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Call Sign : 26-CT-3228 Ham M7VIC Posts : 4028 Times Thanked : 253 Join date : 2019-11-10 QTH or Location : Bedford Equipment Used : Various
Subject: Yaesu FT757GX VFO Fri Nov 06, 2020 10:42 am
Sassing, frassing, brassing, *?*?! 🤬
For the second time my VFO optical encoder / tuning dial has packed up. My fault for having a forty year old radio I suppose! (Do love this radio though, plus it was a great gift from a very good friend)
I've stripped and cleaned it again, all working now but have noticed there's a slight wobble on the shaft. Looks like it's aluminium too rather than a decent steel affair so probably worn from years of tuning.
As usual, it's an obsolete part.....
There's other options available to me,
CAT control - It's a very basic CAT, (Yaesu's first I believe), and in Linux not very eloquent.
Desk Mic - The MH-10ES fist mic I have is great and has up/down buttons to change frequency. Laboriously slow though, but the desk mics of the time had a 'fast' option button...flipping expensive too and I don't like desk mics!
CAT accessory - Years ago there use to be the 'QSYer' keypad that plugged into the CAT so you could type in frequencies direct. Again not very eloquent and you can't 'tune' through the bands by ear. Good luck finding one too!
Second hand replacement - Yeah, that'll be forty years old too, probably worn out and people ask silly money for them. There used to be NOS, (new old stock), in Japan I believe but nothing left now.
Replacement dial - That's where I'm coming unstuck, can't find anything even similar to it that will fit
<*Sigh*> I'll have to keep plugging on.
Just a whinge, a chance to post a photo, (after a year on here and being an admin for a while I really should've learned sooner!), and sharing my woes. Apologies for the latter
It's working for now, I'll just keep my fingers crossed that it lasts.
Thank heavens that despite my bear paw hands and failing eyesight the brain's still working enough to strip my radio!
All the best, Victor
Alan Pilot, Alan - Mirror Man and DX-Digger like this post
It is a common fault. Those encoders are totally unobtanium! Think it is the same as the 767GX. Great radios! But a real bugger. I did see one guy that used another type once, not sure how good it was. But CAT control is a good idea if you can get it up n running. Good luck!
You tried the 767GX? Really nice, I had 2. One really good with the 2m/70cm/6m modules, and one bad, with iffy modules and bad encoder. But still performed well. If you see one a good price. jump on it!
Yeah, like the 767 Jeff. They started going for silly money for a while so the old knackered dogs with missing modules started jumping up in price too. Spotted one at a Ham reseller recently, tidy example with all the modules but the old purse strings have tightened with events over the last year.
I like the older radios but not too old, still lust after my mates FT101. Harder to expand than the flick of the switch on the old 757 though.
Can filter out white noise hash with my old 'radio ear' but can't manage it with the modern DSP stuff. They just sound terrible!
Hey Victor, Look what I just found in my box of stuff. Yup, an encoder for your radio. I forgot all about it. I picked it up years ago, as a spare. No idea if it works, just had to have it as they are like rocking horse poo. Want it? If so, pm me your address, I will send it over.
Do you have the original FC-757AT? If so, you lucky man!
I did scout around for them, dealers wanted £200 plus, eBay chancers were asking similar for unknown origin 'dogs'. In the end I landed up building my own Pi-Network manual tuner which serves well.
Like you I love this radio to bits!
Once you learn how to 'drive' her she brings in the goods. I have a Lowe HF225 which was my main SWL set for many years but the old Yaesu hears stuff the Lowe can't which I initially found surprising. The IF shift knob can often be a god send and although people moan about the 'slow' VFO tuning I've always found it advantageous. Doesn't take long to learn the 'band' and '500kHz' button jump to get around quickly and I have the fist mic with the up/down buttons which I often use for fine tuning. The fist mic always gets good audio reports on TX too.
