18 Sep
1998
18 Sep
'98
5:27 p.m.
THrowing in my $0.02 here...
At 09:07 PM 9/18/98 -0700, Sam wrote:
Ok, so I have a 15W bulb in series with the P/S and it lit up. The fan
didn't start blowing until the second time I powered up, but its blowing,
albeit very slowly due to the limited power I assume.
When its powered down, give the fan a spin with your finger. It should
spin freely. If not, it should be replaced. The older bronze/oilite
bearings dried out and would start to stiffen up after a souple of years of
operation.
I didn't go the full Tony route because doing so
would've required
desoldering the entire transformer which wasn't an attractive prospect.
True 'nuff... Unless you got a very early IMSAI with the point-to-point
wires PS.
I measured the voltages across a power connector and
got 9.4V, +17.56 and
-17.86. A little high but I attribute that to a lack of a load.
That is actually pretty much normal. Keeping in mind that the mains on the
S-100 bus are unregulated and spec'd (such as it is) at +8 and +/-16VDC to
allow for drop under load without falling out of the 'comfort' range for
the regulators on the individual boards.
At this point I feel pretty comfortable that the P/S is
working pretty
well, which surprised me. I expected a fight (but was hoping for the
results I got). These old machines just refuse to die.
The big 'can' caps are a good deal harder to kill than the minis...
I'm going to let it warm up for about an hour
before I start plugging in
boards.
Never can be too safe. In the case of my PDP-8/i which had not been fired
in a known 10+ years, once I had the supplied spun up I ran it in under
(auto) lamp loads for a little over 6 hours (frequently checking for ripple
with a 'scope) before I started reconnecting logic.
But thats just me... B^}
So... 'fess up. Is this the 'door prize' IMSAI?
-jim
---
jimw(a)agora.rdrop.com
The Computer Garage - http://www.rdrop.com/~jimw
Computer Garage Fax - (503) 646-0174