Hi,
I think is quite an interesting repair and restoration and so I thought I'd write it up as it might be useful for someone else !
I got hold of this Kenwood TS-711 with an interesting and slightly confusing fault list ;
- The radio has been modified and has 'additional relays' located within it (!!!)
- Off Frequency by approx 200hz
- S Meter background illumination not working
- VFO tunes but clatters ans clicks at switch on and when non channelised operation (VFO) is selected remains in channel 'click' mode
So nothing particularly unusual for the first three - all easy enough, remove modifications to restore originality, re-align the transceiver (I'd do that anyway!), repair the s meter backlight, but it's the last one that is more interesting - what's that about?
For those readers not familiar with the TS-711/TS-811 range of radios they are a 2M (711) and 70cm (811) multimode transceiver. They can be mains powered or run from 13.8V and are overall even today a very nice base station transceiver. They output around 30W are sensitive and can do the appropriate 12.5Khz channel spacing and with one of my CTCSS units fitted (or an original one with some modifications) will enable use through repeaters.
They do have an interesting tunning operation and that is that the tunning dial has a solenoid on it and when a channelised operational mode such as FM is used (or you can do it manually by pressing the CH Q on the front panel) you heard a fairly loud 'clunk' and the dial then has a 'click' or indented feel to it. When you select SSB or CW or press the CH Q button again you hear a 'clunk' and the VFO has a 'freewheel' feel to it or like a normal VFO.
I can't think of any other way of describing it!
It's really quite a nice approach and as far as I am aware unique to just these models of transceivers.
So upon receipt, sure enough, it's off frequency, the s meter light doesn't work and it has two relays quite nicely mounted inside, and when turned on there are several clunks and then all goes quiet.
It does tune correctly but only with the 'clicks' on the tunning dial - pressing the CH Q button or selecting SSB results in some clunking but no change in tuning style from click mode to 'normal' vfo mode
So I spend some time trying to work out what the relays did - in the end, I gave up - it looked like it was applying external modulation to the microphone for some reason - but easy enough to remove just in case it was having an effect on the other faults - I removed the modification easily enough - so back to standard, no change on any of the other faults.
I replace the S meter illumination with a standard Kenwood backlight bulb - an easy fix!
I'll realign the transceiver at the end so that left the dial issue.
Thinking about it, I'd had one 711 many years ago which didn't quite have the same fault but did have intermittent problems in this area and it turned out to be a solenoid-related problem, so I thought I'd start there.
The solenoid 'frame' is connected to the main VFO encoder and can be removed fairly easily, you need to remove all the knobs and then the front panel - the front panel can then be folded down and by removing two screws from the front and the large but the VFO and solenoid unit can be removed for inspection (after of course removing the relevant leads from their sockets!).
So after doing that I had a look, the design is ingenious a solenoid is used as a piston to move a star-shaped 'cog' around which triggers but a position indication at the right time and also removes the 'click' from the VFO, like I say ingenious.
Well this one wasn't moving freely and was very stiff, and this was what was evidently causing the problem - the solenoid tried to move the cog, failed two or three times as it was stiff and then the CPU stopped it doing it as the position sensor (a microswitch) didn't give the right signal at the right time to indicate it had moved.
At least that's what I think it was doing !!!!
So how to repair it?
Initially, I disassembled the solenoid, piston, and other elements, take care don't lose anything there are a very small circlip, a washer, a spring, and another washer. lose them and you're sunk
After removing them you can remove the 'cog' which does the movement and triggers the microswitch - no need to remove the microswitch (or at least I didn't)
This is the bit that took me some time to work out - the cog is on a spindle that goes inside the VFO encoder housing and it was jammed - or at least very very stiff - I tried to lubricate it carefully but nothing would allow it to move.
So after a little thought, I decided to remove the VFO encoder PCB (four screws) to see what was on the inside of the VFO encoder, after carefully doing that I could see that the 'spindle' actually had a small square piece of plastic that turned and 'lifted' a small piece of metal that provided the 'click' in channelised mode - very clever !!!
This spindle was so stiff it wouldn't move, but after some careful manipulation, I succeeded in removing it. The spindle had a blackish tinge to it and so I cleaned it up with some wire wool and also the hole that it went through as well. After replacing it, it moved very freely and nicely so with a small amount of oil to help it, I put the encoder back together again. Be careful if you push the spindle too far it will drop back into the encode and you will need to disassemble it again !!
I then rebuilt the unit in the reverse order, take extra care to ensure that the circlip holding the 'star cog' is in the right position or the solenoid won't work correctly and once this is back ensure that the washer, spring, washer order is correct to apply a small downward pressure on the metal arm - and the circlip is correctly fitted on top of this - or it will jam up.
It is a complicated little piece of engineering!
When complete you should be able to push the solenoid arm backward and forward easily which will move the 'star cog' and trigger the microswitch - difficult to describe but when you see it - it makes perfect sense!
With that, I put the unit back into the front panel and reconnected the encoder, etc. but before I put everything including the front panel back on I tested that the repair had worked.
Applied power and no clunking noise (a good thing) press the CH Q switch a 'clunk' and the VFO was free - press again and 'clunk' it was back to being a channel switch with steps.
Excellent ! - all working and just about two and a half hours in total, not including an alignment of course!
Now just to do a straightforward alignment - I checked the frequency which was a little high and it will be completed.
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