Hello Andy. Enjoyed the video. Have you heard of any situation where the MFJ-998 powers up but the digital display does not come on? Any thoughts on this? Thank you! Paul KA1GIJ
HI Paul, Glad you enjoyed the video. I'm afraid I have no direct experience of the fault you describe. I would just have to try troubleshooting techniques based on a best guess approach because MFJ will unfortunately not publish any information or schematics for their products. I would be probing around with an oscilloscope looking for microprocessor activity and signals to the display module.
Hello Andy....I am having a similar issue with my 998 at the moment but my analog meters are not working 1 out of 4 transmissions only....its intermittant.... Is this possibly a diode issue on that rf sensing board??? Do you have a schematic for this unit at all?? Do you know what the actual diode part#s are on this board? How can I test these diodes to be sure?? Any help or suggestions welcome 73 Ted VE3SS
Hi Ted, I don’t have a schematic as MFJ won’t provide one. I just had to trace the circuit as best I could, however the sensing board is a conventional design. I do not know what the diode part numbers are but as long as they’re matched it probably isn’t critical. The unit would probably need recalibrating if they’re replaced. Diodes are unlikely to be intermittent. I would be inclined to look for poor solder joints in the unit. Tsp things lightly with a screwdriver handle to see if you can provoke the problem. The solder joints associated with heavy components like the large toroids are known to be problematic.
So...Andy was this part that was replaced an inductor or a resistor ? If it was a resistor, what value was the replacement ? By the way, did the replacement work for this repair ? I have the same mfj- 998 unit. My reflect will tune with vc1, but my forward tune only goes to 40 at vr-1. With that said, my tuner fails to tune an antenna and says oops....low power or something of that nature. It basically will not tune anything right now. Purchased this a few years ago and sat on a shelf. But has never worked properly. I recently downloaded the manual and started trying to do an internal tuning and found that the rear rf board could be the culprit. I only get less then a volt with an input of 100 watts. So you can see my problem at this point. I called mfj and they are going to send me an rf input board at the price of $18.00. Really just wondering if this will actually turn out to be my problem and fix. Thanks....Billy / Albq. N.M. 2 / 8 / 2023
The failed component was an inductor. The video shows the actual component that failed. It looks like a resistor but it is an inductor and it was open circuit. I'm not sure of the value and the video isn't clear enough to read it.
@@SKYHAWK0115 Looking at the video, the failed component appears to be brown, black, brown which means it's a 100 uH inductor. The part is labelled L41 on the board overlay. I would have simply found a suitable replacement in my stock of parts. I'm a retired technician but I still have a quite well equipped workshop with lots of parts on hand. The SWR sensor board is very simple. There's only a handful of components on it and it's easy to troubleshoot. The most complicated part is actually unsoldering and removing the board. I was able to determine that there was no voltage on the FWD connection when RF power was applied. The two diodes tested OK. The inductor was open circuit. The voltage on the FWD connection is likely to be quite low with 100 Watts applied. It should not be zero however.
Yes ...that is exactly my problem. I have a .9 voltage reading as I key up with a 100 watts and vr1 cannot come to a full 100 watt reading as it is adjusted. If you will look towards the bottom of the blue looking component, it says r-64, a 68 ohm 2 watt and the L41 to the right and shows to be a 1000 micro Henry inductor, according to the schematic. I would send you the schematic. But it won't load on youtube message.
Just a little note that this fool belittles people on Social Media if their views are not consistent to his.. He loves the community forums and then belittles then as he feels he is scientifically superior... Which is the field of Chemtrails and Just a little note that this fool belittles people on Social Media if their views are not consistent to his.. FYI Contrails Disapate after a few minutes, They don't hang around all day. Keep taking your boosters, keep you mask on, which as a stated man of science you are pretty silly( ill keep it g rated for now) Ill explain it to you very simply, as you don't seam to be very smart.. Wearing a mask for protection against a Virus is like wearing chicken wire on your face to protect your from mosquitos.. Thats the best way I could explain it to you. Im trying to get to your level.. Seeing the sky with chemtrails and denying them you are in fact a Science Denier.. All the evidence, videos of them spraying Yet you refuse to believe the science, Remember Hallidays Point is a VERY small place.. Best remember that when people find out where you live. They don't take too kindly to people like you calling them names. Thats Just a tip for you personally... But thats me done, your unvaccinated, Unmasked and STIll Covid Free Fan.. Enjoy you booster big fella and when the blood clots come... Ill be thinking of you, having a beer and laughing at the science deniers.
Nice video. Thanks Andy
Hello Andy. Enjoyed the video. Have you heard of any situation where the MFJ-998 powers up but the digital display does not come on? Any thoughts on this? Thank you! Paul KA1GIJ
HI Paul, Glad you enjoyed the video.
