Yaesu FT480R

[Chris 1155]

Thank you for the further thoughts and effort.
We can carry out further investigations as suggested and yes In do have an oscilloscope.
Report back in a couple of days.
Chris G4BYZ

[Chris 1155]

145.520-----2.274 volts
145.521-----2.410
145.522-----2.549
145.523-----2.695
145.524-----2.845
145.525-----3.000
145.526-----3.161
145.527-----3.327
145.528-----3.498
145.529-----2.142
145.530-----2.273
145.531-----2.409
145.532-----2.549
145.533-----2.695
145.534-----2.845
145.535-----3.000
145.536-----3.161
145.537-----3.327
145.538-----3.495
145.539-----2.142
145.540-----2.273

The chart shows the voltage on TP01 at the indicated frequencies.
The holes around the 9122 are not connected to any tracks.
Yes I do have an oscilloscope.
Just to make sure that I am not going mad I have retested the TX frequencies and the are exactly the same as previously indicated. I also checked the receive performance on the suspect frequencies, this is also in error. typical RX frequency of 145.525 operates between 145.518 and 145.520.
I will have another really good look at the board to be sure there are no obvious tracking faults etc. Thanks once again

[Chris 1155]

Jon,
I have been looking at the PLL board and noticed that a track has been cut.
If you look at the circuit diagram you will see that pin 11 of Q27 is connected to pin 8 of Q 07. This connection has been cut on the pcb track. A 2.2K resistor has been connected between pin 11 and pin 8 and a 3.8K resistor has been fitted between pin 11 and earth. The resistors seem to have been fitted with care but the cut in the track looks fairly recent as the exposed end of the track is still bright copper.
Any ideas ?

[Jon_G4MDC]

Thanks for the results Chris!!
Looking at them I think they indicate that the 9122 is doing what it should.
xxx.5x9 is 2.142
xxx.5x0 is 2.274
xxx.5x1 is 2.410
xxx.5x2 is 2.549
xxx.5x3 is 2.695
xxx.5x4 is 2.845
xxx.5x5 is 3.000
xxx.5x6 is 3.161
xxx.5x7 is 3.327
xxx.5x8 is 3.495 allow for a few mV of leeway for measurement uncertainty.

This loop is perfectly following the programming numbers you measured earlier so the
misbehaviour must come from somewhere else.

I had another idea. Please could you do the same exercise but this time on TP09. That is the next oscillator in the chain.
I think we will see misbehaviour on that one - but let's prove it first.

[Jon_G4MDC]

I have just seen your extra note about the track cut.
Trying to work out the effect of that - made harder by the schematic I have is split over several pages of .pdf and it crosses the pages!!

Thinking on it.

[Jon_G4MDC]

I joined 3 parts of the PLL schematic together using paint.net and now I can read from a single sheet.

That line which has been cut is the 40kHz output which is used in loop1 as reference. I don't think it can be to blame for the problem since if it was inadequate/missing the PLL would not lock at all.

I can't see what the motive would be for attenuating it like that. I assume the MB8718, Q27, looks original and unmolested?

[Chris 1155]

145.520-----4.466
145.521-----4.568
145.522-----4.673
145.523-----4.781
145.524-----4.473
145.525-----4.310
145.526-----4.180
145.527-----4.140
145.528-----4.140
145.529-----4.370
145.530-----4.470
145.531-----4.570
145.532-----4.675
145.533-----4.783
145.534-----4.469
145.535-----4.431
145.536-----4.418
145.537-----4.411
145.538-----4.411
145.539-----4.373
145.540-----4.471

The chart show voltages on TP9. Q27 looks original and untouched.
Thanks once again Jon.

[Jon_G4MDC]

Well done for those measurements Chris.

That shows the problem for sure...it takes backwards steps from xxx.5x3 to xxx.5x8 when it should gradually increase like before.Why does it do that?

It holds the answer...

[Chris 1155]

Thanks for those observations Jon.
The logic is beyond me I am sorry to say but at least the symptoms have ben observed.
I have at least managed to fix the squelch problem which was just the wiring on the pot shorting out to the case. Poor insulation.
73 Chris G4BYZ

[Radio Wrangler]

The logic involved is NOT beyond you. Chris. Synthesisers involve some odd mechanisms, but they all make sense once you get familiar with them. You're entering into unfamiliar territory, not impossible territory. THere are areas which seem confusing, even counter-intuitive at first and people experienced with synths talk in jargon (for brevity's sake) which tends to exclude the inexperienced.

Feeling lost is perfectly normal at first, but getting un-lost is quite possible, if you want.

I have an FT480 here (I've dug it out) what I can't find is the handbook with the circuit diagrams, so I've been following the thread based on what snippets have been attached. My background is that my first job post-graduation was designing a 5-loop frequency synthesiser for an HP instrument... talk about landing in the deep end! That's described in the HP journal April 1982. `google will find you a download if you want to take a peek. After that I've done API (analogue phase interpolation) fractional N as well as noise-shaping fractional N synths. For my sins, I got to write the oscillators and synthesisers chapter for the ARRL handbook. THis is deliberately written to have a gentle learning curve to not scare off beginners, it also has to go far enough to entertain the experienced and to not have any oversights that experts can throw rocks at.

Jon is doing an excellent job of leading you through the maze and you have made real progress. Post number 47 represents a very big step. You are now on a trail which shows the fault, and you can follow it to see where it comes from.

