Date: Fri, 5 Jul 2002 22:40:02 EDT From: kc3vo@aol.com Subject: Re: IBM Power Supply?CAREFUL!! VOLTAGE dangerously high, 16.0 volts is absolute LIMIT for FT-817, and it is POSSIBLE that your IBM supply could exceed this voltage under the light load of an FT-817.-------(less than 1/2 ampere on recieve, and about 2.0 amperes max on transmit.)--I believe that the BEST external power source for the FT-817is one of 13.5 to 14.5 volts D.C., fed to the external power connector, with a series connected 3 ampere fuse, and a series connected 2 ohm, 10 watt power resistor, with a capacitor of 4,000 ufd. in parrallel across the leads at the radio end. With this arrangement, you get the higher 12 to 13 volts needed to charge internal batteries, but the voltage will decrease to the 9 to 11 volts that is desirable for cooler, more efficient transmit, during transmit.--YES, power is still wasted, but NOW it is being dissapated OUTSIDE the FT-817, and by a cheap 10 watt 4ohm resistor instead of the expensive solid state devices! 73, KC3VO-Bob Curry ============================================================================ Date: Sun, 21 Sep 2003 21:29:14 -0000 From: "Cortland" Subject: Re: will not turn on Jason, There are two diodes (on my schematic) between the positive power pin and the battery pack. Some newer units have an internal fuse. Either or both of the diodes (and/or the fuse) may have opened. D1084, if it opens, will only prevent operation on internal power. D1085, if it opens will only prevent operation (and charging) on external power. Printed wiring traces carrying short-circuited battery current may also open. Finally, T1035, a bifilar wound choke, isolates the external power receptacle from ground, and this also MAY be affected; some of the very early units experienced catastrophic melt- down when insulation on this choke melted, allowing positive and negative supply leads to short together more or less permanently. Cortland --- In FT817@yahoogroups.com, "kb2sdrjay" wrote: > the chassic brushed against the pos terminal of the unit while the unit > was on. Dumb me still hasn't installed the fuse inline. Has anyone have > this happen to them?? Can you tell me what is the likely > component to fail?? ========================================================================== Date: Sun, 21 Sep 2003 23:52:56 -0000 From: "bg7jba" Subject: Re: will not turn on #1 Try using internal AA batteries and no power cord to see if radio will power up. #2 Look at the plug on the end of your power cord to see if the black platic tip is still intact. #3 When this happened, did you melt the power cord wires or was there any smoke from inside the rig. Does the rig have any smell of smoke or burnt components now? #4 Buy a new power cord. Install 2 fuses, one for the positive wire and one for the negative wire. I had a similiar experience with a Lithium Ion pack. I have a service manual and I repaired mine. You can email me at ka7qor@arrl.net My ICQ# is 237847456 -- In FT817@yahoogroups.com, "kb2sdrjay" wrote: > Hello, > > I have ft-817, while taking the radio out of the case I have for it, > the chassic brushed against the pos terminal of the unit while the unit > was on. Dumb me still hasn't installed the fuse inline. Has anyone have > this happen to them?? Can you tell me what is the likely > component to fail?? > Thanks Jason KB2SDR =========================================================================== Date: Thu, 18 Sep 2003 00:13:37 -0000 From: "n9hmg" Subject: Re: FT817 --- In FT817@yahoogroups.com, "Bernard 19AT332" wrote: > ... > I think,that because the mistake,that my FT817 did get 12volts on his antenna connector,on the cold side. > .... Depending on the extent of the damage, you might be able to replace all the electronics inside the case and a new panel. If the case is melted as well, you'll have to purchase a complete new rig. Actually, it may not be as bad as that. What you describe is DC-grounding the center conductor of the antenna jack and heating up the case with the 12V. I'd guess that you've burned the ground side of the power connector on your FT-817. As I recall, it's a thin metal strip in the power jack. The rig is extremely well-designed, and comes apart and back together nearly intuitively. Before you open the case, though, remove the power cord and install a good set of 8 AA-cells. I strongly suspect that your front panel will light right up. Then, all you have to do is fix the DC ground through the power jack. I don't have my power cord fused, either, but I use polarized connectors and am very careful. 73,tim =========================================================================== So an interesting observation is that though the manual states in some places that the external power supply should be 13.8V, in the spec section the operating voltage is shown as 8 to 16V. At 5W out, my radio draws about 1.9A, regardless of supply voltage. If I run it from a 13.8V supply, it consumes 26W and puts out 5W, so 21W is dissipated in the radio. If I run it off 10V, it draws 19W from the supply and 14W is dissipated in the radio. That's 50% more heat for the 13.8V case. So what's better - following the manual (in some places) or reading between the lines and running the radio cooler? Is there any disadvantage to running the radio at the lower voltage? This is an example of the manual asking more questions, to the careful reader, than it answers. There is a class of people who will ask these questions. And some of them, standing Newton- like on the shoulders of giants, and possessing schematics after the deadline has passed, will actually come up with smarter answers than the original designers. Do you think any of the production engineers at Yaesu have done the research that Bob did to come up with "the fix?" A few other posters did measurements on dead final mosfets that points to a weakness in the design, namely that spikes on the power input can propagate through the drain-gate capacitance and punch through the gate. How many people at Yaesu do you think have this information? A group like this with such a large membership is going to have some pretty smart and open-minded people and, for me, part of the fun is seeing who has figured out what. AF, WN6Q ============================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ================================================================== ==================================================================