DZ HT-7 User manual

Page
DZKit
ASSEMBLY MANUAL
HT-7
40M AM HANDIE-TALKIE
Price: $10.00
DZ CompanY • LOVELAND, COLORADO

Page 2
DZ COMPANY CONTACT INFO
Orders, parts, phone assistance.....................................................................[phone]
Email orders............................................................................................... [email protected]
Email technical support .........................................................................[email protected]
Web site .......................................................................................................www.dzkit.com
Mail:
DZKit
710 Grove Ct.
Loveland, CO 80537
During your first ninety (90) days of ownership, DZ Company will replace or repair free of charge—as soon as
practical—any parts which are defective, either in materials or workmanship. 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 ninety (90) days of ownership, our products, when correctly assembled,
calibrated, adjusted and used in accordance with our printed instructions, will meet published specifications.
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 drop us a line, email us, give us a call, or visit our
website and click on “Support”. That will give you access to free on-line support and a discussion group. Sorry,
we cannot accept collect calls.
Our warranty, both expressed and implied, does not cover damage caused by the use of corrosive solder,
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.
If you are ever dissatisfied with our service—warranty or otherwise– or our products, please write or email the
president, Brian Wood, W0DZ, and he will make certain your problems receive prompt, personal attention.
THE DZ COMPANY, LLC
LOVELAND, CO 80537
YOUR DZKIT 90-DAY FULLWARRANTY

Page 3
Assembly and Operation
Of the
HT-7 40M AM Handie-Talkie
DZ COMPANY
LOVELAND, COLORADO
Copyright © 2009
The DZ Company, LLC
All rights reserved
3-24-09 HT-7
TABLE OF CONTENTS
Introduction...................................... 4
Available Accessories....................... 5
General Assembly/Safety Notes....... 6
Parts List ........................................ 12
Step-by-step Assembly................... 14
Chassis Integration......................... 19
Adjustments and Tests.................... 22
Final Assembly............................... 23
Using Your HT-7 ............................ 27
Theory of Operation....................... 28
Specifications................................. 34
Schematics ..................................... 35
Troubleshooting.............................. 39
Component Locator........................ 40
Notes.............................................. 41

Page 4
Intheearlydaysofamateurra‐
dio,andcontinuingwellintothe
1960’s,amplitudemodulation(AM)
wasthemodeofchoiceforphone
communications.Itswideband‐
width(6kHz)andrichsoundmade
hamradiosoundlikebroadcast
stations.

Eventually,withcrowdedbands
andadesireforsmallerrigs,AM
gavewaytosingle‐sideband(SSB)
operation.Radioshadmoresensi‐
tivityonSSBthanwithAM,so
worldwidecontactsbecameeasier.
AMwasrelegatedto“callingfre‐
quencies”‐justsinglefrequen‐
ciesinthelargeamateurphone
bandswhereAMaficionadoscould
stillenjoythefunofthoseold‐
styleQSOs,whichweretypically
long‐winded,sinceVOXwasnot
usedandswitchingoverfrom
transmittoreceivetooklonger.

NowyoucanenjoythefunofAM
withoutspendinganarmandaleg
withyournewHT‐7Handie‐Talkie.
Notonlycanyouuseitasa
walkie‐talkie,withlimited
range,butyoucan,withanap‐
propriateoutsideantenna,talk
tothe“bigguns”onthe40MAM
callingfrequencyof7.290MHz.
SincetheoutputpoweroftheHT‐
7isjust2Watts,youmaywant
toaddanamplifier,butwhen
bandconditionsaregood,andthe
sunspotcyclecooperates,you
willbeamazedathowfar2Watts
willcarry!

