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Wendymott 18th Jul 2021 5:47 pm

Yaesu FT290
Hi peeps. I acquired a Yaesu FT290 recently, and have done a few changes both on Rx and Tx stages.
However, I would like to add a speech processor / compressor in the Mike casing. I have plenty of SMD SSM2165 vogad devices, and I would prefer an electret mike module.
The problem is the Mike connector is a 7pin plug / socket.I need + V for the vogad / mike supply. I really do not want to change the socket to an 8 pin, have you seen it ?? Has any of our members done such a mod and how did they go about it ?
I could disable one of the push switches as in + /- channel change or the FST button, and it may come to that unless someone has a better idea.
Thanks in anticipation :D

G6Tanuki 18th Jul 2021 6:10 pm

Re: Yaesu FT290
Not sure about your particular circuit but in times-past I built a 1750Hz repeater-toneburst into a Pye "shaver"-style mic casing, using a CMOS chip for the crystal-osc/divider and powering it from a tiny wire-ended NiCd battery of the type intended for memory-backup.

Cunning trick: the battery was charged through a 1N4148-and-5K-resistor combination across the PTT switch; when the PTT was open there was 12V across it and 'stealing' a couple of milliamps to charge the battery was insufficient to cause any issues.

These days I'd use a 'supercapacitor' rather than a battery - either way it should be able to provide a few mA for your processor - just so long as your transmit:receive duty-cycle is sensible and gives the charge-storage-device enough time to refresh itself between 'overs'.

Restoration73 18th Jul 2021 8:40 pm

Re: Yaesu FT290
You might be able to isolate the pin which is normally connected to chassis and rely on the
chassis and the metal mic plug body as the signal ground.

Sparky67 18th Jul 2021 9:04 pm

Re: Yaesu FT290
Could you DC-block the mic wire with a cap behind the fixed connector in the radio and then feed +Ve volts up it to the mod in the mic itself? You might want to current-limit the voltage source to prevent any nasty happenings if a s/c occurs in the mic...!


SiriusHardware 18th Jul 2021 11:58 pm

Re: Yaesu FT290
There is a precedent for this in the form of the old K40 speech processor / compressor microphone which was originally designed for for the USA CB market, ie, for AM and SSB.

Since few CB transceivers had + supply available on the mike socket the solution was as outlined in some of the suggestions above - a small amount of power was drawn from the PTT rail during RX mode to charge a capacitor which provided the compressor IC with a power supply during TX.

I actually often considered connecting an original K40 microphone (which I still have) to my FT290R2, but for some reason never did get around to trying it.

One reason may have been that K40s sounded very harsh on FM which they were never designed for, so it would have made it necessary to carry the original microphone around as well, for FM operation.

Terry_VK5TM 19th Jul 2021 2:38 am

Re: Yaesu FT290
Wendy, if you replace C01 with a non electrolytic 1uF cap, you should be able to drop a current limited 12v on to the mic line without any problem :)

Wendymott 19th Jul 2021 2:56 pm

Re: Yaesu FT290
Well peeps.. you certainly came up trumps with several ideas...its too warm in the workshop at the moment to concentrate.. but I shall certainly be looking into the suggestions :D Thanks all :D

Jon_G4MDC 19th Jul 2021 3:00 pm

Re: Yaesu FT290
The best type of speech processor is generally reckoned to be an RF clipper.
This might be considered. I have built a couple but not put them to use yet so can't comment on how good they are.

Wendymott 20th Jul 2021 12:28 pm

Re: Yaesu FT290
Hi John. Very interesting !!.... another avenue to explore... Thanks :D

Wendymott 21st Jul 2021 8:04 pm

Re: Yaesu FT290
2 Attachment(s)
After a lot of poking and prodding... it seem there were two "spare" wires in the Mike lead. Thus I dont have to "Piggy back" the DC on the AF wire.
Apparently the FST button is there but has no function.... its not even mentioned in the I /B .
I am not going the RF compression route with this one..... however I will seriously look at it for my 2M SSB base station.
I attach the circuit I am going to use...the pcb fits into the old mike area.
The HARD part will be gaining access to the back of the Mike Connector, but a "faint heart never won a fair maiden" .

