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Thread: Astro Spectra AVA and HHCH modification

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    Default Astro Spectra AVA and HHCH modification

    OK, here it is, gang. This is a p25.ca exclusive! I am finally after all these years releasing my AVA-HHCH mods to the general public. There is a lot of rumor, and plain misinformation out there on this subject, so I finally decided to write a definitive article about basically everything I know about them in one neat package. There are those that said it couldn't be done, including Motorola. Well, I found not only one but two ways to make it work. Interested? Download the PDF file and read on!
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    Last edited by Alpha; Apr 29, 2014 at 10:55 PM.


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    That is a fantastic write up Alpha! I'm going add this to my project list! Excellent work.

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    If you do the reset mod, can the HHCH still be used for the astro spectra W3?
    Keith Dobbins N8KLD
    Mainframe Network Engineer/
    Managed File Transfer Engineer
    W8TAP Repeater Engineer
    Parkersburg, WV 26104

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    You know, I haven't tried that. You can easily test whether or not it works by just lifting the collector of the transistor (single lead side) and angling the part up but don't remove it completely. Then you can tack it back down if it proves to be a problem. Once it's up, test it as a W3 and see if just doing that mod alone will bother an Astro Spectra. If all seems OK, then you can know it will work interchangeably. You can leave the transistor up or just take it out completely at that point.

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    Motorola did actually make this, several were available at Dayton back in 2008? Motorla Otaku has a modified AVA, and the HT needs to have a specific Host/DSP. Nice write up by the way, I have some playing to do.

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    I mentioned this in the document. Yes, Motorola did make a later version of the AVA PLN7736 that was compatible with the XTVA HHCH, PLN7737, but that was after many years of them trying to get the HHCH to work with a "Y" cable, which they eventually abandoned and canceled the option.

    As to fimware revisions, the AVA itself had a firmware requirement that was the famous "white sticker" on top of the AVA units, but that is all. The problem is actually a codeplug issue, not firmware. I go into this in more detail in the document, but in short the latest firmware DOES work with the modified AVA/HHCH just fine. This is a bit of rampant misinformation I would very much like to dispel.

    As to Otaku's AVA, it might be one of the many I modified and sold, or it may be one of the newer PLN7736 ones. Plus, I am probably not the only one that figured this out. Motorola developed exactly the same mods that I did in parallel for their PLN736/PLN7737 revisions, except for one minor difference, so sometimes different people will come to the same conclusions.

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    Sorry, I hadn't read all of the doc before I posted. His is a 7736, and does use the 7737 head.

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    Hehe, OK, I figured it was, or he was one of the people I swore to secrecy when they bought their AVA/HHCH setups from me

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    seth and I bought it at Dayton back in 2009, played with it for a while and then Seth sent it to Motorola Otaku along with an 800 MHz Astro Saber III that came with it. It seemed to be the only radio that would work with it (host 5.03 I think), newer firmware wouldn't work with it. I've still got some notes around here somewhere.

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    First off, a big thanks to Alpha for his documentation on converting the HMN4044 to work with the Astro Saber AVA. I really like the Astro Saber radio (with Honeywell H8818-Li short straight batteries), and when I picked up a cheap AVA I never expected it to sound as good as it did. Pro mobile audio and great scan (with 2 priority channels) that has MDC1200 and P25 encryption muting! It hears very well and scans fast. Why spend more for a newer more expensive radio with the same 15+1 scan limit? Anyway, with an added amp it is a great mobile setup, and doubles as a portable when out of the SUV. All that was needed to complete the package was an HHCH. So this was fantastic news.

    I decided to give the Y-cable mod a go, not that I was opposed to the RJ45 AVA mod, but this was an easy way to jump in without removing the AVA from my MotoDIGITAL radio stack box (V/U/900 XPR DMR mobiles with an AVA at the bottom of a 8”x10”x12“ black painted wood box). I bought two HMN4044D HHCH mics off of evilBay and studied the document in preparation of the work ahead. After they arrived I purchased the DB25 parts.

    The mics were said to have come from a “working environment”, but I had no way to test them prior to the modification work. So I preceded to remove the one transistor and jump out the one audio resistor on one mic before modifying the other mic. After building the DB25 pigtail off of the back of the 12W speaker connector, I double checked all connections and gave it a try. FAIL 01/90 displayed over and over no mater what power up sequence or reset I performed. Very disappointing.

