The TS-530/830 mod and upgrade thread

[N8YX]

Using the "+0.5" switch with the Aux Band

Do not adjust your monitor (or your TV). What you're seeing is real (though it wasn't real fun going cross eyed studying the '830 Service Manual for several hours on end).

This is a proof-of-concept shot of the Aux Band-expanded TS-530SP - the guinea pig for the mod series I've documented - receiving my signal generator on the indicated frequency. It's 500KHz up from the "base" allocation we added on Page 2. I'll follow with a several shots out of the manual describing how this works, what needs to be added to the Counter Unit to get the indicated range...then lastly, how to use the +500KHz panel switch to select the additional range as is done with 28 and 29MHz. What we'll end up with is complete coverage from 27-30MHz - useful for the oddball transverter IF. As stated before, don't jeopardize your license by using non-certificated gear on a band which requires it. Listening is fine. Keeping the Heater switch off keeps one honest.

20240405_094213.jpg

[N8YX]

In Post 16 of the thread I touched on programming the Counter Unit (which also controls the PLL Unit). As mentioned before, this is done by a diode matrix - both as-delivered from Kenwood and by the end user who wishes to add an extra band. Snipped from the Service Manual is a pic of the Counter Unit schematic with the matrix and preload areas.



StockCounter.jpg



Q5 is the counter chip. It's programmed in BCD and the various diodes plus Q8 and Q9 serve to put frequency-start information on its preload inputs. Q14 is the PLL Preload output and serves to place BCD information on the PLL control bus.

All of the values are determined by that diode matrix and a bit of theory behind the circuit is contained in the Service Manual. Note that the same Counter and PLL Units are used across the 530/830 series so this information applies universally.

Post 16 covered adding the required diodes for our test range. Next, we'll dive deeper into "why".

[N8YX]

First, the Counter Programming table. Not all possible ranges are described in it, but enough for the user to understand how the counter operates.

CounterPreload.jpg

The astute reader will notice that each indicated segment is 500KHz lower than the start of the band edge it represents. This is due to the VFO frequency being summed with the counter preload values. For a given range to indicate properly, the preload value must be set correctly (via diodes D105-D110). These set the 20/10MHz digits, the MHz digits and the 500KHz starting point (for bands starting with a ".000" MHz value).

Look at the D-C-B-A values, starting at 29.5 and progressing downwards. Notice how they increment by 1. Also notice a couple possible values below 28.

[N8YX]

Next, the PLL Preload information.

PLLPreload.jpg

As in the post above, look at the D-C-B-A values...and spot a couple of curious possibilities below 28.

[N8YX]

Doing a little binary math, we come up with the following permutations and the ranges they enable:

D C B A	Counter Start	Covered Range
1 1 0 1	27.0	27.5 - 28.0
1 1 0 0	26.5	27.0 - 27.5

Either one is easy to implement by itself. Post 16 covered the addition of D102, D106, D108 and D109 to the Counter Unit to successfully obtain 27.0-27.5. A project earlier in the week was re-analysis of the circuit logic and determining what else would be required to get the unit to shift the Aux band up 500KHz, thus covering 27.5-28.0. Turns out that the addition of two diodes is it. These are D101 and D107, arrowed in the pic shown here:

CounterPCB2.jpg

[N8YX]

So what if we want both ranges, like we get with 28 and 29MHz via the "+0.5" push button switch? Turns out real life ain't so simple.

Have a look at the Counter and PLL interconnects, from the main schematic. Examine S7 at the bottom of the picture. Note the "28" and "29" lines.

Counter-PLL.jpg

[N8YX]

And the related Band Switch area:


BandSwitchUnmodded.jpg


The 28 and 29 lines are energized with +9v when the Band selector is on either of those bands. What happens on the Counter Unit is that the switch (an Alps DPDT latching type) is used to send control voltages to two distinct diode groups per band. One for the standard allocation and the next, 500KHz higher. Refer to the Counter schematic (earlier on page) for details of the control logic used for the 28-28.5-29-29.5 bands.

[N8YX]

Using the front-panel switch

What's sorely needed is a third switch pole, to handle the Aux Band control switching independently of the other two. I literally spent hours online last night trying to find one (or a 4PDT version) of that OEM Kenwood part. But there isn't any such animal. Next thoughts were to use a 4PDT relay to switch the control lines independently. That would entail a lot of extra wiring and the potential of the relay going bad at some point.

What if we could re-use some of the existing diode matrix to control the preload data?

D C B A	Counter Start	Covered Range
1 1 0 1	27.0	27.5 - 28.0
1 1 0 0	26.5	27.0 - 27.5
1 0 0 1	28.5	29.0 - 29.5
1 0 0 0	29.0	29.5 - 30.0

Laid out like this, we readily see the commonalities. The only difference between 27 and 29MHz coverage is that the "C" line is being set.

Going back through the Counter circuit and tracing every signal path through the diode matrix when the 27.5MHz band is programmed, one comes up with the following required deltas. Diodes indicates by red arrows are additions from the original information in Post #16. The diode indicated in blue is present when the 29.5-30.0MHz range is selected but it must be absent for the 27.5-28.0MHz range to indicate correctly on the counter.

Counter.jpg

[N8YX]

To make this work we have to somehow logically add D101 and D107 when the "+0.5" switch is pressed, and remove D35 from the circuit at the same time. No major changes can occur to the remainder of the Counter Unit as programming for the rest of the band ranges will be disrupted. If we want to re-use the push-button front panel switch and the associated logic, we have to make the "29" line active with 9V when either the 27 or the 29 band switch position is active, then use those signals on the Counter Unit to steer the band logic.

Proposed change to the RF Unit (Coil Pack):


ModdedBandswitch.jpg

Note the diode in red. It allows for re-use of the 29 line but prevents the 29MHz control signal from interacting with the Aux lines on the Counter Unit.

Modification details of the board to follow.

[N8YX]

Some initial thoughts on the switching arrangement required for the diodes in Post #68:

To re-use the 29.5 range for 27.5, we need to add D101 and D107 to the circuit. A method to electronically control this is required. An NPN switching transistor (2N2222, 2N3904) is ideal. It can be driven from the "29.5" line (diode to base resistor preventing C-B leakage) and is run in an emitter follower configuration. The collector ties to the anode side of the "Aux" band supply bus (see the center portion of the diagram in Post #62). The emitter is in turn tied to the anodes of D101 and D107. Dead-bug construction atop the Counter Board should work well for this.

Conversely, the only time we want D35 out of the circuit is when the Aux band line is active AND the "+0.5" switch is engaged. A PNP transistor run in common collector configuration (emitter to the 29.5 line; collector to the anode of D35) looks to be the best way to accomplish this, Base will be driven from the Aux line via the same diode-resistor arrangement as the other transistor. An NPN is OFF when base current is present and ON when it's not. As long as the Aux line isn't active, the circuit will behave as OEM. Selecting Aux and pushing the "+0.5" switch will turn the transistor OFF and remove D35 from the circuit.

At least that's the present theory. It may become more involved if I haven't figured all the angles just right.