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2N2/XX
Assembly Manual
66 pgs23.11 Mb0

NORCAL 2N2/XX Assembly Manual

NORCAL 2N2/XX V1.2
Assembly Manual
Copyright 2008/2009 by
Jim Kortge, K8IQY
and NORCAL
1
Introduction
300) and assumes the builder has some working knowledge of electronics and electronic parts. To successfully build this transceiver, one needs to be able to understand and follow a schematic diagram, convert resistor and molded inductor value call outs to the equivalent color code, and be able to recognize various capacitor types. In addition, one needs to be able to read and understand this manual, follow the instructions correctly, and work carefully.
A common assembly manual is used for all 2N2/XX rigs, therefore, no parts values are given in this manual, only part designators. This assembly manual is used with the band specific Bill of Material (BOM) and schematic diagram to identify the part values being installed. The schematic diagram for each band contains the actual part value for each designator. Using this approach encourages the builder to become familiar with the schematic diagram of the 2N2/XX transceiver being built so that he/she is familiar with the design of the rig should any troubleshooting be necessary. However, if all of the parts are installed in their correct locations, the rig will perform as designed and no troubleshooting will be required!
With that thought in mind, go slowly and double check your work to avoid having to remove either an incorrect part or a correct part installed in the wrong location on the PC board (PCB). As a suggestion, make a 2X size copy of the schematic diagram. While you are building, check off the parts installed in the brackets [ ] provided in this manual, while also highlighting the part on the schematic as a cross check. When you are done building, all of the parts shown on the schematic should be highlighted. (On 40-meters, the Receive RF Amplifier stage is not built, so those parts will not be highlighted.)
A parts overlay page is included in the Appendix. This page will show how the various transformers and trimmer capacitors are to be mounted. An “F” designates the “flat side” of a trimmer capacitor (TCx designation). When mounting a wound transformer, the primary (“Pri” notation) is always the winding with the most turns. The secondary (“Sec” notation) is the winding with the fewer or equal number of turns, if the transformer is a bifilar type. Transformer T5 is somewhat unique, as it has two secondaries, a 3-turn and a 1-turn. The primary is connected to the locations marked “P” as shown on the overlay, the 3-turn secondary to “S1” on the overlay, and the 1-turn secondary to “S2” on the overlay. All transformers having several turns for the primary and fewer turns for the secondary can be wound with the secondary interleaved between the primary winding turns from approximately centered on the primary winding to near the end where its leads will be soldered to the appropriate pads on the PCB. The location is not critical. An examination of the various figures supplied will illustrate this approach.
This manual is structured to build a section and then test it to assure it is working correctly, before moving on. Space is also provided at the end of each test section to write down your measurements and observations. You are encouraged to do this as it will help later on if you run into problems or need assistance. Using this approach promotes confidence the end product will work, since all of the previous stages worked. If you build a section and it doesn't work properly, do not continue on,
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expecting that the section will fix itself. It will not and the remainder of the build will be compromised. Please fix any and all problems as they occur!
PCB Preparation
[ ] Assemble the four 1-inch hex screws and 1-inch hex nuts to the four corners of the PCB. The
screws go on the bottom side and the nuts on the top side. This hardware holds the PCB up off the work surface and makes it easy to work on regardless of which side is up.
Your PCB should look like that shown in the figure.
Power protection
[ ] Install diode D18
[ ] Install capacitor C87.
Your PCB should look like that shown in the next figure.
- Figure 1 -
3
- Figure 2 -
Test - Apply 12 volts to the board. With a DVM or VOM, measure that more than 11.7 volts appears at the junction of D18 and C87.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Active Power Decoupler
[ ] Install transistor Q21
[ ] Install resistor R96
[ ] Install capacitor C38 matching the polarity markings on the capacitor case with those on the
PCB.
Your PCB should look like that shown in the next figure.
