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Old 14th Sep 2019, 11:52 am   #1
Join Date: Sep 2019
Location: Bicester, Oxfordshire, UK.
Posts: 4
Default Sharp GF9090 bluetooth project

Hello everyone. I've just, literally half an hour ago, impulsively bought a Sharp GF-9090.

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The Sharp GF-9090 Bought one in 1978 for the then very considerable sum of 200 ( 2.25 a week from Mrs Goddard's Littlewoods cataogue) which seems to be roughly what one in decent and full working condition is going for 40 years later. This was and still is a thing of beauty. This thing was my constant companion and assisted in shaping my musical tastes from the age of 16 to my early 20's. To this day, I still get a flutter in my heart when I see a picture of one. To think I will be the owner of one again soon is quite something.

I've pipe dreamed with the idea of one day getting one and either gutting and converting to bluetooth or adding bluetooth to the existing system. (I'm hoping to do the latter) I have minimal electronics knowledge but am an IT Technician/gadget geek so disassembly and having a bash etc holds no fears.

Description described it as not fully working with the cassette playing slow etc (I assume it'll be decomposing belts). I'm hoping it will arrive in a week or so. The first thing I want to do is order a bluetooth board for it.

My first question, and I'm sure it will be the first of many is what output board should I be getting. I am, possibly wrongly, assuming that if I am going to tap into the cassette players preamp, I would need a very low output (or non amplified?) board than if i was gutting the case and feeding directly to the speakers. The speakers are listed as 2x3.5w and 2x5w,

I've seen a Youtube video where someone has done this on the same model but it just shows it working. I've messaged to the poster so am hoping I might get some advice from them.

Finally, thanks for letting me join. Any advice, tips, pointers will be very gratefully received. (And needed!)
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Old 14th Sep 2019, 11:59 am   #2
paulsherwin's Avatar
Join Date: Jun 2003
Location: Oxford, UK
Posts: 19,914
Default Re: Sharp GF9090 bluetooth project

You need a board with a line level or headphone output. You would normally attach the output to the top of the volume control via some sort of switching arrangement, though it does depend on the amplifier design.
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Old 14th Sep 2019, 6:14 pm   #3
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Join Date: Jan 2009
Location: West Lothian, UK.
Posts: 456
Default Re: Sharp GF9090 bluetooth project

A low-tech solution (example only - many other vendors exist)
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Old 17th Sep 2019, 9:42 pm   #4
Join Date: Sep 2019
Location: Bicester, Oxfordshire, UK.
Posts: 4
Default Re: Sharp GF9090 bluetooth project

Well it's arrived and it's love all over again

One speaker dislocated, one speaker grill dislocated, tape deck play seized, waveband buttons dodgy, last 4 toggle switches not working, sliders very rough and 42 years of dust, grease and human DNA in every orifice but lights and vu meters are working and FM radio this beauty sounds just as good to my ageing ears as it did when i owned one back in 1978.

But dear God is it heavy. I thought there must have been 8 batteries in it but no. How on earth did I walk 4 miles to and from work every day carrying one of these? I needed a lie down after putting it on the kitchen counter. It's one serious lump. But my goodness, it is one beautiful lump. My 12 year old daughter, who carries the entire world round in a smartphone, cannot quite get her head round that we used such behemoths.

I'm now seriously considering gutting it and just putting a Bluetooth amp in it (I'd never play tapes or listen to radio) or keeping the amp in and putting a Bluetooth receiver in as I'd really love to keep the vu meters volume and eq sliders active. Decisions decisions!

Some dismantling and the beginning of a cleanup this weekend. More pics anon.
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Old 18th Sep 2019, 5:59 am   #5
Lloyd 1985
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Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
Posts: 1,810
Default Re: Sharp GF9090 bluetooth project

Don’t gut it! I’ve just bought a Bluetooth module, a KRC-86B, which looks easy enough to graft into anything with an audio amplifier in it, it even has an audio input, which it automatically switches to when there is no Bluetooth device connected, so it would be easy to find a suitable place in the circuit to add it in, maybe just before the volume control, so that the original control will still do its job. I’d have to look at the circuit for the stereo to be exactly sure where to put the module.

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Old 18th Sep 2019, 6:33 pm   #6
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Join Date: Feb 2014
Location: Nottingham, Notts. UK.
Posts: 327
Default Re: Sharp GF9090 bluetooth project

Got to agree with the last post. These BT modules are small enough to fit in and leave the rest of the unit intact. Just a word of warning, a lot of these Sharp designs of this period had 'printed resistors' built into the pcb. These are now fragile and simply go to dust. You cannot solder to the ends of these and any connections must be made to a conventional through the hole component.

I'm not trying to put you off, but just be careful. I've recently being fitting a BT module to a GF8585, this has the aforementioned resistors.

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