[time-nuts] HP 5275A

Glenn Little WB4UIV glennmaillist at bellsouth.net
Sun Nov 6 18:16:56 EST 2016

A 2N1038 is in a TO-5 or TO-11 package.
A 2N1038-2 is a modified or selected part.
Is this transistor pressed into a hexagonal bushing that is about 1/2 " 
long with a 10-32 threaded stud for mounting?
If so the bushing/heatsink is part of the transistor.
A google search for 2N1038 will show this this transistor and a similar 
one with the integral heatsink.


On 11/6/2016 5:46 PM, djl wrote:
> Just homemade opto-isolators. Used in choppers, too. The transistor was
> indeed bonded to the heatsink.  Just replace the whole thing with a
> 3-legged regulator? or simply a modern PNP t0-220 with a little heat
> sink on it.
> 73, Don
> On 2016-11-06 15:15, paul swed wrote:
>> Don't know what to say on the transistor. It may have been actually made
>> that way. They did lots of things back then. Yes familiar with the bcd
>> decoder its used in the 5245 class counters also. I think someone was
>> doing
>> some funny stuff at lunch time to come up with that. It was the 60's
>> after
>> all.
>> How about some pix of a 9815 calc. That would be pretty neat.
>> On really old stuff if you can't find the part needed its pretty easy to
>> replace the whole function with modern answers. I know it sort of breaks
>> the original mode but for me at least its a case of getting it going.
>> Regards
>> Paul
>> On Sun, Nov 6, 2016 at 1:59 PM, Adrian Godwin <artgodwin at gmail.com>
>> wrote:
>>> Slightly off-topic, as this is a general repair question. But it's a
>>> TIC.
>>> I'm repairing a 5275A timer (all-discreet count logic to 100MHz, neon
>>> bulb
>>> display, a most amazing bcd to decimal decoder made from neons and LDRs,
>>> 1-2-2-4 decade counters ..) and the current problem is a 2n1038-2
>>> germanium
>>> T05 transistor in the power supply.
>>> It's mounted in an aluminium bush which is then isolated from the
>>> chassis.
>>> I don't think the bush is also a collet but I can't see how to remove
>>> the
>>> transistor. It resists ungentle pushing .. should I push it with a
>>> hammer ?
>>> Or is there a kinder way ?
>>> (I'm hoping to eventually put this into a system with a 101A
>>> oscillator and
>>> a 9815A calculator to measure the ADEV of a Boule electric pendulum
>>> clock).
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Glenn Little                ARRL Technical Specialist   QCWA  LM 28417
Amateur Callsign:  WB4UIV            wb4uiv at arrl.net    AMSAT LM 2178
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

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