4
- Figure 3 -
Test – Apply 12 volts to the board. Measure with a DVM or VOM that 11.5 volts (or more) appears at the left center pad where transformer T3 will be installed.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Main Audio Amplifier
[ ] Install transformer T3; note orientation, “P” side toward the interior of the PC board. There is
no need to solder the mounting tabs; doing so makes it virtually impossible to remove the transformer should it be mounted incorrectly.
[ ] Install transistors Q3, Q4, Q5 and Q6.
[ ] Install resistors R5, R6, R9, R10, R11, R12 and R13.
[ ] Install capacitors C4, C5, C8 and C11.
[ ] Install electrolytic capacitors C6, C9, C10 and C82 matching the polarity markings on the case
with those on the PCB.
5
[ ] Install volume control R80 (marked A10K) to the pads marked “VOLUME” using discarded
leads from previously installed components as shown in the next figure.
- Figure 4 -
[ ] Install the SPKR jack, using the rear terminals, to the pads marked “SPKR” using discarded
leads from previously installed components as was done above. Other controls will be installed on a temporary basis similar to these two elements. Once the rig is completed and working, these parts will be removed and rewired when the PCB and controls are installed in the case.
Your PCB should look like that shown in the next figure.
Test – Connect a speaker or headphones to the “SPKR” jack. Apply power to the board. Rotate the volume control fully clockwise and touch the center pad of the pad set marked “VOLUME”;
- Figure 5 -
6
60 Hz hum should be heard coming from the speaker or headphones.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive/Transmit Keying
[ ] Install the PN2907A PNP transistor at Q8
[ ] Install resistors R17 and R18
[ ] Install capacitors C14, C20 and C21
Your PCB should look like that shown in the next figure.
Test – Apply 12 volts to the board. Confirm with a DVM or VOM that at least 11.5 volts (+V Tx) appears at the collector of Q8 (left pad of R86 location) when the “KEY” pads are connected together.
- Figure 6 -
7
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Mute
[ ] Install the J176 JFET at Q7
[ ] Install diodes D2, D3, and D4. Note cathode ends (bar) so they are installed correctly. The
anode of D3 and the cathode of D2 should be the non-grounded ends.
[ ] Install the two test points provided for the R14 location, then install R14. Using these test
points allows R14 to be easily removed and replaced should the audio level during transmit not be set to your liking.
[ ] Install resistors R15 and R16.
[ ] Install capacitors C12 and C13.
Your PCB should look like that shown in the next figure.
- Figure 7 -
8
Test – Connect a speaker or headphones to the “SPKR” jack. Apply power to the board. Advance the volume control to maximum. Touch the top (ungrounded end) of diode D2; 60 Hz hum should be heard coming from the speaker or headphones. Rotate volume control R80 counter clock wise (CCW) to verify the hum level changes. At full volume, jumper the pads marked “KEY” and verify that the 60 Hz hum is muted.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Audio Preamplifier
[ ] Install transistor Q10.
[ ] Install resistors R19, R20, R21, R22, R23 and R24.
[ ] Install capacitors C27 and C28.
[ ] Install tantalum (tan color, both leads on one end) capacitors C26 and C30 matching the polarity
markings on the case with those on the PCB.
[ ] Install electrolytic capacitors C23 and C29 matching the polarity markings on the case with
those on the PCB.
Your PCB should look like that shown in the next figure.
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- Figure 8 -
Test – Connect a speaker or headphones to the “SPKR” jack. Apply power to the board. Touch the pad on the minus end of tantalum capacitor C30 or the lower pad for L10. The hum volume should be louder than it was before this stage was added.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Local Oscillator (RxLO)
[ ] Install inductors L4 and L7.
[ ] Install trimmer capacitor TC9. The rounded end is the grounded end.
[ ] Install transistor Q11.
[ ] Install resistors R26, R27, R28, R69, R70 and R71.
[ ] Install capacitors C15, C32, C33, C67, C68 and C69.
