Well, I'm completely stymied by it now. I make a living repairing electronic equipment, some of it rather exotic and with no service manuals or schematics. But I can't figure out what's wrong with this radio. So far, I have not found any bad components, including the finals. All the voltage regulators are putting out the correct voltages.? All the voltages I can measure are correct. I just measured the HF TX, V/U TX, VTX, UTX voltages this evening and they are all correct for the correct band and mode. Whatever was smoking over the weekend just before it stopped putting out RF power on any band did not leave much of an odor. I can't detect a smell anywhere on the board. There is RF drive of the appropriate frequency going to the appropriate finals. It has all appearance of transmitting, but there is no power coming out on any band.
I sent a message to Yaesu asking if they could repair it.
73, Zack W9SZ
That's reassuring. I can't find anything wrong with that part of the circuit. And I did have the Tuner/ATAS (menu item 85) set to OFF.
I want to check the HF TX, V/U TX, VTX, UTX and 50M AMP lines next to see if they are getting activated. And the PIN diodes in the transmit chains. Hopefully something shows itself as a problem.
73, Zack W9SZ
On Tue, Jul 19, 2022 at 1:39 AM Eric van de Weyer < groups.io@...> wrote: Hi Zack, ? I believe that the circuit is actually protected against shorts as Q3013 and R3045 work as a current limit to prevent it putting too much current into the antenna. ? I think that Q3008 and Q3009 are used to select the actual voltage to put on the ANT line so one puts about 12V onto the line and the other puts a reduced voltage of around 8V onto it. My guess is that the ANCV line controls the voltage and the ANNG is feedback as to what voltage is being fed to the antenna. ? Also, if you have the antenna selection on anything except ATAS in the menu, then I think the above circuit would be inhibited as it doesn¡¯t require any voltage on the antenna cable unless ATAS is selected. ? I use a mag loop antenna on my FT897 regularly, which has a primary loop connected directly across the coax, and have no problem with it and its circuitry is basically the same as the 857. Hence I don¡¯t think the matching section on your 6 m antenna has been the cause of the problem and I think I would start looking elsewhere. ? Maybe you can literally ¡°sniff out¡± where the smoke escaped from or find the burnt component to get an idea where the problem is ? Good luck with it. ? 73¡.Eric VK2VE. ? ? That could be. I did come to realize something. My 6 meter Yagi has a hairpin match across the input - and the coax. At DC, that would look like a short to whatever the coax is connected to. If the radio was trying to put 12 volts on the 6 meter antenna line, it would've been shorted. I can't figure out what was damaged, though. Q3006 is good. The inductors between the Q3006 collector and the HF antenna connector are OK. When I try to transmit now, there is 12 volts on the emitter of Q3006, but it doesn't turn on 12 volts to the ANT line. If it was doing that before, something was damaged. I did verify that all the the final output transistors are OK and that there is RF drive at the correct frequencies from the MAIN board to the PA board.? The? final output transistors have 12 volts on their collectors and, on transmit, have the correct bias voltages on the base terminals. I can't figure out yet why there's no output. ? On Mon, Jul 18, 2022 at 8:09 PM Eric van de Weyer <groups.io@...> wrote: Hi Zack, ? Looks to me like it¡¯s the circuit which supplies the two voltages to the HF antenna socket to drive the ATAS antenna up and down. The line labelled ANT ends up at the antenna connection on the far right and is DC coupled to it. ? 73¡.Eric VK2VE. ? ? I have been looking at the service manual for the FT-857D and I may see a potential problem. I am not at home now, so I can't check things out. But on page 8 of the service manual, under the PA Unit block diagram, there is a little section labeled "Q3006, etc. 2SB1134 2SA812 2SC4154 ANT DRIVE" with an input labeled ANCV and an output labeled ANNG. The circuitry for this shows up on the schematic on page 55 close to the left side of the page, a little above the center. WHAT exactly does this part of the circuit do? ? On Sat, Jul 16, 2022 at 6:57 PM Zack Widup <w9sz.zack@...> wrote: I went to my favorite hilltop in EN50rl for CQWW VHF, managed to get the 6 and 2 meter Yagi antennas set up in the hot sun (the 6 meter Yagi is BIG), hooked everything up and it seemed to be doing fine. Antennas were working and SWR was good. I called several people over about a half an hour on 6 meters with my FT857D. None of them seemed to hear me. I was only running 10 watts as a QRP Portable Hilltopper. Then I saw smoke come out of the rig and then no power came out. It still received OK. I checked both 50 and 144 MHz and had no power output on either band. So I took everything down and went home (a 45 minute drive). The rig did quite well up till now. I used it in the June VHF contest. I don't feel like digging into it right now to see what went bad. I'm sure I can repair it if I can get the parts. I only had today from about 1 to 6 pm CDT to participate. I can't be on tomorrow. But I'm sad that I didn't make even one QSO.
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