ham international jumbo not transmitting after few minutes

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koberk
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Re: ham international jumbo not transmitting after few minut

Post by koberk » 22 Mar 2012, 19:27

Indeed, tucked in between the 10.240 MHz Crystal and the channel changer, thus making its removal no problem at all...

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Re: ham international jumbo not transmitting after few minut

Post by brightspark » 23 Mar 2012, 01:07

Thank you so much for this - I think i may have found it - Is it C11 560Pf. I used to be on the radio - I am of 137 Division Isle of Man. I would love to get it working.

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Re: ham international jumbo not transmitting after few minut

Post by CaptainKirk » 24 Mar 2012, 11:31

ok the Cybo boarded rigs may not be as good as uniden so what, I love old Cybernet rigs as well as Uniden ones. I rate a Cobra 148 GTL DX MK2 one of the best rigs ever made the Grant is supposed to be better I dont know never had a Grant in my possession.I like the Jumbo 059 its old and it deserves a bit of TLC. its not all about TX quality is it you have to live with the rig on RX as well and a 059Jumbo/MM2 is quite nice to listen on IMO :D
CAPTAIN KIRK-26TM013/26CT013/26UK013 John mobile South Cheshire.

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Re: ham international jumbo not transmitting after few minut

Post by brightspark » 25 Mar 2012, 12:06

Hi, I have removed C11 close to the Crystal. The orange capacitor is marked 561KR does this mean it is 56000pf - which equates to 56NF?

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Re: ham international jumbo not transmitting after few minut

Post by koberk » 25 Mar 2012, 12:24

560pF, peco Farad. Quite small.

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Re: ham international jumbo not transmitting after few minut

Post by brightspark » 25 Mar 2012, 14:15

koberk wrote:560pF, peco Farad. Quite small.
Hi thank you so much you have confirmed something i should have known of course 561KR means one Zero after 56 thus 560PF. I have many spare capacitors but not this value. though i have one marked N56 which take to mean 0.56NF which is a minature square ceramic capacitor which maybe equivalent.

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Re: ham international jumbo not transmitting after few minut

Post by brightspark » 27 Mar 2012, 00:59

I replaced Capacitor 11 560PF and it no longer cuts off. It seems to work fine on both transmit and receive. My ex college teacher seems to think that the Capacitor should be 56000PF not 560PF - which does confuse me. The one i put in is marked N56 which i think is equivalent to 560PF. It is a minature square ceramic type. If i put the wrong value in would it cause problems? Checking the SWR i get a reading of 3.2 - but this maybe the antenna - i am not 100% sure. I have been on channel 52 USB (27.555) and i can't hear any transmissions. Is the band very active during the daytime or quiet at the moment?

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Re: ham international jumbo not transmitting after few minut

Post by koberk » 27 Mar 2012, 09:48

You must make sure the cap is 560pF, otherwise the oscillator will not generate the 10.240 MHz RF whidh the PLL and receiver need.
Sorry to sound pedantic, but all rigs need precise repairs, otherwise you'll end up having to compensate with repairs elswhere.
You report the rig works fine on RX and TX now, so sounds like the job is done, since it now no longer fails after a period of time. So well done.
Your SWR problem is another issue...

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Re: ham international jumbo not transmitting after few minut

Post by brightspark » 27 Mar 2012, 10:07

Hi thanks. I tried the radio today and the SWR is about 1.5 so is suddenly better. I heard some very weak sideband stations and could make out some FM propagation - A few girls on talking - but not strong enough to make out what countries they are from. I thought this year was a high sunspot activity - but i am not sure. When i removed the capacitor - I tried the radio with no capacitor in circuit to see what effects i would get and it was as i expected no transmit or receive and very quiet on FM. But once i put the capacitor in - it was fine. Seems to be working today. I am grateful for your help. It is a good forum

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Ashtec
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Re: ham international jumbo not transmitting after few minut

Post by Ashtec » 08 May 2013, 14:23

brightspark wrote:Hi, I have removed C11 close to the Crystal. The orange capacitor is marked 561KR does this mean it is 56000pf - which equates to 56NF?
I know this is an old post but ive just had the same fault on my own Jumbo today when i was having a chat with Bigpimp on AM...................

Now my own Jumbo has a Superstar UFO fitted to it.....

So my fault was the radio would work for a few min's then it would lose the receiver side of the radio in AM/SSB and the Audio on FM would drop very low then it would come back then drop back out :shock:
But the radio work's fine in TX.
At this i thought i had set the AGC up wrong so i did a test and the voltage at pin 15 was way out and could not be adjusted at this i thought i had a fault in the AGC circuit but i thought i would check the Superstar UFO input's and outputs and the radio's oscillator well the first oscillator i checked was the 10.240's and guess what it wasn't oscillating well it did then it didn't
so after checking a few bits around the oscillator's circuit i found that C11 was at fault so replaced that and its all back up and running.............................

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SOLVED = Re: ham international jumbo not transmitting after few minut

Post by ghost123uk » 29 Jan 2018, 14:10

cubwolf wrote:
13 Apr 2010, 18:32
I am assuming this is the Mk1 with the 059 board in?
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.
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I am seeing more and more cases like this in Jumbos and Multimode 2s etc where C11 (560pf) is going short circuit after a few minutes of use.
Its on the base of Q3 the 10.240 oscillator
Its a mica style capacitor and for some reason in the last 2 -3 years more and more have started failing.
Just popped into this thread to say thanks to "cubwolf" as this fixed a Jumbo I had on the bench over the weekend.
Without the info about this dodgy cap, I might have been AGES piddling around with Xtal and VCO etc.
BIG THANKS,
John
John, on the S. Cheshire / N. Shropshire border. Muppet handle "Grey ghost" and on UK C25 most working days.
Don't just monitor, key up and talk, otherwise everyone thinks no one else is out there !!!

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Re: ham international jumbo not transmitting after few minutes

Post by cubwolf » 05 Feb 2018, 22:57

No problems John.

I change them as a matter of course now with any 059 radio that passes through my workshop.

If you are Facebook feel free to drop by to my page.
Loads of tips on it for these radios including the mods to improve the audio and popping squelch etc

https://www.facebook.com/groups/Cubwolf/

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Re: ham international jumbo not transmitting after few minutes

Post by CaptainKirk » 27 Mar 2018, 21:43

I bought a Jumbo few months ago from Belguim spares or repairs it wasnt TXing in the listing when I got the rig it TXed for a few mins then it stopped and the RX was gone too quiet on FM what was wrong you guessed it C11 all ok now lol. great bit of advice many thanks too.
CAPTAIN KIRK-26TM013/26CT013/26UK013 John mobile South Cheshire.

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