Dave,
Those electrolytics are defective. They have been running hot. Time to replace them. I hope that this helps!
GOD Bless and Thanks,
rich!
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On 9/23/2020 9:39 PM, Dave Casey wrote:
I spoke so highly of my 571 last month. When I recently went to use it, I
was getting some artifacts in the display so I have set out to investigate.
Unfortunately you can tell this wasn't designed in Beaverton because you
have to remove the CRT to get the main board out. There are some large
Roedenstein electrolytics used for supply smoothing that have a bit of a
dome to the end of them. Not sure if these were flat when new, but they
don't appear to be leaky (neither physically nor electrically). There is
significant noise (100-200mVpp) on the supplies, but it's not line ripple.
It appears to be around 2 MHz and is two similarly disruptive pulses around
200ns out of phase.
In the process of disassembly, I have pulled and saved the three EPROM
images. Two run the 8032 controller, and one runs the NS405 "terminal on a
chip" that is used to draw the display and printer output.
I haven't exhaustively perused the images, but the graphics ROM has some
ASCII easter eggs I noticed. After the usual Tektronix copyright statement
is "Written by: Folkert ten Brummelhuis (started). Sjoerd J. Punter" and
soon after "[Makke yn Frysl?n]" which is Frisian for "Made in Friesland",
the province in which Heerenveen is situated. Later in the ROM the phrase
"Joke Mirjam Esther" appears twice, about (but not exactly) 64 bytes apart.
I believe these are three given names commonly used in the region, perhaps
the names of those endeared to one or both programmers.
Dave Casey
On Fri, Aug 21, 2020 at 1:31 PM Dave Casey via groups.io <polara413=
[email protected]> wrote:
I stand corrected; can confirm, my S/N also starts with H. Thanks!
Dave Casey
On Fri, Aug 21, 2020 at 5:12 AM zenith5106 <hahi@...> wrote:
On Fri, Aug 21, 2020 at 05:49 AM, Dave Casey wrote:
Built by Sony-Tektronix.
No,not Sony-Tek. It was built by Tek Netherlands (SN begin with H) and as
far as I remember it was also designed by them.
/H?kan
