[Elecraft] KPA 100 Resistance Checks
I thought the following observations may be of help to anyone having difficulty achieving the KPA 100 resistance measurements on page 44 of Rev H of the KPA 100 manual. I initially performed the checks using a DMM with the PCB illuminated by a 40 Watt bench light a few inches away. Resistance values were very variable and only Q1 and Q2 base measurements were within specification. The other measurements were too low in value and would ramp up and down, with the DMM sometimes indicating a minus resistance value (whatever this meant!). The orientation of all relevant diodes and transistors was checked to no avail, and then I happened to switch off the bench light and hey presto, everything worked properly with all values easily within specification. The two PA transistors appear to be photo sensitive and must produce photo electric currents similar in magnitude to the DMM test current. If I perform the checks with my moving coil multimeter (2000 ohms/volt), the correct resistance readings are achieved with or without the bench lamp on. DMMs are very useful but care has to be taken in understanding the results! Ray -- View this message in context: http://elecraft.365791.n2.nabble.com/KPA-100-Resistance-Checks-tp7569108.html Sent from the Elecraft mailing list archive at Nabble.com. __ 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
[Elecraft] KPA 100 Resistance Checks
I am building the KPA 100. I have just tried the resistance measurements on page 41 of the Alignment and Installation. The resistance measurements for the Q1 and Q2 collectors will flash 11 or 12K ohms then jump down to -6.5K ohms and then count up to -3.5K and then stabilize. When I first checked the J3 red terminal it responded normally in about 20 seconds showing greater than 10 K ohms. Now even that is giving me inconsistent readings. The remainder of the readings in that table for the KPA 100 test points are okay. I saw a similar post in the archives from Dec 2004 but the thread ended without a response. Comments Recommendations would be appreciated 73, KI4DGH Chuck Gehring ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KPA 100 Resistance Checks
I am building the KPA 100. I have just tried the resistance measurements on page 41 of the Alignment and Installation. Sounds like you are maybe running into the photoelectric effect on the PA transistors too. Do you have a strong light on the workbench? http://www.ac6rm.net/mailarchive/html/elecraft-list/2003-11/msg00574.html -- Ward / KG6HAF ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] KPA 100 resistance checks
I've built the KPA 100 up to the alignment and installation steps and made the resistance checks at J3+ and Q1 and Q2 collectors (all of which are supposed to be greater than 10k). The instructions state that the J3+ resistance may initially read 0 because a large electrolytic must charge up and that it may take 20 seconds for the reading to stabilize. My readings at J3+ and the Q1 collector never stabilize above 10k - they start at 0, pop up to a value above 10k, then start decreasing eventually ending around 1-2k. Is this okay? Bob K6VZT ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
