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Author Topic: Yaesu FT857D won't stay powered up  (Read 7133 times)
KI6RJW
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Posts: 24




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« on: January 09, 2010, 07:54:15 PM »

Hello all, I have a Yaesu FT857D, when you hook up the power cord, the radio will immediately power on but after about 10 seconds will shut off, it will not turn back on unless you disconnect power again.  Radio was working fine when it all of a sudden did this.  Any suggestions appreciated.  Thanks.  73  Darryle KI6RJW
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KB2CPW
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« Reply #1 on: January 10, 2010, 02:15:22 AM »

Firstly, check the power cord, Yaesu cords are notorious for bad connections/oxidation at the fuse points especially if used mobile. Then check the power switch. Most modern rigs strobe the cpu to turn the rig on and off rather than make an on/off connection directly from the dc line. See if its sticking. Then check the connection between the head and body of the rig for corrosion or defects. Also check the mic as the optional mic can turn the rig on and off as well. So try removing the mic and turn the rig on to see what happens. Then finally try a reset. Let me know how you make out.. Richy N2ZD
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KI6RJW
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« Reply #2 on: January 10, 2010, 07:10:51 PM »

I tried the reset, no go.  I disconnected the microphone and tried that, still no go.  I then tried a new patch cord from the control head to the main body.  No go.  I will check the power connection at the fuses next.  How do I check out the function of the power switch to see if it is sticking?  Darryle KI6RJW
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KB2CPW
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« Reply #3 on: January 11, 2010, 12:33:27 PM »

The power button strobes the cpu which in turn operates a relay that powers up the rig. It may be stuck, try to shut it before it shuts itself or work the power button a multitude of times to see if it is just sticking. Also pop the covers off of the rig and make sure every connector inside is seated and the boards are tight. Check all of the RJ style jacks for crossed fingers and oxidation. Sometimes a greenish tarnish will form across some of those phone style connections. You can use a soft eraser to clean them.

  I've been running an 857 mobile for about 8 years and not much goes wrong with them. The only problem I had with the one in my car is it was a very early one and it needed some protection added to the firmware to prevent static issues that freaked out the radio. Other than that, running it mobile, sometimes an inductor would lift off of the board in the PA and I would have to go in and tack things down with an iron. Pretty good track record for a radio thats been bouncing around for 200 thousand miles in my car.
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KI6RJW
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« Reply #4 on: January 11, 2010, 08:42:15 PM »

Ok, some more updates on this, a friend has another FT857D so I used it to switch out the mic. cable, mic., control head cable, then the control head itself, I placed everything from my 857 to his and his worked fine, mine still would not stay powered up, so I guess this narrows it down to something in the main unit itself.  Any ideas on where to look next.  I am going to try and go into town later this week where I can get on a DSL connection and download a service manual and schematic for it.  Any suggestions ahead if time appreciated.  Thanks again.  Darryle KI6RJW
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PE1HZG
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« Reply #5 on: January 12, 2010, 02:56:35 PM »

There is a white flexfoil cable between the PA board (on the bottom) and the main board (on top). You might want to take it out and re-seat it.

What does the voltage on the display say during the 10 seconds it runs?

Have you (or someone else) fiddled with the service settings (wrongly named "hidden menu" - if you don't know what I mean, so much the better).

What lot number do you have? The serial number looks like 9N99888888. I'm interested in the first 4 digits/letters.

During the 10 seconds it works, can you make a full-power FM transmission, so full 50W on 2M?

During those 10 seconds, can you switch it off and on again?

If you or your friends have a DTMF mic, try the power button on the DTMF mic. Note that most of the other settings don't work w/o changing menus - just check the power button on the mic, that's all.

Is this with a bare unit, that is, nothing connected to ACC plug? Are you using an ATAS antenna? Does this also happen if both antennas are disconnected?

If you press the power button only briefly, the radio will switch from slow tuning to fast tuning and vice versa. With fast tuning mode, a "running puppet" shows on the display. Can you confirm that in these 10 seconds, you can switch on/off the fast tuning mode?

73,

Geert Jan PE1HZG
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WD8T
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« Reply #6 on: January 12, 2010, 05:38:40 PM »

Have you checked the power source yet to see if that might be the problem?  I don't see anywhere mentioned if this is a base or mobile setup.  Always a good idea to check the power supply/source first before you go digging around inside the radio.
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KI6RJW
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« Reply #7 on: January 12, 2010, 06:13:29 PM »

First to answer WD8T, it does not matter what is used for a power supply, it is actually on an Astron, I also have a Pyramid 32 and also have a home brew 150A, It is not a power supply issue at all.  

To answer PE1HZG

(There is a white flexfoil cable between the PA board (on the bottom) and the main board (on top). You might want to take it out and re-seat it.)   I will check this tomorrow.

(What does the voltage on the display say during the 10 seconds it runs?) 14.2V

(Have you (or someone else) fiddled with the service settings (wrongly named "hidden menu" - if you don't know what I mean, so much the better).) This radio has not been modded or any "hidden Menu" changes made ever.

