My FT818 has been sitting unused for 6 months, power it back on today and the receive is deaf on all bands. That includes FM broadcast all the way down to AM broadcast and all amateur bands in between (no means of checking 70cm as this is my only 70cm radio and no local repeaters to listen to).
Not a single bar of signal on the S meter even on strong local FM broadcast stations, local repeater or local 40m stations which should be S9+. And can’t hear anything that would normally be bellow S9 though I can hear what would normally be S9+ stations.
Same behaviour on front and rear antenna sockets, so not the antenna select relay. Switching to front with antenna connected to rear drops the rx from attenuated to none, as expected (and vice-versa).
TX works fine. Can activate the local 2m repeater and listen to myself on SDRs on 40m as expected. Power out reads normal on external meter. SWR shown as expected for the band / antenna combo.
On rx the ATT and RF gain both attenuate / de-attenuate the signal as expected when tuned into a strong station, so I assume both pre-amp and main rf amplification are functioning to some degree (is that what ‘att’ does in the menus, turns off the pre-amp?)
Other than checking for loose connections, foreign bodies (there are none), I’m not really set up for detailed troubleshooting here - both in terms of gear and eyesight / fine motor control for SMD stuff. Basic gear like DVM, but no scope to look at signal levels with.
I did a couple of times have a similar problem with the radio on 80m when out in the field which I put down to moisture as a few days on a warm windowsill sorted it out. But the fact that this is all bands from MF to 2m must narrow down the possibilities to circuitry common to all bands.
Thought I’d check if this rang any bells with anyone before going further.
Hi Matt,
Have you tried a Factory reset?
Also, I think the Preamp is called something else in “Yaesu-Speak” in the FT8x7 model menus (IPO) and if you have turned off whatever they call it by mistake receive performance is affected.
I recall that a Yaesu model, FT857?, sometimes went deaf due to dirty relay contacts. There was a relay cleaning sequence built into the firmware, which quickly cycled the relays. Maybe there’s a similar feature on the FT81x?
This was my first instinct - dirty or stuck tx/rx path switching relays - especially after a 6 month period of disuse sitting in a caravan on the very humid west coast.
Focus on qrz.com seems to be on D0001 which as far as I can tell switches UHF / VHF+HF receive pathways. Apparently this is a common fail point. I’ll get a diode tester on that as soon as I wake up sufficiently. If there was anyone local on 70cms then I could check the theory, but we’re a UHF-free zone here!
“Yaesu-Speak” in the FT8x7 model menus (IPO)
Thanks for clarifying as I’d missed that one. Enabling / disabling IPO further attenuates the already-attenuated signal (HF) and cannot be selected in the menus (VHF). So I guess the HF pre-amp is working (doing something, at least).
No filters ever installed.
Factor reset performed anyway with no difference - except to wave bye-bye to all those pre-entered repeaters!
See the original post - adjusting RF gain attenuates / de-attenuates the already attenuated signal as expected. So the potentiometer and associated gain adjustment all work. Ditto AF gain. Squelch works as-per normal, when enabled.
Hi Matt,
Ignore me, I’ve just read your write up again, you have no S meter…
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Is there any change if you use earphones/external speaker cf internal speaker? See above…
Pretty certain issue is in the RF rather than AF circuitry as the displayed signal strength is S9 lower than expected. Audio volume is fine for really strong stations (e.g. local VHF broadcast, local 2m repeater).
Not quite the same problem but my FT817 stopped working on 2m and it turned out to be one of the PIN diodes on the relays. It was burned/charred but I missed it when checking and it took a second pair of eyes to find it.
The RF switching diode is very sensitive. I had the diode in my 817 blow when I used a Microset VUR-30 2m/70cm linear amplifier. Needless to say, I sold the amp and have used separate amps ever since without any problems… hmm
On mine, one of the tiny two hole balun transformers in the RX chain appears to have been the source of something corrosive that oozed out and dissolved the vias. This was around the IF cans. What I saw under the microscope were slightly greenish crystals growing out of the vias - most obvious from below.
It turned out to be fixable.
The FM path diverges in the IF, so seeing if FM also has no signal tells you how far along the RX the fault is.
I have tried injecting the rx RF directly to the main board, with no improvement - which eliminates the rear board as the cause.
Looking at the block diagram the questionof whether FM broadcast is affected or not will narrow things down. I get no S readings on FM broadcast - but can hear statoons.
Can someone check if the S meter usually works on FM broadcast for me? It’s handled by a separate fm on a chip and may not be designed to trigger the S meter.
Are you talking the calibration menus reached by pressing obscure button combos on power up? No - I’ve not dared venture in there as I believed I would need to be able to inject accurate reference signals to do anything useful in there.
If you’re talking about the normal menus, can;t see any gain settings in there relevant to RX. Or did I miss something?
Steps taken so far (with a lot of guidance from from KI4NR - for which many thanks):
I’ve checked all the easy to check diodes along the signal path as far as the IF.
I’ve tried injecting antenna-level RF at various points up to the start of the IF to eliminate various blocks of the RX path from contention - resulting signal levels unchanged (taking into account the effect of bypassing the pre-amp)
I’m not really set up to check connectivity between all components - but the above test should eliminate all points along the RF path to the start of the IF anyway.
I really need a signal generator and scope / analyser to do anything more useful. Look at the various documented reference-point levels given a reference input.
But I had enough in the bank for a replacement second-hand radio, or the test gear. And plumped for the former. Short sighted, I know. But test gear will have to wait.
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The thing that really puzzles me is the broadcast band FM signal. Looking at the block diagram that is separated out by the first 2 diodes on the main board, and handled completely separately all the way to AF. Yet I’ve eliminated everything up to that point as responsible. So either the FM broadcast signal is not attenuated - it’s just not showing on the S meter for some reason, or it is attenuated and it makes no sense!
Yes, the calibration menu. I’m not suggesting anything other than taking a look. The first three items set IF gain for different sections of the HF bands, the next three are for 6, 2 and 70cm IF gain, then the next four set metering. There is a Youtube video comparing the readings for an FT817 and an FT818 which may give a ball-park idea of if the settings on your rig are normal. Just a thought, probably no help.
A signal generator and a spectrum analyser makes it easy to track the signal through. It is a pity that nanovna sw does not support offset frequency mode.
Instead of a spectrum analyser, you could use another RX that can work at the IF frequencies, if it has a useable s-meter, probing through a high R or little C. That would let you follow the RF/IF signals through with a probe. (if it’s another rig, take the mic out to prevent the obvious happening)
btw, is it an '818 or an '817? Seems pretty early for an '818 to be dying.
