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EIP 545B Frenquency counter

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douardda:
Hi everybody,

I recently purchased an inexpensive EIP 545B on eb (one of the devices recently sold from Israel).



I received a few days ago, and the unit was, as adevrtised, not powering up, but also very dirty, with a bit of rust.



But after a good cleaning, the device seems to work



Now, I'd like to try to modify it to install the Power Meter (Option 2). This has been done by http://www.qsl.net/n/n9zia/vision/ and reproduced several times y SimonDialogs http://www.simonsdialogs.com/2014/09/eip-545a-microwave-counter-power-meter-upgrade/, but only for the 545A model, not the 545B I have.

Both models looks very similar, but not completely, for example, the GPIB board is different: the GPIB address is set via the test number '90' on the B model, whereas on the A model, the "test" 90 is used to configure the YIG calibration curve (it's on test 91 on the B model).

[edit] CPU boards are pretty different also[/edit]

So there are differences in firmwares, which makes me think I won't be able to simply use the EPROM images for the A model.

Has anyone ever tried this procedure on a 545B?

Has anyone have a 545B with option 2 and is willing to dump the EPROMs and make the files available somewhere?

Thanks,

David

PS: for a few more details on the repair of the unit, see my blog post


 

douardda:
I've been digging a bit this power meter option, and I'm a bit puzzled by the modification made by WB4BPP (aka J. L. Trantham) on http://www.qsl.net/n/n9zia/vision/

Looking at the service manual for both 545A and the 578B (for which the Service Manual is also available and since it has the same CPU board than the 545B, it's probably a better source; the A107 board seems identical on all the versions), I cannot find anything related to the added EPROM on A107.

The differences of the schematics between the version with and without the Power Meter option only consists in the addition of U12 (8bit DAC) and CR3 (Schottky diode) and the removal of the "direct path" resistors R40 and R39 (as described in WB4BPP procedure).

So I wonder what these extra chips are used for (the U19, U20 and U21).

No doubt however that this option 2 must be "activated" somehow in the software, so I still need the main CPU's EPROM content for a 545B with option 2...

David

douardda:
A closer look at these schematics, on the left are 2 tables with the unused references (Ref. Des. Not Used) and the power rails for each chip, and sure enough, U12, U19, U20 and U21 (as well as CR3) are listed as unused on the board without option 2 and added in the power rails in the version with option 2.

So It seems that they are not drawn on the schematic but needed nonetheless...

If I have the courage, I'll reverse ing. this missing part of the schematic, for the sake of understanding :-)

douardda:
In fact, in the service manual is this description:


--- Quote ---The POWER METER PROM (Option 02 only) contains a  logic comparator (U21), a 2K  x 8  PROM (U20), and  a  bus driver (U19).
The logic comparator is connected to the microprocessor address bus, and  is configured to decode the 2K address range from 4000 Hex  to 47FF Hex.
The comparator output drives the chip select of the PROM and the bus driver.

The  PROM contains the Power Meter program as  well  as the power correction factors.
Bus driver U19  is  used  as  a buffer for driving the microprocessor data bus
--- End quote ---

so maybe a modified A107 board is enough, without the need for a modified firmware of main CPU board...

douardda:
I've been looking a bit at the ROM dumps provided by GBPPR, as well as the EPROM dumps I just made from my unit, and I am pretty sure a modified A107 board will be enough to activate the power meter (no need for extra ROM images on the CPU board).

Also, the instructions they give for the modification talk about the calibration data, but not in details. In fact, the service manual says:


--- Quote ---The power meter contains 690 correction factors. stored in PROM.

The 150 "power vs power" correction factors compensate for variations from
square law in the detector and power meter circuits. They are divided into
three tables. The first table corrects variations below 10 GHz. The second
corrects variations between 10 and 20 GHz. The third corrects variations above
20 GHz.

The 540 "power vs frequency" correction factors compensate for variations in
the detector output at different frequencies. "Power vs frequency" corrections
cover 0-27 GHz every 50 MHz. ' The power meter is calibrated at the factory
using specialized automatic test equipment.

Recalibration in the field is not recommended.

--- End quote ---


These values are stored at the very beginning of the EPROM. And looking at the calibration data of the unit used to extract the EPROM content for this Option 2 provided on GBPPR, it's clear that it has been calibrated only in the range 0-18GHz since from address 0x1FE, the same value (0x1A) is repeated again and again till the end of this calibration table (0x1FE is 150 (0x96) + 360 (0x168), and 360 because there are 360 50MHz steps in the 0-18GHz range).

I've ordered the parts I am missing to try this mod (probably next year :-) )

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