Hardware Hackin' the oldies

[N4VGB]

Search around for info on the TS-440S and modding it for AM.

Properly adjusted, the TS-440S is a pretty good AM rig right out of the box.

If (and this is a BIG "IF") the rig's ALC set point is dialed back and the stock Murata 455KHz AM filter replaced with the one used in an R-2000.

I have a '440S in my lineup. I know what a completely 'stock' one sounds like on the air (and looks like on a 'scope) and I'm not overly eager to operate the rig in AM TX as it was delivered from Kenwood.

Being an old time broadcast engineer, my old friend had quite the professioanl test gear setup. His 440 was very clean on a two tone test with a spectrum analyzer and produced perfectly shaped trapezoid patterns on his scope, sounded great on the air. He used an Amp Supply LK800C linear with 3 Eimac 3CX800A7 tubes, plenty of reserve power, so very little distortion added.

[AF6LJ]

Good sounding AM is a pleasure to listen to.

[N4VGB]

Good sounding AM is a pleasure to listen to.

On a quiet band with a single conversion receiver having no filters, it's amazing.

[AF6LJ]

Good sounding AM is a pleasure to listen to.

On a quiet band with a single conversion receiver having no filters, it's amazing.

That really makes me want to find an elegant way do make the 820 receive AM. It's the only single conversion receiver I currently own.
.....
Come to think of it I have an idea or two...

[N8YX]

That really makes me want to find an elegant way do make the 820 receive AM. It's the only single conversion receiver I currently own.
.....
Come to think of it I have an idea or two...

Hint:

Find an R-820 and set them up for transceive... ;)

[AF6LJ]

That really makes me want to find an elegant way do make the 820 receive AM. It's the only single conversion receiver I currently own.
.....
Come to think of it I have an idea or two...

Hint:

Find an R-820 and set them up for transceive... ;)

That would probibly be a better approach.
What I would like to do is get away from the whole PLL business
I'd love to have a R-599, yah I know so would just about everyone else who has ever used one.

[N8YX]

A bit of follow-up on two particular FT-901 Eham reviews:

Not a bad radio....the receive could be a little more sensitive, it does drift an unusual amount for a radio like that, and it does not have general coverage receive...it's okay.

Worst radio I have ever seen....terrible, drifty, all over the place, overdriven audio.....terrible.

Pass me some of whatever it is this guy was smoking when that verbiage was posted.

I have had one of mine sitting on 14.300.0 for the past two weeks (under VFO control, yet) and in that entire time it has not drifted at all. Zip, zero...you get the idea.

Additionally, it'll easily hear a 0.1uV signal out of the generator in SSB/CW modes, even on 10M.

Methinks these WonderHams need to quit evaluating hacked-up, CB-fied examples of a piece of gear...especially if they lack the skills or knowledge to discern a correctly functioning model from one that isn't.

[N8YX]

FT-901 #2 finished.

In addition to the 'factory' bands, it now covers 30 and 12M. I reconfigured the WWV spot for 10MHz and added 24MHz to the "AUX" spot.

The easiest way to mod one of these rigs is to find a junker FT-90x and lift any required parts from it. In the case of a '902, one can directly salvage and substitute the crystal oscillator components, including those for the "missing" (unmarked) AUX band position. One can also use parts from a junked FT-901, but you'll have to order the required crystals.

The short "how to" list:

1) Remove XTAL and VCO assemblies from radio
2) Add and/or replace components at the WWV and "AUX" spots in each assembly. Pay close attention to the type of slug-tuned inductors, padder capacitors and bias resistors used for each band segment. You can work from a '902 schematic if unsure of which parts to use, or consult the WARC-conversion articles which can be found 'round the Internet.
3) Replace XTAL, VCO assemblies
4) Remove counter assembly from radio. Depending on which band(s) you're adding, you'll need to do a little hardware reprogramming of the counter's display programming matrix. Again, there are several articles available which explain the ins and outs. There is also a "secret" display programming line; an in-depth description of counter programming is found elsewhere in this writeup.
5) After counter has been tested, install it in rig.
6) Align new XTAL/VCO tuned inductors per Yaesu's service manual. Ensure that the PLL locks all the way across each new band's tuning range.
7) Invert radio and remove two shielding plates from the PA and Trimmer A/B/C areas.
8 ) Rewire band switch segments S1E, S1G and S1I to enable receive and transmit preselector peaking. This involves running jumpers from the "WWV" and "AUX" switch contacts to the 10, 15 or 20M contacts...depending on what combination you've elected to add. There is a gray wire which runs from one side of L09 (a chassis-mount, slug-tuned inductor) to the WWV position of S1I. This should be removed when you jumper the WWV contact to the 20M contact on the same wafer.
9) S1R is the PA screen-grid voltage selector switch. Jumper the "WWV" and "AUX" positions to the rest of the contacts if you want to transmit on both spots; omit one or the other if you don't. More on this in a bit.
10) S1O is the PA tank coil switching deck. You'll need to add wires from the unused WWV/AUX contacts to the PA tank coil (a toroid) or jumper them to the nearest band segment. This is dependent on the new bands to be added.
11) Remove upper PA shield and tubes. Remove PA input circuit board and locate C01, a 100pF, 1KV rectangular mica capacitor. Remove it and replace with a 100pF, 1KV (or better) silver-mica unit. The OEM part has been known to fail shorted and will allow screen voltage to get into the rest of the radio...
12) Replace all items removed in Step 11.
13) Align the rig per Yaesu's service manual. Watch yer a$$....there's high voltage on the trimmer boards.
14) Replace all covers.

Correspondence with Jean, ON4AEF led me to a modification article he authored...and which contains the following:

"The WWV position is wired for receive only and the cached AUX( 11 M) band position is standardly full wired for TRX."

"Due the fact the AUX(11 M) bandswitch position is originally fully wired for transmit and receive, we do nothing here."

That's true of a Euro-spec '901 but not one bound for the States. I recently got hold of a counter assembly from a European FT-901 and the "Aux" position was wired by the factory to indicate 27.xxx.x MHz! :shock:

Connecting Pin 2 of Q2910 to the "Aux" band switch counter input pin enables the readout; it's the only "vacant" pin on a U.S.-spec '901. Evidently, Yaesu "built" this logic into the counter programming matrix on purpose. You'll need to change this line's programming if you wish to use it for 12 or 17M. A couple of 1N4148 diodes to pins on Q2910 will do it. Tack the anodes to pins 1 and 6 for 17M; 5 and 14 for 12M. The cathodes are twisted together and soldered beforehand; their junction is tied to the counter's "Aux" input pin via a length of wire. Use heat-shrink tubing over the pin connection and over the diode junction.

30M programming is a bit more complicated. Jean's article provides a good explanation of what's needed.

By omitting the screen voltage connection on Wafer S1R for the 'Aux' spot, one can set this range up just to receive. This is similar in concept to what Yaesu did with the early FT-101 series with their marked "11M" band switch position.

All of the above is a moot point on the '902. IIRC, there's no easy way to "reprogram" its ASIC-based counter for frequency ranges other than those programmed in at assembly time. And since the rig already covers the WARC bands...