Wendymott 30th Jul 2021 9:15 pm

Re: Yaesu FT290
Hi Peeps...... HELP !!! Please
My first FT290 is now in a good place... as in.. it works well in both modes. However, there was one on Ebay which was a "reserve".. just in case my primary radio needed parts. It was bought as.. "Spares or repair". Well, as I had success with my first I decided that "repair" was a possibility.
The controls function and the display is in good condition. The 10.81 Mhz I.F strip on RX is comparable with Set one. What appears to be wrong is the VFO is operating at approx - 6 Mhz below carrier than -10.81 Mhz. And there is no frequency shift with the set frequency control.
I looked at the alignment procedure for the VFO and there is no change in the L/O frequency when adjusting the 18.74 Mhz oscillator as per the manual. Set one confirms a fault. I compared all the voltages on the connectors of both modules (front panel) and all seem ok.
Obviously the PLL is sick.... has anyone out there had any experience with the uPD2819 PLL going faulty.
Over to you :D :D

Terry_VK5TM 31st Jul 2021 1:17 am

Re: Yaesu FT290
UP2819 - is pin 7 high or putting out a pulse train (high = pll locked other = unlocked)

And is the 5.76MHz xtal working (pins 2 & 3).

And the obvious one (measured on the actual IC pins) - +5V (Pin 1) and GND (Pin 13)?

Is it receiving data from the MCU ? Pin16 = CLOCK, Pin 17 = DATA & Pin 18 = LATCH <- should be a positive pulse at the end of the word transfer.

Edit: There are also a lot of very low value electrolytic caps around the PLL ic and tuning voltage buffer that I would be suspicious of as well.

Radio Wrangler 31st Jul 2021 6:56 am

Re: Yaesu FT290
I have a funny feeling there is a scrap FT290 damaged by nicad leakage sitting around somewhere. It's been there for about 20 years with the intent of finding another for spares, which never happened. I'll see if I can dig it out.

I think the digital controller side of it got 12v or so in lots of wrong places via the conductive electrolyte shorting things.


Wendymott 31st Jul 2021 11:17 am

Re: Yaesu FT290
Hi David and Terry..... Terry... All points covered.....I have used the good one for comparisons and it all seems to check out. EXCEPT Pin 7..... will check that :D.

David.. can I PM you re some sort of acquisition :D

Wendymott 31st Jul 2021 1:15 pm

Re: Yaesu FT290
Well the good news is... The controller pcb module is fine :D Pin 7 of the loop IC is hunting.. as in pulsed...the VFO tunes to RF in - 10.81 I may look on ebay for a loop IC. Even though offers of a scrap FT290 is imminent .
The HARD part will be removing the Base plate screen ..BIG Iron needed.

Terry_VK5TM 31st Jul 2021 1:57 pm

Re: Yaesu FT290
Don't jump too fast - what do you get on pin 14?

Should be the product (I think) of 18.7414MHz (X02 & Q3009) and what ever Q3001, 002 & 003 is producing.

Edit: You should get a frequency between 2 & 5.99MHz at pin 14 as you tune across the band.

Wendymott 31st Jul 2021 2:36 pm

Re: Yaesu FT290
2 Attachment(s)
Hi Terry.
On the DUFF "Radio B" one.. I get two frequency carriers... one on say 134.23 and the other on 131.18... neither move when tuning is rotated.... on the Good one Radio "A" ..I get a lot of Hash / carriers... But they shift with the tuning pot.
See attached photo's

Terry_VK5TM 1st Aug 2021 12:26 am

Re: Yaesu FT290
1 Attachment(s)
Can you reach pin 10 of connector J02 on the CPU board?

Is the voltage varying somewhere between 0 & 5V when you tune?

The 131.19 frequency should vary as you tune - this does not come from the PLL chip but from the CPU.

Attached pdf is block diagram with the PLL and frequencies you are seeing lower left - sounds like Q3004 is not mixing.

You'll need to zoom to about 400% to see it clearly.

Radio Wrangler 3rd Aug 2021 11:34 am

Re: Yaesu FT290
Scrap FT290 found!


Wendymott 3rd Aug 2021 12:06 pm

Re: Yaesu FT290
EXCELLENT David :D Please pm me to arrange where and when :D

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