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
