Tony wrote: Ah. Ok then. I never worked with ECL, so that is totally unknown territory for me. You had a jump start then :-) I continued working on the 11/34 console board. Made a few new measurements (display and keypad). I am still figuring out what I have seen. I am a bit reluctant to remove an IC from the board, put in a socket and a new IC, just to find out that I overlooked something and the replaced IC was not bad. I have the impression that the strobe pulse to latch the 74175 that outputs the 3-bit code to the 7447 display driver is issued at a way to low rate. I seldom see this pulse, but expect it to see quite often as it must for multiplexing the display ... To support this repair I will write up a webpage with the LA pictures. I will mention the URL here. Very soon ... thanks for all input so far, - Henk, PA8PDP. This message and attachment(s) are intended solely for the use of the addressee and may contain information that is privileged, confidential or otherwise exempt from disclosure under applicable law. If you are not the intended recipient or agent thereof responsible for delivering this message to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify the sender immediately by telephone and with a "reply" message. Thank you for your cooperation.