ThanksfortrustinginDZKitto
providenotonlyuniqueelec‐
tronicproducts,buttogiveyou
hoursofbuildingfuntoo.
INTRODUCTION

Page 5
AVAILABLE ACCESSORIES
HTA‐3Tuner.Thisisthe
“DuckerI/L”madebyMiracle
AntennaofCanada.Addsabout
30dBofgaintoyourHT!
HTA‐257”ExtendableWhip.
AlsomadebyMiracleAntenna
ofCanada.Usewithorwith‐
outtheHTA‐2tuner.
HTA‐1BatteryPack.Includesbuilt‐inovercharge,overdischarge,
overdrain,short‐circuitandreversedpolarityprotection.Weight:
10.4oz(370g).Dimensions:2.6"(66mm)x2.1"(53mm)x
1.7"(43mm).MustberechargedusingLithiumIonchargeronly.Not
forusewithNiCdorNiMHchargers.Canbechargedinusebyconnec‐
tionofa12VDCpowersupply,orgotowww.batteryspace.comtoorder
aninexpensivechargermadeforthisbattery.

Page 6
1.Asyoutightenascrew,itis
veryimportantthatyoudo
notstripthethreads.All
screwsshouldfastensmoothly
withoutresistance.Ifa
screwappearstobehardto
fasten,something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care‐
fullyandtrytoseewhyyou
arehavingdifficulty.Abbre‐
viations:PH=panhead.FH=
flathead.M/S=machine
screw.
2.Allreferencestoleftand
right,frontandbackare
withthechassisinanorien‐
tationsuchthatthespeaker
facesyouandthetextreads
correctlyfromlefttoright.
3.Eachcircuitparthasitsown
componentnumber(R1,L4,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.
4.Mostelectronickitsthatare
returnedforservicehave
poorsolderingjobs.Please
takeamomenttofamiliarize
yourselfwithpropersolder‐
ingtechnique.Anddonot,
underANYcircumstances,use
corrosive(“acid‐core”)sol‐
der!Thatwillvoidyourwar‐
rantyandrenderyourkitin‐
operative.Alsobesureto
avoidtheuseofproducts
thatmaybecalledsolderbut
arereallyglue.Soldering
shouldonlybedoneinan
areawithgoodventilation
andwithaproperlyheated
solderingiron.
5.Capacitorsareidentifiedby
theirtype—disk,polysty‐
rene,polypropylene,electro‐
lytic,trimmer,etc.)andca‐
pacitancevaluesarein
microfarads(uF)orpico‐
Farads(pF,oftenpronounced
“puff”).Polarizedtypeshave
thepositivepinmarkedon
thesilkscreenandalsohave
asquarepad.
6.Inductorsarerepresentedei‐
therbytheirinductancein
nanoHenries(nH),microHen‐
ries(uH),milliHenries(mH)
orbythenumberofturnsin
thecoilifyouaredoingthe
winding.
7.Diodesaremarkedwithaband
onthecathodeend.ThePC
boardshaveabarsilk‐
screenedacrossonesideof
thecomponentoutlineanda
squarepadwhichidentifies
thecathode.
General Assembly Notes

Page 7
Mostkitbuildersfindithelpfultosepa‐
ratethepartsintocategoriesforquick
identification.Muffintinsandeggcar‐
tonsservethispurposeadmirably.
8.ICshaveanotch,beveledside
and/oradotrepresentingthe
sidecontainingpin1.When
youholdanICwiththenotch
pointinguporthebeveled
sidetoyourleft,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.

ItisCRITICALthatyoumountpo‐
larizedpartscorrectly!Double
checkyourworktobesurethat
allsuchpartsmatchthephotos.























IC—pin1(throughholepart)
Electrolyticcaps—negativeterminal
Diode
Cathode
Anode

Page 8
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,aligning,testing
andusingyourkit.

