February 23, 1973 HA-202 Bulletin No: 2 Meter Amplifier HA-202-1 Service Seminar I. Output Transistors 1. Detecting Failure a] Will not tune up to full power, one transistor may be open. b] Output trimmers fall beyond 1/2 turn from preset [into 50 ohm load]. If non-ideal load is used, 1 turn should be the key denoting output failure. c] Measure with ohm meter for shorted or open transistor. These transistors may check GOOD and still NOT operate. 2. Replacement - The following sequence is important to prevent damage to transistors. a] Remove Transistor Nuts First - Be sure to hold the tab with a pliers. b] Then remove the print board mounting screws. c] Unsolder leads of transistor[s] & solder in new one [s]. d] Install print board screws. e] Install nuts on transistors. Be sure to hold the flat tab with pliers. Tension may break heat sink bond resulting in very sort transistor life. 3. Operates in Class C mode. a] Ideal for FM. Not for AM or SSB [distortion results]. II. Supply Considerations A battery should be used. Tolerated voltages are between 12 and 16 volts. Expect the full load of 7 amps. If a battery eliminator is used, more than one-half volt P-P ripple will induce hum in the output. III. Insertion Loss Expect to experience loss of power when the amplifier is not keyed up, [low drive power]. 1. The unit exhibits a 1.5 to 1 VSWR when not keyed up causing any wattmeter connected in the drive circuit to read erroneously. 2. The higher VSWR while the unit is not keyed will cause the output of the driver to be slightly detune. This VSWR will be lowered considerably when the units keyed up because the reactance will be tuned out of the drive line by the input circuit. The power meter should be connected between the amplifier output and the dummy load. Any readings between the driver and amplifier can be misleading. Suggested reading: ARRL Handbook - Transmission Lines. IV. Load High VSWR results in mistuning of the output trimmers. 1. Check for indications of arcs across the mica in the output trimmer. They must be replaced if any found. V. Drive Considerations Please avoid any usage outside of 5-15 watt specification. Failure of the transistors may occur if too high. The amplifier may not key up if power is too low. VI. Mounting Thermal conditions are always a consideration. Suggest not to be mounted in engine compartment. Consider mounting low in the trunk allowing for the heated air to rise. The specs call for a range of - 30 deg F. to 140 deg F. VII. Tuning Up A slight additional power level can be achieved by tuning the unit with the cover ON. We will be providing a cover with holes in it for service only. DO NOT recommend to the customer to drill holes in HIS unit. The cover provides for a dust free environment which may help increase the relay contact life, among other things. VIII. Connections You may recommend, if desired by the customer, to change the phono connectors to BNC's. SO-239 connectors exhibit a bump in the line. DO NOT use or recommend these. IX. Cables Supplied All the specifications were measured using the full length of cables supplied. Do not expect any less performance because the full lengths were used. X. Schematic Error The top condition of ferrite bead L8 goes to the collector of Q2. NOT to the junction of C11 and C12 as shown. -------------------------------------------------------------------------------------------------------------------- November 16, 1973 HA-202 Bulletin No: 2 Meter Amplifier HA-202-2 Low Power Output [Less Than Driver Power] Encountered unit which was drawing low current and had low output [less than input power] upon measuring with PKW-3 [set up to measure more than 30 VR-F] it was found that the relay had a large [20V] drop across terminals 4-3 when keyed. A couple quick "swipes" with a burnishing tool cured this problem. -------------------------------------------------------------------------------------------------------------------- September 26, 1978 HA-202A Bulletin No: 2 Meter FM Amplifier HA-202-3 Trimmer Capacitor Substitute The first production run of the HA-202A will incorporate a substitute trimmer [PN 31-52] at locations C1, C2, C15 and C16 due to unabailability of the new type trimmers [PN 31-87] at this time. The second production will incorporate the #31-87 trimmers. First production manuals will be inserted [PN 591-2721] to instruct customer to use #31-52 trimmers. It is not necessary to change the #31-87 trimmers, unless arcing is a problem. The #31-87 trimmers have a thicker mica insulator. -------------------------------------------------------------------------------------------------------------------- July 30, 1979 HA-202 Bulletin No: 2 Meter FM Amplifier HA-202-4 Relay [PN 69-70] NLA This relay is being replaced with [PN 69-91]. Since this isn't a direct replacement, a modification kit [PN 830-37] has been made available at a cost of $12.00. The HA-202A Amplifier is already supplied with the #69-91. -------------------------------------------------------------------------------------------------------------------- Thats everything I hold up to 1989 that covers the HA-202. Enjoy! -------------------------------------------------------------------------------------------------------------------- That completes the HA-XX series. 73 de Joe W7LPF/4 [NNN0KUU] QWCA - SOWP - NCVA - FISTS - RCC Gordonsville, Va 22942 [Orange Co]