The old car has a green vacuum fluorescent display for the clock and OBC.
On a cold and damp day it tends to show all the segments until it warms up
then comes good. The obvious thing would be to simply fit a spare - I have
a couple - but my late car includes a dimming function for when the lights
are on - the earlier units, and my spares, not. And it is uncomfortably
bright at night without the dimming function. I've checked for dry solder
joints - but some of it is thick film construction, which I don't really
understand.

Any ideas?

--
*It's lonely at the top, but you eat better.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
"Dave Plowman (News)" writes:
The old car has a green vacuum fluorescent display for the clock and OBC.
On a cold and damp day it tends to show all the segments until it warms up
then comes good. The obvious thing would be to simply fit a spare - I have
a couple - but my late car includes a dimming function for when the lights
are on - the earlier units, and my spares, not. And it is uncomfortably
bright at night without the dimming function. I've checked for dry solder
joints - but some of it is thick film construction, which I don't really
understand.

Any ideas?

I would guess damp/condensation, causing leakage to the grid connections
to the tube (and/or the anode plates if it's a multiplexed display with
multiple anode plates).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 18/01/13 12:15, Andrew Gabriel wrote:
In article ,
"Dave Plowman (News)" writes:
The old car has a green vacuum fluorescent display for the clock and OBC.
On a cold and damp day it tends to show all the segments until it warms up
then comes good. The obvious thing would be to simply fit a spare - I have
a couple - but my late car includes a dimming function for when the lights
are on - the earlier units, and my spares, not. And it is uncomfortably
bright at night without the dimming function. I've checked for dry solder
joints - but some of it is thick film construction, which I don't really
understand.

Any ideas?

I would guess damp/condensation, causing leakage to the grid connections
to the tube (and/or the anode plates if it's a multiplexed display with
multiple anode plates).

That is a cogent thought, in which case washing with alcohol and
spraying with a spirit based lacquer might sort it.



--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

A lot of theolder calculators seemed to suffer this way after some years. I
think its due to degradation of internal insulation which lets the voltage
leak to other electrodes. Certainly, I never found an external reason for it
as those early things ere very very simply built. I got the feeling that the
little inverter was the most taxing part.
Maybe someone else knows what the problem is with those.
I guess they are pretty high impedance, so any leakage will probably light
the segments.

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Dave Plowman (News)" wrote in message
...
The old car has a green vacuum fluorescent display for the clock and OBC.
On a cold and damp day it tends to show all the segments until it warms up
then comes good. The obvious thing would be to simply fit a spare - I have
a couple - but my late car includes a dimming function for when the lights
are on - the earlier units, and my spares, not. And it is uncomfortably
bright at night without the dimming function. I've checked for dry solder
joints - but some of it is thick film construction, which I don't really
understand.

Any ideas?

--
*It's lonely at the top, but you eat better.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
The Natural Philosopher writes:
On 18/01/13 12:15, Andrew Gabriel wrote:
In article ,
"Dave Plowman (News)" writes:
The old car has a green vacuum fluorescent display for the clock and OBC.
On a cold and damp day it tends to show all the segments until it warms up
then comes good. The obvious thing would be to simply fit a spare - I have
a couple - but my late car includes a dimming function for when the lights
are on - the earlier units, and my spares, not. And it is uncomfortably
bright at night without the dimming function. I've checked for dry solder
joints - but some of it is thick film construction, which I don't really
understand.

Any ideas?

I would guess damp/condensation, causing leakage to the grid connections
to the tube (and/or the anode plates if it's a multiplexed display with
multiple anode plates).

That is a cogent thought, in which case washing with alcohol and
spraying with a spirit based lacquer might sort it.

You can buy conformal coating sprays for this purpose.
Obviously, need to make sure it's completely dry before
applying.

If the car interior has got excessively wet, then driving
with the heater on full blast and some ventilation might
fix it, if it dries out the moisture inside the car.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Andrew Gabriel wrote:
I would guess damp/condensation, causing leakage to the grid
connections to the tube (and/or the anode plates if it's a
multiplexed display with multiple anode plates).

That is a cogent thought, in which case washing with alcohol and
spraying with a spirit based lacquer might sort it.

You can buy conformal coating sprays for this purpose.
Obviously, need to make sure it's completely dry before
applying.

If the car interior has got excessively wet, then driving
with the heater on full blast and some ventilation might
fix it, if it dries out the moisture inside the car.

Thanks for the replies. The car lives outside all year long and isn't used
every day. However, it didn't do this when newer. Perhaps I'll try giving
it all a good clean and dry it out then use a coating.

--
*Experience is something you don't get until just after you need it.*

Dave Plowman London SW
To e-mail, change noise into sound.