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No receive or transmit

 

I recently picked up a non-working 847 to replace the display on mine. The numbers on my 847 were losing some of the segments but the inoperable 847 had a good display. It was an easy swap and now my 847 has a good display. The OP I bought the salvage 847 from told me he had purchased it from an estate sale but the rig was 'deaf' when he connected an antenna and powered it up. ?I hooked it up to a watt meter and dummy load and the rig will not transmit on any band. I started the alignment procedure and discovered the PLL adjustments showed minimal voltage (.022 volts) at TP20001 and would only change a few thousands when I adjusted T2001 through T2005. ?
?
I am wondering where to go at this point to start troubleshooting this issue. Is it worth pursuing trying to repair this non-working rig or put it on the shelf to salvage parts from in the future?
73,?
--
David Rutledge
AL5M
Re: No modulation on HF?

 

Will do this saturday, I'll let you know. Thanks
Re: No modulation on HF?

 

--
Greetings from Erik Rothuis (PA2ER), Terborg Netherlands.
Re: No modulation on HF?

 

Put the transmitter in SSB.
Mic gain 12 o clock position.
Inject a 1KHz tone at 3mv level to the MIC jack (pin 8 = mic input, pin 7 = ground)
Use a old amplified computer speaker, to trace the 1KHz tone, at the points below:
  1. Q1053 (M5207L01) pin 4,
  2. With a DC voltmeter, Q1053 pin 3, must be around 2.5 Volts, and changing when rotating MIC Gain,
  3. Q1053 pin 2, amplitude changes when rotating MIC Gain,
  4. Q1081 (BU4053BCF) pin 14,
  5. Q1038 (NJM2902M) pin 7,
  6. Q1038 (NJM2902M) pin 8,
  7. Q1081 (BU4053BCF) pin 15,
Please let us know your findings.
--
Greetings from Erik Rothuis (PA2ER), Terborg Netherlands.
Re: No modulation on HF?

 

Thank you. I also notice that at the ssb there is no signal, of course im only using a osciloscope
Re: No modulation on HF?

 

The ic is a m5207L01 that is a stereo volume controller. PIN2 = output, PIN3 = control 0-5 volt, PIN4 = input.
The datasheet can be found here
?
--
Greetings from Erik Rothuis (PA2ER), Terborg Netherlands.
Re: No modulation on HF?

 

These chips were are current mirrors, you will not see the mic signal around here, look upstream towards the modulator and SSB filter.

73

Andrew

?Get BlueMail for Android ?

On 21 Aug 2024, 03:57, at 03:57, "HI8RMQ via groups.io" <rafael_mota@...> wrote:
This is the preamp area, the left top ic manages audio input into
hf,vhf,and uhf.
Part is not clearly readable, but I think is Q1063 or Q1053.

Yellow line is the traced path from 1Khz audio input from mic.
Blue is the command data to control the audio to be output in the red
line.
Red line measures noise, not the 1Khz signal as I think it should.
Maybe a more experienced mate could observer something from this.
Re: No modulation on HF?

 

This is the preamp area, the left top ic manages audio input into hf,vhf,and uhf.
Part is not clearly readable, but I think is Q1063 or Q1053.
?
Yellow line is the traced path from 1Khz audio input from mic.
Blue is the command data to control the audio to be output in the red line.
Red line measures noise, not the 1Khz signal as I think it should.
Maybe a more experienced mate could observer something from this.
?
?
Re: No modulation on HF?

 
Edited

HI8RMQ if you want us to point you at the possible fault. You have to gif answers to our questions consistently. And gif answers to what you are asked.?
--
Greetings from Erik Rothuis (PA2ER), Terborg Netherlands.
Re: No modulation on HF?

 

开云体育

Please just make a video and post it as private on YouTube. Folks can then see exactly what’s going on and broach a comment.


De Spence G5STO

Sent while portable! please excuse typos.

On 20 Aug 2024, at 12:30, Andy Bosworth via groups.io <sidthepop@...> wrote:

?
Great, if power output is ok on FM and CW then your PA is working.
Do you have the same low SSB on VHF?
Where were you feeding audio in to the rear? Which port on the back?
Finally, what test equipment do you have?

On Tue, 20 Aug 2024, 12:14 HI8RMQ via , <rafael_mota=[email protected]> wrote:
Very low audio, so SSB on HF is at much 3W.
Powers on other modes all fine, AM, FM, CW, but theres no audio noticeable on FM or AM.
Just happens on HF.
?
?
Re: No modulation on HF?

 

Great, if power output is ok on FM and CW then your PA is working.
Do you have the same low SSB on VHF?
Where were you feeding audio in to the rear? Which port on the back?
Finally, what test equipment do you have?

On Tue, 20 Aug 2024, 12:14 HI8RMQ via , <rafael_mota=[email protected]> wrote:
Very low audio, so SSB on HF is at much 3W.
Powers on other modes all fine, AM, FM, CW, but theres no audio noticeable on FM or AM.
Just happens on HF.
?
?
Re: No modulation on HF?

 

Very low audio, so SSB on HF is at much 3W.
Powers on other modes all fine, AM, FM, CW, but theres no audio noticeable on FM or AM.
Just happens on HF.
?
?
Re: No modulation on HF?

 

Further up the discussion he stated 100 watts FM on HF, so PA is fine.
Perhaps the OP could clarify if any power on AM, CW and FM on HF, just so we are not getting confused.


Virus-free.


On Tue, 20 Aug 2024 at 01:37, Erik Rothuis via <erothuis=[email protected]> wrote:
So no power in HF in FM mode? Then the fault is in the HF PA section, Q3002, or the preceding BPF.
--
Greetings from Erik Rothuis (PA2ER), Terborg Netherlands.
Re: No modulation on HF?

 

So no power in HF in FM mode? Then the fault is in the HF PA section, Q3002, or the preceding BPF.
--
Greetings from Erik Rothuis (PA2ER), Terborg Netherlands.
Re: No modulation on HF?

 

Correct. The modulation in HF is very very low, talking very loud may give 3 or 4 w
Re: No modulation on HF?

 

Correct me please if i am wrong.
The TS says that there is no modulation in phone and in digital mode, on HF?
There is modulation on 2 meter, and 70 centimeter, in all modulation modes, digital and phone?
--
Greetings from Erik Rothuis (PA2ER), Terborg Netherlands.
Re: Receiver Audio Volume

 

Receivers ok.
Problem is on HF, all bands.
Audio input management? is indepent for HF, VHF, UHF, so I guess the module that handles the HF audio is bad somewhere. Sadly I dont have a signal tracer.
Re: Receiver Audio Volume

 

Does the receive signal strength also increase?? Is it the same on every band or only one band.? It could be dirty/arced relay contacts or a relay with bad solder joints (common on most HF rigs of the era).? There are relays for each band to switch in and out the band pass filters and there are RX/TX relays.
?
Mikes Radio Repair
KC3OSD
Re: Receiver Audio Volume

 

First of all check your powerkabel, connectors, fusses, and fuse holders, for bad contacts.
--
Greetings from Erik Rothuis (PA2ER), Terborg Netherlands.
Re: No modulation on HF?

 

Late to the party.? So from the sounds of it you have no modulation or very little in any mode.? SSB, AM, FM or data.? That should be rather easy to troubleshoot.? Just inject a audio signal (10mV at 1kHz) into the mic jack and signal trace the audio through the TX audio chain.? All you need is a oscilloscope or even a antique signal tracer will work.? Just follow the mic audio chain using the block diagram.
?
Mikes Radio Repair
KC3OSD
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