[time-nuts] HP 5275A

djl djl at montana.com
Sun Nov 6 17:46:05 EST 2016

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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Dr. Don Latham
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

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