lamps (was Re: 7503)


david@...
 

Those 237 little incandescent
lamps in the 7A12 were cute the way they lit up the little buttons,
but it didn't take them long to figure out that it was a maintenance
nightmare.
I don't think they ever did figure it out... it's just as hard to change
the lamps in the later plugins like the 7B92A. To me, it makes no sense
to put every transistor in a socket, but solder in the incandescent lamps.

I think 7A12s are great because it's so much faster to switch ranges with
the pushbuttons than it is to twist knobs on a 7A18/7A24/7A26. The
biggest maintenance problem I've had with them (and 7A13s) is failure of
the white relays.


Miroslav Pokorni <mpokorni@...>
 

The reasoning on socketing transistors and soldering incandescent lamps can
be very much skewed by your background. I remember from school that one of
assistant professors described transistor as 'a device that does not have
repeatable characteristics'; he did not think much of their reliability,
either. Incidentally, that guy came to school from telecommunication
business and in that kind of business lamps are widely used and considered
reliable, though they socket lamps.

I would guess that size of socketed lamps forced the use of soldered ones
and everything else was just a frosting on the decision.


Regards

Miroslav Pokorni

-----Original Message-----
From: david@slack.com [mailto:david@slack.com]
Sent: Friday, October 12, 2001 8:56 AM
To: TekScopes@yahoogroups.com
Subject: [TekScopes] lamps (was Re: 7503)

>Those 237 little incandescent
>lamps in the 7A12 were cute the way they lit up the little
buttons,
>but it didn't take them long to figure out that it was a
maintenance
>nightmare.

I don't think they ever did figure it out... it's just as
hard to change
the lamps in the later plugins like the 7B92A. To me, it
makes no sense
to put every transistor in a socket, but solder in the
incandescent lamps.

I think 7A12s are great because it's so much faster to
switch ranges with
the pushbuttons than it is to twist knobs on a
7A18/7A24/7A26. The
biggest maintenance problem I've had with them (and 7A13s)
is failure of
the white relays.


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dhuster@...
 

They must've figure something out, Dave. In the 453/454, they used
neon lamps for panel annunciators. In the 465/475 they went to
incandescent lamps everywhere. With the 465B, they decided to change
over to LEDs. On my stuff at home, when an incandescent lamp blows
out, I replace it (and all of its brothers and sisters in that
section of the equipment) with LEDs if I can get them to fit (it
might take a little machining of the LED). There's usually a series
resistor somewhere on the circuit board that you can replace to set
the LED current to its correct value.

Dean