[ ] Install crystal X5; it will be one of two marked LO or XX. Place a spacer (made from brown
10
bag paper) over the crystal leads before soldering it to the PCB or leave a small space between the case and the PCB. This will keep the crystal case from shorting out PCB traces. Ground the crystal case with a short piece of wire to the provided adjacent ground pad.
Your PCB should look like that shown in the next figure.
- Figure 9 -
Test – Apply power to the board. Measure the LO output at the top of resistor R28 with a suitable device. Either an oscilloscope or RF Probe with readout device can be used. The output should be at least 1.8 volts peak-to-peak, or 0.60 volts RMS when measured on an oscilloscope and 0.7 volts peak when measured using a typical passive RF probe connected to a DVM.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Product Detector
[ ] Install mixer M1. A black dot on the part and a white dot on the PCB denote the location of
Pin 1. Solder the pin 1 lead only. Reconfirm this part is oriented correctly before soldering the
remaining leads.
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[ ] Install resistor R25.
[ ] Install capacitors C25 and C31.
[ ] Install molded inductor L10.
Your PCB should look like that shown in the next figure.
Test – Connect a speaker or headphones to the “SPKR” jack. Apply power to the board. Measure the mixer drive at the top of resistor R28. It should now show an output level of at least 0.60 volts peak-to-peak, or 0.27 volts RMS when measured on an oscilloscope and 0.2 volts peak when measured using a typical passive RF probe connected to a DVM. Connecting an antenna to pin 3 of mixer M1 or the left pad for C37 should provide atmospheric noise (static) at the audio output.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Post IF Amplifier Crystal Filter
[ ] Install resistor R29.
- Figure 10 -
12
[ ] Install capacitor pairs C37/C114, C34/C35, and C39/C115. Some of these capacitors may not be
used at the IF frequency employed in your rig. Unused capacitors are shown on the schematic
with a value of 0 pF.
[ ] Install crystals X6 and X7. Place a spacer (made from brown bag paper) over the crystal leads
before soldering it to the PCB or leave a small space between the case and the PCB. This will keep the crystal case from shorting out PCB traces. Ground each crystal case with a short piece of wire to the provided adjacent ground pad.
Your PCB should look like that shown in the next figure.
Test – Connect a speaker or headphones to the “SPKR” jack. Apply power to the board. Connect an antenna to the output side of capacitor C39. Listen to the restricted noise bandwidth due to the crystal filter. If doing this test in the evening, you may be able to hear a shortwave broadcast station on the IF frequency of your rig.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
- Figure 11 -
13
Receive IF Amplifier
[ ] Wind and install transformers T10 and T11. Each time a wire passes through the center of the
toroid, it is counted as 1-turn.
[ ] Install the MPSH10 transistors at Q12 and Q13. These devices look similar to several of the
other plastic encased transistors. Make sure the correct pair is selected.
[ ] Install diodes D5 and D6. Make sure the cathode ends (bar) are oriented correctly.
[ ] Install resistors R30, R31, R32, R33, R34, R36, and R95.
[ ] Install capacitors C18, C41, C44, C45, and C46.
Your PCB should look like that shown in the next figure.
Test - Connect a speaker or headphones to the “SPKR” jack. Apply power to the board. Connect an antenna to the primary side of transformer T11 or to the right pad where C36 will be installed. You should hear band noise, mostly static, at a very loud level.
- Figure 12 -
14
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Main Crystal Filter
[ ] Install capacitor pairs C36/C111, C53/C56, C55/C113, C54/C57 and C52/C112. Some of these
capacitors may not be used at the IF frequency employed in your rig. Unused capacitors are
shown on the schematic with a value of 0 pF.
[ ] Install crystals X1, X2, X3, and X4. Place a spacer (made from brown bag paper) over the
crystal leads before soldering it to the PCB or leave a small space between the case and the PCB. This will keep the crystal case from shorting out PCB traces. Ground the case of each crystal with a short piece of wire to the provided, adjacent ground pads.
