UK Vintage Radio Repair and Restoration Discussion Forum

UK Vintage Radio Repair and Restoration Discussion Forum (
-   Vintage Amateur and Military Radio (
-   -   Yaesu FT290 (

Bazz4CQJ 16th Sep 2021 11:57 pm

Re: Yaesu FT290
I once spent quite some time colouring in various lines on the schematic of a receiver. So the power lines, the AGC and one or two other things, and very pleased with myself, I then went off to scan it. Shock-horror - the scanner did not detect the ink in the pens which I had used. I've never heard of such a thing before but those pens did not scan :(.


Terry_VK5TM 22nd Sep 2021 5:22 am

Re: Yaesu FT290
1 Attachment(s)
About 80% done - only the pdf version today.

Errors? - more than likely, so if you find any, please let me know.

I will adjust/finish the various power rail colourings once I have completed the drawing - the yellow one needs toning down a bit.

Bazz4CQJ 22nd Sep 2021 11:09 am

Re: Yaesu FT290
Looks very good. The yellow is fine on the monitor, may be harder to see if printed on white paper?


Terry_VK5TM 22nd Sep 2021 11:17 am

Re: Yaesu FT290
That's what I'm thinking - to the point I might do a PDF with 2 pages, one coloured power lines and the other black as per the original.

Terry_VK5TM 24th Sep 2021 5:38 am

Re: Yaesu FT290
1 Attachment(s)
Finished - and note this is for the FT290R only.

The PDF has 2 pages, one with coloured power lines (major lines only and I did tone down the yellow line a bit) and the other is B/W .

Obvious disclaimer that it may not be 100% correct, so please let me know if you find any errors.

There are a couple of places, where it was very hard to read the other PDF's I have here, with question marks against them, so still to be sorted at some stage.

mickm3for 24th Sep 2021 10:17 am

Re: Yaesu FT290
Hi thank you for putting in all the work to redraw the circuit will make repairs to this rig a lot easier thanking you Mick

G0HZU_JMR 24th Sep 2021 3:57 pm

Re: Yaesu FT290
1 Attachment(s)
Looking good!
I had a quick skim over the new PDF and spotted a few things. I've not compared against the original but here's a list and an image below showing some of the things I spotted.

C7 looks to be missing its ground.

There is a 'C31' and a 'C31?'
I think 'C31?' is C51.

Cap ref des and value missing on pin 14 of the uPD2819. Is this C29 ?

Transformer T01 looks to have gone slightly out of alignment with the net wiring.

C92 C97 text 0.001 needs a slight nudge to prevent a slight foul. This is by the PA driver transistor.

C55 has no value. It seems to be the same on the original so I guess the value is unknown.

Some of the electrolytic caps have a + and some don't.

PL01 logo missing from the bulb.

S01 logo missing from switch near the micro.

F.B. logo missing from Q2022 base.

BATT logo missing from reg unit battery.

LO2 logo missing on tele antenna toroid.

Is it possible to have a text search function? eg to search for C31 for example? I'd only add this feature if it was easy to do though.

It looks like a huge improvement and best realised when trying to go back to the old scanned originals. They look really fuzzy in comparison.

Bazz4CQJ 24th Sep 2021 8:30 pm

Re: Yaesu FT290
Good work Terry!


Terry_VK5TM 24th Sep 2021 10:16 pm

Re: Yaesu FT290
Thanks Jeremy.

I'll go through and tidy that all up.

I knew there were some '+'s' missing from the caps and plain forgot to add them before posting it.

Will check to see if I can add the text search without it messing up the resolution.

Terry_VK5TM 24th Sep 2021 11:28 pm

Re: Yaesu FT290
I have been through and fixed up as per Jeremy's list but will hold off posting the revised file for the moment - 2 reasons - I suspect there may be more corrections to be found and I have seen a few instances where the drawing can be tidied up somewhat to make some of the long interconnects easier to follow.

In reference to C55 - I went through the parts list and there is no listing for it so I suspect it is internal to the transformer (there are a few without values like that).

Also removed the '+' signs from the caps as they are not in the original.

As to making it text searchable, it can be done, but the automated OCR in my software misses a lot of it, so I will have to do it manually which is going to take a while to do - I will leave this until I'm pretty certain most or all errors have been found.

Denis G4DWC 29th Sep 2021 2:34 pm

Re: Yaesu FT290
First off, thank you so much Terry for reproducing this fine circuit diagram for the FT290.