Phase locked loops are loops of course, and if one is misbehaving, there is wrongness all around the loop... it flows around the loop, so everywhere looks wrong. The trick is to look at one stage at a time, and although the input to a stage is wrong, is the output of the stage what a good stage would give, if fed from that wrong input? We're looking for a stage whose output is not appropriate to the input it's getting. The input and the output are wrong, but do they fit together with what the stage is supposed to do? If they fit together, then that stage looks like it is doing what it is supposed to, so move on to the next stage. Scopes and frequency counters pay for their keep here.

If necessary, I'll find some diagrams and see if I can help, but Jon's doing a nice job and I shouldn't interfere unless I'm wanted.

The FT480 is a rather nice rig when you've got it going, though the FM filter on receive and the deviation setting on transmit are nuisances for 12.5kHz spacing. Since active amateurs numbers have dropped so much, there turned out to be no need to split the 25kHz channels, and the CTCSS requirement on repeaters seems to have almost killed them off. If you want to do 2m SSB from a favourable site, GM1EHK used to work around Europe as openings happened and down into England on a dead flat band from Lochgelly in Fife armed with I recall a 5 0r 6 element quagi and a house on rising land. He was using about 1 watt!

David

[Jon_G4MDC]

I have been mulling it over and it seems most likely that the output of Loop3, the TC9122 which is behaving correctly, cannot be reaching Loop 2 which is misbehaving.
Between the two is a division by 100. It could be here that the problem lies.

My next suggestion is to put your oscilloscope on TP07 which is the input to Loop 2 phase detector. Expect to see a signal of around 680 to 685kHz. What does it do as you tune the same range?

Does it change in amplitude - how much of it is there anyway?

Does it gradually increase in frequency in a smooth way or does it have the glitch where it increases at first and then drops back over the 5x3-5x8 range?

Crossed with you David - I cut my teeth on that ARRL section back when!! Glad you have fished out your 480R - we might be asking how yours behaves on TP07!

[Radio Wrangler]

In the middle sixties, a schoolfriend's father had lent me a '56 edition ARRL handbook and I'd virtually memorised it. When asked to write a chapter, I was gobsmacked and thinking of what I owed the handbook, it got my best effort. Feedback over the years has been very encouraging.

Hmm... divide by 100 and relatively stable results. Is the waveform a bit foxy at its input, causing double counting sometimes?

David

[Chris 1155]

Thank you both Jon and David.
I will get the scope out over the weekend and report back.
Chris.

[Jon_G4MDC]

The further this goes, the more I wish I had an FT480R...
There is one for sale. Must not buy it!

I have an FT897 with a dicky display. I should save the funds to fix it.But it doesn't have the soul and it never has had.

What to do?

[Chris 1155]

I also have an FT897 and FT817 bought s few years ago in a fit of madness.
What wonderful pieces of equipment but with no soul.
Probably explains why I use a FT101E for HF and FT225RD for VHF. In the car or portable I use an FT290 which I have fitted with CTCSS. FT270 for 70cms and Ascom ex PMR for 4m.
I have a KW Victor and Eddystone 888 for AM on 80m alongside a 1154/1155 for special occasions.
I am not a particularly keen operator, the real interest of course is fiddling around, hence the 480 and a list of other dinosaurs . Not up to me to lead you astray but giving in to temptation of this kind is not a mortal sin yet, as pointed out by Jan.
73 Chris.

[Radio Wrangler]

The FT480 is a nice, driveable rig with decent ergonomics.

The FT817... well I was once in a very famous shack surrounded by some very well known callsigns, the top brass of the FOC, and several with over 300 countries confirmed on QRP. They were trying to figure out how to turn down the deafening sidetone! Giving in, they eventually just switched the damnable thing off.

When asked if I knew how.... "Mallet?" i suggested.

David

[Chris 1155]

Hello Jon and David,
I am still here but have been so busy over the weekend that I have not got any further with the 480.
Hope to get on in the next couple of days and will post results.
Chris.

[Jon_G4MDC]

No worries, was wondering if we had any new findings to mull over but I can bear the suspense.

[Chris 1155]

The waveform on TP07 is shown in the picture.
The amplitude is plus 3.5 volt and minus 1.0.
The waveform does not alter at all when the frequency of the radio is changed.
The frequency of the signal is as follows.
145.520--678 hz
--------1--680
--------2--681
--------3--681.4
--------4--681.9
--------5--682.4
--------6--682.9
--------7--683.4
--------8--683.9
--------9--679.2
-------30--679.9
-------31--680.4
I am not sure what you can make of this but can do more tests if required.
Regards
Chris G4BYZ

[Jon_G4MDC]

Hello Chris, that looks fairly in order. The results on 520,521 and 522 are a little out of line with the others but 523 to 531 are what I expected to see, increasing nicely at 500Hz per step. Maybe the ones at the low end did the same but it a took a while to get the "eye in" on the counting. It is sure now that we can't blame the signal here disappearing or dropping in amplitude below some threshold.

We have to think now about what is going on in the TC5081 Phase Detector Q3014. It is about the only thing left! I think it would be good to look with the 'scope at frequency and level seen on TP08. That is the other input to the phase detector. It should follow the same frequency table but I don't think it will. It will have the jumps.

Beginning to wonder if it is the non-polarised capacitor in the loop filter C69 might be to blame here after all...?

It is noticeable that the handbook says adjust L17 for 3.5V at TP09 when the frequency is set for 145.0099 with Mode Switch to FM. The table for your measured Voltages on TP09 was up around 4.5V.
It can be this loop has drifted and is running out of range. Try adjusting L17 as handbook before changing any more bits!