    I decided to try the second mic, so I did the mods on that one and gave it a try. FAIL 01/90 showed and I just turned off the power supply in disgust. When I switched it back on after a beer break, the mic booted up and showed the normal display characters. (yeah!) While doing the mods inside, I twisted the mic element audio leads and moved them away from the semi-conductors and the TX audio sounds clean and robust, even with the original 39 Ohm resistor. But after turning on the backlight, only the function keys lit up and not the display area (shucks!) I unplugged the mic and plugged it back in again. Still no backlight in the display area. I don’t know if this is normal for this mod or if this is a defect with the mic. The other mic doesn't work at all, so maybe I received defective microphones. I can’t make a claim now that I modified them. So what do I do next? Will this ever work correctly? Is something missing???

    Then I re-examined the pinout for the Y-cable. Here is how I read it:

    AVA - HHCH
    3 - 4 (ground)
    4 - 5 (data)
    14 - 12 (mic audio)
    15 - 1 (SW? noticed no pin on the HHCH DB25 connector, so no connection to anything)
    17 - 23 (busy)
    24 - 22 (unswitched B+…mic stays on even when the radio is off or removed)

    That leaves these underutilized pins on the HHCH connector:

    14
    18
    24
    25

    What do these other pins do? I did a Goozle search for any schematic I could find on the HMN4044_ and came up with nothing. I did a search for a service manual and could not find one. Does anyone have a pinout for the W3 HHCH?

    I tried to read Alpha’s “sticky” on the eight pin RJ45 pinout and could not make much identification on what all the leads do. Why eight connections on the RJ45 version and only five active connections on the DB25 Y-cable?

    Originally I did not put a reset switch on my Y-cable, but after finding it a pain to unplug the mic almost every time on radio power-up, I did install one remotely up on the front lower left corner of my radio stack box…but then the mic no longer worked! The switch was disconnecting B+, but it would show FAIL 01/90 every time after the reset. Why? I suspected the somewhat thin wire I used created a voltage drop, and after replacing the thin wire with heavier wire it went back to working the way it was before. I now have a reset button, but I think I want to change it out to an on/off button instead so I can turn off the mic when not in use. I would still prefer powering the mic with switched B+ if I can find it on a pin somewhere.

    Also, I have 3 different Astro Saber radios with different firmware from early 5 with a 512 vocon to the latest 7 version. Makes no difference on anything.

    So I’m a little confused on the lack of connections, loss of display light, and I wonder if the full mod to a PLN7737 with the RJ45 connections will work any better. Does that need resets all the time, as well? Does that work any better?

    Can anyone shed some “light” (pun intended) on the subject?

    Thanks,

    Phil

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    Hi, Phil. Thanks for your interest in the project! Let's see if I can help to decode my gibberish a bit more for you. Too bad about the HHCH purchases, you got eBay'ed again No, it is improper to not have the display back-lit, it should be like the keyboard and be lighted as well. You might try carefully taking apart the dead one and see if you can swap out the display LED's, I believe they are located to either side of the display module. You might also be able to take voltage readings and see if something is missing or whatever.

    More info on the Mystery Pins:

    14 - Unknown Data signal. Scope shows some kind of toggling signal, but no connection seems to be necessary. Maybe a BUS (-) differential signal or something?
    18 - Ground (loops back to pin 4)
    24 - Speaker Audio + Balanced Pair (for handsets?)
    25 - Speaker Audio - Balanced Pair (for handsets?)
    SW? - Not sure, may be external foot switch for emergency? Again, no connection seems necessary.

    8 connections reduces to 5 by dropping the audio pair and the Mystery Data lines, which are not needed. The actual HHCH only needs 5 signals to function.

    As for switched B+, maybe try the other B+ pin on 11 of the AVA instead of pin 24? Otherwise, you might try checking the AVA schematics, or run a voltmeter up and down the DB-25 while turning the unit on and off, until you find a B+ that appears to be switched. If you find one, post it to the thread for general information, please!

    The PLN7737 conversion with removal of the extra transistor DOES remove the need for external reset that I have found. Also it fixes the "Unswitched B+" problem, as the HHCH is powered by the 5V VCC (which acts like switched B+) inside the AVA.

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    Thanks Alpha for the followup. This really is great work.

    Copy that on all the above notes. Understood on the display lamps. I'll see if I can use the other dead mic for parts, or maybe fix that one. Yes, I got screwed by evilBay...again. This is the norm these days. Almost everything I got in recent days had an issue. I'm looking at KVL's right now and that is way too risky...plus I need to learn more about them before purchasing.