I often see people use these old girls with the RF gain cranked fully clockwise and sometimes with the RF preamp on too - that only rewards you with more noise! I usually have the RF gain at 12 o'clock which is ample gain and reduces receive noise only shifting it slightly clockwise for some weaker stations. If I have a strong station and a weak one on frequency I'll flick the AGC to fast to compensate the differences. I think the only time I've had the RF gain turned up is on the quieter upper end of the HF bands when atmospheric noises are quieter.
I've even used her for digital FT8 transmission too which took some faffing about but she did do rather well at it.
She's definitely a keeper, especially as I've got to know her inside-out with a couple of repairs, (none of them involving a "re-capping" ) I can see her as my main set for many more years to come, she's already done 40 years and bound to do a few more.
Hi Victor yes i have all three FC-757AT and the FP-757HD that drives it all together.I did lose the link cable between the radio and ATU but manage to find one from good old radio world. I really like old radios the sensitivity on the ft-757 is amazing i did a test between that and my IC-7300 and it wasn't that bad for a 40-year-old radio to be honest. The only thing i have to do is sort out the battery which is a pain to unsolder, i think i will leave that alone the only thing i have done with the rig is the Wideband mod which was easy and give the switchs inside a good old clean. Will i every sell her ? no way shes a keeper for sure , ive seen prices of these rigs with all 3 components go up. one thing I was going to ask does yours drive out more than 100W? also, do you have a roger bleep on yours? I watched a video of a qso i had and notice i had a roger bleep enabled. Regards Tony
The battery on those radios are a bit of a faff to change. What I done on my 767 was run 2 wires to the battery terminals to the rear of the case. Then in a neat tidy place I added battery case for nicads. Job done! No more opening up, and de soldering.
kilomike, Victor and Alan - Mirror Man like this post
You are indeed a lucky man then Tony, you've got the whole kit-and-caboodle!
Looks like you've got a nice tidy example too, I have seen some in rather poor states. (But still asking silly prices on the bay!?!)
They don't have a 'roger beep', they're usually fitted by those that use this type of radio for CB or sometimes a beep circuit is contained within a microphone. I've always found a quick word of 'over' or 'back to you' is far less annoying than a beep on SSB.
Yeah, mine drives over 100W into a power meter and dummy load but obviously I don't use her hard sticking to my Foundation licence 10W limit and she'll sit there all day at that without the fan kicking in. Should also mean the PA stage will last forever. The Japanese 757SX version only kicked 10W out to start with but I've never come across one.
Jeff, (53 Prefect), is spot on with the battery issues. Much easier to 'clip' out the old battery and carefully solder on new leads onto the old battery tabs. Similar story with the tuner battery. (She's just like me without the battery, works OK but forgets everything! )
If you haven't come across it, the following link gives some details :-
The full service manuals are available on line for free too should you need them, just have a quick search. There's two PDF versions doing the rounds, one with clear legible text but terrible graphics and another with better graphics if somewhat lighter text. Don't pay some rip-off merchant for a 'download'.
Even if you can't read circuit diagrams etc. the disassembly instructions are a god send. (The amount of units where the screw tabs are broken from forcing them open is unbelievable!)
Anyway Tony, I hope that helps you sort the old girl out.
Glad to see someone else enjoying this particular model of old radio.
Hello Victor i drive mine on 10W all the time when using it but did notice that it gave a bit more via the dummy load, anyway don't want to upset any ham ops near where i live so i keep to my license rules .. 11m is a different story ...
Hello Victor I guess i spoke too soon, i noticed i don't have any audio on FM the FM mode RX is dead, with bad eye sight now i don't fancy repairing this. Do you know anyone who fixes HF sets now days? Or maybe its a easy fix have you come accross this problem..
Is it only bad on FM? Do all the other modes work OK on all the bands? Does FM work on any band?
I've got to admit, I seldom use mine on FM it only being required for 10m unless of course the wide-band switch has been flicked for CB use rather than MARS/WARC.
If all the other bands work in all the other modes and only FM is affected regardless of squelch setting then there may be a problem with the RX/TX switching circuitry. Yaesu unusually used this circuitry as part of the squelch process for the FM detector chip(!)
