On 2023/04/18 8:48 p.m., Tony Duell via cctalk wrote:
On Wed, Apr 19, 2023 at 2:37 AM Tom Hunter via cctalk
<cctalk@classiccmp.org> wrote:
... or four $20 power transistors to protect a 10 cent fuse like on the DEC
VR-14 display.
In general the transistor(s) will fail short-circuit, thus taking out
the fuse too.
Some switch-mode power supplies use special fast-acting fuses which
can actually be more expensive than the chopper transistor.
-tony
In the end replacing the capacitors got the supply running. And I
checked the resistor that looked overheat, and it was 34R which is
within 15% of the value shown on another 1001 supply that is close to
the one (same part numbers and values for a number of the parts) in my
ADM31.
The supply puts out +5VDC, +17VDC (unreg), -17VDC (unreg), and 70VDC
(unreg).
The board appears to work - I have 5VDC on the MB, and I get a BEEP, and
there is some sort of data happening on the DB and I am getting data on
the Vertical, Horizontal, and Video signals to the monitor. Monitor
isn't lighting up - no HV (I've recapped it too), so I have to put on my
monitor hat next.
Stay tuned if interested...
Oh, I am missing two key caps for the ADM31, anyone have spares? Not
sure what is printed on them at this point, but any caps would be better
than missing ones to start!
Thanks,
John :-#)#
--
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