After having been dormant for 5 years (and possibly longer), I was warned by the seller that the rig would need some 'TLC'. Surprisingly, it didn't need as much as I expected...
Comments on first inspection, no TX at all (the accessory plug which powers the heaters for the 6JS6C's is missing) and the receiver is as deaf as a board. I don't expect the FT-101 to hold its own against modern receivers on IMD and sensitivity, but it should certainly not be deaf... The S meter normally shows absolutely zero on perfectly readable signals which show S9 on the FT-990, but will blip to S9+25 on stronger signals with nothing in between. Something very strange going on here...
|5th June 2004: Attention initially went to the relays, these being mechanical items and obvious candidates for further inspection. The contacts on the antenna changeover relay (ringed) looked pretty sick with the contact plating flaking off, so I decided to replace it. The original was an Omron MX2P part which is no longer available. Yaesu recommend attaching an Omron MY2 to the existing relay base to get round the problem, although the MY2 is a much more substantial relay.|
|This is the MY2 replacement shown above
wired to the smaller base of the existing relay. It really is a
squeeze to get in, the 'flying saucer' capacitor has to come out of the PA
cage to get the new relay in, and the plastic cover has to come off the
relay or it just won't fit at all.
Click the pic on the left for a larger version, or indeed for any pictures on this page.
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|It's still deaf, but at least consistently the same level of deafness
now that the relay has been replaced. The RF board had a weird PCB
attached to it with a Plessey SL640 mounted on it. A mod to use a
DBM for first stage mixing instead of the dual gate FET? Very
strange as a bit of surfing on the name of the board revealed that it was
meant to use an MC1496...
On a hunch, I carefully took hi-res pictures of the wiring arrangement of both sides of the modified board and removed the mod. The tracks which were cut as part of the modification were reinstated, and the ceramic caps which had their leads cut were replaced with new items. Voila - plenty of sound on all bands, and the S meter works properly.
|RX is sorted, onto the TX. The
FT-101 will not transmit if the accessory plug is missing, as this one
is. It's used to jumper the two blue wires on pins 1 and 2 in order
to power the heaters of the 6JS6C's. This is not as dim as it
sounds, the reason is to do with the optional transverter stealing power
from the transceiver and preventing the output valves from heating up and
drawing current by having the link missing between pins 1 and 2. Temporarily fixed for now with a jumper
wire across the two pins.
Note: Since writing this, MattD from the uk.radio.amateur newsgroup kindly mailed me an accessory plug FOC, so I now have the proper plug. Cheers Matt!
|I'm on the home run now, only a couple of
problems left. No CW keying (turned out to be a tarnished 1/4"
jack socket), and low output on 14MHz and above, like about 3-5W maximum.
The 14MHz+ problem turned out to be alignment errors with the permeability tuned coils shown on the left, I'm still working on it, but the 6JS6's will pull an easy 300mA+ now with the carrier control at moderate settings and plenty of RF output.
|Everything is now ship shape, and alignment has been completed. The RX is sensitive now, and the TX is putting out plenty of power on all bands.|
|24th October 2004: This TX has still not been put on air and has
developed an intermittent fault on both RX and TX. This has been traced
to the trimmer capacitors for the band change oscillator, and some other trimmers
are showing signs of cracking.
An order has been placed with Mouser in the USA for replacement Japanese ceramic trimmers which have now arrived. Every ceramic trimmer in the unit will shortly be replaced (and there are plenty of them).
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