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I did things a bit differently. I removed R79 and R80 (the voltage divider is no longer needed or wanted) and shorted the R80 location with a solder bridge (a short piece of bare wire or an SMD 0 ohm "resistor" would also work), so what used to be the reference terminal now connects to ground. That leaves C10 and C25 in place as bypass caps on the output.

As I received the rig, there was an electrolytic capacitor soldered across R80, which so far as I can tell is an incorrect placement of it; it's presumably C11, which is a 470uF part on the schematic but was a 47uF in my rig, and it was bypassing the part of the voltage divider that goes to ground. I moved that cap so one end is at the ground end of the R80 location (not that the end matters since it's turned into a short, but that end is closer!) and the other end goes to the same land as the red lead of the regulator -- in other words, the input. (With the?correct polarity of course.) I believe that's where it is SUPPOSED to be according to the schematic.

I think it will be easier for? people to cut out the LM338 and solder the regulator leads to the stubs. I DID disassemble the radio so I could desolder that part and it was a major pain; you have to undo a?lot of stuff to?get?to the bottom of the main board. If you instead cut out the regulator, you can get away with removing only?the top cover (disconnect the speaker cable and set the top aside) and loosening the front cover (supporting it so you don't have to disconnect the ribbon cable for the display which is a pain to put in) so you have room for your screwdriver. The leads on the LM338 are long enough that you'll probably be able to reuse it in another project even after cutting it out.

To cut out the LM338, remove two of the three screws (one end and center) that hold the bar that presses down on the PA transistors and the regulator and loosen the third screw. Pivot the bar out of the way. Remove the spacer from the middle transistor; now that the bar will only be pressing against two parts it's no longer needed. Cut the leads of the regulator (it's the TO-220 component closest to the power connector) near the PCB, leaving enough of a stub to solder the regulator leads to.

Solder the regulator to the stubs. The black wire goes to the leftmost position (while looking at where the LM338 used to be from the front of the radio), the white wire goes to the center, and the red wire to the right. That does NOT match the order of the wires on the switching regulator; you have to cross the black and white wires. I put electrical tape on the back of the regulator board so I could bend it down near the main PCB without having to worry about shorting anything. It should NOT be behind the pressure bar.

Put the pressure bar back into place, making sure that the central screw is snug and then tightening the other two so the transistors are held down well.

On Sun, Sep 11, 2022 at 9:02 PM Ashhar Farhan <farhanbox@...> wrote:

Goody,

It might be better to solder the ground to the nearby mounting hole's tinned collar.?

The switching regulator needs a low impedance ground.

- f

On Mon, Sep 12, 2022, 12:37 AM Anthony Good <anthony.good@...> wrote:

I figured it out.? Here’s what I did, translated into directions.? These are preliminary, your results may vary.

1.? Take off the top panel and disconnect the speaker.? Lay this aside.

2.? Disconnect the white ribbon cable going from the Pi to the touch screen display.? There are little black tabs on each side of the connector on the display unit that need to pop straight out in the direction of the ribbon cable to release the ribbon cable.

3.? Disconnect the brown and black wire (touch display power) from the digital board.

4.? Remove the gray ribbon cable out of the digital board by pulling the gray ribbon straight backwards.

5.? Loosen the two nuts on the right side holding the metal bracket that the Pi and the digital board is mount to.? Do not take the nuts entirely off.

6.? Pull the Pi and digital board assembly straight up to remove and set aside.

7.? Remove the four screws holding the main board to the chassis

8.? Disconnect the two red wires from the power switch on the back panel

9.? Remove screws on the four back corners of the outside of the chassis to remove the back panel along with the main board.

10.? Put the rest of the chassis with the screen and controls aside.? Carefully place the back panel and main board on your workbench and loosen the three screws holding the bar that presses the two final transistors and the LM338 regulator on to the back panel heatsink.? Remove the bar and three screws.? The main board should be loose from the back panel now.

11.? Unsolder the LM338.? With the front of the main board facing you, it’s the first three pin device from the left on the back on the back that was against the heatsink.

12. Solder the black (ground) wire of the new switching regulator to the negative side of the orange electrolytic capacitor.? This capacitor is soldered on top of R80, a SMD resistor.

13. Solder the red switching regulator wire (+13.8 volt input) to the right-most pin where the LM338 used to be.? This is the input pin shown in the diagram below.

14. Solder the white switch regulator wire (output) to the middle pin, where the LM338 used to be.? This is the output pin shown below. ?(The first pin of the LM338, labeled “Adjust" below, will remain open.

15.? Place the main board against the back panel.? Place the bar that presses the final transistors to the heatsink place.? Place the three screws back in, but do not tighten all the way.? Leave them rather loose.

16.? Place the main board and back panel together back into the main chassis.? Line up the three front jacks (mic, earphone, cw key) to the holes in the front panel.? Carefully push the back panel into place until it mates correctly with the side and bottom panels.

17.? Line up the main board with the four screw holes.? Place the four screws in, starting them, but leaving them slightly loose.? After all four are started, tighten all four.

18.? Tighten the three screws that are in the bar that presses the two final transistors on to the back panel heatsink.? Use your best judgement. ?(I tightened until the two final transistors would not move with me pressing my finger nail on the side of them.)

19. (Optional step) ?Connect the power.? Turn on the unit and use a voltmeter to verify that the white lead from the new switching regulator has about 5.4 volts on it.? If it is not close to 5.4 volts, stop and troubleshoot.? If it’s good, turn off the unit, disconnector the power, and proceed.

20.? Re-assemble the remaining parts of the unit.? Slide the pi and digital board subassembly back in, being sure to have the pins on the bottom meting correctly with the connector on the main board.? Be sure to connect the gray ribbon cable to the back of the digital board (it is keyed so it can be inserted only one way), the white ribbon cable to the display unit (blue side down, silver side out), and black & brown power cable for the display going to the digital board (brown is down, black is up).? The assembly manual has pictures that can help ().

21.? Reinstall the top panel, connecting the speaker to the digital board prior to putting the top panel on.

22.? Connect the power, and power up!

73

Goody

K3NG

On Sep 11, 2022, at 10:09, Anthony Good <anthony.good@...> wrote:

Are there instructions for installing the new regulator board

On Sep 10, 2022, at 11:32, Anthony Good <anthony.good@...> wrote:

Received my kit here in W3 land.? Yeahhhhh

73
Goody
K3NG