The readout operates in parallel with the BCD output from U2015
(frequency counter and latch). I would start by tracing backward from
there. One or both of the digital signals (E or F) from schematic 12
is probably missing. I would take a close look at Q2120.
The readout is a pretty standard DVM design which Tektronix used
variations of on a lot of their instruments.
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On Wed, 20 Feb 2013 06:58:15 -0000, "Michael" <af7u@...> wrote:
Hi all,
I have a 7L13 Spectrum Analyzer out in the field, it's not in front of me right now but I will pick it up later this week. I've seen the unit and the 'Center Frequency' LED read-out is stuck, and reads '0000', also the same value is being sent to the CRT display. The analyzer is sitting in a 7000 series mainframe and the mainframe works fine in every other way. In fact, the spectrum analyzer works fine, just the 'Center Frequency' display stays on zeros. The 'Tuning' works and adjusts correctly. It is used with a TR-502 and that combination also works, you just don't know where you are frequency wise. You can place a frequency counter on the AUX out of the TR-502 and manually scan the bandwidth and read the frequency on the counter. It appears everything is fine, just the readout is non-functional, or at least stuck on zeros. I thought it was curious the display in the 7000 is also reading zeros too. I will have it in front of me next week but I thought I would see if
anyone had any thoughts before I open it up.
Thanks in advance,
~Michael - AF7U
David Hess