GF-9090

[Quanghoster]

Hi all,
This is my first project and chose the GF-9090 as I had one as a teenager in the 80s....to many years ago to think too deeply about, lol.
Here are some pics from phase one...clean and repair.
My plan is to get all functions working then upgrade the speakers, bulbs to programmable neopixel LEDS, add Bluetooth support and WiFi for Internet radio. I've a software and electronics background so I'm hoping I'll achieve these and post my approach on this thread. Been interesting reading what others have done with their projects. .
Andy

 

[Northerner]

Nice to see it getting a proper bath!

Interested in the use of programmable leds too...looks like you can do a lot with them

 

[Reli]

Welcome, and good choice of a box to modify, they are built fairly well

 

[Quanghoster]

Thanks both. These things seem to have plenty of space in them to fit bits. I'll be using an ESP32 processor to drive the LEDs and be the hard of the modern mods. Looks like the tweeters are shot. If I can't find replacements I'll look for some coaxials and use the tweeter slots for something else - I'll see how the LEDS look back-lighting them.

Apart from a low level record level on the left channel it's all working well now so I can start to work on the fun stuff over the next few days:

 

[T-STER]

Great choice I love these boxes and i will be reading with interest on the mods. I have wanted to add BT etc to a box for ages and still not plucked up the courage to have a crack, i have all the bits here to!

 

[Lasonic TRC-920]

Welcome, and good choice of a box to modify, they are built fairly well

I agree, these are very plentiful so your not gonna catch hell for cutting up a grail

PLUS they sound fantastic, plenty of power on tap to push some new speakers.

Interested in what speakers you put in.

Welcome to the site, looking forward to seeing your final product.

 

[Quanghoster]

I'm trying to avoid as much cutting as I can though .

I've made some progress with fixing the remaining fault and all seems to be working well atm. The Left channel is now recording at the same level as the right. Adjusting the bias level to the left head using my cheap USB scope helped, along with a head clean.

The pots were here...


Tracks cut to make use of the radio's input to the amp. I'll use a processor controlled audio switch to switch between radio and new functions. Need to find the right chip for this yet...


Loaded some neat software from GitHub (https://github.com/kodera2t/ESP32_OLED_webradio) onto my development board. I've hooked this up to a small OLED display (think I can get away with putting this in front of the APSS LEDs). This will hopefully eventually display the track from the Internet Radio station playing or MP3 from an SDCARD.
The Phono plugs are connected to a 24bit DAC which provides good quality audio from the web stream. The level is a little high from the radio input so I'll need to add an Attenuator to the board I insert.


This evening I've been working on the Neopixels and have a couple of them set up and working with the code above - though it needed a tweak at first as the SDK it was written with had been updated.

These will replace the bulbs for the vue meters and radio tuner. I may also add some to light up the speaker grills. My plan is to replicate the warm orange colour of the existing bulbs, but be able to change colours for a bit of fun .

I'm thinking, at the moment, the SD Card reader for MP3's can be mounted on the mic panel somewhere on the left side. I need yet to figure out where to mount buttons to control the source selection.

I picked up where to cut into the radio audio from a post I found on this site. The good thing is that I can use the tape deck to record from Internet Radio stations if I want to. Maybe later on I'll see if I can record them to the SD Card, but that may be a bit more of a challenge.

Need to start pulling these things together onto a proper prototype board next, insert Neopixels and decide what speakers to use. The Tweeters I ordered aren't quite small enough so I think I'll go with a couple of new coaxials after all...

 

[Quanghoster]

So, my new speakers came today. Not exactly a straight swap but with the aid of the 3d printer I was able to make a couple of spacers that assist with the mounting. The spacers also give me the option of a little customisation. I'm thinking of a couple of things... inserting the NeoPixels into them and possible re-printing the spacers with "glow in the dark" material for some additional impact - the LEDs could be used to re-energise them...







These are 2 way co-axials which will, hopefully, make up for the dead existing tweeters. The cones look like they will stand an unexpected shower more readily than the originals...

 

[Quanghoster]

Ok,
So slight change in plan as now using a raspberry pi zero w and mpd to deal with playing digital music and internet radio stations

This system will live in a small box tucked away behind the vu meters. The OLED display will be mounted in front of the APSS LEDs.

I've ordered a panel mount USB cable which will fit in a panel I'll make to replace the existing one for the external mikes. I'll put it into a recess so that usb drives don't stick out too much and get broken off in transit. If this doesn't work out then there is always the batter compartment. I'm sure I'll find a much smaller battery to replace the 8 D cells which will give me some room for other things.



MPD is an awesome application that will play internet radio stations as well as MP3s stored on a USB stick. I'll use an MPD client, such as M.A.L.P on my phone to control play of these and I have a custom app written in python that will display the track and artist info on the OLED. If MPD isn't running the script will switch audio back to the GF-9090 analog radio.



The PI Zero W also has support for receiving audio via Bluetooth. I've had this working from my laptop ok. I'll get the OLED to display "Bluetooth" when my phone is connected to it.


This next week I need to get the NeoPixel backlights and audio switch working...

Injecting the audio into the radio audio path works well, though I have some humm atm, so need to improve on the screening of the audio cables. I can reduce the output of the DAC with MPD to make the level the same as the radio.

With M.A.L.P doing most of the user interface work I don't have to add much to the blaster, though I will try and squeeze in a button or two for next/previous track and maybe switch between MPD and Radio.

As This all will rely on wifi I need to set things up so that the PI will set up it's own WIFI Access Point, if it cannot logon to the home router. This will make it great for beach parties... let's hope for a nice hot summer in the UK ...

 

[Northerner]

Far too low tech and simple for me lol

Sounds super impressive, the parts that I follow at least. Looking forward to seeing the end result

 

[Quanghoster]

Thanks. It should be an interesting combination of old and new tech

 

[goodman]

Looks very good. I waiting to see next steps...

 

[Quanghoster]

So, things have gone reasonably well so far. I have the basic system working and I'm starting to design and print mounting brackets for the new components. I've also purchased a couple of DC-DC convertors to provide regulated 5V.

I've added and tested an audio switch. Could only find a surface mount version so that has now been soldered on to a breakout board and mounted onto a new prototype board with an Arduino Nano.



I had issues with the ADC on the Raspberry Pi taking up the DMA channels, and I needed another channel for the NeoPixel software. So, I decided to move the NeoPixel and audio switch control to the Nano. The RPI communicates with it and the OLED display using the I2C bus. A Python script on the Pi monitors MPD to see what is playing and updates the OLED accordingly. The script can also detect if MPD is not playing anything and, if that's the case, will tell the nano to switch back to the Analog Radio audio source instead. This seems to work quite well as I can pick any tracks listed on the USB Drive, may play lists or select an internet radio station all with my phone. So no issues with user interface as yet.



I've also found some instructions to set up the RPi so that if it cannot connect to my home wifi network, it will create an access point for itself, so I can connect to the RPI hotspot with my phone to control it when outside.


Hopefully some more picks next week once I've got the brackets finished and the neopixels installed.
Andy.