DZ DZKit Saguaro Use and care manual

Page
DZKit
ASSEMBLY, SERVICE
& USER’s MANUAL
SR-74 “SAGUARO”
SHORTWAVE RECEIVER
DZ CompanY • LOVELAND, COLORADO

Page 2
DZ COMPANY CONTACT INFO
Orders, parts, phone assistance ..................................................................... [phone]
Email orders ............................................................................................... [email protected]
Email technical support ......................................................................... [e-mail]
Web site ....................................................................................................... www.dzkit.com
Mail:
DZKit
710 Grove Ct.
Loveland, CO 80537
During the first year after shipment, DZ Company will replace or repair free of charge—as soon as practical—any
parts which are defective, either in materials or workmanship, and any incorrect or missing parts. You can obtain
parts directly from DZ Company by writing us, emailing us or telephoning us. And we’ll pay shipping charges to
get those parts to you—anywhere in the world.
We warrant that during the first year after shipment, our products, when correctly assembled, calibrated,
adjusted and used in accordance with our printed instructions, will meet published specifications. Once
assembled, if the product fails to operate correctly, we will help you determine which subassembly requires
service. If return is found to be necessary, you must then ship that subassembly, or whole unit if applicable, to the
address below at your expense, and we will repair or replace it at our option and return it to you at no charge.
You will receive free consultation (except for the cost of your long distance phone call) on any problem you may
encounter in the assembly or use of your DZKit product. Just write us, email us, give us a call, or visit our
website and click on “Support”. That will give you access to free support. Sorry, we cannot accept collect calls.
Our warranty, both expressed and implied, does not cover damage caused by the use of acid-core solder,
water-soluble flux solder (without appropriate washing), or any corrosive or conductive flux or solvent, defective
tools, incorrect assembly, misuse, fire, customer-made modifications, floods or acts of God, nor does it include
reimbursement for customer assembly or setup time. The warranty covers only DZKit products and is not
extended to non-DZ allied equipment or components used in conjunction with our products or uses of our
products for purposes other than as advertised.
This warranty applies only to the first owner of the product and is not extended to subsequent owners.
This warranty gives you specific legal rights, and you may also have other rights which vary from state to state.
THE DZ COMPANY, LLC
710 GROVE CT.
LOVELAND, CO 80537
YOUR DZKIT 1-YEAR LIMITED WARRANTY

Page 3
Assembly, Operation and
Troubleshooting
Of the
Saguaro SR-74 Shortwave Receiver
DZ COMPANY
LOVELAND, COLORADO
Copyright © 2023
The DZ Company, LLC
All rights reserved
5/13/2023 Rev D Saguaro
TABLE OF CONTENTS
Introduction ....................................... 4
General assembly notes ..................... 5
Kit-building procedures ..................... 9
Safety notes...................................... 10
Soldering instructions ...................... 11
Chassis parts/cable identification .... 13
Step-By-Step Assembly
Chassis ........................................ 21
Controller circuit board .............. 33
Voltage Tests ............................... 40
Final assembly ............................ 45
Quick Start Guide ............................ 48
Detailed Operation ........................... 50
Linux Setup...................................... 55
Theory/Troubleshooting .................. 61
Schematics ....................................... 65
Specifications................................... 69
PENDING:
This device complies with part 15
of the FCC Rules. Operation is
subject to the following two con-
ditions: (1) This device may not
cause harmful interference, and
(2) this device must accept any
interference received, including
interference that may cause unde-
sired operation.

