Hitachi 3d7 modernization project (BT audio/calling and lithium)

[IVH]

Hey guys,

A few might know me from my thread about the repair of my hissing Hitachi 3d7. Now that the problem is (hopefully) finally found, I can start with the 'modernization' of this boombox.

I know there already are many bluetooth built-in projects, but I've found none where one uses a module like this.
The module I'm using supports buttons (play/pause, vol up/next track and vol down/previous track), bluetooth calling and of course audio. For 9$, it's a steal.
Here is the link for those interested: http://www.ebay.fr/itm/371406194317?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I will update this thread each time I make progess.
If you got any ideas, feedback or even criticism, I would be happy to hear em !

PART 1: Reallocation of the tape deck buttons for bluetooth control.


I want it keep it as original as possible from the outside, so I won't drill any holes for the buttons (pictured here). I'll thus abandon these buttons altogether and use the tape deck buttons instead, which is way cooler too btw.


The buttons shipped with the module have one common ground, and each has a separate cable. When a button is pressed, it closes the circuit between ground and it's cable.
The 'play', 'rewind' and 'forward' tape deck buttons will be reallocated.
Here are some pictures, I think they are quite self-explanatory:

This is the common ground, for this I used some screws and a piece of copper from electrical wire. This will be soldered to the scews, I hope that this will hold well



I then hot glued the wires on the switches, those will make contact with the ground when a switch is pressed (at least I hope so ).







The new wires will be soldered to the wires that are now connected to the buttons that came with the module.

This will be updated soon !

Greetings,
inse

 

[trippy1313]

Interesting. I'm curious to see how this turns out. I assume you'll have to install some buttons to the outside of the box?

Personally I never thought of the fast forward/rewind because I usually hook it up and just have the device on me. But I suppose if the media device was in another room, that might be pretty useful. Cool project.

 

[IVH]

You're right, I had to install 2 buttons. I believe that's a pitty but it turned out better than I thought.



I'm using an arduino to monitor the voltages of the different cells from the lipo battery. To prevent overdischanging it. The arduino controls 2 relays, those completely disconnect the battery from the boombox and the arduino itself. This boombox could theoretically be put away for a year and still have the same charge left.
The red button is a push button that bypasses the relay and thus turning the arduino on, the arduino will almost instantly turn the relays on and thus be ''self sustaining''. I could have used a tape deck button instead of drilling a hole but when I though of it it was already too late
The switch switches an additional 12v transformer used for the build in lipo charger.

Here are a couple of photos of the discharge protection and charging circuit:





Here you can see the bluetooth module wired up to the main board, the orange wires are used to power the module and mounted to the tape type switch to turn it on and off.



This is the box with all the anti rattling foam hot glued into place:



For some reason I forgot to take a photo when everything is wired up and mounted into the box. I guess I was too exited to put it together. I will post a photo of that as soon as I'll have to get it apart again, as it's a pain to get the back off with hitachi's stupid 15cm deep screw holes...

The media buttons work fine, but it's true there isn't a real use to it, I just thought it was a cool thing to add But still my friends used it alot when I told them about it ! They said it was easier to use the buttons then take the phone and skip a track.

And if any of you is still looking for a bluetooth module, the one I use is absolutely great ! Can't recommend it more. It even has a spot to solder a bluetooth antenna on (a coper wire). This did greatly improve the range. the antenna could even be mounted outside of the box for an even better range.

 

[Cpl-Chronic]

That's pretty DOPE!!! Having the pre-wired plugs to splice into your audio points, power, switching, etc. in one convenient little baggie of kit...

Including antenna pad...

Pretty f'en epic if you ask me...

 

[IVH]

@chronic Yeah I love it ! I used it for a few weeks and a started to forget how many devices are build into it. It just feels like 'one'.

I took it apart today to take some photos and built in the isolated dc-dc converter and a lithium battery indicator
I decided to buy an isolated dc dc converter to get rid of these annoying noises related to currents going through the audio ground wire, even though that's still better than ground loop noise, it's still worth the few bucks to get rid of it.

So here are some photos from all the build in components:




This is the lipo charger:




And the bluetooth module:

 

[BoomboxTaff]

Sell it to me for 200 euro's please

 

[IVH]

Sell it to me for 200 euro's please

Even for 600 euro I wouldn't sell it but hey, I can provide you all the info to make it yourself!
This is a good start: https://m.ebay-kleinanzeigen.de/s-anzeige/hitachi-3d7-mk2-commander-6100ds-3d-super-woofer-multi-band/562206175-172-17912

 

[BoomboxTaff]

Well I finally got a mint one like yours and everything works, I am so Happy.

I'll still buy yours 600 euro's when you sell lol

 

[IVH]

Wow! Yours looks so mint, not a scratch, really cool.
It looks like you just cleaned it, it's a pitty dust is so well visible when it settles on this box.
I think it's in an even better condition than mine, I'm almost jealous

 

[BoomboxTaff]

Yes, i think all the black coloured boxes show up the dust. I keep them in in a plastic bag after i have cleaned then.

It's good we both have one now, I'm happy.

 

[mack]

Hey guys,

A few might know me from my thread about the repair of my hissing Hitachi 3d7. Now that the problem is (hopefully) finally found, I can start with the 'modernization' of this boombox.

Hi Inse, I really love both your boombox and your mod!

I have a TRK-7620E, and after seeing yours I've decided I need to make it work in this century as well...

First of all, I need to make sure everything works as intended: the box is quite old and has been in a not-so-clean storage for a while, so an overhaul is planned.

I'd love then to add bluetooth (I got hold of the same device you're using on your build) and I also like the way you used those controls -I'd like to investigate how to perform the same task without giving up the ability to play tapes tho, as I do have quite a bit left from another era...
I also plan to use its microphone in the same place as the original rec mic of the 3D7 to cater for handsfree needs.

So, apart from the obvious 'clean it up and fix everything that doesn't work and/or hisses', I guess could really use your help in making sure I don't screw up things: can you help me with some basic schematics, or maybe just some more details on how to hook up the bluetooth module to the main board without blowing everything up?
And a question on your setup: how did you work around the need of having to put the deck in rec mode for playback? Maybe a line-in mod or...?

Last in the list: can you give some more details on your LiPo battery mod? That looks really interesting too..

Cheers,
M.