[time-nuts] HP 5275A

Adrian Godwin artgodwin at gmail.com
Sun Nov 6 23:08:22 UTC 2016


Yes, further searching reveals that although the 2n1038 is T05, the -2
version is X26 - mounted in a stud by the factory. So it could well be
glued. 2N1038s aren't unobtainable though, so I'll keep it original if I
can. Even though a 7915 would be fine !

I was a bit puzzled by the insulators. Very metallic-looking. Then I
realised they're BeO. Pretty unusual these days (no, I won't be machining
them) so another reason to keep a T05 in there.

On Sun, Nov 6, 2016 at 10:46 PM, djl <djl at montana.com> 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
>> WB8TSL
>>
>> 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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>
> --
> Dr. Don Latham
> PO Box 404, Frenchtown, MT, 59834
> VOX: 406-626-4304
>
>
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