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
