--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/content/eip545b.rst Wed Dec 20 23:33:53 2017 +0100
@@ -0,0 +1,155 @@
+===============================
+ EIP 545B RF Frequency Counter
+===============================
+
+:author: David Douard
+:Category: Electronics
+:Tags: test equipment, RF, EIP, 545B, counter
+
+
+I recently purchased a broken EIP 545B microwave frequency counter on ebay. It
+was very inexpensive (around 150€ delivered), but obviously, non working.
+
+.. image:: {filename}images/eip545b/closed_unit.jpg
+ :alt: The EIP 545B RF Counter
+
+The device was described as "does not power up", an is clearly not in very good
+condition. Quite dirty, battered, with the band 2 BNC connector ruined.
+
+But inside, it was **very** dusty and a bit rusty:
+
+.. image:: {filename}images/eip545b/inside.jpg
+ :alt: Once opened, it's very dusty
+
+The YIG filter looking not so good:
+
+.. image:: {filename}images/eip545b/rusty_yig.jpg
+ :alt: The rusty YIG filter
+
+
+I quickly checked, and indeed, nothing happened when I tried to power it up. In
+fact, the fuse was blown. So, instead of just give a try with a new fuse, I
+decided to disassemble it completely to clean it up, check the power supply
+independtly, then inserting the boards one at a time.
+
+
+PSU
+===
+
+So the first step has been to check wether the PSU is working fine. Overall, it
+looks OK:
+
+.. image:: {filename}images/eip545b/psu.jpg
+ :alt: The A101 PSU board
+
+There are many tantalum capacitors in this unit, including on the PSU board:
+
+.. image:: {filename}images/eip545b/psu_tantalums.jpg
+ :alt: Tantalum capacitors on the PSU board
+
+But they seem OK, so I gave it a try with no load, but using a variac to rise
+the input voltage slowly:
+
+.. image:: {filename}images/eip545b/psu_test.jpg
+ :alt: Testing the PSU board
+
+I plan to build myself a nice isolation transformer unit using this variac, a
+true isolation transformer I have and the power meter shown on this picture,
+but that's another story.
+
+The results are ok so far, voltages are OK. The PSU seems to work just fine.
+
+Cleaning the unit
+=================
+
+The next step has been to completely disasseble the counter in order to clean
+it properly.
+
+It's a quite simple unit, easy to disassemble, so it took me only a few hours
+to do so.
+
+My only complain is to be obliged to disolder a few wires to disassemble the
+components from the back panel.
+
+I'e washed every part I could in my kitchen sink, with dishwashing soap and a
+duster, includind the A100 interconnect board.
+
+Other PCB board have been cleaned with a small tooth brush, some cloth, and
+isopropyl alcohol.
+
+I also tried to remove a bit of the rust from the YIG filter using some
+scotch-brite, but I could not really clean it without disassembling it, and I'm
+not sure wether it is safe to open the enclosure of the YIG filter or not (if
+it's sealed with special gas for example). Also, I wanted to check if it works
+before doing anythno stupid.
+
+Reassembling and testing
+========================
+
+Then I started to reassemble the unit, just putting back togother the front
+panel, the CPU and the PSU.
+
+Once powered, nothing happened, the display did not lit... It happened I forgot
+to put back the 7805 regulator dedicated to the front panel (and mounted on the
+aluminium chassis for heat dissipation). Doh!
+
+Once fixed, the unit did power up, and reacted to some keys:
+
+.. image:: {filename}images/eip545b/test_cpu.jpg
+ :alt: Testing the unit with only the CPU board
+
+So far so good. Now the time for testing the other boards.
+
+After inserting all the boards but the optional A102 GPIB board, the unit still
+powered up, but the keyboard was mostly unresponsive, and the "remote" led was
+lit. Putting back the GPIB board did the trick.
+
+I also had to plug the 10MHz In/Out switch back (located on the back panel),
+since the default (open) position is for "External Reference".
+
+Now I can interact with the device. In band 3, and I can hear a small noise,
+typical for a YIG coil sweeping the range... Good sign!
+
+Let's put some signal, first a 6MHz on the band 1 input:
+
+.. image:: {filename}images/eip545b/working_band1.jpg
+ :alt: Testing a 6MHz signal on band 1 input
+
+It works! I quickly checked band 2 (using a piece of wire since the connector
+is broken), and it seems to work fine. And band 3:
+
+.. image:: {filename}images/eip545b/working_band3.jpg
+ :alt: Testing a 1GHz signal on band 3 input
+
+
+I've checked up 2GHz (the max frequency I can generate using my Anristu MG3670B
+signal generator.
+
+A quick test showed that the sensibility is not as expected: could not measure
+any signal below -12 ou -13dBm.
+
+
+Next steps
+==========
+
+Next steps for this unit are now:
+
+1. Finishing the repair, changing the broken BNC connector, the broken fan
+ (which was in fact the culprit for the blown fuse), as well as, maybe,
+ removing the rust from the YIG filter.
+
+2. Make some performance tests and calibrations (as far as I can do using my
+ equipment).
+
+3. I also want to try to install the Option 2 (Power Meter). This procedure is
+ pretty simple (as long as I manage to program a few 2716 EPROMs with my
+ `MiniPro TL866`_ universal programmer) and has been done by several_
+ people_, but always on the 545A model, not the B model. Not sure if I can
+ use the EPROM images kindly provided by GBPPR_...
+
+
+
+.. _people: http://www.qsl.net/n/n9zia//vision/EIP_545A_Modification_Instructions.pdf
+.. _several: http://www.simonsdialogs.com/2014/09/eip-545a-microwave-counter-power-meter-upgrade/
+.. _GBPPR: http://www.qsl.net/n/n9zia/vision/
+.. _`MiniPro TL866`: http://autoelectric.cn/EN/TL866_main.html