Tektronix 4014-1 troubleshooting advice
derschjo at gmail.com
Fri Mar 27 11:54:41 CDT 2015
On 3/27/15 9:05 AM, Jon Elson wrote:
> On 03/27/2015 12:03 AM, Josh Dersch wrote:
>> Hi all --
>> Picked up a Tektronix 4014-1 terminal. It's in pretty good shape,
>> nice and clean and it's in nearly-working condition except that the
>> storage behavior isn't quite right.
>> On power-up, write-through doesn't. (That is, characters don't get
>> stored to the tube.) Clearing the display via the RESET/PAGE key
>> clears a roughly elliptical region in the center of the display but
>> leaves the outer edges a mess. The cleared region stores characters
>> properly. You can see the overall effect here:
>> After a 2-3 minutes of warming up the area cleared by RESET/PAGE
>> increases. I haven't run the terminal long enough to see if it
>> eventually completely erases the screen (while the power supply
>> appears to be within tolerances, I still need to rebuild/reform it so
>> I'm not going to run it too long yet).
> Let it fully warm up. My guess is the cathodes in the flood guns are
> getting weak. Allowing them to fully warm up will probably help
> some. Also, as others have suggested, there may be some voltage
> adjustments that need to be set.
> But, the final adjustment is to set some of the voltages on the guns
> for optimum performance. there is a VERY critical adjustment of the
> flood guns (I think that's the right term) to get the storage to be
> stable as long as possible. Too much or too little flood beam causes
> the stored image to either bloom or fade. Then, the erase is
> performed by changing some voltage on the storage grid and pulsing the
> flood guns, and secondary emission (I think) erases the charge on the
> storage grid. It has been 30 years since I had to mess with a
> 4010/4014 series, but I THINK I still kind of remember how they work.
> Have you checked bitsavers for a manual?
Yes, as I said I've been studying the service manual (on Bitsavers),
which in typical Tek fashion is extremely detailed and helpful. It
outlines the whole alignment procedure, but I figured I'd ask here first
-- since this is a nearly 40-year-old terminal I'm interested to know if
anyone on the list has dealt with similar issues and if there might be
common failure points to check out before trying to re-align the thing.
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