Page 4
The Saguaro SR-74 provides a
unique twist on an old concept:
shortwave listening. Shortwave
radios of yesteryear first used
super-regenerative circuits,
which were tricky to operate.
This was followed by the super-
heterodyne concept, still in use
today, in which oscillators,
mixers, filters and amplifiers
combine to turn an RF signal into
audio.
Today, it’s possible to sample
the entire RF spectrum and do the
entire radio — amplification, de-
modulation and audio output
streaming — all in software. The
Saguaro does just that. RF sig-
nals from your antenna are fed
directly into a “Software-Defined
Radio” (SDR) that is commercially
available (the SDRPlay RSP1A). It
is controlled from on on-board
computer called the “Raspberry Pi
4B,” a Linux-based PC with a
fast processor and either 4G or
8G of RAM. A DZKit-designed con-
troller reads the pots and tuning
knob and passes that data to the
Raspberry Pi for control of the
SDR. A program running on the
Raspberry Pi provides the graph-
ical user interface and controls
the SDR.
We’ve also added an internal
Morse Code practice monitor with
adjustable speed, volume and
pitch, and with Iambic, Ultimatic
and Manual modes! Just plug a
straight key or paddles into the
back panel minijack.
Thanks for trusting in DZKit to
provide not only unique electron-
ic products, but to give you
hours of building fun too.
INTRODUCTION
Some famous shortwave radios from yesteryear

Page 5
1. Most screws in this kit are
Phillips Panhead Machine
Screws. For simplicity, we
refer to them simply as
“screws” unless a different
style is used. These may be
stainless steel or zinc-
plated steel.
2. PC boards attach to the sheet
metal using metric M3 screws
with attached lock washers
(“SEMS” screws), but there
are some exceptions, which
are explained in the steps.
3. As you tighten a screw, it is
very important that you do
not strip the threads. All
screws should fasten smooth-
ly. If a screw appears to be
very hard to fasten, some-
thing else is probably wrong—
a cable could be in the way,
you are trying to use the
wrong size screw or something
else is wrong. DO NOT FORCE
SCREWS! Instead, inspect the
assembly carefully and try to
see why you are having diffi-
culty. Screws with locking
compound on them are normally
a little harder to fasten.
4. A PC within arms reach of
your workbench is useful in
helping you locate the parts
on the boards. The PCB layout
files for all boards are on
the included flash drive. To
find the location of a part,
simply install and run the
“ExpressPCB” program (free
download from
www.expresspcb.com) and open
the board you wish to work
on. Press “Ctrl-F” to find a
part, and then enter it in
the box that pops up (e.g.,
“R1”, without the quotes).
The program will show you ex-
actly where that part is lo-
cated. Take a few minutes to
familiarize yourself with
this program before beginning
construction. You can also
find parts manually by just
looking for the part on the
silkscreen, but on dense
boards, this can take a long
time. We highly recommend us-
ing ExpressPCB to locate
parts.
5. All references to left and
right, front and back are
with the chassis in an orien-
tation such that the front of
the radio faces you.
6. Each circuit part has its own
component number (R1, C4, Q3,
etc.) R1 on one assembly will
not be the same as R1 on a
different assembly, so be
sure you are looking at the
right set of parts when com-
paring part numbers with the
printed parts list. Check off
each part at the beginning of
each section to make sure all
the parts are there. If you
find any missing, give us a
call or email us and we will
rush a replacement to you.
7. Most electronic kits that are
returned for service have
General Assembly Notes

