Serial Number:9011904
Year of Manufacture: 1968 (6836 date code on Bendix power transistors)
Date of Receipt: 2019 Jul (for repair)
Source: BWS/GO
State upon Receipt: Low sensitivity on receive. Overall good condition for age.

Date:2019 Dec
Procedure: Manufacturer schematic redrawn into sensible form.

Date:2019 Dec
Symptoms: Low sensitivity on receive.
Analysis: Q101 had been replaced with a 2N404. This is Ge but compared to the intended 2SA239, far too low frequency, and higher capacitance.
Solution: Q101 replaced with 2N4121. While Si, the specs are a better match, far higher frequency and 5pF Cob close to the A239. Also higher gain. Reception now seems good, SSB ham nets on 20m readily received.

Q101 replaced again, with 2N1742, Ge with very similar specs to A239. Works well. 

2N404:  B:4.08 E:4.29 C:0.35
2N1742: B:4.18 E:4.37 C:0.34
2N4121: B:4.10 E:4.81 C:0.32
V+12L=12V, RFG max, antenna open.

Date:2019 Dec
Analysis: Antenna input clamp diodes for receive had been snipped out of circuit. Both diodes measure open. The diodes appear to have been connected to the antenna connector rather than the receive side of the T/R relay. They would have blown when the transmitter was keyed, this would have left Q101 unprotected and perhaps led to its destruction via static/spikes and thus attempted substitution.
Procedure: Diodes replaced with Si, connected on receive side of relay.

Date:2019 Dec
Procedure: VFO dial light & socket had previously been replaced with a different base style not mounted securely. Replaced with similar to original style bayonet socket.

Date:2019 Dec
Procedure: Knobs and front panel cleaned. The 2 screws of the VFO knob each have a broken-off side on one side of the drive slot, the screws cannot be loosened normally. Some cleaning of interior.

Date:2019 Dec
Procedure: NOTE: This unit has had the RCA socket for an external VFO input rewired as an output for the speaker.
NOTE: The pin numbering of the Cinch female plug for power differs from that of the Japanese male chassis-mount socket.

Date:2020 Jan
Procedure: Power plug wiring redone, to include power switch in line circuit.

Date:2020 Jan
Procedure: Operating with 12V only (no HV), in transmit mode TDRV shows signal of ~ 0.8-1V PP (fund. 12.5MHZ@7.6MHz) on 40M, ~0.6V PP (fund. 9.1MHz@3.9MHz), on 80M.


  Unit Log
Yaesu FTDX-100 		bhilpert
2019 Dec