[time-nuts] HP 5275A

Adrian Godwin artgodwin at gmail.com
Tue Nov 8 20:08:20 EST 2016


I'm pleased to report this TIC is now running again (albeit with some
temporary hacks, such as a 7915 regulator).

There were a couple of dried-out electrolytics, the shorted series-pass
regulator referred to above, and an open-circuit 2N708 controlling the
timebase gating. Another 2N708 died when I failed to push a PCB fully into
its socket. They're rather delicate flowers - Silicon, but only 15V Vceo :
a bit tight when used as switches with a 15V or 13V rail. Replaced with
BC237s, though that's perhaps a bit slow.

This is the HP5275A from france that  Poul-Henning Kamp mentioned in march
2015. It's been sitting here a while waiting for some attention
‚Äč
 VID_20161109_003111.mp4
<https://drive.google.com/file/d/0B8q6sqvuGdFfMDI2aXA0NnFWRTg/view?usp=drive_web>


Paul Swed : I'll add some HP9815 porn when I get it reading the 5275A
outputs.


On Mon, Nov 7, 2016 at 2:46 AM, Howard Davidson <hld42 at att.net> wrote:

> The real hack in the 5245 Nixie tube decoder is that the neon lamps were
> the memory element.
>
>
> hld
>
>
>
> On 11/6/2016 2:15 PM, 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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>>
> --
> Howard L. Davidson
> hld42 at att.net
>
>
> _______________________________________________
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