(What lot number do you have? The serial number looks like 9N99888888. I'm interested in the first 4 digits/letters.) 6M68

(During the 10 seconds it works, can you make a full-power FM transmission, so full 50W on 2M?)It stays powered on for about 6 or 7 seconds and it does have output, about 25 watts react on the meter prior to shutdown

(During those 10 seconds, can you switch it off and on again?)  No

(If you or your friends have a DTMF mic, try the power button on the DTMF mic. Note that most of the other settings don't work w/o changing menus - just check the power button on the mic, that's all.)  Has no affect

(Is this with a bare unit, that is, nothing connected to ACC plug? Are you using an ATAS antenna? Does this also happen if both antennas are disconnected?) Bare radio, nothing connected.  

(If you press the power button only briefly, the radio will switch from slow tuning to fast tuning and vice versa. With fast tuning mode, a "running puppet" shows on the display. Can you confirm that in these 10 seconds, you can switch on/off the fast tuning mode?)  I will check this.  

73,

As I stated originally, hitting the power button does not have an effect to turn the radio on or off at all.  I have tried a different control head, another new control cable as well as another mike.  I took everything off of the non-working radio, placed it on a known working radio and everything functions fine.  Place the known working controls on the nonworking radio, and the radios still does not work.  So I am thinking this eliminates the control head, control cable, microphone and the interconnections.  I am thinking it must be something with either the relay or something going wrong when the microprocessor is powering up.  I talked to Yaesu tech support and of course all they want to tell me is to mail it to them.  Hope this narrows things down some.  Darryle KI6RJW
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K0BG
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« Reply #8 on: January 12, 2010, 06:46:47 PM »

Mail it to them! Better yet, use Fed Ex, and insure it.

You can give everyone here a synopsis of every little bitty problem, readout, voltage measurement, you name it, but unless they're Yaesu techs, the chance they'll come up with the fix is remote. Oh yes! Some things are really simple, and we've all dealt with those. But...

The last one I repaired (I bought a working, no problem radio from a local amateur who assured me everything worked), acted similar to yours, except it took about 10 minutes to die. The problem, after tracing the 5 volt regulated line and replacing the regulator, turned out to be a bad, surface mounted cap, soldered to the board on the underneath side. Oh! And that little printed circuit jumper mentioned previously, also needed replacement.

Again, send it to Yaesu, and have them fix it without all the falderol.
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PE1HZG
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Posts: 57




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« Reply #9 on: January 14, 2010, 03:46:42 AM »

Hi Darryle,

Thanks for your response. Let's see if I can help (that is, if you want to fix this yourself)

1. Flexfoil: the main board on top, including the PA driver stages, are fed through this flex foil. You can (carefully!) pull it up straight, then re-seat it. Probably best if you grab it on the blue tab, not on the foil itself. Chances are that after all these years, the connection has gone a little soft (haven't had that on my 8x7's yet, but I had this on other equipment w/ this foil)

2. Serial: 6M68, 2006, but more important, lot 68. Yaesu made a number of changes in the power-on circuitry over the years, but I believe yours is good to go.

You might want to check to make sure you still have good power on the radio once it switches off: I am a bit suspecious of the power supply/cabling, still.

Specifically, measure the voltage on pin 8 of the MIC plug (to GND). You should measure 14.2 volts, and it should go to ground if you briefly press the power button. 13.8V should still be there once the unit switched itself off.

A little background info (check the schematics that came with the radio): the circuit of interest is around Q1031 (left of the main CPU, Q1049). When you press the power button (either on front or on the microphone), you ground the common cathode of D1033.
This grounds the gate of Q1031, and causes 13.8V ("13.8VUS") to go via Q1031, to Q1028 (5V voltage regulator) and Q1030 (power-on reset circuitry, only gives a short pulse). If all is well, the CPU Q1049 will switch Q1035 which keeps the gate grounded and hence the radio on. Note that the CPU also knows the power button is pressed, via the other diode of D1033.
If you switch the radio off, all that needs to happen is for the CPU to stop driving Q1035.

Measuring this is not trivial, because most of these components are on the *bottom* of the main (top) PCB. But, you're working on the DC circuitry of the board, so you don't need the green coax (receiver input), or the red coax (transmitter output). You can safely operate the radio with these disconnected. (if you feel uncomfortable with leaving the driver stage unloaded, pull jumper J1004 and flip switch S1001).

What I have done, is:
1. Remove the top PCB, disconnecting everything (flexfoil, coaxes, cable to front, cable to mic plug.
2. You are going to flip the board around the side that has the flexfoil and you don't want to short the PCB, so put some tape over the right ledge of the enclosure as the PCB will rest on it
3. Re-connect flexfoil and flip the board upside-down; connect front module. I found it easier to connect an external speaker on the 3.5mm jack instead of re-connecting the internal speaker.
4. Now you can measure. Believe me, you're going to learn about the Adobe reader zooming functions.
5. Note that Q1014 (7808 stabilizer) gets hot. This is normal, since it's not colled now. The other device that needs cooling (Q1105) is just the LF PA, and it doesn't get warm at all if you keep the volume down.

Hope this helps, and let us know how it goes,

Geert Jan PE1HZG
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PE1HZG
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Posts: 57




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« Reply #10 on: January 14, 2010, 03:48:13 AM »

That should be 14.2 volts, not 13.8 volts, on the MIC plug, sorry. Basically, it's the input voltage, with a 47K resistor (R1157) in series.
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