Page 6
Most kit builders find it helpful to sepa-
rate the parts into categories for quick
identification. Muffin tins and cardboard
egg cartons serve this purpose admirably.
poor soldering jobs. Please
take a moment to familiarize
yourself with proper soldering
technique. And do not, under
ANY circumstances, use corro-
sive (“acid-core”) solder!
That will void your warranty
and render your kit inopera-
tive. Also be sure to avoid
the use of products that may
be called solder but are real-
ly glue (e.g., LePage's Liquid
Solder, nothing more than me-
tallic-grey colored airplane
glue).
8. Soldering should only be done
in an area with good ventila-
tion and with a properly heat-
ed soldering iron.
9. Resistors are identified by
their values in Ohms, Kilohms
(K) or Megohms (M) and by col-
or codes. Your kit uses resis-
tors of several types. Axial
leaded resistors have color
coded bands on them. For 5%
resistors, the first two bands
represent the numeric value
and the third band represents
a multiplier, which is a power
of 10. Thus, a 56 Ohm resistor
is Green-Blue-Black. A 10KOhm
resistor is Brown-Black-
Orange, and so on. The fourth
band is the tolerance — no
band represents 20%, a silver
band 10%, and a gold band 5%.
Your Saguaro uses mostly one
percent or better resistors,
which have 4 bands for the
value. A 4.75K resistor is
Yellow-Violet-Green-Brown. We
have placed resistors of given
types in individual bags for
you, but should they get mixed
and you have trouble reading
the color code, we recommend
an inexpensive volt-ohmmeter
be used to check the values. A
fluorescent light is also use-
ful to “bring out” the colors,
and a magnifying glass is also
handy.
10.Capacitors are identified by
their type — disk, polysty-
rene, polypropylene, electro-
lytic, trimmer, etc. — and ca-
pacitance values are in micro-
farads (uF) or picoFarads
(pF). Polarized types have the
positive pin marked on the
silkscreen and also have a
square pad.
11.Inductors are represented ei-
ther by their inductance in
nanoHenries (nH), microHenries
(uH), milliHenries (mH) or by
the number of turns in the
coil if you are doing the
winding.
12.Diodes are marked with a band
on the cathode end. The PC
boards have a bar silkscreened
across one side of the compo-

Page 7
nent outline and a square pad
which identifies the cathode.
13.Transistors have either a tab
or a flat side that you can
match to the silkscreened com-
ponent outline. Most transis-
tors will need to have their
leads “sprung” a little to fit
in the holes. Do so carefully
to avoid breaking the leads
off.
14.ICs have a notch, beveled side
and/or a dot representing the
side containing pin 1. When
you hold an IC with the notch
or the beveled side up, pin 1
is in the upper left corner.
The silkscreened outlines on
the board all have notches and
pin 1 also has a square pad.
15.To insert an IC, rest the IC
on its side on a hard surface
Slowly roll the entire chip so
that all the leads on that
side are bent inward at once
and the same distance. Do
about half what appears to be
required. Check the leads
against the socket or PCB and
then roll the other side in-
ward the same way.
16.It is CRITICAL that you mount
polarized parts correctly!
Double check your work to be
sure that all such parts match
the photos. See Detail 1.
Detail 1. Identifying polarity of
diodes, transistors, ICs and po-
larized capacitors.
Transistor — Flat side
Diode — band on cathode
IC — pin 1 (through-hole part)
IC—pin 1 (SMT part)
Electrolytic capacitors — negative side

Page 8
Abbreviations and definitions of terms used in this manual:
PC = Personal Computer
PCB = Printed Circuit Board
PH = Panhead
FH = Flathead
M/S = Machine Screw (typically M2.5, M3, M5 sizes)
P/L = Patch lock (material added to threads to help screws stay in)
PCB-mt = Printed Circuit Board mounting
AMP MTA = Tyco Electronics connector with .1” pin spacing
IDC = Insulation Displacement Connector (MTA connectors are IDC type)
Ribbon cable = Flat cable with connectors on each end
Header = PCB-mounted connector
CA = Cable Assembly
A word about what lies ahead…
This manual is designed to allow you to build confidence in your kit-
building ability as you go along. You start by adding parts to the
chassis and then building and installing the controller board. You
will then be able to turn on the power and measure some voltages be-
fore loading ICs that could be damaged if the voltages are wrong. This
will give you confidence that the kit-building is progressing normal-
ly. You will also be able to use a PC to help you locate parts on the
boards using the PCB layout files that we have included. The project
concludes with integration of the circuit boards and cables into the
chassis. So let’s get started!
NOTE: Your kit includes ten feet of specially formulated no-lead, no-
clean Alpha Telecore solder. This should be enough to complete your
kit. It uses a tin, silver and copper alloy, and a non-aggressive
flux that does not require cleaning. DO NOT USE FLUX REMOVER OR WATER
after building the circuit board. It will leave a gummy residue.

