[time-nuts] FW: Need HP-113AR info to replace missing part.

[Bill Hawkins]

Dan,

The 113BR manual shows two 2N458A transistors. The type is
not critical. Any of today's PNP power transistors rated for
40 volts CE should work. You could even tweak the design to
use power FETs.

If the transistors blew, and weren't just lifted for another
project, then check the two 1000/35 electrolytics near them.
A shorted cap will take out one of the transistors. There are
no current-limiting parts, not even a fuse. The -20 regulator
also has a 2N458A with no current limiting.

A shorted motor could also do it. The light bulb that shines
on the one second pulse detector is required to run the motor.
It is only identified as DS-1, so you'll have to look further
if it is bad. If the motor doesn't run, that could overload
the transistors. An open 1000/35 cap will also stop the motor.
Mine was open, but the transistors were OK.

If the clock was run constantly, the motor could have bearings
that scream at 1 KC. I put mine in a box lined with fiberglass
insulation to kill the noise. Bearings can be replaced.

While you're in there, look for leaking wet tantalum capacitors.
The residue is usually white.

All that aside, it's a mechanical marvel worth restoring.

Bill Hawkins


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Dan Durgin
Sent: Friday, March 23, 2007 4:18 PM
To: time-nuts at febo.com
Subject: [time-nuts] FW: Need HP-113AR info to replace missing part.

I recently bought a 113AR frequency divider clock.
It is missing two TO-3 type transistors on one side of the cabinet.
I think they were 2n458 units.
Can someone tell me if I'm correct so I can order them and get it going.
Daniel Durgin
Ocean View, Hawaii
KA1AFJ
ddurgin at aloha.net