I seem to have missled ...
In the above post I'm referring to the Difference in X2 of 24MHz - not the Xtals' own timebase to 10.240MHz.
In my rush to get the post completed in-between tasks - I lost sight of the meaning in the paragraph...I'll take the ding for not proofreading this better...
So what I was referring to is the 24MHz difference between the 10.240 you're using and the required new frequency you have to apply to get the newer channels.
The VCO works on the 33MHz for 40 channels - you're WAY up - nearly 2MHz higher = pushing the upper limits of the frequency imposed on the VCO as well as all parts involved - to close to 37MHz if not higher.
So hence the 24MHz reference (~34MHz-10.240=24MHz) - even at 33MHz difference as triple the original timebase of 11.325 at X3 - it's evident that you are running into a rolloff / passband issue when the VCO is using frequencies that high.
Have you reworked the signal path caps the Tripler output uses? Mostly, the 47pF ones (C88 / C89) - else even the removal of a turn on L15 is the only thing I can think of to improve the higher bandpass the VCO needs to produce an output. The output is at the highest expected design of <36MHz - so you're working without a net...C88 and C89 - may need to be tweaked - as in a lower value, I suggest 33pF and re-check TR20 and TR29 for a better Hfe upgrade. The loop phase detect filter of C80 and C81 - are they Electrolytics now? Else the R100 6.8K might need to be lowered to as low as 3.3K in order to get enough drive thru the loop.
IT would appear that you got this thing to fire - just the losses even one of the SSB modes - means the drive of that particular mode is not as strong into the tripler.
IF you have a scope and a means to RF detect probe and run it into a meter - thinking the Noise Blanker section setup a dual diode doubler to increase the voltage detected and use a DVM as a mthod to maximize versus a scopes own problems with loading unless you have the tips for it - a test jig that lets you tweak the caps in the tripler section to improve it's output - else the only thing you have to work with is TP10 - not a bad way to go but it uses the TR20 output to show anything - I was looking further down into the tripler and into the LINEARITY of the two varactors that you are using on the radio - the two in that section I'm referring to D69 and D35 - both varactors are tricky, and one is padded with 18pF ACROSS as in paralleled with it affecting the overall performance of that varactor working with the tuning section one the goes to L59, L22 and L23.
So with the output - if it's not strong enough - is what you have done to it enough? I mean like - take a look at C116 - a 2pF coupling cap - that takes the entire 2nd varactors' output D69 out the Emitter leg across R144 (1K) that - and along with C212 acts as a tuning fork (peaking) for the base of TR30...sending it to the tripler...
I mean, be careful here - at that age - you're lucky to even get it to go into the 27.8MHz region as part of the channel plans.
It's why I asked about the age or year the radio was built - age is against you when it comes of the NPO and frequency sensitive parts, but it was designed back then using a hand drawn method that was very impressive in layout. The bane is it left a lot of areas with diminished capacity and ability to take the frequencies this board uses without inherent losses in trace thickness widths let alone the gaps between the trace routes
The above is for suggestions - not cast in stone - your mileage may vary...
:+> Andy <+:
