Hey folks. For some time now I've been working on the innards of the 70900A/B spectrum analyzer LO modules. With the recent recovery of the Receiver Personality program, which is software that gets installed into a 70900 to turn it into a high-performance signal analysis receiver, I decided to kick that work into high gear. I've now successfully reverse-engineered the functions of the address mapping PALs and the memory subsystem on the MEM-PLUS CPU board present in many 70900s, to make it possible to upgrade the RAM chips on the ROM/RAM boards.
The Receiver Personality software coexists with the normal spectrum analyzer firmware; you can switch back and forth during operation with a button press. It has no effect on normal spectrum analyzer use. This software, and possibly others, requires that a 70900 have Option 512, which is higher-density memory on the ROM/RAM board. It seems very few 70900 CPU boards were shipped with this option. This software also requires that the 70900 have firmware release B.05.00 or later, and have an MC68020 processor.
In this context, I am now prepared to offer, as a paid service, some upgrades to certain 70900 (both A and B) modules.
Given a 70900 that has the MEM-PLUS option installed, I can upgrade the RAM to give it Option 512. I can also update the firmware to the last release, B.06.04. While it's here, I can also replace the battery, and the failure-prone capacitors on the power board if required. I can also install the Receiver Personality software, if desired.
I am happy to share the information required for anyone to perform these upgrades themselves, however, I thought it reasonable to offer it as a service for those who don't want to risk ruining their expensive 70900. There are several reasons for this. First, these modifications require quite a lot of extraction and soldering of surface-mount components. Then, there's finding/procuring all of the required replacement components, and removing/reprogramming/replacing the PAL chips, which are soldered. If a firmware update is desired, that also involves the extraction, out-of-circuit reprogramming, and replacement of multiple surface-mount flash chips. My company has the proper equipment to perform these tasks correctly; I do this type of work professionally as my full-time job. I will charge for this service; that's to be discussed off-list.
I've performed these modifications on three of my own 70900s with flawless results.
My company has a substantial stock of the required replacement SRAM chips, PALs, batteries, and capacitors.
Again, your 70900, A or B, must have the MEM-PLUS option installed for this to work. I can tell you how to determine that if you don't already know. And before anyone asks, no, I cannot repair failed EYO (YIG) modules.
Contact me off-list at mcguire@... if you're interested in this service.
Thanks,
-Dave
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Dave McGuire, AK4HZ
New Kensington, PA
Dave McGuire