Hi all,
I'm new to this group, I'm italian, apologies for language errors ;-)
I have a Tek 494P (fantastic!), but as you well know it is a ¡°time bomb¡±.
I have repaired it many times, but now I am facing a new problem that I cannot solve:
the SA immediately (at startup) gives the 1ST LO error, then the frequency counter error.
As you can see in this picture
the counter ... does not read
It wasn't like that right away: it would start randomly, and sometimes it depended on the ¡°center frequency¡± (meaning it worked on some frequencies, and not on others) - now the fault is always there, whatever frequency range and span is used (max span, < 10Mhz/div, < 500 kHz div).
In the past I have had many problems with the (in)famous A50 board, and looking at the diagrams there were many variations between the 494, 494A and the 27xx series. But now that doesn't seem to be the problem (if I'm not mistaken).
I have extension cables for the boards (homemade), but I would need other boards for swapping (and I don't have them).
Any suggestions on where to start looking? All the obvious analysis has been done (e.g., power supplies).
cheers
Federico
fedevirgo@...
p.s. if someone have spare boards to sell ... rise your hand :-)
