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Hi, I am trying to repair an FT847 for a friend, the rig works perfectly on all bands except 2mtrs. On 2mtrs nothing is heard or transmitted; it won’t hear my sig genny at all. I have injected a signal directly into J3001 144RX on the RF Unit and that isn’t heard, I should add that the frequency display is working perfectly. Next I examined the Local Oscillator signal on J3010, we checked this for 70cms (which we knew was working) and could see the signal 45MHz above displayed frequency, all well and good. I then switched to 145MHz and couldn’t find the LO at all on my spectrum analyser. Now this is the ‘fun’ part, when I tuned below 140Mhz, say 139.999MHz a local oscillator signal appeared 45MHz higher, as expected, but would switch off as soon as I reached 140MHz!!!!! We have tried a CPU reset but that didn’t make any difference. Has anyone got any suggestions, we’d really appreciate some inspiration. Sincere thanks. Paul G0ODP, John G0KFM
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Hi, have you checked the voltage on TP2002 on the PLL board? Shall be between 0.5 an 6.5 from 108 to 139.995 and between 0.5 to 6.5 from 140.000 to 173.995.
The switching of the two vco's is done by Q2015 and Q2016, you should see the switching on TP2004 and TP2005 when passing 139,995.
The signal to Q2015 and Q2016 comes from Q2027 which is controlled by the main CPU on AF-CNTL?
I hope you can follow my thoughts.
Nils
SM7DVO
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Nils: Did you make a typo error ? I have been reading along. You said .5v to 6.5v? on the lower range and then you said the same voltage .5v to 6.5v on the upper frequency range. There was no change.? 73 de VE3XC
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Nils, Dennis, thanks guys, either way this has given us a starting point for tomorrow...... we had given up for today, I needed to spend some time with the wife!!!!!? However tomorrow is another day and this is a GREAT starting point. I will update the group with results. ? Thank you so very much. ? Paul G0ODP ?
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From: [email protected] <[email protected]> On Behalf Of Dennis Surek via groups.io
Sent: 16 March 2021 06:47 PM
To: [email protected]
Subject: Re: [YaesuFT847] 2mtr xmit/recv issue - LocOsc Freq Issue? Nils: Did you make a typo error ? I have been reading along. You said .5v to 6.5v? on the lower range and then you said the same voltage .5v to 6.5v on the upper frequency range. There was no change.? 73 de VE3XC
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Nope. No error, that 0.5 to 6.5 feeds first The 'low' vco and over 140 The 'high' vco.
Nils, Dennis, thanks guys, either way this has given us a starting point for tomorrow...... we had given up for today, I needed to spend some time with the wife!!!!!? However tomorrow is another day and this is a GREAT starting point. I will update the group with results. ? Thank you so very much. ? Paul G0ODP ? ? Nils: Did you make a typo error ? I have been reading along. You said .5v to 6.5v? on the lower range and then you said the same voltage .5v to 6.5v on the upper frequency range. There was no change.? 73 de VE3XC
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Check the band split diodes to see if some disabled 144 by accident. They are used to make bands legal in other countries
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Nope. No error, that 0.5 to 6.5 feeds first The 'low' vco and over 140 The 'high' vco.
Nils, Dennis, thanks guys, either way this has given us a starting point for tomorrow...... we had given up for today, I needed to spend some time with the wife!!!!!? However tomorrow is another day and this is a GREAT starting point. I will update the group with results. ? Thank you so very much. ? Paul G0ODP ? ? Nils: Did you make a typo error ? I have been reading along. You said .5v to 6.5v? on the lower range and then you said the same voltage .5v to 6.5v on the upper frequency range. There was no change.? 73 de VE3XC
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Hi Charles, THANKS, I’ll check that as well and let you guys know. I appreciate your support. ? Paul, G0ODP ?
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From: [email protected] <[email protected]> On Behalf Of charles
Sent: 16 March 2021 19:49
To: YaesuFT847 <[email protected]>
Subject: Re: [YaesuFT847] 2mtr xmit/recv issue - LocOsc Freq Issue? Check the band split diodes to see if some disabled 144 by accident. They are used to make bands legal in other countries
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Hi Charles, can you tell me which are the ‘band split diodes’, I can’t see any reference to them in the service manual, which board are they on. Thanks again. ? Paul, G0ODP ?
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From: [email protected] <[email protected]> On Behalf Of charles
Sent: 16 March 2021 19:49
To: YaesuFT847 <[email protected]>
Subject: Re: [YaesuFT847] 2mtr xmit/recv issue - LocOsc Freq Issue? Check the band split diodes to see if some disabled 144 by accident. They are used to make bands legal in other countries Nope. No error, that 0.5 to 6.5 feeds first The 'low' vco and over 140 The 'high' vco. ? Nils, Dennis, thanks guys, either way this has given us a starting point for tomorrow...... we had given up for today, I needed to spend some time with the wife!!!!!? However tomorrow is another day and this is a GREAT starting point. I will update the group with results. ? Thank you so very much. ? Paul G0ODP ? ? Nils: Did you make a typo error ? I have been reading along. You said .5v to 6.5v? on the lower range and then you said the same voltage .5v to 6.5v on the upper frequency range. There was no change.? 73 de VE3XC
?