    Back to the HHCH mod; I looked for AVA schematics all over and could only find a block diagram without detail on all of the other pins. Even if I found a switched hot lead, I would not risk tapping it without knowing how much current it could supply. My HCHH gets a little warm, so I guess the regulators inside pull some current...plus my thin gauge wire (bad choice) voltage drop indicated some amperage draw. Wouldn't want to pop a transistor or regulator without knowing for sure. I will look for a schematic or find a service manual somewhere. Until then an on/off switch is easy enough.

    Oh...and yes, there actually is a lack of key functionality on old firmware 04.01.05 (that is my 512 vocon radio). It displays ok, but you can't change zones or modes. Odd thing is that this older radio does MDC1200 DOS muting and PL reverse burst (in scan) muting better than my late radio with the latest firmware. I checked all codeplug parameters side by side and they are the same, so something is different. The newer radio does PL sensitive scan where the old one doesn't (locks up on scan with CSQ carrier or wrong PL code). Win some, lose some. I'm just glad the HHCH works...well almost. I need to fix the upper display lamps. I would bet it is a failed transistor driver and not the LEDs. I need a schematic for that too! Hard to believe these are not out there somewhere.

    Thanks again,

    Phil

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    We have the HHCH service manual and schematics posted! It's hiding in: 68810996C77-O_ASPlus_SM_Cntrl Head Service Manual, the W3 HHCH is fully documented! I wish I had known this back when I figured all this crap out to begin with! Here's the thread where it's posted:

    http://communications.support/thread...olette-Manuals

    Schematics for the AVA are still elusive; I believe there is a manual out there for the older Saber-only SVA version, but by the time they made the Astro AVA version, they were on this new kick of deciding that electronics were disposable, and there was no point in publishing schematics and service manuals beyond block diagrams anymore.

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    This place is great. Thanks again. Now I will see if I can fix my defective HHCH heads. I just downloaded a bunch of those and will have a looksee.

    Phil

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    Isn't it though?

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    Quote Originally Posted by N2HUC View Post
    First off, a big thanks to Alpha for his documentation on converting the HMN4044 to work with the Astro Saber AVA.
    Agreed! Thanks Alpha.

    Quote Originally Posted by N2HUC View Post
    The mics were said to have come from a “working environment”,

    But after turning on the backlight, only the function keys lit up and not the display area (shucks!) I unplugged the mic and plugged it back in again. Still no backlight in the display area.
    I'm guessing mine came from the same 'working environment' as yours. A little rough and the disp backlight didn't work.

    I pulled the LEDs and it seems that one of the two on each side was toasted, the lenses were blown out! I popped the good ones on a single side (they are in series) and that half works.

    I think that the correct xref for the LEDs used for the display are the Citizen CL220G. I can't find stock of them, and never tracked down a suitable side-emitter replacement. If you do, let us know!

    http://www.nicomatic.co.uk/pages/pro...ness/cl220.htm

    Here is my annotated schematic with all of Alpha's excellent mods as well as jumper locations for possible additional hackery.

    HMN4044 Mods on Schematic.pdf

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    Wow, nice work, safe! Nice to see the precise differences between an HMN4044D and the PLN7737, I saw there were a few other minor changes I hadn't previously noticed. The mods seemed to work OK without some of them, but it's nice to see exactly what I was trying to accomplish confirmed on paper. Thanks!

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    Sounds like someone plugged it into the wrong radio. I bet there's a radio with a blown audio PA to match.

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    I did that once. You know you screwed up, too. The mike sends gentle whiffs of smoke out the crevices..... And then there's the stench. (for awhile)
    Apparently NOT a radio professional.

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    Quote Originally Posted by com501 View Post
    I did that once. You know you screwed up, too. The mike sends gentle whiffs of smoke out the crevices..... And then there's the stench. (for awhile)
    Aww, i though i had an SP radio meant for covert installs that used smoke signals instead of the horn and lights alert.

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    Looks great.. is link to pdf still here?

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    I just jumpered the resistor (near mic element) on HMN4044D for louder audio, and removed the transistor and the two resistors. (reset mod).

    Mic still works perfectly, with better sounding audio, on a W3 ASTRO Spectra.

    Also, I swapped the mic element with one from a XTS5000, and it sounds sharper/cleaner.

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    Quote Originally Posted by Alpha View Post
    As to Otaku's AVA, it might be one of the many I modified and sold, or it may be one of the newer PLN7736 ones.
    It is a PLN7736A. I still have it, and I'm open to cracking open the case and taking board pics if there's still any serious interest in these units.

    Personally I'd like to see a revision to the APX VA for an O3 HHCH, but the likelihood of that ever happening is slim to nil.
    "The Girl Scouts found several hungry REACT members at the finish line..."

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