well as being my vehicle for passing GCE 'O' Level Computer Studies; I didn't get a computer of my own until Christmas '82, a VIC-20, so the NewBrain was where I wrote my passing-grade applications "Contact" (an address cardfile manager) and "MemTools" (a Z80 assembly aid). The NewBrain saw solid service until about '86, when it was usurped by a Tatung Einstein, and placed back into its box.

A couple of months back my Mum said she'd found it tucked away and forgotten in a dusty corner, and thus over this last weekend it joined the ranks of the (many) other 8/16-bit machines in my museum collection. I recalled that it had suffered the 'dry joint' problem with the PSU connector (it had been repaired once in '85, and then the second failure a year later precipitated its' retirement) so when I plugged it in I didn't expect to get any activity out of it - and sure enough, it did not wake from its' 24-year slumber.

Sadly it looks very much like a couple or more of the power-caps in the PSU had not aged well, as after about five minutes of being plugged-in there suddenly came a series of sharp snapping 'pop' noises from the PSU brick, and a surprising amount of magic smoke escaped. I quickly unplugged it, but of course it is badly damaged internally - you can now hear various bits of dead capacitor rattling around inside (the saving grace is that it wasn't actually hooked-up to the NewBrain at the point it bought the farm).

I was already musing over the possibility of replacing the flakey PSU connector with some more modern adaptor, to cure the dry-joint problem and avoid a repeat of it - but with the actual PSU now likely to be permanently dead, I am wondering if there is some well-established way of giving a NewBrain a proper 'power overhaul' and hooking it up to something like an ATX PSU, or perhaps taking some off-the-shelf transformer brick and engineering a modification for it?

I gather there may also be a problem with the reset-timer caps, which apparently can suffer aging badly, but I shall cross that bridge if and when I come to it.

All suggestions welcome - I want to wake this beast once more!

 

#2 26-10-2010 23:26:01

cdesp
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Re: NewBrain Resurrection

 

#3 27-10-2010 19:53:30

Saphir17
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Re: NewBrain Resurrection

Hi Istar...

Yes, all cap's need replacing. A sign of fluid deposits around the cap is a sure tell that it's broke.

Change them all anyway, it's not that expensive. Just be sure to get the low-profile caps. 7mm i height is max.
The 10uF timing caps can be lowered to 6.8uF. It's starts a bit quicker then...
Remember to clean the holes and pads on the PCB before you solder a new cap in.

The hole (Via) can be so corroded that you don't get connection to the other side of the PCB
Best practices is to clean and then fill the hole with solder to check it filles the via and flows to both sides of he PCB.
The empty it again to refit a new cap.

Use a solder wick and a sharp scalpel to scrape any corrosion off the pads.... and be careful not to cook the traces so they come loose.

If some of the chips are in placed in sockets, take them out and put them in again. There might be some bad connections in then sockets after all these years.

There is a good chance that it will come to life again, since it's your own and not "beat-up" one from Ebay... :-)

Good luck
Michael


Aarhus, Denmark
NewBrain's: Model A & AD, ExpansionBox, DiskController + Drives, ROM-Box
 


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