Elenco F-1300 Universal Counter Timebase Mod - diyAudio
Go Back   Home > Forums > Design & Build > Equipment & Tools

Equipment & Tools From test equipment to hand tools

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 19th July 2014, 12:35 AM   #1
diyAudio Member
 
Join Date: Apr 2008
Default Elenco F-1300 Universal Counter Timebase Mod

Back in 2002 I purchased an Elenco F-1300 universal counter for US$220. The unit offered a high-resolution frequency function below 35 kHz that I thought would be useful for audio work. Instead of measuring the number of input cycles during a 0.1 or 1 second gate time, the F-1300 measures the number of cycles of the master clock during one cycle of the input and then calculates the frequency. Thus for a 1 kHz input you could read 1000.000 Hz with a fast update of the display.

The only issue I have with the stock F-1300 involves the stability of its crystal-controlled timebase. Perhaps the accuracy spec of +/- 10ppm/year with a warm-up time of 30 minutes (I measured close to 60 minutes to final equilibrium) is acceptable for some work. However, I felt I could do better. The timebase circuit incorporates a 10 MHz crystal with gain provided by an inverter from a 74HCU04. I thought the counter's performance could be improved by replacing the timebase circuitry with a temperature-controlled crystal oscillator (TCXO).

There are many possible TCXOs that one could use. I settled on a $20 unit I purchased on eBay from a Chinese company called LogiFind - stores.ebay.com/logifind/. Listed as an "Ultra precision Crystal Oscillator" the spec sheet said that precision was +/- 1 ppm with a 1 ppm/year max ageing rate. The supply current spec of 20 mA max shouldn't overtax the F-1300's regulated +5V supply. The oscillator comes in a standard metal DIP can with four pins. Pin 1 is no-connect so there is no possibility of voltage-controlled frequency trimming. Shipping to the USA was much faster than month or so quoted during the eBay purchase.

To mount the new TCXO I first removed the old timebase components - X32, R29, C34, C35, C36 and C361. The crystal and trimmer are thru-hole and have to be unsoldered from the board bottom which is easy to get to. Prior to mounting the TCXO I soldered a 0.047 uF decoupling capacitor between pins 7 and 14, about halfway up the can leads.

TCXO pin 8 solders to the C35 pad that goes to the R29 pad and then pin 13 of the 74HCU04 (U30). Pin 7 goes to the ground side of surface mount capacitor next to C73. Pin 14 touches the board near a via hole so I first insulated it with a bit of electrical tape on the board. Then I ran a wire from the pin to the +5V pad between C362 and C363. Finally to secure the TCXO I ran a thin cable-tie through the C36 trimmer hole, around the TCXO and back down the hole. See the photo.

I am very happy with the modification. Now after the counter powers up I get an instant reading of 10.000000 from a rubidium standard. The only down-side to this project is that the F-1300 has been discontinued by Elenco. You will occasionally see one for sale on eBay but I have not discovered any other source. But if you are able to obtain one, perhaps this mod will prove useful.
Attached Images
File Type: jpg F-1300-TCXO.jpg (134.4 KB, 12 views)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
NAD 1300 - Problem with static dman535 Solid State 3 19th April 2014 01:20 PM
abletec alc1000-1300 fransiscan Class D 5 29th December 2012 04:48 AM
Technics SL-1300 without ground cubby2k Analogue Source 4 20th April 2011 09:09 PM
Amp cases, Borbely preamp, Elenco scope, aluminum Jason_N Swap Meet 10 9th July 2009 04:24 AM
celestion 1300 mekons123 Multi-Way 1 3rd November 2006 12:11 AM


New To Site? Need Help?

All times are GMT. The time now is 11:03 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2