Your PCB should look like that shown in the next figure.
Test - Connect a speaker or headphones to the “SPKR” jack. Apply power to the board. Connect an antenna to the right pad of C52 or to the upper pad where R37 will be installed. You should hear band noise, mostly static, at a loud level and very restricted in bandwidth due to the action of this crystal filter.
- Figure 13 -
15
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
Receive Post-Mixer Amplifier
[ ] Wind and install transformers T4 and T9. T4 can be wound with either a pair of wires twisted
together at 8-10 turns per inch and then wound on the core, or with the pair of wires wound in parallel. Either method will yield a suitable transformer. An example of each method is shown in the next figures.
- Figure 14 - - Figure 15 -
[ ] Install transistor Q14.
[ ] Install diodes D7 and D24. Note cathode ends (bar) so they are installed correctly.
[ ] Install resistors R35, R37, R38, R45, R46, R47, R48 and R49.
[ ] Install capacitors C59, C60 and C61.
Your PCB should look like that shown in the next figure.
16
- Figure 16 -
Test - Connect a speaker or headphones to the “SPKR” jack. Apply power to the board. Connect an antenna to the upper-right pad of T4 or the pin 2 pad of where mixer M2 will be installed. You should hear band noise, mostly static, at a very loud level and very restricted in bandwidth due to the action of the crystal filters. As you are listening, rotate trim capacitor to change the LO frequency being injected into mixer M1. Starting with the capacitor at minimum capacitance, (the highest sounding static) rotate this trimmer until the lowest sounding static occurs. This adjustment will be used to optimize the LO injection point to center the received signal in the middle of the main crystal filter in the final receiver alignment.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
VFO
[ ] Wind and install inductor L13. Use the supplied shouldered nylon washers on either side of
toroid and the nylon screw and nut to secure it to the PCB. Tighten until the wound toroid is snug, but do not over tighten and strip the screw threads. Cut off excess screw material protruding through the nut.
[ ] Install trim capacitor (orange color) TC6.
17
[ ] Install Q9
[ ] Install diodes D8, D9 and D10. Note cathode ends (bar) on D8 and D9 so they are installed
correctly. D10 (a MV1662) looks like a transistor with only two leads and has no markings on it, just colored bands.
[ ] Install resistors R52, R55, R56, R58, R59 and R60.
[ ] Install trim potentiometer R78 and control potentiometer R54. R54 is wired using leads from
previously installed components and oriented so that when wired to the PCB, the terminals are pointing as shown in the next figures.
- Figure 17a - - Figure 17b -
[ ] Install polystyrene capacitors C76, and C77. This set of capacitors is mounted “on end”
as shown in the next figure.
- Figure 18 -
18
[ ] Install capacitors C42, C43, C62, C63, C64, C65, C66 and C74.
Your PCB should look like that shown in the next figure.
- Figure 19 -
Test – Apply power to the PCB. Connect an RF probe or oscilloscope to the top of resistor R60. The RF probe should show an output level of approximately 0.16 volts. On an oscilloscope, the waveform should approximately match that shown in the next figure.
- Figure 20 -
If a frequency counter is available, connect it to the top of R60 and measure the frequency. The
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displayed frequency will change with the rotation of R54, the tuning potentiometer. The high frequency end of the VFO tuning range is set by trim capacitor TC6 and the low frequency end by trim resistor R78. Adding in the RIT circuitry (in a later step) will change the tuning range and span of the VFO.
Your Measurements/Observations - ______________________________________________ ____________________________________________________________________________
VFO Buffer
[ ] Install Q15
[ ] Install resistors R61, R62, and R65.
[ ] Install capacitor C81.
Your PCB should look like that shown in the next figure.
Test – Apply power to the PCB. Connect an RF probe or oscilloscope to the top of resistor R62.
- Figure 21 -
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