Category Archives: EIP 545A Microwave Counter: power meter upgrade

Upgrade of the EIP (now Phase Matrix) 545A counter – option 2, power meter

EIP 545A Microwave Counter: power meter upgrade

EIP 545A Microwave Counter: Option 04, a dead eprom, and a noisy fan

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Another one of the EIP 545A counters, that are for some reason very frequently seen at my workshop. The reason for this instrument being here on the bench is simply for the fact that I found it on ebay, for a very reasonable price, non-working, but with the 04 OCXO option.

The option 04 provides 10^-9 level frequency stability, per day.

The actual OCXO unit is an Ovenaire 49-38c model 10 MHz oscillator. Very similar OCXOs are used in various HP equipment of the time.

The first item to fix – the very noisy fan. An ETRI model 126-LF-182. Fortunately, a very common 115 V model.

Replacing fans, you can’t just go for the flow rating, but you also need to consider flow direction, static pressure (mostly related to the blade shape and RPM), noise level, lifetime, and bearing type (ball bearing).

Found a very similar NMB fan, which is available from new production, at a reasonable price.

For comparison, the ETRI data put into the NMB pressure vs. flow characteristics, as red dots. Indeed, quite similar.

When changing the cable, from the old to the new fan (EIP uses a special connector, so I needed to re-use the old connector) – seems EIP didn’t trust their crimping, the cable was additionally soldered to the crimp pin.

The new fan installed, make sure to use some insulation tubing (not present in all EIP counters, but was present in this one, and a good idea, because the fan cable runs directly underneath the top cover, and over time, could be damage and expose mains voltage to the case (not a good thing!).

Next fix – a broken tantalum on the front panel (capacitor was OK, but one wire broken off) – fortunately, it could be soldered from the top, because disassembling the from panel is quite a time consuming task.

Finally, all these things fixed, but still a non-working EIP. It would not even count low frequency, or show any reaction on the display. All voltages OK. That’s strange – most likely something with the CPU, data bus, or similar. So, swapped the main CPU/control board with a know-good assembly, and the EIP came back to life. After some checking and probing, found one EPROM that had corrupted data – no wonder it didn’t start up.

While cleaning the power supply (removed the card from the main board), another issue showed up: EIP didn’t use sufficient thermal grease to make good contact of the assembly cage (used as a heat sink), and the heat conductor of the power supply assembly. All screws were tight, but no contact.

So I cleaned up everything, and added some more generous amounts of a good thermal compound.

This is the top view: you can see the OCXO auxiliary power supply to the left, and the OCXO in the right upper corner.

Also quite interesting, this unit has seen some pretty famous owners, including, Bell Labs, AmerSatCo, and Verestar, Inc. – probably, it has seen good use, also judging from the noise fan, which has 50 khours+ lifetime.

One all had been fixed and confirmed running, I could not resist to also add the 02 option Power Meter Upgrade to this unit, it is in the end just few eproms, and some additional parts for the A107 assembly.

… counting at 10 GHz, and showing the power.

EIP 545A Microwave Counter: power meter upgrade

EIP 545A Microwave Counter: El Salvador’s brittle leg disease

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One more EIP 545A made it to my workshop, all in good shape, but not counting any microwaves, or other signals. The “gate” LED stays on permanently, and no counting also with the test function 01, which directs a 200 MHz signal to the counter chain.

Looking at the schematics (fortunately, there is a full service manual available), the issue needs to be with the A107 gate generator assy. And, easy find, no 100 kHz signal present. So something must be wrong with the 10 MHz to 100 kHz divider. Soldered a wire to some of the signal points, and needed to go all the way back to pin 1 of the 1st divider, which is a decade counter. No signal present.

The EIP 545A has all-socketed ICs, so pulled the IC from the socket, and 1 leg missing! The leg number 1 that needs to take the 10 MHz and put it into the silicon chip. Temporarily soldered a wire onto the IC, and it solves the issue, but not a good permanent solution.

Also the other pins are very brittle, when you touch them, and bend a little bit, they break off, rather than bend. This is quite common for some old Texas Instrument TTL chips, not quite sure way – maybe some precipitation hardening of the copper material they used, or an interaction of the copper core with the tin/lead top layer. We don’t know, but it seems to be particularly common with El Salvador’s chips.

Here, a close-up of an (intentionally) broken leg.

Also the LS175 on the same board, although it was all good electrically, shows quite severe brittleness. I replaced with right away (with a 1977 date coded LS175, also from Texas Instruments!).

The LS490, unfortunately, none to be found in my basement storage of all kinds of electronics parts. Many counter TTLs, but no 490. An the offers, they are pretty pricey, and I want this instrument to be fixed today, rather than waiting days for some overprices NOS TTL ICs to be delivered.

