7854 fixed, now for some newb questions


Nenad Filipovic
 

Dear All,

A few days ago I've become a proud owner of a mint condition 7854 with the
calculator keyboard (still in its original plastic wrap). What was wrong
with it - exploded capacitor in the integral EMI filter of the power
connector. It splattered a load of brown goo on the outside, the filter
itself bulged so hard that I couldn't pull it out at first. I was already
thinking about a conspiracy of fancy US gear against European line voltage,
but then noticed that the filter itself is "Made in Switzerland", splendid.

Cute mainframe, especially the programming mode that constantly reminds me
of the T-800's red first person view from Terminator 2. And that postfix
notation gets me talking like Yoda after a long programming session. It's
my first 4-bay mainframe from the 7000 series, so I have a lot of questions:

1. Excessive brightness on power up. My 465 does this as well, when powered
up from cold state the image comes up quite bright, somewhat defocused, and
then settles to normal after ~10min. Not a major showstopper but it's
annoying to have to turn it down on every power up, and then back up once
it warms up. On the 7854 it seems more pronounced on scope trace
brightness, and less pronounced on readout brightness. Any suggestions?

2. My unit is a late model, it does not have the usual memory backup power
connectors at the back, but instead a memory backup switch. What is the
life of that backup battery inside, should I replace it? I read that long
thread about 7854 RAM/ROM board upgrade, ROM rot was reported as a common
issue on 7854s, are the late models free from this problem?

3. Sticky buttons. I remember there was a thread discussing this, but could
not find it in the group archive. There were talks about plastic swelling
over time and getting stuck in those tight tolerance holes, so filing away
hole edges was proposed as a solution. I wonder if this issue could be
fixed without taking everything apart? Keywords to find the original sticky
buttons thread would also help (I've read "7854 build in keyboard sticky"
but it's not that one).

4. Noisy fan. It's not worn out, it's the sheer speed that creates the
noise. I'm not sure if it's original, so I was wondering if it's normal to
be so noisy? Of course it keeps the scope quite cool (even with the
monstrous 7L18), but November in Europe is chilly so most tech stuff like
it. I'm wondering if it would be safe to turn the RPM of that fan down?

5. I don't have the 7B87, so am I missing much? To be honest, at the moment
I do not have any proper time bases to experiment with (while waiting for
7B10 and 7B15 to arrive I'm temporarily using the 7L18's sweep to mock time
base functionality). I would like to use my 7854 to record single shot
events, I hope a delaying time base + it's internal trigger would be
enough. Not sure what I'd really gain with the external sampling clock
input of the 7B87?

Best regards and thanks,
Nenad Filipovic

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