R71: Poor RX Audio-Garbled SSB audio on one or more bands in my R71.
Audio may cut out altogether. Some bands may sound OK. Problem may be temperature related.
Bad trimmer capacitors on PLL unit, HPL VCO section. To fix: Replace plastic trimmer capacitors C78, C88, C97, and C107 with ceramic equivalents. Remove excessive wax from around replacement trimmers to prevent wax contamination. We suggest using a 12 pF trimmer capacitor for C97 instead of a 6 pF as listed in the service manual. This will allow you to properly adjust the HPL lock voltage for that band. While you have the PLL unit lifted, rework cracked solder around the regulator section and at the two ground springs.
R71: Loud, high pitched squeals coming from inside my R71.
DC-DC converter transformer has a loose core. Replace T1 transformer (TO-9) on the display unit.
R71 Distorted RX and TX: PLL Modification Technical Bulletin
Technical Bulletin describing modification to PLL.
R71: Erratic display i.e., frequency listed will be out of the normal operating range of the radio.
Rotating the VFO knob may cause strange characters to appear in the display. Cycling the power switch a few times may restore operations temp.
Resolder cracked joints at J1 and J2 connectors on RAM unit, then reprogram. If this does not help, substitute RAM unit with a known good one. If the substitute RAM unit works properly, then the RAM unit must be replaced.
R71: Poor audio quality on most bands.
Noise seems to be internally generated and is present whether or not an antenna is connected.
Dried out capacitors C128, C129, C130 and C137 on PLL unit are causing the 5 and 8 volt regulators to oscillate. Replace capacitors. Most of these capacitors are light blue when new. If they have turned brown or gray, they are old and dried out.
R71: No power up. No display, No lights. Problem may be intermittent.
- Cracked solder joints on regulator unit.
- Loose board mounting screw on the regulator unit that provides ground to the board.
- Cracked solder joint(s) where power transformer mounts to regulator unit. To fix: Remove the regulator unit from the radio and resolder all suspicious solder joints on the regulator unit. Pay particular attention to the solder joints at heat sink-mounted transistor Q1 on the regulator unit. Modification: After tightening the regulator unit to the chassis, at the chrome screw with the spacer, apply a solder bridge across the spacer to form a solid electrical connection between the board and the chassis. This will prevent future failures due to bad connections at this joint. The power supply on the R-71A receiver runs quite hot, and problems with the regulator unit are common. We recommend inspecting and servicing (if needed) the regulator unit in all R-71A receivers that are in need of repairs.
R71 AC hum in audio; the radio may seem to vibrate during operation; pilot lamp may be dim. Inspection reveals excessive AC ripple on 13.8 line in radio.
Bad bridge rectifier D1 on regulator unit. Replace bad D1 bridge rectifier (KBPC102).