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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 10th Sep 2018, 10:52 am   #1
Colincolin
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Default Clansman PRC320 stopped transmitting

Hi all;

I have had my 320 about a month and it has been transmitting AOK.

I opened it up to do the replacement of the capacitors in both the synthesizer and power supply.
Put it back together, RX works just fine but it has stopped transmitting. What could I have done? Any suggestions would be welcome.

Cheers Colin vk2jcc
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Old 10th Sep 2018, 8:32 pm   #2
G6Tanuki
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Default Re: Clansman PRC320 stopped transmitting

What happens when you press the PTT? Do you get the 'unready tone' ??

Also, when you opened it up did you rotate the front-panel range-select knob? The mechanical drive between the front-panel-unit/mainboard and the rear unit [where the RF PA stages and output BPF/ATU lives] is by way of a semicircular profile on the front-unit spindle which engages in a "D"-shaped hole in the rear unit.
Misalignment of this when reassembling means that the RF PA stages/ATU/BPF won't rotate in synchronisation with the rotation of the front-panel range-select control: the result is not good.
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Old 10th Sep 2018, 10:48 pm   #3
Colincolin
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Default Re: Clansman PRC320 stopped transmitting

Hi,
Thanks for your reply.
When I press the PTT no tone heard, can hear transmission on my other radio when I whistle or operate the cw key but nothing on the power meter or field strength meter. I was aware to not touch the torrent tuner when the two halves were apart. It was transmitting just fine. I can hear on receive on both lsb and USB. The synthesizer is obviously working.

Cheers Colin vk2jcc
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Old 13th Sep 2018, 7:56 pm   #4
Sparky67
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Default Re: Clansman PRC320 stopped transmitting

I have had the chassis-mount D-type connectors not fully mate when the two sections were reunited Colin. On one set I had to take the gasket out to get it to work again. May be worth trying...?
Cheers,
Martin
G4NCE

Last edited by Sparky67; 13th Sep 2018 at 8:02 pm.
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Old 15th Sep 2018, 12:54 am   #5
Colincolin
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Default Re: Clansman PRC320 stopped transmitting

Thanks , I did try this but still no output.

Cheers

Colin
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Old 15th Sep 2018, 2:42 pm   #6
G6Tanuki
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Default Re: Clansman PRC320 stopped transmitting

Does the meter do anything when you press transmit?

[Put the mode switch to 'tune' for this].

Does the current drawn increase significantly when you try to transmit?

One issue I recall is that the 'trombone' that links the output of the radio back into the ATU can become intermittent in its sliding bit: this causes either periodic deafness on receive (usually when returning to receive after a period of transmission) or if the resistance varies during transmit it can cause the power output to drop back dramatically then go up again a few seconds/milliseconds later. The trombone comes apart for contact-cleaning once you prize out the little clip.
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Old 15th Sep 2018, 10:26 pm   #7
Colincolin
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Default Re: Clansman PRC320 stopped transmitting

Hi thanks for your reply. When the PTT is used the meter swings around to the 3 o'clock clock position. I am taking the output directly from the t/r output into a power meter and dummy load. Not sure how to measure current as its difficult to get in between the battery and thev320 to hook up a meter. I am currently trying to check continunity between the PA out put stop and the LPF. Not easy to get into to do measurements.
Trying to find test on locations is half the problem.
Cheers
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Old 17th Sep 2018, 11:40 pm   #8
Colincolin
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Default Re: Clansman PRC320 stopped transmitting

Well I appear to have continuity between the PA and filter. There is 24 volts on the PA board( 2b). Still got me tossed what the problem is. Voltages all check out on motherboard, psu has 110 volts 12 volts 6 volts and 3 volts present.
Cheers
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Old 10th Dec 2018, 9:42 am   #9
oh6eog_
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Default Re: Clansman PRC320 stopped transmitting

Did you get this sorted out? I have also had the issue of the two D-connectors between the main and PA-section not connecting fully. Sorted this out by moving the washers on the bolts holding the D-connectors to sit below and not above the connector. This makes the connectors push a bit further into each other, making good contact.

But I also have a vague recollection of a +24V line which was supposed to go high on TX, but it didn't. Or was it the +6V TX line to the PA that was the problem. I can't remember. What I do remember is that it was a pain to do fault finding on that problem. I hade the PA boards out of the aluminium casing, at least enough the get the D-connectors loose so I could have the sections connected together and still be able to do measurements on the PA. But you whould be able to check both the +6V and +24V withe the PA intact. Just taking the "aluminum jacket" off the main section of the rig. I think it was a faulty transistor on the little board next to the filter board that caused the line not to go high. I know I ended up desoldering that card in order to change something on it at least.
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Old 12th Dec 2018, 10:08 pm   #10
M3VUV51
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Default Re: Clansman PRC320 stopped transmitting

I had a similar problem on my 320 a few years ago,went deaf and no tx or rx,was a small coax had come unsoldered from the vhf filter in the back of the radio,als put a cap accross the headphone jacks while i was in there to cut down hiss,may not be your issue but worth a look.,73 m3vuv.
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