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) APX-6 BC-458 “ T-368 BC-458 “ BC-348A thru Q Models RT-68 R-389 R-390 R-390A AM-494 SCR-522

Popular 144-220-432 Equipment AM-494 AMP (2 X 4X150A) 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 VE2ZAZ – W3RJW – K7XC 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-337T 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 4CX400A tube.