SA-5010, verification of factory modification, JPG copies sent direct .

[JF]

Terry Perdue wrote on 9/20/2010 regarding a SA-5010 circuit error:

 > Just to correct some mis-information, there was no 'circuit error'
 > that halved the available memory space - believe me, our
 > Evaluation  department would have caught that. I'm quite certain
 > that the ONLY things that changed between the original SA-5010 and
 > SA-5010A were the color scheme and the addition of two small
 > bypass caps on the paddle inputs, to prevent a high RF field from
 > causing problems...
 > There were no firmware changes either. Maybe someone can tell me
 > where C4 was in the circuit. I don't recall any cap being removed.


Hello Terry,
No, it wasn't mis-information, and a circuit change to the SA-5010
keyer was described to me by the Heath factory to correct the memory
shortfall problem that evidently only occurred in early runs. Your
post stirred me to dig through old correspondence and amazingly I
still have some of the 1982 letters with the corrected schematic
received from Heath in reply to my query, and FYI JPG copies are
attached to this E-mail.
(NOTE to List readers - attachments must be sent direct, will not
  be included on the Heath List.)

As you will see, the Heath reply came from Matt Adrian, Supervisor,
Technical Products Consultation. His letter kind of rambles on about
fixing the paddles sending random dots and dashes without being
touched, but my original letter asked about the memory problem, not
the paddles. Looks sort of like their reply was a form letter sent
out to different end users. I never had the problem with the keyer
sending dots/dashes without touching the paddles, and certainly
never asked about it.

Just looking at their corrected schematic I couldn't see right off
why it would cure the memory problem, so I wrote to Heath again and
they verified it. Sure enough, after I made the C4 change the full
memory capacity became available.

I didn't say C4 (.01) was REmoved, I said it was moved - originally
it connected the collector of Q1 directly to the junction of R3 and
pitch control R39; Matt Adrian said to cut C4's connection to the
R3/R39 junction and move it to the other side of R3, where it
connects to the junction of R3 and pin 12 of U9D. Just looking at
it, I couldn't see right off why that would fix the memory problem,
so I wrote to Heath again and they verified it. Sure enough, after
I made the C4 change the full memory capacity became available.
Just how many early SA-5010's were affected by this I don't know.

About speed settings being a little off - you wrote:

 > Also, the speed you set from the keypad IS accurate as long as
 > the Sending Speed is set to the same value. When the Sending
 > Speed is set lower, the overall speed won't be what you set.
 > For example, if Speed = 20, Send Speed = 10, the average speed
 > won't be 10.

I guess I didn't make that clear - the effect of spacing changes
on wpm was not what I was talking about. As I was interested in
passing the 20 wpm test I made a bunch of character-counting
measurements on the random-length strings actually generated over
periods of a few minutes by the keyer in code practice mode, and
as near as I could tell by comparing them to the former Morse
test standard of 5-character words:

- Alphabet characters only, 20 wpm setting gave 17 wpm actual,
                             24 wpm gave 19.6 actual.

- Mix of letters and numbers, 20 wpm gave 20 wpm actual.

So, apparently the accuracy depends on the character mix. Anyway,
I'm sorry to say it's not important any more due to the recent
licensing changes made by the FCC.

73
John   KE5ZB

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