My Trc-920 Bluetooth Install

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trippy1313

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So a few months back I tinkered with the Bluetooth modules our good member blu_fuz put us onto in this thread:

https://boomboxery.com/forum/index.php/topic/23129-m70-m90-with-hardwired-bluetooth-module-mod/

I got a couple myself, played with them on a trc-931 for a while to see how they work, different ideas to install, but never completed an install.

So last week I finally decided to buck up and finally complete an install, but on my Trc-920 instead. Here goes...

I wanted to run this off of a switch in line with the power switch, so it would only worked when the box was powered on, but also switchable on its own, so it wasn't always on with the box.

And since these are meant to run off 12v, I noticed although this is considered a 12v radio, it actually runs at 14v when plugged into the wall. So I also wanted to install a 12v regulator to make sure the module doesn't burn up, as previous tests burnt up a couple modules at 15v.

Here's a couple pics, I'll explain a little more along with them.

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This is the module with the 12v regulator connected to it. I cut the RCA ends off, so I could solder the positives to the audio inputs on the box.

2016-05-25 23.01.17.jpg
This is how the RCA cable is, basically the negative is around the positive audio wire. I uncovered it back and cut the neg so I could be sure they didn't short out.

20160525_123634.jpg
Here is the left and right (red/white) positives soldered to the input posts. As you can see I put heat shrink around where I cut back the RCA cables.

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This is where I installed my switch. The wire storage has this expanded area, big enough to reach my finger in. It's hidden completely from the outside, all I have to do is pop the battery door off real quick and flick the switch. We'll see if that was a good idea or a hassle later. But it has the wire coming from the radio power switch, the from this switch to the module, via the 12v regulator.

Now with the problem I had. This module shares the same power ground with the audio ground it seems. Probably typical, I have no clue. So with me testing before, I found if I ground the module, AND use the L&R audio negatives, it has a high pitch sound. Which is why I cut the audio negative, I was just going to use the module's ground. So I soldered it to the negative audio input side. Well that made a terrible ticking noise, even with the volume all the way off, the speakers ticked. Weird. Then I played around for a couple hours a day, thinking it had to be a power issue.

Long story slightly shorter, DON'T use the audio negative as a ground!!! I found the best place to ground this module is the main ground on the box. Now it's crystal clear. Since this module uses the same ground with the audio, I think it was sending a power signal through the speakers??? I don't know, just my guess. Here some pics of where the correct ground for this module should be on a 920.2016-05-25 22.54.14.jpg2016-05-25 22.50.54.jpg

And here's the module completely wired in, zip tied up to look, well, as nice as a Lasonic wire nest can look.20160525_102634.jpg

Not sure what else to say... I love it. Tested it for about 5 hours today, crystal clear. Works great. Any questions or comments please bring them on.
 

blu_fuz

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Perfection!


I ran into the same issue on my M90 internal BT mod. There was tons of feedback /noise with the RCA ground attached and the BT module ground attached. Just to clear things up, you put the NEGATIVE/black wire from the module to the chassis ground of the radio? The NEGATIVE wire from the RCA's is not hooked up anywhere?


I removed the chassis ground to eliminate most of the noise only because the RCA jack pads on the PCB are a pain to get at on the M90, or I would have done it the way you did by removing the RCA ground.


Do you have any more info on the 12V regulator, part number, wiring sketch?
 

trippy1313

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blu_fuz said:
Perfection!


Just to clear things up, you put the NEGATIVE/black wire from the module to the chassis ground of the radio? The NEGATIVE wire from the RCA's is not hooked up anywhere?



Do you have any more info on the 12V regulator, part number, wiring sketch?
Exactly. The RCA negatives are not being used at all. Just the module ground, connected to what appears to be the main, first chassis ground.

And yes I'll take a picture of the regulators package that shows the sketch and explain what I did there too. But go figure... RadioShack.

Edit: here's the regulator. There's two spots you can ground it. I snipped of the center ground prong so it wouldn't touch, and soldered a wire to the backside ground tab. Then connected that ground, and the module ground together, at the chassis ground.
20160526_081005.jpg20160526_080923.jpg20160520_164904.jpg

So on that last pic. The blue wire on the bottom, is voltage input, from the radio power. The red on the top is voltage out, to the module. And ground wire is soldered to the ground tab on the backside.
 

trippy1313

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JustCruisin said:
Awesome! :thumbsup: those Kenwood speakers must pound?
They do! I realized my Lasonic speakers were bad and tried a different pair before those, but I think they required too much wattage, the radio could barely make any sound at full volume.

These Kenwoods specs were a pretty low wattage, with a pretty high sensitivity, and cheap. Now I haven't has it past halfway for more than 5 minutes. Just too loud, and the bass... very nice.
 

T-STER

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Awesome, i want to do this to one of my M70s so a bit more of a guide is very helpful, nice one!
 

trippy1313

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T-STER said:
Awesome, i want to do this to one of my M70s so a bit more of a guide is very helpful, nice one!
Exactly. I don't think I would have tried if it wasn't for Joe's install on the m70/m90, and Chris'a description and video of his 920. Those helped a ton, so thanks to you guys.

That along with tons of threads on this site and other audio sites. I'm pleasantly surprised I got it working so well.
 

blu_fuz

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Thanks for contributing this with the pictures edited. That should help a lot of people try to DIY. :yes: :cool:
 

trippy1313

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blu_fuz said:
Thanks for contributing this with the pictures edited. That should help a lot of people try to DIY. :yes: :cool:
Yeah, I was going to explain it, but looking at my pics its too hard to just say, "solder to the main ground," and hope people get it right.

There's so many wires and spots all over this thing!!!
 

trippy1313

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Thanks!!! Maybe if I make it to Vegas I'll have to bring it. I'd love to hear how you guys think it sounds compared to a stock one. Mine were bad so I never knew it's true sound.
 
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