I'm afraid I have no direct experience of the fault you describe.
I would just have to try troubleshooting techniques based on a best guess approach because MFJ will unfortunately not publish any information or schematics for their products. I would be probing around with an oscilloscope looking for microprocessor activity and signals to the display module.
Hello Andy....I am having a similar issue with my 998 at the moment but my analog meters are not working 1 out of 4 transmissions only....its intermittant....
Is this possibly a diode issue on that rf sensing board??? Do you have a schematic for this unit at all?? Do you know what the actual diode part#s are on this board?
How can I test these diodes to be sure?? Any help or suggestions welcome
73 Ted VE3SS
Hi Ted,
I don’t have a schematic as MFJ won’t provide one. I just had to trace the circuit as best I could, however the sensing board is a conventional design.
I do not know what the diode part numbers are but as long as they’re matched it probably isn’t critical. The unit would probably need recalibrating if they’re replaced.
Diodes are unlikely to be intermittent. I would be inclined to look for poor solder joints in the unit. Tsp things lightly with a screwdriver handle to see if you can provoke the problem.
The solder joints associated with heavy components like the large toroids are known to be problematic.
So...Andy was this part that was replaced an inductor or a resistor ? If it was a resistor, what value was the replacement ? By the way, did the replacement work for this repair ? I have the same mfj- 998 unit. My reflect will tune with vc1, but my forward tune only goes to 40 at vr-1. With that said, my tuner fails to tune an antenna and says oops....low power or something of that nature. It basically will not tune anything right now. Purchased this a few years ago and sat on a shelf. But has never worked properly. I recently downloaded the manual and started trying to do an internal tuning and found that the rear rf board could be the culprit. I only get less then a volt with an input of 100 watts. So you can see my problem at this point. I called mfj and they are going to send me an rf input board at the price of $18.00. Really just wondering if this will actually turn out to be my problem and fix. Thanks....Billy / Albq. N.M. 2 / 8 / 2023
The failed component was an inductor. The video shows the actual component that failed. It looks like a resistor but it is an inductor and it was open circuit. I'm not sure of the value and the video isn't clear enough to read it.
Andy...where did you get the swr sensor inductor with the proper micro Henry's as a replacement and how did you know the value of the part ? Thanks
@@SKYHAWK0115 Looking at the video, the failed component appears to be brown, black, brown which means it's a 100 uH inductor. The part is labelled L41 on the board overlay. I would have simply found a suitable replacement in my stock of parts. I'm a retired technician but I still have a quite well equipped workshop with lots of parts on hand.
The SWR sensor board is very simple. There's only a handful of components on it and it's easy to troubleshoot. The most complicated part is actually unsoldering and removing the board. I was able to determine that there was no voltage on the FWD connection when RF power was applied. The two diodes tested OK. The inductor was open circuit. The voltage on the FWD connection is likely to be quite low with 100 Watts applied. It should not be zero however.
Yes ...that is exactly my problem. I have a .9 voltage reading as I key up with a 100 watts and vr1 cannot come to a full 100 watt reading as it is adjusted. If you will look towards the bottom of the blue looking component, it says r-64, a 68 ohm 2 watt and the L41 to the right and shows to be a 1000 micro Henry inductor, according to the schematic. I would send you the schematic. But it won't load on youtube message.
@@SKYHAWK0115 Look me up on QRZ and send me an email. I'm VK2AAK.
$1600? Holy cow!
Australian dollars :)
Good video mate 73 Tom Vk3ftom
Just a little note that this fool belittles people on Social Media if their views are not consistent to his.. He loves the community forums and then belittles then as he feels he is scientifically superior... Which is the field of Chemtrails and Just a little note that this fool belittles people on Social Media if their views are not consistent to his.. FYI Contrails Disapate after a few minutes, They don't hang around all day. Keep taking your boosters, keep you mask on, which as a stated man of science you are pretty silly( ill keep it g rated for now) Ill explain it to you very simply, as you don't seam to be very smart.. Wearing a mask for protection against a Virus is like wearing chicken wire on your face to protect your from mosquitos.. Thats the best way I could explain it to you. Im trying to get to your level.. Seeing the sky with chemtrails and denying them you are in fact a Science Denier.. All the evidence, videos of them spraying Yet you refuse to believe the science, Remember Hallidays Point is a VERY small place.. Best remember that when people find out where you live. They don't take too kindly to people like you calling them names. Thats Just a tip for you personally... But thats me done, your unvaccinated, Unmasked and STIll Covid Free Fan.. Enjoy you booster big fella and when the blood clots come... Ill be thinking of you, having a beer and laughing at the science deniers.