Don, Thanks you for this tip, and yes, I now realize my windings on T4 are not exactly as shown in the manual. However this realization raises a broader concern.
Here is what happened. I wound my toriods using a winding tip I'm sure I picked up on the Elecraft list some time ago. To wind the toriods, I put the wire(s) to be wound on the core through the toroid core half way, pull up the two ends at a 12 o'clock point on the toroid core then wind one lead counter clockwise to about 7 o'clock and the other lead clockwise to about 5 o'clock. I now realize that this will result in the toroid being would in reverse to probably the standard winding practice of starting only one long lead at 7 o'clock on the toroid core and then winding all the required turns on the core around to about 5 o'clock. I have now pulled, T4 and rewound it exactly as shown in the manual. I am ready to reinstall it but before I do, here is the broader concern. I have also reverse wound T3 as well as each and every other toroid core on the KPA-100! Do you think this will create problems such that I will have to remove, rewind and reinstall all the toriods, just certain toriods or is it just T4 that is an issue? What makes me wonder is that I built my entire K2 and the KBS2 using the "12 o'clock high two-lead core winding system" and the K2 works just fine for me but then I can't verify if the my K2 is really performing exactly to specifications because I don't have test facilities to do so. I would really appreciate your comments on this issue before reassembling the circuit board back onto the heatsink in case I need to make other changes to the toriods. Thank you. Bill, VE2WMA -----Original Message----- From: Don Wilhelm [mailto:w3...@embarqmail.com] Sent: Thursday, January 30, 2014 4:50 PM To: William Moore; d...@w3fpr.com; elecraft@mailman.qth.net; 'Mike Harris' Subject: Re: [Elecraft] [K2] K2-100 Test and Alignment Issues Bill, Regarding T4, there is one other possibility that I did not mention before. If the direction of the windings is not as shown in the manual, it will work "backwards" which may be what you are observing. As for the minimum voltage of 1.4 volts, that is WAY too high. The bridge should null to less than 14 millivolts with 15 or 20 watts flowing through it. You could do a sanity check on it by attempting to null the bridge by monitoring the DC voltage at U5 pin 3 rather than U5 pin 1. The voltage on U5 pin 1 should be the same as at pin 3 if U5 is working OK. If you still have a high voltage at U5 pin 3, then try doing the balance (nulling) while monitoring U5 pin 5. If you can obtain a null at U5 pin 5, then for certain T4 is wound in the wrong direction. 73, Don W3FPR On 1/30/2014 4:39 PM, William Moore wrote: > Don and John, > > Thank you so much for coming to my aid with these baffling (to me) problems. > I have undertaken both your suggestions but still, unfortunately, no joy. > > The J3+ issue The J3+ lead now gives a voltage reading of -0.225 volts while > covering the PA transistors with a thick cardboard and a mostly darkened > room. I can also confirm, absolutely, that no 13.8 volt current has ever > passed through J3 or the Aux 12 volt line to the K2. > > The Wattmeter issue. I reset R26 and 27 to 43K and tried once again to > balance the wattmeter with C1. Twisting C1 with a plastic handled screw > driver, I got the voltage at Test Point 4 down to 1.4 volts but I am not > sure if that is what you mean by "close to 0.0 volts". At the same time, > glancing at the K2 LCD it still shows a 9.9::1 swr and the watt meter on my > Kenwood AT-200 antenna tuner bypassed to a dummy load indicates the K2 is > pumping out a full 15 watts. Varying C1 while looking only at the K2 LCD, I > can get 1.0::1 SWR but the power out on the LCD registers 0.1 watts while > the AT-200 wattmeter says the K2 is still pushing 15 watts to the dummy > load. Varying C1 does not change the 15 watt output on the KAT200 watt > metre. It always remains at a constant 15 watts. > > I then disassembled the KPA-100 circuit board from the heatsink. I checked > that all the components you listed were the correct values and oriented > properly i.e., D16 and D17. I checked the solder joints until my eyes > crossed with a lamp having a magnifying lens in the centre of the > fluorescent bulb. I found no solder bridges, unsoldered leads or poorly > soldered solder pads. I thinks John's problem that he referred to in his > post was a solder bridge between R24 and R26 but I found this junction was > clean of any hint of a solder bridge. I found no protruding grounding leads > anywhere. I am quite sure but, not absolutely sure, that T4 is wound (12 > turns twisted wire counted inside the core), wired and soldered correctly > with no leads shorting. The T4 solder pads are full with bright silvery > solder, no craters and the solder flows through the holes to the top of the > circuit board. > > The only variable that I can see left is to pull T4, rewind and reinstall. > However, before I do this, is there any other measurements, checks or > procedures that I have overlooked or new ones that can be suggested? > > My career background is in the field of business and economics so I kind of > feel like I am an auto mechanic trying to diagnose and perform surgery on a > complex cardiology problem. That is to say, I really appreciate your help. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
