National company HRO 500 replaced sawtooth detector, diode and coupling capacitor

Update from THE FUTURE. Wed Aug 28th.
I tuned the Two IF cans and the MIXER can on the SYNTH for best LOCK on band #3
Meaning I would turn the synth tune one way until it unlocked. Then the other way to lock.
Then further until it unlocked.
Then I fiddled with the Mixer and the two IF cans to get the WIDEST lock possible spanning the desired frequency. This seems to be the BEST way to turn the mixer and the two IF cans
After this and hours later I fired up the HRO 500 and could LOCK on all bands 1 to 5.
Although not accurately on bands 1 and 2.
indeed I have all of the frequency indicator drum OUT to change the light bulbs STILL!
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Seems I would have LOCK on the scope showing but the bi-stable indicator for the LOCK light
STILL showed unlocked.
Well that is not cool. Or even fair.
So I replaced the diode with a new silicon diode - signal diode.
And increased the coupling cap from 1uf to 2.2 uf.
May have improved the reality a bit.