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Thanks lads, I know what you mean nomad So I'm am not at the radio but the problem is still in my head. So tr 2o takes in the tripled crystal freq. Also the frequency generated by the vco, I still not sure how the vco gets its frequency from, It them mixes them and sends on the signal to the...

A few days away in the rain in west ireland.... perhaps the sun will shine.

Ok theres a good deal of info there to check . I have to take a break away from it now for a few weeks worse luck. So Is it ok to resume when I get back . J

Thank you. It's just such a beautiful radio, and the fact it brought many contacts from USA and Europe. In fact my father made several friends in USA and developed into writing letters. Back in those late seventies early eighties, there were no mobile phones set etc, so for us it was amazing to...

Good Morning all i must say ye have great patience to stick with this problem, thank you . Its very good of you to take the time and explain it so well. The diagrams are fantastic. I started exploring the low pass filter stage, checking capacitors, no change but then i checked out...

Thanks Andy, i have checked all the vco voltages and they appear right to whats in the schematic except for pin 10 thats only 2.01 and pin 5 is 6.9 v i have checked tr 20 out of circuit and it also is ok but the voltages at its collector are only 4.8 and 4.03 at the base. i have checked...

Ok so far if checked tr 20 it has emitter 33.975 Collector variable and base 35.475 mhz And tr29 emitter can't measure anything Collector 33.975 and base 11.325 ...

Thanks nomadradio That's great information So I will try to investigate that area I will try to find if 11 3258 is working for a start. Your explanation of how it works really clarifies what I need to do next. I will send on the results. For information like you just gave there, would lou...

good morning and thank you all for the help. so i have replaced the voltage regulator regulator and the new voltages are pin 1.......... 8.3 pin2 ......... 13.5 pin 3 ....... 8.3 pin 4 ...... 0.0 pin 5 .... 13.5 pin 6 .. ... 8.8 pin 7 ..... 0.00 pin8.. .5 Now i...

Good morning, bluster day here in Ireland thank you all for the comments. Yes i have changed all the capacitors except the tantalum ones. As regards c135 when i remove it the radio transmits a and receives but does not change frequency when i turn the channel selector. Now i have replaced c 135...

ok so i have made a discovery:sneaky: I was checking out the capacitors and i found that c 135 was not connecting properly, i have re soldered it and now i find 1 that the rx audio is much lower....i can hear stations 2 its not switching to tx no output if i unsolder the c135 again it all...

650 watts...tube?

Thanks Magnum. A great radio in its day

thanks Woody

Sitting out the storms in west ireland

hi Andy thanks for the quick reply, i have tried what you said, ithe display shows the new channel. I tried a short tx on channel 20 and i can receive it audio and all on the sdr but the frequency is 27 405 regardless of the channel number displayed. THanks again

Hello first to say what a great forum youn have here, i have been reading the articles trying to fix a cobra 2000 i bought new in the eighties. My father and i used it a lot in them golden dx days. Anyway it was put away in a room where it stayed for many years untill recently when i thought i...