Instructions | 45W RF SSB CW AMP (EBAY) DIY Build = 55W Upgrade

1

SMT parts

Install all the SMT parts first as per the BOM file here, do not place C16 and there is no C33 supplied. Do this by dressing one pad of every component with a bit of solder, then holding the part with a tweezer on the pads, reflow the solder joint. then apply solder to the other pad(s) of the part. You will have excess SMT parts. You can replace Q3 with a 2n2222 as I did, optionally.
2

Fit the TO-220 Transistors, Q1, Q2, Q4- note pics in file section

Bend the transistors' leads up 90° just before they thin down...use a bird beak pliers to stabilize the pins near the case to do this. Bending at the thin part of the lead is about a mm off. Place the PCB on the Heat sink and mark the holes left for Q1,Q2 & Q4. Then Place Q1,Q2 & Q4 Tabs on these marks, leads up. Fit the PCB down so the leads pass thru the pad holes and place 1/4" (6mm) spacers at either side of the PCB as per the picture in the files section. Tack solder ONLY the left pin of each transistor so that its TAB hole is easily accessible from the top of the PCB. Then mark these tab 3mm hole centers with a sharpie for a drill (2.5mm, or 3/64") and 4-40 tap.
3

Heat sink Prep (6"x6"x6mm base suggested) fins should be about 1.5" or 20mm deep.

Drill (2.5mm or 3/64") and tap (4-40 or 3mm) the screw holes. Obtain 1/2" pan head screws to match. Place the PCB with the
transistors on the heat sink and align the TO-220 TAB holes to the tapped heat-sink holes. Melt the solder joint on the transistor to make any adjustments. Install the 3 screws and remelt the joint again to stress relieve. Now solder all the remaining transistor leads.
4

Wind the binocular cores and the L1 choke

T2= 7:3 Ratio, 0.4mm magnet wire
T3=3:7 ratio 1mm magnet wire. Center tapped primary (3 turn)
L1 = 9 to 10 turns of 1mm magnet wire.
5

Install through hole parts

T2, T3, L1, R3, R19, L6,L7, U1 and R10 (add wire leads to SMT part) . Also install a jumper from the Q3 collector to the empty T1
center pad. SMA signal & output gold connectors. Optional Deadbug 2n2222 can replace Q3. Note the assembled PCB image in
the files section. T1 is no longer required.
6

Perform basic Ohmmeter checks

Verify that the Vcc to ground is not a short circuit and the TO 220 Tabs are insulated from the heatsink with the sil pads and shoulder washers and are firmly screwed down.

Ensure RV1 and RV2 are adjusted so that the gate pins of each of the IRF530 (pin1) measures a few ohms to the PCB ground ( SMA connector case)

Discussions

bcmoore wrote 08/27/2022 at 18:51

Hi, I just got this amp kit and would like to do your modifications. Can you tell me a source for the thermistors? I have V3.06 of this amp. It appears to differ from yours in that T1 has separate primary and secondary windings. It looks like you have a version 3.08. Can you post the schematic of your version? Also how can you implement a 3:7 winding for T3, if the primary has 3 turns? It seems the center tap would be at 1.5 turns, on the wrong side of the coil. Thanks

Regards, Brian KA1FT

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garello wrote 10/01/2017 at 19:42

Could you possibly post the LT spice file?

Andy, KM4TRT

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garello wrote 10/01/2017 at 19:26

Looks like a complete and lucid hack discription. i ordered one and intend to do your mods. I didn't read where you used the amp or what you used it on.

My bitx 20 has 2 IRF510s for output for about 8-10 watts. Would I better off taking power from the stage before output, rather than trying to turn down to such a small output? Or is there another way (attenuater of some sort?)

Thanks

Andy KM4TRT

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45W RF SSB CW AMP (EBAY) DIY Build = 55W Upgrade

Discussions

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