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Thread: Scholder Johnson GM300

  1. #1
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    Default Scholder Johnson GM300

    So, I'm a little lost here on trying to convert a few GM300s with the Scholer Johnson LTR UHF firmware in them back to Motorola conventional firmware. I have made perfect copies of the GM300 conventional firmware on some 27C256 EPROMs ready to go, but if I try to just simply switch out the SJ CVT-400 PROM, the radio acts like its brain dead and of course doesn't respond to any Motorola RSS.

    I have asked some other radio techs about this and even posted on Batlabs about the right process, all so far what some people have told me that I need to find the SJ RSS for the radios to first reset the radio back to "Motorola Mode" so then I can use Motorola firmware and everything with the radio as the SJ firmware changes the flash memory...which sounds plausible to me, but still not making sense. However, I have read too that the SJ converted radios also need a "special RIB" to even talk to the radios.

    Can anyone here set me straight with this? I have a bunch of these and it seems to be just a waste if I can't get them alive again.
    Last edited by WQNV648; Jan 09, 2013 at 03:57 AM. Reason: spelling of Scholer Johnson


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    Ask SJI I have found their customer support to be exellent. if there is software that they use I am pretty sure they wil send you a copy if you ask nicely.

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    I might do that to see if they know about converting them back.

    I found the software actually but according to this: http://www.idaco.com/Cvt2.pdf I also need their "PGM-2 Programmer" which I would be interested in looking at a schematic of...

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    I have a programmer but the big chip has had the numbers removed. the small chip is a dc14c232cn


    http://pdf1.alldatasheet.com/datashe...S14C232CN.html

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    No idea if this guy frequents BL anymore, but he claims to be able to blank the boards:

    http://batboard.batlabs.com/viewtopi...choler+Johnson

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    It would be interesting to see what SJI says about reversing the proceedure.

    Much as we dont discuss the use of Lab tools here these radios no longer meet FCC narrowbanding spec but are ideal fopr ham use. I think this might work.

    -get a copy of toolkit
    -install a maxtrac prom in the radio
    -use the blank board option
    -use RSS to initialise the board

    you may have to reblank the board using maxtracs lab (not maxtrac)

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    I was hoping to use the new GM300 procedure that doesn't require the Maxtrac conversion, but, you gave me an idea.

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    I wrote that thread on BL 7 years ago it looks like. I have since forgotten the exact procedure and lost the info I had. From memory, you leave the SJ chip in at first so you can use the SJ software. There is a special key sequence that enables 'lab mode' (my description) and allows you to blank the board. I have no special programmer so use your Motorola RIB or equiv. to do it. Once the board is blank, swap proms and drop a Motorola prom in it's place. Use the Moto RSS to re-initialize the board. You can initialize with standard RSS you don't need lab or anything special. As was already stated a friendly email to SJ telling them you are doing this for ham use will likely result in the software and procedure being sent back. They seem like good people there.

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    That makes sense! Now, I just need to find the magic menu....

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    I agree with JeepFrog SJI is very helpfull. Once you have the steps you can always repost here.

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    So after a nice conversation with oddly Mr. Johnson, he told me the GM300 conversions were an interesting endeavor because they wanted to use the same CVT-2-400 firmware PROMs as the MaxTracs. The GM300 were basically converted to think its a MaxTrac much like the old Batlabs procedure on their GM300 page. He suggested putting in a Maxtrac EPROM and go from there.

    So I found a Maxtrac EPROM, and now Maxtrac RSS can read and write the radio. Using Lab, I blanked the radio and initialized it. VOILA! It works!

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    That's interesting, that's exactly what didn't work for me the first time around. Good to hear you got it though.

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    Maybe you used the wrong maxtrac prom. WQNV648 do you know what prom you used ?

    Also thanks for keeping the thread updated. A special thanks to SJI and Mr. Johnson for the exellent customer support.

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    Yes, I do have the part numbers for the PROMs....once I get back to my desk I will postem.

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    Quote Originally Posted by Notarola View Post
    I have a programmer but the big chip has had the numbers removed. the small chip is a dc14c232cn
    If we are talking about the same programmer board, then your "sanded" chip is Motorola MC68HC705C8... There should be 8-pin EEPROM also.

    By the way, I have microcontroller chip that was saved from a PGM-2 board that had to be destroyed (it was dumped with some PLCC chip from dead 286 PC motherboard ), but I do not have EEPROM contents to make it work.

    EEPROM contained unit ID and licensing information (how many radios you are allowed to convert to LTR).