HK3490 mod

[fvzeppelin]

After finding out that my poor sounding HK3490 has a really good main amp (main inputs available on the back), I had the idea for my new project:
Take out all the things which disturbe (mainly the DAC, input, and video PCBs) and leave the good stuff in (mainly the main PCB and the front incl. display and tactilce switches). Then add something like a Raspberry (the PSU already offers +5V) with a good DAC (and 15V) to play network streams and control the rest.

Not sure if this is too big for me, but hey... 😉

So, if someone has experience with this kind of mods or if someone knows more details about the interfaces between the boards (more than I can read in the service manual) then feel free to share your knowledge 🙂

Attached the first "impressions" - don't know when there will be the next update... 😉

 

[JonSnell Electronic]

I doubt it will work as it uses the I2C bus to self test before it will power up.
See page 67 of the service manual.

 

[fvzeppelin]

The I2C is only used on the DAC and input PCBs, isn't it? I want to replace these, anyway.

 

[fvzeppelin]

Display Hack: check

It's all not that complicated
Cheers 😎

 

[fvzeppelin]

First time working

Finally, I got all the relevant parts working:

• I used a DS preamp from here thanks to (Carl Huff), which I modified with serial potis
• I used the original serial VFD, keypad, and remote
• Everything is controlled by an Arduino Mega

Works like a charm and sound a LOT better than the original 😀


But there are still many things to do (as you can see):

• clean up wiring
• build an appropriate input PCB
• use original tone control potis (currently I abuse keys for tone control)
• ...

Cheers!

 

[Dirttracker73]

Wow, cool project. I see you added a couple jumper wires😉. I also like HK amps. Their amps sound good and have modest power ratings.

 

[fvzeppelin]

Wow, cool project..

Thank you! 😎

I see you added a couple jumper wires😉.

Indeed 😉 In the original amp, most of them were FFCs. But cleaning up the wiring is the most important next step for me.

I also like HK amps. Their amps sound good and have modest power ratings.

I call this amp "monster" after this mod 😉 But actually, HK helped me a lot by building a very modular amp and by writing a very, very good service mnual Without these prerequisites, this project would not have been possible for me.

 

[fvzeppelin]

I doubt it will work as it uses the I2C bus to self test before it will power up.
See page 67 of the service manual.

Your guess was wrong 😉

 

[fvzeppelin]

Arduino library to control input PCB

After a long time, I re-animated the HK3490's input PCB by hooking up to the DATA, CK, and ST lines of the input switch ICs and the volume/loudness control IC 😀
For those who are interested, you can check my library to control he TC9162, TC9163, TC9164, and TC9459 ICs here.

 

[Fjpederse]

Hi!
I'm sitting with a 3490 that i really love, but would like to give her an overhaul. I saw you changed the caps. Did you only change the electrolytic caps? Did you do anything else to the original boards?