1.Doapartsinventory.Checkoffeachpartinthepartslisttobe
sureyouarenotmissinganything.Ourmethodofbaggingpartsis
differentfromallotherkitvendorsandwillmakethetaskmuch
fasterandlesserrorprone.Butdespiteourvaliantefforts,mis‐
takescanhappen.Ifyouaremissinganyparts,calloremailus
andwe’llrushreplacementstoyouimmediately.
2.Donotremovepartsfromthebagsuntilcalledfor,toavoidmixing
partsup.
3.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electronicproducts(not
justkits!),sotryextrahardtodoitright.
4.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
(needle‐nosepliers,wire‐cutter,wirestripper,Phillipshead
screwdrivers,wrenches,solderingiron,solder,insulatedtool,
awlorothersharp‐endedtool,scissors,magnifyingglass,etc.)If
you’retired,takeabreak.Enjoybuildingyourkit!
5.Makesurethatyouareloadingthepartthat’scalledforinthe
rightholes.Onceloaded,itcanbehardtofindamisloadedpart.
Beespeciallycarefultoloadpolarizedparts(ICs,transistors,
diodes,electrolyticcapacitors)therightdirection.Ifyouare
notsureaboutanystep,call,writeoremailus!
6.Onceyou’vedoneastep,putacheckmarkinsidetheparentheses.
7.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(especiallyoninsulatedmagnet
wireusedontoroids),loosescrewsandelectronicparts,reversed
polarizedcomponents,etc.Sometimesithelpstohaveafriend
checkyourwork.
KIT-BUILDING PROCEDURES

Page 9


Yoursafetyisofutmostimportancetous.Pleasereadthisinforma‐
tionbeforeyougetstarted,andremembertheserulesasyoucontinue
buildingandtestingyourkit.

1.Alwayshaveahealthyrespectforelectricity.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necessaryforagivenstep.
2.Whenmeasuringvoltagesinsideelectronicequipment,itisgener‐
ally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.Thismaysoundobvious,butdonotinsertanypartsinanyportion
ofyourbody.
10.Usecommonsenseindealingwithunfamiliarthings.Ifyoudon’t
understandsomething,callusoraskafriendforhelp.
Safety First!

Page 10
SOLDERING INSTRUCTIONS

Poorsolderingaccountsforalmost90%ofallkitbuildingproblems.
Thephotographsbelowshowexamplesofthemostcommontypesofbad
solderconnectionsandagoodone.Ifyoulocateanyofthesebadsol‐
derconnectionsinyourkit,correctthemasdescribed.Studythis
sectioncarefullybeforeyoustartbuildingyourkit.
Useagoodquality,variabletem‐
peraturesolderingironwitha
conical,narrowtip,andsetthe
temperatureto750degreesF.Use
thin,non‐corrosive,rosincore
soldertoassembleyourkit.Keep
thespongedampandwipethetip
onthespongeaftereachsolder
step.
Solderblob.Inthisexample,
solderflowedontoalead,but
theheatwasnotmaintainedlong
enoughforittoflowontothe
circuitboardpad.Solution:re‐
heattheconnection,touchingthe
irontoboththecomponentlead
andthepadatthesametime.
Solderbridge.Solderthat
stretchesfromonetraceorpad
toanothercreatesashortcir‐
cuit.Solution:Holdtheboard
upsidedownandreheatthearea.
Theexcesssolderwillflowdown
thesolderingiron.Anotherso‐
lutionistousea“solder
sucker”orsolderwicktoremove
excesssolder.Soldersuckers
workwelloneortwotimesona
givenconnection.Ifusedtoo
much,theycanpullpadsand
tracesoffofPCboards.
Agoodsolderconnectionlooks
likethis.Solderflowsevenly
ontoboththepartandthePC
boardorchassiscomponent.Itis
shinyandeven,notlumpyand
dull.Thecomponentliesflaton
theboard.Leadsthatareprop‐
erlysolderedcannotbemovedin
thehole.Youcanfindbadsolder
connectionsbymeasuringthere‐
sistance,usinganohmmeter,be‐
tweenthecomponent’slead(where
itattachestothebodyofthe
part)andtheotherendofthe
trace.Ifitreadsinfinity(or
veryhigh)theconnectionis
open.

Page 11
STATIC PRECAUTIONS
Manyofthecomponentsinyour
kitcanbedamagedbyexposureto
staticelectricity.Pleaseread
thispagetofamiliarizeyourself
withthecausesofandsolutions
tothisproblem.

Whentheclimateisdry,youcan
generatethousandsofvoltssim‐
plybywalkingacrossacarpet.
Whenyouthentouchametalob‐
jectyoucanfeeltheeffectsof
thisasyoudrawaspark!That
samespark,oftentoosmallto
seeorfeel,candestroysensi‐
tiveelectroniccomponents.You
MUSTtakeprecautionswhenwork‐
ingwithelectronicstoprevent
damage.

Thebestsolutionistooutfit
yourworkbenchwithanti‐static
devices—floormats,grounded
solderingirons,andworkmats
withgroundedwriststraps.If
thesearenotpracticalforyou,
theveryleastyoushoulddois
todischargeyourselftoground
afteryousitdownandbeforeyou
touchanyelectronicitems,by
touchingagroundedobjectsuch
asthecornerofawall.

Inadryenvironment,simply
standingupaftersittingina
non‐groundedchaircanalso
chargeyouwithelectricity.If
youstanduptostretch,forex‐
ample,besuretore‐groundyour‐
selfbeforegettingbacktowork.
Don’twearinsulatedsoleshoes
andavoidNylon,woolorother
static‐producingmaterialinyour
clothing.

Ifyourworkareaflooriscar‐
peted,sprayfabricsofteneron
itusingahandspraybottle.
Fabricsoftenerisconductiveand
willbleedawaycarpetstaticfor
afewhours.

Don’tuseaplastictableunless
youhaveagroundedworkmaton
it.Useametaltableifpossi‐
ble.

Catsarenotoriousforinducing
staticintoyourworkarea.Don’t
allowthemanywherenearyour
workbench!

Allelectroniccomponentsare
susceptibletostatic,butsemi‐
conductorsandassembledboards
containingsemiconductorsarethe
mostpronetodamage.Thesein‐
cludediodes(includinglight‐
emittingdiodes[LEDs]),transis‐
torsandintegratedcircuits
(ICs).
Youareawalkinglightning
bolt!Becareful!

Page 12
HT-7-2 Board Parts
Item Ref Description Qty
1 C2
10uF/25V 1
1 C26
22uF/16V non-polar 1
2 C12
330uF/16V 1
2 C6
470uF/10V 1
3 D3
1N5404 1
4 J1, J2
3.5mm mono minijack, right angle, PCB-mount 2
5 J3
BNC Jack, right angle, PCB-mount 1
6 Q2
2N5109 NPN Transistor 1
7 Q3
2SC2166C NPN RF Power transistor 1
8 RV2
10K trimpot - vertical 1
9 RV1
1K pot with switch 1
10 S1 4 pole double throw momentary switch 1
11 T1 T36-1 1
12 T2, T3
FT37-43 2
13 J4 2-pin right-angle MTA connector 1
14 U2 LM380 audio amplifier IC 1
15 Y1-Y7
7.287MHz HC49/U crystal 7
16
Screw - 4-40 x 1/4" PH Phillips M/S 1
18
Hex F/F spacer - 4-40 x 3/8” 1
20 TO-220 Heatsink 1
21 TO-220 insulator with adhesive backing 1
22 Partially loaded HT-7-2 board 1
Red 26# magnet wire 12”
Green 26# magnet wire 12”
Bare wire 6”
RG-178B/U coaxial cable 7”
19 #6 Nylon washer 1
17 Screw—4-40 x 3/8” PH Phillips M/S Plastic 1
Heat shrink tubing 4”
2
5
7
6
19
8
18
14
12
15 21
3
4
16 20
10
9
1
11 13
22
17

Page 13
Item Description Qty
1 HT-7-1, -3 mic preamp/mixer boards (assembled) 1
2 Bottom chassis 1
3 Top chassis 1
4 End chassis 1
5 DC power jack - 5.5x2.5mm chassis mount 1
7 Hex key, .05” 1
8 PN41 switch button, gray 1
9 Speaker 1
10 S/N sticker 1
11 Snap rivet 1
12 Screw - 6-32 x 1/4" FH Phillips M/S Black 4
13 Screw - 6-32 x 3/8” PH Phillips M/S 2
14 Nut - 6-32 KEPS 5
15 Nut - 6-32 hex 1
16 #6 Solder lug 1
17 #6 Nylon washer 2
18 Angle bracket 2
19 Knob 1
20 2-pin female connector with 2” red/black wires 1
Heat shrink tubing 4”
Insulated hookup wire, white, black, 24AWG 12”
Insulated hookup wire, red, orange, 24AWG 8”
RG-178B/U coaxial cable 8”
6 DC power plug 1
Chassis Parts 1
2
3
4
6
7 8
1312 14 15
109
11
16 17 18 19
5
20

Page 14
RefertoPictorial1forthefol‐
lowingsteps.

()Loadandsolderthetwomono
minijacks,J1andJ2,where
shown.Besuretheylieflat
againsttheboard.Becareful
nottodamagetheplastic
bodieswiththesoldering
iron.Notethattwoofthe
tabsextendingintotheholes
intheboardareplastic,so
donotapplysoldertothese.

()LoadandsolderRV1,thevol‐
umecontrol.Besurethatit
liesflatagainsttheboard.

()LoadandsoldertheBNCcon‐
nector.Besureitliesflat
againsttheboard.

()Loadandsolderthe2‐pin
right‐angleconnectoratJ4.
Thisconnectormountstothe
bottomoftheboardandex‐
tendsoutintotheopening.

()LoadandsolderD3,thelarge
1N5404rectifier.Insertthe
sidewithaband(thecath‐
ode)intothesquarepadwith
thepartorientedvertically.
Bendtheanodeleaddownand
intotheotherhole.Solder
bothleadsandclipexcess
leadlength.

()LoadandsolderRV2,the10K
trimpot.Clipexcesslead
length.

()LoadandsolderT1,the6‐pin
DIPtransformer.Thepin
markedwithadotmustgo
intothesquarepad.

()Loadandsoldertheseven
crystals,Y1‐Y7.Besurethey
lieflatagainsttheboard.
Itdoesnotmatterwhichside
theletteringgoeson,but
mostbuildersprefertoline
themupsothatthetext
readsthesameonallcrys‐
tals.Clipexcesslead
lengthsaftersoldering.

()Insert3”ofbarewireinto
theholesjustbelowthe“Y1”
and“Y7”texttotherightof
thecrystals.Placeitso
thatyoucansolderittothe
topofallthecrystals.Sol‐
derthetwoends,thensolder
ittothetopofeachcrys‐
tal.Donotuseanymoreheat
thannecessary.

()Loadandsolderthe330uF
electrolyticcapacitor(C12).
Besuretheblackstripeis
onthesidewiththeround
pad.Thelongerleadisthe
positivelead,anditgoesin
theholewiththesquarepad
(alsomarkedwitha“+”on
thesilkscreen).

()Loadandsolderthe470uFca‐
STEP-BY-STEPASSEMBLY - HT-7-2 Board

Page 15
Pictorial1.ComponentplacementonHT‐7‐2Board

Page 16
pacitor(C6)inthesameman‐
nerasthepreviouscapaci‐
tor.

()Loadandsolderthe10uF/25V
electrolytic(C2)inthesame
mannerastheprevioustwo
capacitors.Thiscapacitor
hasasmallerradius.

()Loadandsolderthe22uFnon‐
polarizedcapacitor(C26).
Theorientationofthisca‐
pacitordoesnotmattereven
thoughoneleadislonger.

()LoadandsolderU2,the14‐
pindual‐inlinepackage(DIP)
IC.Besurethatpin1is
placedinthesquarepad.The
notchontheendofthepart
isclosesttotheedgeofthe
board.

()LoadandsolderQ2,thetran‐
sistorwiththemetalcan.It
canonlybeinsertedonedi‐
rection,butmakesurethe
tablinesupwiththemarking
onthesilkscreen.Makesure
thistransistorliesflat
againsttheboard.

()Insertall12”ofthered
magnetwireintoanFT37‐43
toroidcore,leaving2”out‐
side.Wrapthewirenine
timesaroundthecore,pull‐
ingtightlyoneachturn.Re‐
memberthateachtimeyou
passawirethroughthecen‐
terofthecorecountsasone
turn.Spreadtheturnsout
evenly,coveringabout2/3of
thetoroid.Cuttheexcess
leadoff,leaving2”outside
sothatthetwoleadshave
thesamelength.Savethere‐
mainingwireforusewithT3.
Wrapthe3‐turnsecondaryus‐
inggreenmagnetwirearound
thetoroid,overlappingthe
primaryasshowninDetail1.















Detail1.T2winding

()PlaceT2flatagainstthe
boardandinserttheprimary
(red)leadsintotheholes
marked1and2.Insertthe
greenwiresintotheholes
marked3and4.Pullthe
wirestightfromthebottom
oftheboardsothatthetor‐
oidliesasflataspossible.
Cuttheexcessleadlength
Green
Red

Page 17
0.4”
4‐40x1/4”panheadmachinescrew
heatsink
4‐40x3/8”spacer
Transistor
ThermalsilTMinsulator(applystickysideto
heatsinkandremovematerialcoveringthehole)
Pictorial2.Q3preparation
ThermalsilisatrademarkofAavidThermalloy,Inc.
Detail2.Coaxialcablepreparation

Page 18
off,thenremovethewhole
partfromtheboardandtin
theleads,removingthe
enamelfromthewire.

()Re‐insertT2intotheboard
andsolderallfourwiresin
theirrespectiveholes.

()Loadandsolder4‐poledouble
throwmomentaryswitchS1.
Makesureitliesflat
againsttheboard.Donotat‐
tachtheplasticbuttonto
theendatthistime.

()WindtoroidT3inthesame
mannerasT2,butuseonly
threeturnsofredmagnet
wirefortheprimaryandfive
turnsofgreenwireforthe
secondary.Prepareitsleads
aswithT2,andthensolder
itinplaceontheBOTTOMof
theboard,allowing1/16”
clearancebetweenthetoroid
andtheboard.Theredpri‐
maryleadsgointotheholes
markedT3‐1andT3‐2andthe
greensecondaryleadsgointo
holesmarkedT3‐3andT3‐4.
Thecenterofthetoroid
shouldbeplaceddirectly
overthecenterhole.

()PrepareRFpowertransistor
Q3asshowninPictorial2.

()InsertQ3intoitsholesfrom
thetopsideoftheboardand
lineupthespacerwithits
hole.Solderthethreeleads
ofthetransistorandattach
thespacertotheboardusing
a4‐40x3/8”plasticpanhead
machinescrewanda#6Nylon
washerplacedbetweentoroid
T3andtheboardasshownin
Detail3.
Detail3.Q3installation


()CuttwolengthsofRG‐178B/U
coaxialcableto3.5”.Refer
toDetail3forpreparation
ofallcoaxialcableassem‐
blies.

()Solderthecenterconductors
ofonepieceofpreparedco‐
axialcablebetweenpadsla‐
beled‘A’andconnectthe
shieldsto‘GND’.Loadthis
cableonthebottomofthe
board.

()Repeatthepreviousstep,us‐
ingpads‘B’and‘GND’.

Page 19
RefertoPictorial3forthefol‐
lowingsteps.

Cutthestrandedcoloredwiresto
thelengthsshownbelow,strip
theleadsto1/8”,tinthemand
solderthemasfollowstothetop
oftheHT‐7‐2board:

()SPKR+5”[White](strip/tin
thelooseendto1/4”)

()SPKR–5”[Black](strip/tin
thelooseendto1/4”)

()Twistthewhiteandblack
speakerwirestogether,about
2turnsperinch.

()DCin+2”[White](strip/tin
thelooseendto1/4”)

()DCIn–2”[Black](strip/tin
thelooseendto1/4”)

()Twistthewhiteandblack
DCinwirestogether,about2
turnsperinch.Solderthe
whitewiretothecenterpin
oftheDCpowerjack.Solder
theblackwiretotheside
pinontheDCpowerjack.Re‐
movethenutandwasherfrom
thejackandsavethem.

()Sandwichthespeakerbetween
theelectretmicboardand
thepreamp/mixerboard(HT‐7‐
1)usingtwo6‐32x3/8”
screws,two#6Nylonwashers
(betweenthespeakerandthe
HT‐7‐1board),one6‐32KEPS
nut,onehexnutandone#6
solderlug.Thesolderlug
mustbepositionedfacingthe
speakeronthesamesideas
thespeaker’sterminals.Be
verycarefulnottodamage
thetrimpotswhentightening
thenuts.Seedetail4.Note:
thescrewswillberemoved
aftertesting,whenthe
speakerandmicboardsare
permanentlyinstalledinthe
chassis.









Solderthesewirestothebottom
oftheHT‐7‐2board:

()Mic51/2”[White]

()Amp51/2”[Orange]

()MicPwr51/2”[Red]Note:
RevAboardshavetwoother
partsattachedtothispad.
Becarefulnottodislodge
them.

STEP-BY-STEPASSEMBLY - Chassis Integration
hexnut KEPSnut
Detail4.HT‐7‐1mounting
Positionmicboard
onothersideof
speaker

Page 20
()Stripandtinthecentercon‐
ductorto1/8”andthebraid
to1/2”oneachendofthe8”
RG‐178B/Ucoaxialcable.Sol‐
derthecenterconductorto
“RFin”andthebraidto
“GND”.SeeDetail2.

()Cuta2”lengthofblack
strandedwire,striptheends
to1/4”andtintheends.
Solderoneendtothesolder
lug.Attachtheotherend
aroundthelugonthespeaker
markedwitha“‐”butdonot
solderit.

()Findthetwistedwhite/black
wiresgoingtoSPKR+/‐onthe
HT‐7‐2boardandsolderthe
whitewiretothe+terminal
onthespeaker.Attachthe
blackwiretothe‐terminal
andsolderthetwoblack
wiresonthisterminal.

()Solderthethreeloosewires
tothebottomoftheHT‐7‐1
boardasfollows:

()White:Mic(Becareful
nottodislodgethemagnet
wirethatconnectsthispad
totheelectretboard)

()Orange:Amp

()Red:Pwr

()Slideheatshrinktubingover
theRG‐178B/Ucoaxialcable.
Solderthecenterconductor
to“RF”onthebottomsideof
theboard.Soldertheloose
barewirethatisattachedto
thecrystaltothebraid,
thencutthebarewirenear
thepointwhereitattaches
tothecrystal.Slidethe
tubingoverthebraidandap‐
plyheatuntilitshrinks
overtheconnection.Re‐
solderthebarewiretothe
crystal.

()Rotatethevolumecontrol
counterclockwiseuntilit
clicks(off).

()Ifyouwillbeoperatingthe
HT‐7fromaninternalbat‐
tery,attachthebattery
wirestotheprovided2‐pin
cable(CA1),whichconsists
ofaredandblackwire
crimpedtoanorange2‐pin
AmpMTAconnector.Stripthe
endsofthewiresandthose
ofthebatterytoabout1/4”
each.Placeheatshrinktub‐
ingovertheinsulatedpor‐
tionofthebatterywires,
thentwistthewireendsto‐
gether(redtored,blackto
black)andsolderthem.Then
slidetheheatshrinktubing
overthesolderedconnections
andheatthemwithaheatgun
orsolderingironuntilthe
tubingshrinksoverthecon‐
nections.Plugtheconnector
ontoJ4ontheHT‐7‐2board.

Important:TheHTA‐1batteryis
protectedinternallyfromover‐
voltageandoverchargecondi‐
tions.Ifyouareusingsome
otherbatterypack,besureit
canhandledirectconnectiontoa
powersupply.