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Look up mods for 847 I remember seeing something about out of band and Mars mods? It's not diodes but chip resistors around back up battery
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Hi Charles, can you tell me which are the ‘band split diodes’, I can’t see any reference to them in the service manual, which board are they on. Thanks again. ? Paul, G0ODP ? ? Check the band split diodes to see if some disabled 144 by accident. They are used to make bands legal in other countries Nope. No error, that 0.5 to 6.5 feeds first The 'low' vco and over 140 The 'high' vco. ? Nils, Dennis, thanks guys, either way this has given us a starting point for tomorrow...... we had given up for today, I needed to spend some time with the wife!!!!!? However tomorrow is another day and this is a GREAT starting point. I will update the group with results. ? Thank you so very much. ? Paul G0ODP ? ? Nils: Did you make a typo error ? I have been reading along. You said .5v to 6.5v? on the lower range and then you said the same voltage .5v to 6.5v on the upper frequency range. There was no change.? 73 de VE3XC
?
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Hi Paul, I have just uploaded a file from Yeasu regarding mods to the frequency coverage of the 847.
The alterations are done by removing or adding link resistors near to the backup battery.
Leighton. GW3FSP.
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Hi Leighton, thanks for this, I'm meeting John tomorrow and 'round 2' will definitely look closely at these jumpers and the other suggestions. I've spoken to John and quizzed him as to whether he has made any changes at all, or whether he has lent the rig out and someone else may have made changes. He assures me neither is the case, further, the rig used to work fine on 2 mtrs.
So I'm inclined to the view that we are looking at some component failure. John tells me he may have operated the rig on 2 mtrs with his dual band antenna coax plugged into the 70cms antenna socket. Curses!
Anyway, tomorrow will be a day for STRONG coffee, bacon sarnies and lots of magnified circuit board scrutiny!
Again we appreciate all the helpful comments, FINGERS CROSSED!!!!!
Paul, G0ODP
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of gw3fsp via groups.io Sent: 17 March 2021 06:30 PM To: [email protected]Subject: Re: [YaesuFT847] 2mtr xmit/recv issue - LocOsc Freq Issue Hi Paul, I have just uploaded a file from Yeasu regarding mods to the frequency coverage of the 847. The alterations are done by removing or adding link resistors near to the backup battery. Leighton. GW3FSP. -- This email has been checked for viruses by Avast antivirus software.
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Nils, we did some checking of the voltage to the VCO on the PLL board as you suggest by looking at TP2002. On VHF band 108-139.99 the voltage varies from 2 to 6 volts measured (roughly) on my digital scope. When the radio is tuned passed 139.99 the voltage jumps to 7v and remains at that through to the end of the band and then switches back to 2v at 108MHz. ? Nils my technical knowledge is limited but I wonder what generates the variable voltage, is that done by the CPU or by the registers. I guess I am hoping that the failure is with Q2016 the switching transistor pair! ? My next test was going to be to check the voltage on pin 12 of Q2027 to see if that is varying, but before doing that I wanted to seek opinions. If Q2027 only switches the varying voltage between pins 4-7(HF) and pins 14-11(HF-VHF-VHF-UHF) then the fault could be back at the processor! ? At this point I’d really appreciate your thoughts as to the best next step. ? Sincere thanks again. ? Paul G0ODP and John G0KFM ?
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From: [email protected] <[email protected]> On Behalf Of Nils Ostman
Sent: 16 March 2021 06:30 PM
To: [email protected]
Subject: Re: [YaesuFT847] 2mtr xmit/recv issue - LocOsc Freq Issue? Hi, have you checked the voltage on TP2002 on the PLL board? Shall be between 0.5 an 6.5 from 108 to 139.995 and between 0.5 to 6.5 from 140.000 to 173.995.
The switching of the two vco's is done by Q2015 and Q2016, you should see the switching on TP2004 and TP2005 when passing 139,995.
The signal to Q2015 and Q2016 comes from Q2027 which is controlled by the main CPU on AF-CNTL?
I hope you can follow my thoughts.
Nils
SM7DVO
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When it jumps to 7 the VCO is un locked
I think 2 v is locked OK
Compare with a working band
Wd8axa
?
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From: [email protected] [mailto:[email protected]]
On Behalf Of paul warman via groups.io
Sent: Thursday, March 18, 2021 11:27 AM
To: [email protected]
Subject: Re: [YaesuFT847] 2mtr xmit/recv issue - LocOsc Freq Issue
?
Nils, we did some checking of the voltage to the VCO on the PLL board as you suggest by looking at TP2002. On VHF band 108-139.99 the voltage varies from 2 to 6 volts measured (roughly) on my digital scope. When the radio
is tuned passed 139.99 the voltage jumps to 7v and remains at that through to the end of the band and then switches back to 2v at 108MHz.
