Government Surplus equipment Why consider using and modification

Government Surplus equipment Why consider using and modification considerations

Using Such Equipment • • • Proven design Cheap Availability is generally good Documentation usually available Components are top quality

Past equipment • • BC-457 (Command Sets) BC-458 “ BC-348 A thru Q Models R-389 R-390 A AM-494 SCR-522 APX-6 T-368 RT-68

Popular 144 -220 -432 Equipment • AM-494 AMP (2 X 4 X 150 A) • SCR-522 (2 meter AM 15 watts) • AM-6154/55 Modifiable to 2 – 220 - 432 MC AM=6155 350 – 400 watts All bands Readily available Reasonably priced – $250 -350 plus tube

AM-6155 • • Conversion data easily attainable High quality Tetrode tube (lower drive requirements) Cavity tank circuit design Desk top unit -heavy. No special tools needed to complete mod.

• • • A few evenings (Weekend timeframe to mod. ) In stock at Fair Radio Sales – Lima, Ohio Numerous mod procedures on line VE 2 ZAZ – W 3 RJW – K 7 XC Plenty of assistance available Can be made to appear as an attractive piece of table top amplifier.

AM-6155 AMP • Must build a new grid input circuit • Must build a new grid negative voltage regulation circuit. • Modify AC input to operate on 220 VAC • Blower may be noisy • For tabletop usage install a god set of rubber feet • AC input connect may be modified

AM-6155 Improved Grid Bias Ckt. • • • Uses a LM-337 T Negative regulator Uses 9 parts Can be mounted a small PC board Construction not critical Plenty of space inside to mount Advise that you test first on the bench

Modification suggestions • Remove input coupling knob and shaft • Close front hole with a rubber plug • Remove black name plate from front of cavity unit. • Erase the unused lettering • Painting is optional • Use 4 good quality rubber feet • (remember the unit weighs about 80 pounds)

Tune up and operation • • Turn unit on – power light should come on Check meter readings Wait at least two minutes Turn on high voltage switch – HV light should Come on. Again, check meter readings Key unit via external pnono jack in rear of amp

Operation continue Key unit and adjust bias pot for 70 – 80 ma. Check voltage on screen and HV Screen 40 = 400 volts High voltage = 20 or 2, 000 volts Apply a small amount of drive (2 – 5 watts) and adjust input tune for maximum Ip • Connect a watt meter to output and again adjust input tune, plate tuning and outputcoupling for maximum output. • • •

Operation Cont. • NOTE: If another watt meter available place in the drive input so you can monitor the input and output power simultaneously. • Apply NO MORE than 10 to 13 watts. • Output, if all meter readings are with in limits should 275 to 350 watts. • Plate current (Ip) should not exceed 300 ma. For an 8930 – 350 ma. For a 4 CX 400 A tube.