After that I'm afraid extensive work is required to diagnose/repair the radio. It's usually a sign of a PIN diode gone somewhere on one of the boards and there are a heck of a lot of them!! (I changed all of mine on the LPF board after the 20m relay stuck.) Getting to the bottom of this type of problem can be a nightmare to resolve and eats up a lot of time.
There's not many about who can still repair this type of radio unfortunately or those that can need to charge accordingly. To simply uncase the radio will eat into an hourly charge rate let alone diagnosing from there on after. When I initially researched servicing on my example all the major repairers wouldn't touch it with a bargepole!
We can only blame governments and modern society for the 'cost of living' not the repair guys who need to cover that.
I have no idea of your background or the radio's history apart from what you've posted here. I'd say that if you were an licenced Amateur Radio operator then like me, you'd have no real use for FM modes and carry on happily. If you are using it as a CB radio setup then lack of FM is probably a problem for you. If you possess the required electronic skills then you could pursue the problem yourself and take it as a 'passionate' restoration, (like me ). Otherwise it could cost a small fortune for someone else to repair if they are willing to do it in the first place.
In my own defence of restoration of my radio, I am a retired electronics engineer that worked in R&D as well as the semiconductor industry not as a radio repair engineer. But just like a car mechanic can utilise their skills to fix a petrol lawnmower or motorcycle I can utilise my skill set accordingly in repair of my own electronic items. This however has usually required me to beg and borrow appropriate test equipment so I do not have a permanent setup to offer repairs for anyone else.
Not that I'd really want to anyway, I once worked in the 'service' sector and 'customers' can be flipping horrible!
Well, that's not much help is it?
I do remember someone 'resourcefully engineering', (what others refer to as a bodge), a similar FM problem by tying off the appropriate squelch line on the FM detector with a resistor. If I come across it or figure it out I'll let you know in case it helps. (Would probably help an old radio if the RX line is 'floating' but not if there is a problem elsewhere.)
Thanks Victor, it looks like two diodes need replacing
https://qrpblog.com/2017/11/yaesu-ft-757gx-fixing-some-common-faults/ I'm going to leave it as it is, I open the radio up last night and everything in there is too tight to work with. I found another post relating to this radio so, someone might find this useful. everything else works ok touch wood thanks for the reply.
If we were mates and lived around the corner from each other I'd happily have hobbled over on my crutches to have helped out.
The QRPblog link you've provided does look like decent knowledge with sound engineering. It's when you get the stab-in-the-dark resolutions that surround cutting all the diodes and 're-capping' that you have to avoid.
It is tight in the old 757 but I'm sure that if even myself with with my bear paw hands and failing eyesight can do it then anyone can.
Enjoy your wonderful FT757 setup Tony. It's great that there are people out there that enjoy these old radios.
.....even if the FM doesn't work.
I've enjoyed the chat about it and given you a 'thanks' vote accordingly. Be great if I catch you on air one of these days.
Hope you get this update on this posting. I'll send you a PM too but post here in case it's of help to anyone else also.
Further to your FM mode query on the FT757GX I had a bit of a play around. As I said I don't usually use FM modes but did summer 2020 with a bit of DX to some German lads on Euro CB frequencies. Of course as it was a bit of summer skip I was running some power.
The thing I've noticed since due to your enquiry, (again down to the weird FM setup in this radio), is if you have the 'DRIVE' control turned down anti-clockwise the FM detector stops working! From the looks of the circuit diagram it seems like this is the same for all of them, not a fault on mine. That might explain why users of this radio for FM CB tend to blow the finals or burn out the Low Pass Filter choke - they're burning 100W FM!!!!
Now, I did the mod mentioned in the PA0FRI link I gave above clipping R179 so that the 'DRIVE' control also works on SSB modes. This up to now has done me fine.
This however also gives full output power control in the FM modes but again as you turn anti-clockwise to turn the power down the reception still fails due to the FM detector weird circuitry......
The work around for this seems to be in the external ALC circuitry.....
