Burned out groundtrace. This failure could give one of the two following symptoms: 1. Rig works OK but external power is not accepted by the rig. 2. Rig is dead. Tools needed: A small (25 W) solderiron Fresh and high quality soldewick Materials: 0.5 mm hookupwire High quality solder Procedure: Unsolder C1452 (the yellow electrolytic capacitor) and T1035 (the green RF choke) Cleanup the burned out trace and replace it with hookupwire. I used two pieces, one from the power connector to capacitor hole and one from there to the choke hole. That's it and remember to fuse your powerlead...! ============================================================================ Several folks on the list helped me located a burned power trace on the '817. My radio was only working on the internal battery and would not accept power from the external power jack. At first I thought the problem was the switch in the power connector but it turned out to be a burned trace from the power jack. I was unable to find the burned spot with my eyes but with the help listers it was located with an ohmmeter. I tried to put a single strand of copper wire over the repair but could not get it to stay in position. SMT type soldering aids would be helpful. The burned spot was quite narrow only a few hundreths of an inch. The jpg in this folder shows the repaired spot which seems to be working well. I hope this helps you. My repair was made with a Weller soldering station at half power with the 'stock' tip which is really too large. Be careful not to move any of the SMT caps nearby. Do it quickly and with a steady hand and it should work fine. 73 Paul K3PG ============================================================================ Date: Sun, 22 Aug 2004 16:19:55 -0000 From: "Randy" Subject: Re: Poly resettable fuse in ND's? --- In FT817@yahoogroups.com, "Dave" wrote: > In my own personal experience with these fuses at work, they don't seem to operate fast enough under full fault conditions. I would personally use a fast acting wire ended fuse. > > Just my personal thought that's all, others may feel different. > > Dave > GM7UED > > Subject: [FT817] Poly resettable fuse in ND's? > > > Does anyone have any particulars about the Poly resettable fuses used > in the ND models to help keep folks out of the BFC? > You know, current rating, mfg part #, or whatever? Seems like a good > thing to add to a non-ND... > > 73, > Randy K4QO > High speed isn't the desired characteristic for the job I imagine why the Polyfuse was added. In fact, slow speed is... I think the point of the Polyfuse was to stop a sustained high current draw as would be found if the drivers or finals were in oscillation and doing the thermal runaway to the BFC membership. Speed would be problem on voice peaks or other short duration current excursions so the Polyfuse is a good choice. High speed tripping would be a problem. There are some of us on the list who believe that many of the BF's are caused by the drivers and/or finals going into an uncontrolled oscillation caused by the right combination of factors not common to all '817s. Low internal battery voltage is just one of the factors - IE: the BFC members who put their 817 on the shelf (working) to come back to a radio with no transmit power. (So, if you are putting your '817 up for a while, remove the internal battery pack.) The supply (battery and external) voltage is always connected to the finals and drivers in this radio design even when the radio is switched off. Perhaps Yeasu finally saw the driver/final oscillation potential and decided to limit a long term high current draw with the Polyfuse. 73, Randy, K4QO ============================================================================= Date: Sun, 22 Aug 2004 13:06:14 EDT From: kc3vo@aol.com Subject: Re: Re: Poly resettable fuse in Radios? Polyfuses ALSO reduce instances of "Burned Circuit Boards", and give added protection if the USER does something stupid, such as attempting PROLONGED tuning into high SWR at high power, or operation with a missing or shorted antenna. Normal fuses DO NOT RESET, and would mean a trip to the repair facility, whereas SOME instances of overload can be handled by the "Polyfuse" without permanent damage, and they RESET after power is removed, without need to send the radio in for service.--73, KC3VO, Bob. ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================ ============================================================================