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Messages - N2NXZ

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31
Equipment / Re: Panaxis FME 500 issue
« on: August 14, 2018, 2145 UTC »
If I was to try anything more,it would be the hand wound oscillator coil that has the tap on second turn.I do not like how it looks and may be the issue.I recall even when it was built fresh that was a critical key to PLL locking.
I may try one last time to make a new coil and try again.
Here are some notes from the manual regarding that coil -





32
Equipment / Re: Panaxis FME 500 issue
« on: August 14, 2018, 2024 UTC »
Well,may as well share the build.
I made the main case from 030 gutter stock and the heatsink was bought from a local surplus store.
Mouser and RS did the rest -








33
Equipment / Re: Panaxis FME 500 issue
« on: August 14, 2018, 1939 UTC »
Yes...you just tweak the trimmer cap until the PLL locked.If you had trouble,you would squeeze or spread the coil a bit.It did not take much to get it to lock.
When it was first built,I powered it up and made simple tweaks and it worked perfectly.
Something else is wrong and getting to a point now I may have to replace everything.
6 IC`s total with one being the PLL which I already replaced recently.
I do not think I am going to mess with it anymore as I do not want to invest into something that is just for fun and has no real use.
After all,it is not legal to run with a full blown antenna or amplifier anyhow...pure novelty.
The fun went away after I built the entire system and tested it out.
I have the 15/25 amplifier and stereo generator as well all in a hand made metal case and heat sink.
I had to build the amplifier PCB myself back when RS sold etching kits.
Even a ON/OFF rocker switch and stereo in jacks.
The thing is a work of art,too bad it is DOA.
I would attach a photo of this but not sure how on this forum.
Jim

34
Equipment / Re: Panaxis FME 500 issue
« on: August 14, 2018, 1843 UTC »
Well,new caps came today and replaced all tantalum and electrolytic.
Already replaced the main RF transistors and variable capacitors.
Replaced the 4 mhz xtal.
Tried both PLL IC chips.
Re-soldered ALL joints fresh.
Used a new power supply.
Checked all dip switches and they seem to get frequencies in ballpark range since the PLL is not locking.
Tempted to replace all ceramic disc caps but feel that is not going to do much.
Now thinking about the other IC chips but easier to replace them all than try and test each one...not to mention,how do I test them?
Replacing diodes and resistors also seem not worth the effort as I can not believe they are bad.
When I first built this thing,never remember having such a hard time getting the PLL to lock,it was pretty straight forward.
I wonder if I replaced with wrong type of 4 mhz xtal now but just seems so unlikely.
I have not replaced the voltage regulator but will do that now since I have one.
Jim


35
Equipment / Re: Panaxis FME 500 issue
« on: August 10, 2018, 1349 UTC »
Thank you all for the tips.
I had cleaned the entire PCB with alcohol and tooth brush.
Re-soldered ALL components fresh using no clean flux.
Removed all IC`s as they are all in sockets,re-seated them also thinking maybe poor connection.
Tried a replacement PLL IC.
Replaced both RF transistors,trimmer caps and some electrolytics so far.
Soon as the other new supplies arrive will replace those too.
I am not modulating it yet,just testing the unit on a 50 ohm dummy load for now
My power supply sucks and think that could be one issue.I have another PS and will try it again once the new components arrive.
I think I have a good shot to getting this working once everything is freshened up a bit.
Power supply could be the issue and was also thinking that.It is very old and probably dirty voltages.
To me,the entire system was a work of art and building it was a great challenge.
Will post new info sometime next week.
Jim

36
Equipment / Re: Panaxis FME 500 issue
« on: August 09, 2018, 0025 UTC »
Still thinking the caps may have changed over time.
Only thing that could be different from just sitting around.
I do not think IC chips fail just sitting in a box.
Have to rebuild the common components and see how it goes.
Jim

37
Equipment / Panaxis FME 500 issue
« on: August 08, 2018, 1618 UTC »
Going to take a shot in the dark and hope someone is familiar with the older Panaxis FME 500 exciter.
Mine was build years ago and worked perfectly.I had put it away working about 20 yrs ago and recently took it out to play around.
It powers up,but PLL does not lock.Searched around for a replacement PLL to see if that was bad,actually found one but was not easy.
Swapping that out did nothing new.
Finally went through all solder joints,swapped out the 470uf electro and both 10uf`s...a slight better improvement but still no lock.
Swapped out the 2 main RF transistors and all 3 trimmer caps and even re-wound a new coil and tap.
Although it appears to tune better and wants to lock,still drifting all over.Green LED lights on/off/on/off ...etc.
Depends how close my hand is to circuit or what I touch.
Sometimes it acts like it will lock,but never stays that way.
I just ordered new 47uh cap and all tantalum`s to see if they deteriorated over time.
After that...not sure what else to do and hope someone has an idea I am missing.
Jim

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