QRP Labs PA Assembly Instructions Manual Download Page 3

 

Rev 1.03 

3

 

2. Parts list 

 

Unused parts are coloured grey 

– these are used only in the full build. 

Resistors 

R27   

 

0.33-ohm, 2 watt resistor  

(none)  

 

10-ohm resistor 

R2, 19  

 

15K resistor (2 pieces) 

R4..10, 28 

 

1.1K resistor (8 pieces) 

R3, 11..18, 24 

2.2K resistor (10 pieces) 

R20

, 22

 

 

3.3K resistor (1 pieces used, 1 piece not used) 

R21, 30 

 

330-ohm resistor (2 pieces) 

R23   

 

8.2K resistor 

R29   

 

47K resistor 

R1 

 

 

4.7K trimmer potentiometer resistor 

R26   

 

3.3K resistor (not supplied) 

R25   

 

4.7K trimmer potentiometer resistor (not supplied) 

 

Capacitors 

C1, 2, 3, 7, 8  

1uF capacitor (5 pieces) 

C5, 6   

 

1uF capacitor (2 pieces) 

C4 

 

 

1nF capacitor 

 

Semiconductors 

IC1 

 

 

74HC595 8-bit shift register, 16-pin DIP package 

IC2 

 

 

7805L 5V regulator, TO92 package 

Q3, 4   

 

2N3904 NPN transistor, TO92 package 

Q1, 2, 6, 8 

 

2N3906 PNP transistor, TO92 package 

Q5 

 

 

2SC4242 NPN power transistor, TO220 package 

Q7 

 

 

IRF510 N-channel power MOSFET, TO220 package 

Q9 

 

 

BS170 N-channel MOSFET, TO92 package 

 

Miscellaneous 

16-pin socket  

16-pin DIP socket for IC1 

10-pin header 

10-pin 0.1-inch header  

Heatsink 

 

65mm long PCB-mounting heatsink and pins 

Insulation sets 

2 pieces silicone rubber insulation pads + washers for the TO220 transistors  

Nut and bolt   

12mm long M3-size bolt and matching nut 

FT50-43 

 

FT50-43 toroid 

Wire   

 

100cm 0.33mm diameter wire 

PCB   

 

80 x 37mm Printed Circuit Board (PCB) 

 

Summary of Contents for PA

Page 1: ...mbly of the PA kit which omits raised cosine envelope shaping or the power modulator with fold back current limiting It is easier to build this way but the functionality is less The kit has a PCB of s...

Page 2: ...03 2 The following diagram shows the simplified circuit diagram of this HF PA This diagram includes a 10 ohm resistor modification which is highly recommended and will be described later in this docu...

Page 3: ...6 1uF capacitor 2 pieces C4 1nF capacitor Semiconductors IC1 74HC595 8 bit shift register 16 pin DIP package IC2 7805L 5V regulator TO92 package Q3 4 2N3904 NPN transistor TO92 package Q1 2 6 8 2N3906...

Page 4: ...pplied to the IRF510 gate this is supplied by 4 7K preset potentiometer R1 via the 3 3K resistor R20 A trifilar output transformer wound on an FT50 43 toroid provides matching to the 50 ohm output The...

Page 5: ...st to detect and correct any mistakes as early as possible immediately after soldering the incorrect component The board is quite compact to fit the required 80 x 37mm PCB dimensions Removing a compon...

Page 6: ...frequent intervals by vias Note that the heatsink is not electrically connected to ground or anything else The area right under the heatsink has no ground plane on the top layer This is to prevent the...

Page 7: ...Rev 1 03 7 3 1 Inventory parts This is the full list of parts Many are not used in this simplified build Please refer to the parts list...

Page 8: ...GREEN The 4 7K preset bias adjustment potentiometer with label 472 PURPLE Optionally you can install header pins Many people prefer to solder wires to header pins rather than in holes Or you may wish...

Page 9: ...ease read and follow these steps carefully Firstly the wire The best way to un wind it without tangling it up is to think of what the kit packing person that wound it up did Then reverse his steps So...

Page 10: ...a vice if you have one If you don t then you have to get creative and think of something Here I taped it to the edge of the desk Now you can twist the screwdriver at the free end repeatedly until you...

Page 11: ...idal core Now tin the last few mm at the ends of each wire You can do this by scraping off the enamel then tinning with the soldering iron or hold the wire end in a blob of molten solder for a few may...

Page 12: ...The photograph right shows a joint where the soldering iron has not been held long enough on the joint The enamel has not properly burnt off the wire and there will be no electrical connection to the...

Page 13: ...icture shows how the transistor assembly must be put together before soldering On the side of the heatsink with the large gap the silicone pad is placed on the heatsink where the IRF510 transistor wil...

Page 14: ...nk this is to ensure that even if the soldermask accidentally got scratched there would be no contact between the heatsink and ground or any other electrical connection 3 6 A recommended modification...

Page 15: ...Rev 1 03 15 The modification is illustrated in the following diagram and picture...

Page 16: ...requires a supply voltage of typically 12 or 13 8V The amplifier may draw 1 or 1 5A of current so remember to use a well regulated good quality power supply capable of this Use thick wires to the PA...

Page 17: ...r the gate of the MOSFET is where there is zero idle current through the IRF510 transistor and where increasing the bias voltage any further would result in idle current starting to flow This point ha...

Page 18: ...output power of this PA kit in your application has a significant bearing on how you enclose the project Remember that the heatsink will dissipate a considerable amount of heat The heat dissipation w...

Page 19: ...made with the full assembled kit This simplified kit assembly does not suffer voltage drop across the power modulator nor does it have any attenuation in the leakage gate Due to this the output power...

Page 20: ...y 02 Jan 2017 1 0 Initial revision 09 Mar 2017 1 01 Corrected typos in toroid core type 04 May 2017 1 02 Corrected section 3 3 to say four jumper wires not three 29 Nov 2018 1 03 Corrected BS170 in pa...

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