Newsgroups: rec.radio.amateur.misc,rec.radio.amateur.equipment,rec.radio.amateur.homebrew,sci.electronics,rec.radio.scanner From: galen@picea.CFNR.ColoState.EDU (Galen Watts) Subject: Hold Function for Radio Shack Frequency Counter (Did It!) Sender: news@yuma.ACNS.ColoState.EDU (News Account) Message-ID: Date: Sat, 13 Nov 1993 17:31:35 GMT Nntp-Posting-Host: storm.cfnr.colostate.edu Organization: College of Natural Resources, Colo. State Univ. Lines: 20 How to add a hold function to the Radio Shack RF Frequency Counter: Ground TP17. In the schematic, TP17 is pin one of U3, connected to +5V thru a 47k resistor. On the circuit board, TP17 is on the display side, just right of the lower-right corner of the IC. Grounds are about 1/4 inch below and to the right, the three non-tinned points in the large area of metal. I grounded TP17 directly and the display stopped. After lifting the ground, the counter resumed counting at the beginning of a sampling cycle. Personally, I would ground TP17 thru a 1k resistor. I haven't performed the mod to my RS counter, since the pads are VERY small and my fine-tip iron is at work. I will try the 1k Hold mod on Monday and give a report (unless somebody beats me to it). An amplifier mod to increase the sensitivity is in the works, reports to follow. Happy Trails to You, Galen, KF0YJ Newsgroups: sci.electronics,rec.radio.amateur.misc,rec.radio.scanner,rec.radio.amateur.equipment,rec.radio.amateur.homebrew From: galen@picea.CFNR.ColoState.EDU (Galen Watts) Subject: RS FREQ COUNTER HOLD MOD!!!!!!!!! Sender: news@yuma.ACNS.ColoState.EDU (News Account) Message-ID: Date: Mon, 15 Nov 1993 19:15:32 GMT Nntp-Posting-Host: storm.cfnr.colostate.edu Organization: College of Natural Resources, Colo. State Univ. Lines: 18 How to add a hold function to the Radio Shack RF Frequency Counter: Ground TP 17. In the schematic, TP17 is pin one of U3, connected to +5V thru a 47k resistor. On the circuit board, TP17 is on the display side, just right of the lower-right corner of the IC. Grounds are about 1/4 inch below and to the right, the three non-tinned points in the large area of metal. TP17 is the tinned pad next to a SM resistor marked '473' for 47k. I rigged a momentary switch to ground TP17 thru a 1k resistor (you never can tell) and it works just fine! I drilled a small hole to mount the switch just above the plastic depression so I could push the button with my right thumb. A small toggle switch would fit. I'll be trying the other TP's to see what wonderful things RS didn't put on the front. Galen, KF0YJ