?
Nils my technical knowledge is limited but I wonder what generates the variable voltage, is that done by the CPU or by the registers. I guess I am hoping that the failure is with Q2016 the switching transistor pair!
?
My next test was going to be to check the voltage on pin 12 of Q2027 to see if that is varying, but before doing that I wanted to seek opinions. If Q2027 only switches the varying voltage between pins 4-7(HF) and pins
14-11(HF-VHF-VHF-UHF) then the fault could be back at the processor!
?
At this point I’d really appreciate your thoughts as to the best next step.
?
Sincere thanks again.
?
Paul G0ODP and John G0KFM
?
?
Hi, have you checked the voltage on TP2002 on the PLL board? Shall be between 0.5 an 6.5 from 108 to 139.995 and between 0.5 to 6.5 from 140.000 to 173.995.
The switching of the two vco's is done by Q2015 and Q2016, you should see the switching on TP2004 and TP2005 when passing 139,995.
The signal to Q2015 and Q2016 comes from Q2027 which is controlled by the main CPU on AF-CNTL?
I hope you can follow my thoughts.
Nils
SM7DVO
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Paul, NB I'm not an expert in any way so take my aswers considering that!
You have checked the backup battery?
You did a reset in the service menu?
The voltage at TP2002 is not behaving normal but with a steady 7V you should get a not varying signal from th "high" VCO. Maybe around 220 MHz
Measure at TP2003 when tuning 460MHz, yoy should see the voltage drop from 6.xV to 1-2V indicating that the rig switches between the two VCO's? (MD2003 and MD2004) for 70cm. The procedure is the same for 2M
If that works? you can also check TP 2006 and TP2007 when passig 460MHz, those two should change state.
The same goes for your 140 problem. Check TP2004 and TP2005 and see if something happens when you pass 140 MHz.
If the switching TP2004/2005 fails the problem might lie in the main CPU on af-cntl board.or the EEPROM. It's rare that CPU's fail but Murphy can have paid a visit.
The early 847's had a bug in the software which made the CAT malfunction.
Since the software is mask programmed in the CPU the only way to fix the problem was by replacing the CPU.
Certified servicepartners got a bunch of chips and I think that there is still some collecting dust at those guys.
Good luck and keep us informed!
/Nils
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Nils, Charles, thanks again for your replies, we’ve stopped work for today and will probably not start up again until next week, we only have 2 good eyes and 1.5 steady hands between us so progress is slow! ? It’s a good job you cannot see my red embarrassed face, no I haven’t checked the battery, I’ll do that next!..... I’ve just checked it, it is 3V ok..... phew! ? We did do a service reset which didn’t make any change. ? We didn’t listen to the receiver during today’s test BUT we did listen the other day and as I recall the high end of the band (140MHz +) was very quiet as if no L.O. was being applied..... In fact I’ve just remembered there was no local oscillator signal on the output coax, we monitored this on the spectrum analyser and could quite clearly see the signal drop as we passed 139.99 MHz. I will check that more thoroughly next time. I will carry out the rest of the tests as well next time. ? As you will be aware the PLL board is buried under the chassis and beneath another circuit board so it is quite a balancing act to hold the test probes, hold the board open adjust the rx tuning and the ‘scope......?? you need octopus hands! But we are having ‘fun’ slowly tracking through the stages. ? Thanks again fellas, have a great weekend and for sure I will update you with our findings and if any of you get over here when this damned virus has gone I will buy you a pint or 3 of best English beer. ? Best regards ? Paul, G0ODP ? ?
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From: [email protected] <[email protected]> On Behalf Of Nils Ostman
Sent: 18 March 2021 04:54 PM
To: [email protected]
Subject: Re: [YaesuFT847] 2mtr xmit/recv issue - LocOsc Freq Issue? Paul, NB I'm not an expert in any way so take my aswers considering that!
You have checked the backup battery?
You did a reset in the service menu?
The voltage at TP2002 is not behaving normal but with a steady 7V you should get a not varying signal from th "high" VCO. Maybe around 220 MHz
Measure at TP2003 when tuning 460MHz, yoy should see the voltage drop from 6.xV to 1-2V indicating that the rig switches between the two VCO's? (MD2003 and MD2004) for 70cm. The procedure is the same for 2M
If that works? you can also check TP 2006 and TP2007 when passig 460MHz, those two should change state.
The same goes for your 140 problem. Check TP2004 and TP2005 and see if something happens when you pass 140 MHz.
If the switching TP2004/2005 fails the problem might lie in the main CPU on af-cntl board.or the EEPROM. It's rare that CPU's fail but Murphy can have paid a visit.
The early 847's had a bug in the software which made the CAT malfunction.
Since the software is mask programmed in the CPU the only way to fix the problem was by replacing the CPU.
Certified servicepartners got a bunch of chips and I think that there is still some collecting dust at those guys.
Good luck and keep us informed!
/Nils
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Nils Ostman
gw3fsp