Yet another 7L5 issue (7L5 / 7854) below 10 kHz
The dot frequency displays with the decimal point in the wrong place below 10 kHz (Fine mode on); the displayed number must be multiplied by 10. The 7L5 tunes correctly to 9.750 kHz, for example, but displays 0.975 kHz
Tek documented this in Service TekNotes in November of 1982. Strangely, they never produced or published a fix as far as I can discover. Does anyone have a solution, or ideas for one?
I wrote about a related problem in this message:
I also have the same issues with my 7L5/7854 as you reported (improper
reset and CF display below 10kHz), and my conclusion is that 7854 readout
processing does not conform to specification, so it's the 7854 firmware
issue. I summarized a part of it in the conversion document posted here:
So until someone dares to do brain surgery on 7854 ROMs, I doubt there's
much we can do. Tek did not touch it back in '82, so I figure it wasn't an
These recent microfiche scanning operations might reveal some project
documentation on 7854 firmware, though I'd be amazed if somebody fixed a 30
year old bug :) 7854 is still hard to beat even today.
Hi Cliff,toggle quoted messageShow quoted text
Yes, in my opinion the "below 10 kHz" problem is purely on the 7854 side,
as my 7L5 displays CF correctly in both 7633 and 7104. I did not bother
much with it as I simply got used to it, and with GPIB data it is possible
to implement a fix for it in capturing software.
The reset anomaly is also present in mainframes other than 7854. In my 7854
it powers up at 3778kHz most of the time, but not always. In 7104 it does
1788kHz or something similar. I did not get into it deeper as it did not
bother me nearly enough as the very annoying mV issue in LIN mode on 7854.
The last is definitely a 7854 fault.
Is your 7L5 the older (SN below B069999) or the newer version? Mine is the
older. I think I remember I read somewhere that the older version is prone
to the reset problem, but can't say for sure.
On Sun, Dec 8, 2019 at 5:34 PM Cliff Carrie <cliffcarrie@...> wrote: