Bring That Old Rig Back to Life

Brian Harris, WA5UEKcosmophone@yahoo.com

September 12, 2011

Shack Photo Courtesy K0EOO

Why Use Old Gear?• Fun to Use• Easier to work on (spacious, no special tools)• Replacement parts readily available• ESD, Surge and Lightning Resistant• Uses mostly standard components• More forgiving of operator error• Costs less (most of the time)• Does not depreciate (and may appreciate)

RestorationCleaning

• Remove rig from cabinet (place all knobs, screws, nuts, etc. in a marked jar)

• Remove loose dirt, dust, dead bugs, etc. with compressed air or a brush• Remove tubes (only after you are sure you know where to put them back)• Clean tubes with alcohol so as to not remove markings• Clean chassis with damp cloth and Q-Tips (water or alcohol)• Optional – after sealing transformers, IF cans, chokes and meters

w/plastic and masking tape, spray chassis top with Simple Green and clean with toothbrush

• Rinse well with tap water followed by distilled water• Important – keep water away from dial scales• Dry thoroughly in sun or oven on lowest setting

RestorationTool List

• Large Soldering Gun• Small Soldering Iron• Solder Sucker and Solder Wick• Magnifying Glass• Hand Tools• Bristol and Allen Wrenches• Non-Metallic Alignment Tools• Brushes• Alcohol, Dexoit, Lithium Grease, Simple Green, Fader Lube,

Mobile One

RestorationEquipment List

• Analog VOM • Digital VOM• VTVM with RF probe • RF Generator (Alternative - SS transceiver with adjustable power)• Audio Generator • Capacitor Analyzer (Alternative - Variable HV supply with VOM)• Signal Tracer• Oscilloscope • Tube Tester• Sweep Generator• Grid Dip Meter• Noise Generator• Frequency Counter

RestorationInformation, Safety and Initial Work

• Purchase manual or download from BAMA Mirror (http://bama.edebris.com/manuals/)

• Inspect and make note of loose or disconnected wires and modifications• Replace 2 wire power cord with 3 wire (large blade to return, small blade to fuse

and green direct to chassis)• Add fuse if necessary (i.e. Johnson transmitters) on rear panel or under chassis• Tighten tube sockets and ground lugs• Verify correct transformer voltages• DeOxit on wafer switches, relay contacts, tube pins and tube pin sockets• Fader Lube on all potentiometers• Test tubes if you can• Lubricate panel bushings, gears and variable capacitor bearings with Mobile One

synthetic or lithium grease

RestorationElectrolytic Capacitors

• Power Supply Filter Capacitors - Reform or Replace?Reform:• Make/buy/install a solid state rectifier replacement(s)• Use Variac to apply AC voltage slowly - 10VAC, 25VAC, 50VAC for 10 minutes each,

75VAC for 30 minutes, 100VAC for 30 minutes, then 120VAC for 30 minutes• Feel electrolytics. If they are warm, replace them.

Replace: (recommended)• Rebuild cans or disconnect cans and install new axial leaded capacitors under

chassis using terminal strips

• Test for expected DC voltages (be careful, keep one hand in your pocket)

RestorationOther Capacitors and Resistors

• If present, replace all Sprague Black Beauty capacitors• If you can, measure leakage and values of other capacitors (with the

exception of the pink/red/burgundy silver micas and dogbone style, as they seldom go bad), replacing as necessary

• Inspect and measure all carbon composition resistors, replacing as necessary (metal film replacements will work in most all applications)

• Install tubes• Verify voltages at tube pins are correct, take copious notes• If it works at this point, it’s time for alignment• If not, it’s time for troubleshooting

TroubleshootingReceiver Basics

• Work back to front• Is there noise with volume control at max? If so, skip to IF stage

checkout• Introduce audio signal in 1st and 2nd audio stages• Introduce modulated IF signal from RF generator or Grid Dip Meter• Introduce RF fromF generator or transceiver or Grid Dip Meter

TroubleshootingTransmitter Basics

• Work front to back• With a dummy load and in-line SWR/Wattmeter check for power output

If not, listen for desired signal with receiver• No signal? Check signal levels starting at VFO with VTVM or Scope• Inject low level RF signal in early stages

Line Voltage

• Most vintage equipment was designed for 110-115VAC• Line Voltage today is typically 120 to 130VAC• Increased AC input voltage causes increases in internal voltages, power

dissipation and heat• Component life is indirectly proportional to heat• Tube life is indirectly proportional to filament voltage and power

dissipated

Solution: Lower the line voltage, but how?• Variac• Bucking transformer • Constant voltage transformer

InformationComponents, Assistance, Reference Material

• http://www.mouser.com• http://www.digikey-com• http://www.boatanchors.org/filtercap.htm#SP-6 (how to rebuild canned electrolytics)• http://www.harbachelectronics.com/001 (Peter Dahl transformers)• http://www.mcmaster.com/# (good source of hardware)• http://bama.edebris.com/manuals/ (free manuals)• http://tubes_tubes_tubes.tripod.com/id4.html (knobs, tubes, transformer rewinding)• http://www.esrcvacuumtubes.com/contact_esrcvacuumtubes.html (tube source)• http://www.nostalgiaair.org/ (reference links)• http://www.tubesandmore.com/ (Antique Electronic Supply)• http://www.smallparts.com• http://www.qth.net (mail lists for boatanchors, heathkit, drake, national, hammarlund, hallicrafters, etc.)• http://k9sth.com (Glen Zook – Richardson)• http://www.angelfire.com/electronic/funwithtubes/Testing_caps.html (how to test capacitor leakage)