Looking at the datasheet, and schematic, it is a simple :10 divider, there are many of these – including the much more common LS390, and the pin arrangement is almost identical.

We only need to route the output of the 1st divider (a :2 divider) to the input of the next stage – and the LS390 will work like a LS490. The red lines show the additional connection needed (you need to bend up the pins, because they are grounded on the EIP A107 board).

…A107 board with the LS390 installed.

With these fixes, the 100 kHz signal came back! And the gate LED flashing!!

Tested with the test function 01 for some hours, and with some shaking and bending of the boards – just to be sure that the repair is permanent – all counting along fine. Also in band 3, no issues, and very good sensitivity all the way up to 18 GHz.

The last thing to do to before the unit will leave the workshop – adjusted the TCXO to the right frequency, it was only off by a few Hz, after many years of aging.

EIP 545A Microwave Counter: power meter upgrade

EIP 545A Microwave Counter: another power meter upgrade

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This is just a brief update on an earlier post, related to the power meter option for EIP counters, EIP Power Meter Upgrade. The current 545A came without any options, even without GPIB, and I was not quite sure if the firmware power meter option firmware would work, even if no GPIB option is present. Well, easy enough, put it to test.

545a upgrade eproms

It didn’t take much, a few (rather old 2516, and 2532) EPROMs, a resistor, some spare ICs, and a few inches of solder…

545a board

Here, the result: all working just fine, counting away at several GHz, and power reading appears to be resonably accurate. I would not substitute it for a proper power meter, for calibration purposes, but the power meter option is a handy feature for any quick test and confirmation.

545a upgrade test

EIP 545A Microwave Counter: power meter upgrade

EIP 545A Microwave Counter: power meter upgrade

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This time, not really a repair, but an upgrade.

Every lab or repair shop dealing with really high frequency circuits needs one: a microwave counter. The EIP 54x series has certainly been (and still is) one of the workhorses of the industry. EIP is now Phase Matrix, still selling counters. But I guess, not an easy tasks – there are quite a few of the EIP counters around, and they do have some little issues with tantalum capacitors, etc, but all in all, the EIP counters are really marvelous instruments, rock solid.

The 545A:
eip 545a counter

In my own shop, there are two 545A counters (18 GHz, N connector), and also a 548A, which is similar, but covers up to 26.5 GHz (3.5 mm connector). The 548A can go to frequencies as high as 110 GHz, with some external mixers. While these have provided good service over the years, they are all lacking ‘option 2’, the build-in power meter. At microwave frequencies, having a combined power meter and counter has a considerable advantage – no need for changing cables, no need for splitters or couplers – just the push of a button. And not always do you want to connect a circuit under test to a valuable 18 GHz+ spectrum analyzer or measurement receiver…

Fortunately, there are clever people around, at the Green Bay Professional Packet Radio club (“GBPPR”), which kindly provide the ROM images and some circuit modification info on the web – to convert a regular 545A, to an option 2 545A!

Well, first we need to collect some parts, a low capacity Schottky diode (HP 5082-2835, 1 pF max.; original EIP circuit uses a different kind, but really any low capacity Schottky will work), a DM8136N (a comparator/address decoder), a 74LS244 buffer, and an AD7524JN (8 bit DAC) – plus, a 10k resistor. Except for the DM8136N, nothing uncommon at all.

The only tricky part, at least here – the 2532 EPROMs. These aren’t accepted by any of the programmers around, and they need a high programming voltage. So first, put together a little programmer that attaches to an ATmega32L, and with the data transfered by USB.

2516 eprom programmer
It’s really crude – I don’t anticipate a lot more 2532 EPROMs that need programming, except for the EIP….
I had some 2532A around which are working perfectly fine, just lower programming voltage. The 2532A/2532 – they can be handled by some 2732 programmers, for reading the contents, with a little socket adapter (2532 and 2732 have different pinouts!) – but strangle, the same programmer doesn’t work for writing to the these old beasts.

The second type, they are 2516 EPROMs, no problem with a 2716 programmer.

After fiddling around with the EPROMs, the little programmer, the adapter sockets – a few hours later – that’s now the set of parts:
eip option 2 upgrade parts

These are the boards, A105 and A107, with the parts installed – red rectangles: additional parts; yellow: removed parts (resistors R39 and R40).
eip 545 board modifications

I would suggest to put all parts in sockets, like EIP did. Then you can change your counter back, to non-option 2, should you ever want to.

After a bit of soldering – that what we have – a working option 2 EIP 545A.
eip 545a option 2 power meter working
The power meter can be switched off – if you need the extra digits. Typically, I don’t.

All that is left are the original EIP EPROMs, programmed in San Jose, California. Collectables.

eip original eproms

Any questions, please let me know!