Radios such as the old Kenwood TS-520S had issues running low power and the typical 'fix' was to hook up a 9 volt battery with a potentiometer control to give a negative, (reverse), voltage to the ALC and hence control power output. The perfect fix for QRP operators.
After a quick play around I found the same circuit works on the Yaesu!
I also had a dig around and found a 'control box' that someone published details to but using a power supply to get around the battery issue. (Although the battery should last a long time.) Link below :-
It works and very well too for all the other transmission modes. As this has sparked my interest I may be playing with this myself further and will post details as I progress.
Anyway mate, hope that helps you out. (Much easier soldering a battery, pot and phono lead up than digging inside the radio!)
Check out the 'DRIVE' on your radio by turning it fully clockwise in FM mode and see if your FM reception comes back. If it does, have a go at the ALC circuit for power control.
Feel free to share this out, it's not exactly like it's my original idea, just a discovery after your enquiry that does come in handy. Hopefully it'll help other people keep these old girls in working and useable condition.
Hello Victor thanks for the update regarding the FM work around, no its still the same here
for me sadly. As long as I have the other modes working it isn't a worry yet, i don't really use FM on the rig but was wondering why it stopped working all of a sudden. I guess that's what happens having a 40 year old rig. Any way much appreciated for the effect you digging around i hope this helps out others. Regards Tony
The optical encoder used in the entire FT series of that era, was an OEM specific ALPS brand product.
Sadly, it was the weakest link in the whole kaboodle - doubt you could source a spare even from Yaesu (the only source back in the day, and unlikely but possible NOS if you're luck today).
First indication the encoder is acting up is when it skips or you have to cycle back n forth to get it to change freq (usually due to the shoddy bearings wearing out), if it only register one direction or not at all, it can be a logic fault or a encoder LED acting up - the photosensors seem to last).
If you are careful and i mean careful, if you can dismantle and diagnose a duff encoder LED and can find a suitable sized replacement, they are repairable. If bearings are shot, harder but doable as ALPS used a limited range of sized shafts and subsequently bearing races - so potentially if you can extract the bearing race from a same size but incompatible ALPS item that hasn't got shot bearings, it's fixable.
Can't suggest examples of bearings/shaft donors as it was over twenty years back i had to sort out the prob on a 747GX i had as a receiver (preceeding my RAE pass). Ironically, the set i was given had literally the whole kaboodle of option modules, filters etc and the then hyper expensive and practically spares for radio lifetime, bar the encoder which reliably died a week later.
Still have a fondness for it, went over to CAT control after refurbing the encoder at least twice in as many years. There was a mod board you could patch onto the existing module PCB that once you programmed the MCU on it, it would do alien encoder translation, but back in the day the cost of a dev kit & programmer was as much as a cheap VHF mobile, so i never explored that avenue.
I did some time back now strip apart the whole encoder assembly somewhat tentatively not knowing what to expect. When the black 'dust' fell out I had a feeling it would be quite horrific. The spindle/shaft was indeed worn out along with a plastic shim/washer which all mixed together with what must have once upon a time have been the lubricant.
A replacement spindle was found with funnily enough another ALPS encoder which although slightly shorter did the job nicely. Replacement shims were made up along with a thoroughly good clean of the whole assembly which was quite the mess.
The whole thing works wonderfully smoothly and has been is use for a fair while now as my main HF radio.
I've since found out that a previous owner did have the radio languishing in their van where I can only assume the rise and fall in temperatures assisted in it's demise.
There were quite the number of modifications/add-ons for it back in the day from what I've seen in old magazines such as the MCU board you mention along with a CAT control frequency keyboard. All interesting stuff lost in the mists of time but I suppose a self build option is possible.
In the mean time this old radio is working wonderfully now bagging me worldwide contacts and I have truly fell in love with the old girl. Turned down to 10 Watts she hardly breaks a sweat and the so called VFO 'drift' problems is nowhere near more than a few Hertz at warm up now that she languishes nicely in a nice warm house where my shack resides.
Hopefully she holds out before my demise but if not I'll happily put some care into her whilst my now bat-eyes and bear-paw hands still work!