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Author Topic: Panaxis FME 500 issue  (Read 2027 times)

Offline N2NXZ

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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

Offline Pigmeat

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Re: Panaxis FME 500 issue
« Reply #1 on: August 08, 2018, 2320 UTC »
There were enough of those things floating around in those days. I'm sure someone here will have an answer for you.

Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #2 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

Offline ThaDood

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Re: Panaxis FME 500 issue
« Reply #3 on: August 09, 2018, 0251 UTC »
Does yours come with the IC sockets? If so, try prying up the IC's out, then reseat them back in. That's worked on Ramsey FM-25 FM TX's as well. Also, be sure that you have very clean P.S. powering it at +12VDC. Another thing is to check the AUDIO IN. Is it for standard AF, or optioned for wide MPX audio from the FMX unit? I've seen where you have to have an RFC in series with that. Couple of things to check. Hope ya get 'er going, and I like seeing Ernie's gear still rockin' after all these years.
From DC to light, I take a huge spectrum bite!

Offline TheRelayStation

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Re: Panaxis FME 500 issue
« Reply #4 on: August 09, 2018, 1607 UTC »
something i do in cases like this is use a can of "duster" upside down as "freeze spray" and a hair dryer as heat, both applied in small areas around the PCB and the components to narrow down the area of defect.
also, using the bristles of a tooth brush to "brush" and locate a component that may have become loose and the plastic end of the tooth brush to tap around the circuits/PCB looking for cold solder joints and loose components or connections.
this type of troubleshooting is performed with the unit on while watching to see if there are any changes in operation.
depending on where it was stored, if there was high fluctuations in temperature and humidity, there will be expanding/contraction of components/solder joints as well as electrolytics that may have "dried out" and adjustments fixed with wax that may have moved out of place.
im not sure if this unit used any of the component glue to stabilize the components to the PCB but lots of older electronics were severely plagued by this yellow glue becoming conductive when it dried out and turned a dark yellow or brown color.
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Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #5 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

Offline Pigmeat

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Re: Panaxis FME 500 issue
« Reply #6 on: August 11, 2018, 0206 UTC »
Glad to hear the old horse still has some life left.

Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #7 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


Offline TheRelayStation

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Re: Panaxis FME 500 issue
« Reply #8 on: August 14, 2018, 1851 UTC »
is there an adjustment "can" for the PLL ?
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Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #9 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

Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #10 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 -








Offline TheRelayStation

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Re: Panaxis FME 500 issue
« Reply #11 on: August 14, 2018, 2107 UTC »
that is a very nice, clean and professional looking build - i wish i could get my hands on it, i would fix it for you.
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Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #12 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 -





Offline ThaDood

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Re: Panaxis FME 500 issue?
« Reply #13 on: August 15, 2018, 2016 UTC »
This might sound dumb, and simplistic, but have to tried rocking each DIP switch ON / OFF. I've seen them get flaky for contacting with time. And, try grounding the master crystal case, with clip leads, to chassis GND. Just some more passing thoughts. I don't think that I've missed that you may have tried that, but....
From DC to light, I take a huge spectrum bite!

Offline N2NXZ

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Re: Panaxis FME 500 issue
« Reply #14 on: August 16, 2018, 1445 UTC »
Great suggestion and have fiddled with the dip switches in all ways possible.I was tempted to solder the frequency of choice as fixed to eliminate dip switch issue.
I may try that but have to remove the DIP completely.I hate messing too much with things as I do not want to ruin the traces and pads.
We all know what happens when we goof around too much.
I`ll try solder wick and take it off.
I even thought maybe when I resoldered everything,some solder bridged under a component...so need to really keep looking it all over.
I had to walk away from it or everything starts to look the same after awhile :)