Mike, Yes, it sounds like you have it adequately analyzed and I do agree with your conclusions. FP U3 has a bad pin 14 output and the MCU input for ENC A also has a problem and is dragging the signal down.
73, Don W3FPR Mike-WE0H wrote: > Hi Don, > > OK, I can see those signals on pin 6 & 16 easily. Pin 14 is dead. It > stays low. I am using DC coupling. ENC-A is only going to 2v and ENC-B > goes to 5v. Both those data lines show data when the encoder is spun in > either direction. Both lines will either rest at zero or a high state. > But, ENC-A high is 2v not 5v. ENC-B high is 5v. Something is not right > with ENC-A. If I pull the jumper wire from the encoder's ENC-A line and > put the scope on the encoder's ENC-A terminal, I now get the 5v p-p > signal that I would expect out of the encoder. So with that said, the > MCU is not letting the ENC-A data line swing from 0-5v. It only allows a > 0-2v swing which is not enough. Would you agree the MCU is faulty & the > U3 IC? Having two IC's giving troubles is rare but this radio suffered > from severe spikes on the 14v line which shorted a electrolytic cap and > one final transistor. > > BTW, I am copying this to the Elecraft reflector so it is in the > database for someone else down the road. This is definitely a strange > problem with this radio. I think we are getting closer to the solution. > > Mike > WE0H > > > > Don Wilhelm wrote: > >> Mike, >> >> Do you have the 'scope vertical amp set to DC? This is logic level >> switching and the DC levels are significant, not the peak to peak >> variation. Yes, the levels must be above or below the switching >> thresholds. >> On the /ENC RD line, compare it to the levels at FP U3 pins 6 and/or >> 16 - it should be similar. >> To really tell the whole story, one would have to use 3 probes on the >> 'scope - trigger on the /ENC RD signal going low and observe the state >> of the ENC A and ENC B signals at that time. >> >> Elecraft does repairs, but only on complete kits. If this is the >> route you need to go, contact [email protected] for further >> information and obtain an RSA number with instructions for packing and >> where to send it. >> >> 73, >> Don W3FPR >> >> Mike-WE0H wrote: >> >>> Hi Don, >>> >>> OK, on that line which is pin 14 on U3, there is only a couple mv but >>> no pulses. The state of that line never changes. The other strange >>> thing is the ENC-A data level only being 2v p-p verses ENC-B which is >>> a full 5v p-p signal. Shouldn't both ENC data lines be a full 5v p-p >>> TTL signal? >>> >>> Worst case, does Elecraft take in repairs direct? I could send in >>> both display boards if that is the case. I sure wish I had test >>> boards to swap in, to verify which board is causing the issues. >>> >>> I received the final amp rebuilding components the other day but I >>> will wait to install them until after this dead VFO issue is repaired. >>> >>> Mike >>> WE0H >>> >>> >>> >>> Don Wilhelm wrote: >>> >>> >>>> Mike, >>>> >>>> Other than the wiring paths for ENC A and ENC B signals through the >>>> connectors and to CB U6 pins 8 and 16, >>>> there is nothing else for these two signals. However, for the >>>> encoder to be read, the /ENC RD signal must be at a low level and >>>> that signal is generated from FP U3 pin 14. Look for low going >>>> pulses with your scope. If they are not present, FP U3 may be at >>>> fault. >>>> >>>> 73, >>>> Don W3FPR >>>> >>>> >>>> Mike-WE0H wrote: >>>> >>>> >>>>> Hi Don, >>>>> >>>>> Ref K2 #6698: >>>>> >>>>> I tried a new encoder but it did nothing different than the >>>>> original encoder. Tonight I see that ENC-A is only 2v p-p while >>>>> ENC-B is 5v p-p. This is measured right on the encoder terminals >>>>> and on the U6 MCU chip. I don't see any resistor network pull ups >>>>> on these lines. Do you think the MCU could have gotten hurt with >>>>> the spike on the 14v VCC line that shorted the one final and that >>>>> VCC filter cap? I see data on both ENC lines when I spin the >>>>> encoder. The Encoder VCC is a solid 5.0vdc. All other functions >>>>> work on this radio except anything where I need to turn the encoder >>>>> to access something in a menu or change anything. The radio >>>>> receives fine on whatever the display freq is and transmits fine on >>>>> the same freq on all bands. I just can't change any VFO digit other >>>>> than the far right digit, or if I spin the encoder shaft left & >>>>> right, it will slowly increase the displayed freq but not go down. >>>>> >>>>> Mike >>>>> WE0H >>>>> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.424 / Virus Database: 270.14.49/2480 - Release Date: 11/04/09 > 07:37:00 > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