Page 9
The steps involved in building a kit are listed below. Be sure to fol-
low them and you will have a lot of fun building, testing and using
your kit.
1. Check off parts as loaded. Each board kit contains a list of parts
used on that board. We have checked off each part on the right side
of the page as it is inserted in the bag. As you remove a part from
the bag and load it on the board, cross out its “reference designa-
tor” (e.g., “R1”) on the left side of the page. Our method of bag-
ging parts is different from all other kit vendors and will make
the task much faster and less error prone. If you are missing any
parts, call or email us and we’ll rush replacements immediately.
2. Parts have been pre-sorted. Do not remove parts from the bags until
called for, to avoid mixing parts up (especially resistors).
3. Find a picture online. The parts lists are also included on a flash
drive that is shipped with your kit. Almost every part has a hyper-
link to the vendor. Make sure you are connected to the Internet,
and click the part to get a picture and information about it.
4. Pay attention to soldering techniques. Keep your soldering iron
clean by using a wet sponge, use appropriate heat and maintain heat
long enough to make good solder joints. Solder problems are the
number one cause of problems when building kits, so do it right!
5. Some boards have been pre-loaded with surface mount parts. Be care-
ful not to flex these boards to avoid having parts snap off.
6. Take your time! We know you want to get it done and start using it,
but doing it wrong will only delay that moment. Before you start,
set up a ventilated, static-free work area with enough room to
build the kit. Prepare parts bins and get the tools you will need.
If you’re tired, take a break. Enjoy building your kit!
7. Make sure that you are loading the part that’s called for in the
right place. Once loaded, it can be hard to find a misloaded part.
Be especially careful to load polarized parts (connectors, ICs, di-
odes, electrolytic capacitors) in the right direction.
8. Once you’ve done a step, put a checkmark inside the parentheses in
this manual. This helps you remember where you left off when you
build in stages.
9. After you have assembled a circuit board, take a moment (just one)
to marvel at your handiwork, then spend a few more minutes critiqu-
ing it! Check for solder bridges, unsoldered or insufficiently sol-
dered connections, solder blobs, loose screws and electronic parts,
reversed polarized components, etc. Sometimes it helps to have a
friend check your work.
Kit-Building Procedures

Page 10
Your safety is of utmost importance to us. Please read this infor-
mation before you get started, and remember these rules as you contin-
ue building and testing your Saguaro.
1. Always have a healthy respect for electricity. The voltages present
inside the Saguaro can be as high as 260VAC, and high currents are
available (up to 2 Amps DC). Use a power supply with overcurrent
foldback or crowbar protection so that in case of high currents the
supply will shut down. Set the output current only as high as nec-
essary for a given step.
2. When measuring voltages inside electronic equipment, it is general-
ly a good idea to use only one hand, wear rubber-soled shoes and
avoid areas with standing water. However, remember that slightly
humid environments can prevent static electricity that could damage
the electronic parts! Use a humidifier in dry climates.
3. Do not work on powered electronics by yourself if at all possible.
Have a parent, spouse or friend nearby. If you must work alone,
keep a telephone handy in the event you run into problems.
4. Soldering irons are hot. They can burn your skin and cause damage
to workbenches and carpets. We recommend you use one with an auto-
matic shutoff in case you forget to turn it off when you are done.
5. Do not work on electronic projects when you are tired. We know you
want to finish it, but accidents are more likely when you are
tired. Take breaks! Be careful!
6. Use proper ventilation in your work area. Solder contains tin and
lead (or tin and silver), and solder fumes should not be allowed to
“hover” near your work. Open a door or window, use a fan, and be
cognizant of the potential dangers.
7. When clipping leads, use eye protection and/or be sure to direct
the flying leads down into a nearby trash can. As you gain experi-
ence clipping component leads, you will learn how to clip them so
that they fall harmlessly away from the board.
8. Be careful not to cut yourself when handling sharp objects such as
connectors and sheet metal. Keep some tissues, bandages and antibi-
otic ointment nearby in the event of an injury.
9. Use common sense in dealing with unfamiliar things. If you don’t
understand something, call us or ask a friend for help.
Safety First!