Now then, many years ago I had a problem with my FT290. As far as I recall, it was tuning the same parts of the band twice although the display indicated correctly. In other words, Tuning 144 to 145 was OK with the display indicating correctly but 145 to 146 on the display was still tuning 144 to 145. I located the problem to one of the two SIL Resistor Networks RB01 and RB02 to the right of Q01. At the time I purchased two of each from a dealer which fixed the problem. As those two Resistor networks don't have their values on the circuit and as I still have the spare ones in one of my component drawers I thought I would measure them which may help others in the future.

Both Networks have a white Dot which I will refer to as Pin 1 and which would normally be the common point of a commoned resistor pack. I measure the following on RB01:-

1-2 149.33k 1-3 248.85k 1-4 450.58k 1-5 49.68k
2-3 298.91k 2-4 501.11k 2-5 99.66k
3-4 600.62k 3-5 199.24k
4-5 400.91k

It looks like Pin 5 is probably supposed to be common which, after taking account of the tolerance would give :-

5-1 50k 5-2 100k 5-3 200k 5-4 400k

I measure the following on RB02

1-2 293.32k 1-3 343.53k 1-4 443.46k 1-5 645.70k 1-6 243.46k
2-3 149.90k 2-4 249.98k 2-5 451.84k 2-6 49.82k
3-4 300.09k 3-5 502.42k 3-6 100.07k
4-5 602.60k 4-6 200.09k
5-6 401.87k

RB01 is shown with a through connection but I don't think that's the case from measurements. I assume that only three of the resistors are used and that the through connection is only shown to save space on the diagram. I'm not keen to open my working unit to verify this.
Anyway there should be enough info above to check these networks.


Wendymott 30th Sep 2021 9:58 am

Re: Yaesu FT290
Thanks Terry VK5TM for the excellent work you have done.. I didnt realise.. when I started the thread that so much would come out of it.
At present I am building a 2M Transceiver using a lot of the Filters / Crystals from one of my scrap 290's, not copying, but utlizeing parts of the circuit.. why re invent the wheel ? The redrawn schematic is so helpful.

Terry_VK5TM 30th Sep 2021 12:09 pm

Re: Yaesu FT290
Thanks Denis - will follow that up.

Cheers Wendy - good luck with the project.

Terry_VK5TM 1st Oct 2021 3:30 am

Re: Yaesu FT290
2 Attachment(s)
Uploaded 2 pdf's - one is B/W power lines and the other is coloured power lines - decided to keep them as seperate files.

They are also higher resolution than the previous ones.

These have all Jeremys corrections in plus a couple others I found.

Also rearranged some of the interconnection lines to hopefully make it a bit easier to follow.

Re Denis' measurements, they sound about right as the resistors are for the ladder network of the D to A output of the processor (it's the tuning voltage), I'm not inclined to take the covers of mine at this stage to confirm - Wendy - if you have the control board out and handy, could you do the measurements?

Ref doing the text recognition - still to come as it has to be done manually and I will only be putting in the component id and the various inter-board and other labels - don't see the need to do the component values.

Wendymott 1st Oct 2021 10:37 am

Re: Yaesu FT290
Hi Terry. I can measure the resistor networks..but to me its pointless, as A..they are very stable, and B, if one did fail,it would be virtually impossible to replicate the section thats failed..buying a "scrapper" would be my solution. Best say its a "Resistor network" and leave it at that.

Terry_VK5TM 1st Oct 2021 10:43 am

Re: Yaesu FT290
Agreed, it is not likely they will go faulty.

Would be nice to know the values though, just for completeness.

As an aside, the same network is used in several different radios of the time and none of those manuals list the values either.

Jon_G4MDC 1st Oct 2021 2:11 pm

Re: Yaesu FT290

Denis G4DWC 1st Oct 2021 5:34 pm

Re: Yaesu FT290
Regarding the Resistor Networks


Originally Posted by Terry_VK5TM (Post 1410880)
it is not likely they will go faulty.

Well mine failed which is the reason I measured the unused units so it might help someone in the future.

I can't say I agree agree with Wendymott that they would be impossible to replicate. If one failed it would be pretty straightforward to make up a tiny PCB with some 0603 or 0402 SMD resistors. This is preschool playgroup stuff.


Terry_VK5TM 1st Oct 2021 11:05 pm

Re: Yaesu FT290
Denis, that's interesting, any idea why they failed?

The networks could probably even be replicated with 1/8w resistors for those that have problems with SMD bits.

All times are GMT. The time now is 12:27 pm.

Powered by vBulletin®
Copyright ©2000 - 2023, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.