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A forum for the discussion of matters of a technical nature. All such activities are undertaken at the readers discretion and own risk. If you don't know what you are doing, don't blame us if it all goes wrong!
Otter wrote:If you look at the service manual for the TRC 454 Link a full synthesiser is described using only the crystals you have mentioned.
I guess then that the empty socket might be a crystal for the priority channel only.
Seeing as that is a prehistoric radio, in modern terms, there is no way of getting a priority channel by CPU fiddling or channel switgh jiggery pokery, so the above answer would seem sensible.
If you can get the PLL working, once you have done that try switching to priority to see any voltages around that holder. Also have a look, with magnifying glass to see if any witness marks on the holder sockets. I doubt if a crystal has ever been inserted.
ALSO TURN PRIORITY SWITCH TO OFF ON FRONT PANEL!!!!
With the priority switch in the auto position the red LED now lights up and I'm getting 5.8v and 2.2 at the socket for the crystal but nothing when switched to the off position.
The LED didn't light up before I changed the two components I mentioned and I fitted a crystal in the socket so there should be evidence of marks.
Typo error on the PLL's pin 4, it's 1.5MHz not 15.000MHz.
Pin 5 is 5.12MHz and Pin 6 is 10.00Kc's.
zephyr wrote:George,
The B has a different PLL but does you'rs have the crystal that's missing in the one i have?.
So far I've found D608 and Q602 faulty, the 7.5v zener diode was short circuit and the transistor D325 open circuit, the diode goes to the solder land of the base of Q602.
The PLL has 6.5v Pin 18, and Pin 1 is switched on to 5.6v from channel 33 to 40 indicating that the channel switch is working as it should, Pin 7 the LD is at 0v and Pin 4 Fin is at 15.000MHz.
Pin 11 of the 7473 is at 4.62v.
Yup and the 'B' has mic gain as well, along with a dual squelch control for main/priority
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I looked again at the audio chip and it looked as if someone had re-soldered the pins, so I removed it and fitted a new one.
It's now got receive and transmit but it's not as it should be there's still a problem with the transmitted audio, what there is, is crap.
Irishman1127 wrote:Dave, I looked at mine, and it does have a crystal in there in that socket. 26.610Mhz
CH9 Monitor crystal.
For the priority channel. 26.610 + 0.455 = 27.065MHz = CH. 9
"To this day the words Stirling bridge conjour pride in every Scotsman's heart, while to an Englishman those same words conjour literally no feelings at all." - Cunk on Britain S1 E1
Well yes. It say that its for the priority on the little door. Its totally dead Tim. Not a meg out of it. I think the PLL is toast. I have the mike for it too. I might look into fixing it. Its an unusual piece. If I change my mind ill let you know mate...
Irishman1127 wrote:Dave, I looked at mine, and it does have a crystal in there in that socket. 26.610Mhz
CH9 Monitor crystal.
For the priority channel. 26.610 + 0.455 = 27.065MHz = CH. 9
Makes perfect sense that a plug and play Xtal socket would be for use of a user defined priority channel!
On the its now working on RX but with poor TX, a bit of further dabbling is obviously required, at least I assume the PLL is channel functional, as they are quite difficult to source!
It is both TXing and RXing but from channel 11 to 40 there's TX power but no audio and the external bench counter drifts from around 19 to 22MHz.
There is audio from channel 1 to 10 but it's not right and the mic has to be right up to my mouth.
Monitoring the radio on another radio it's TXing on the correct frequency all the way from 1 to 40 but with the counter connected to the chassis it's as above apart from channel 1 to 10 then it reads the correct frequency without drifting.
This radio only has one test point that I can find and it's just marked TP without any number by it, none of the resistors or capacitors have any screen print for them, so I'm in the dark even if I could find the right schematic.
George,
Thank's for letting us know the missing crystal's frequency. If you're not getting shut of the radio to otter and would like to part with it I'm sure the owner of the radio would appreciate it, that's if I can get it working as it should first.
I'm always up for a different radio and I love a repair challenge, so I'm hoping George and I can come to a deal. Having said that, if you have given up on the one you have there I could be interested in that one. The first thing I would do is to get Sams Photofact CB #141
"To this day the words Stirling bridge conjour pride in every Scotsman's heart, while to an Englishman those same words conjour literally no feelings at all." - Cunk on Britain S1 E1
Otter wrote:I'm always up for a different radio and I love a repair challenge, so I'm hoping George and I can come to a deal. Having said that, if you have given up on the one you have there I could be interested in that one. The first thing I would do is to get Sams Photofact CB #141
Same as me, love a challenge and have taken on a few
doing the same old stuff gets boring after a while.
Well, I don't do repairs for anyone but myself so I can choose my challenge and take as long as I want over it. Doesn't always work because my President Richard has just stopped transmitting with TR50 open.
The radio has to appeal to me. No valves etc.
"To this day the words Stirling bridge conjour pride in every Scotsman's heart, while to an Englishman those same words conjour literally no feelings at all." - Cunk on Britain S1 E1
Mhmm, I've started doing a few for a little extra pocket money but really only volunteer my services for jobs that interest me.
I like to tinker and build as you know but I do like taking the repairs that are 'too difficult', are something I've not worked on before or are a little out of the ordinary where I can learn and enjoy it.
Day job doesn't challenge me so I need something to keep the brain ticking.
