RIAA in FreeView box - UK Vintage Radio Repair and Restoration Discussion Forum

llama · 21st Sep 2014, 4:04 pm

Didn't quite know where to put this: TV (SCART output), Audio (RIAA), Modern (STB), Tips (useful, I hope) . . . so I ended up here having put stuff together.

A relative needs a turntable: I "found" a Pioneer belt-drive with mag cart in the loft and for this, bought a cheapish pre-amp off ebay - about £15. All tested fine with a new belt bought online from Maplins.

But the pre-amp uses PP3s so I searched the workshop for a powered box to put it in. I'd bought several obsolete FreeView boxes without remotes at a rally a few years ago, costing only pennies. Prodding around inside I found 14 volts DC at the end of a fairly chunky rectifier. I built a little LM317 regulator (240 R o/p to adj, 1k3 adj to gnd giving 8.3 volts). Actually this was unstable 'til I used the recommended input and output decouplers.

By snipping out the little RF tuner I found space for the RIAA PCB and fitted a DIN socket in a reamed-out aerial socket-hole. This was to match the cable out of the Pioneer.

I took the output to Left out and Right out of the TV SCART, snipping the original connections. I also used the audio gnd, taking it directly to the RIAA PCB.

So now it plays through the TV and the original FreeView video output keeps the TV happy in case it objects to no video on its AV input. There was bad hum, even with the Pioneer earth wire connected. I found that it mattered which of my SCART leads I used - with a decent quality one it is silent.

Makes me want to build other useful stuff inside some of the other gash FreeView boxes.

Graham

21st Sep 2014, 4:10 pm

Making homebrew stuff pretty can be a bit of a pain at times, those freeview boxes can look quite good.

paulsherwin · 21st Sep 2014, 7:10 pm

Yes, they're a useful size for project boxes. Old router boxes are also good.

21st Sep 2014, 4:04 pm	#1
llama Octode Join Date: Jun 2006 Location: St Osyth, Nr Clacton, Essex, UK. Posts: 1,482	RIAA in FreeView box Didn't quite know where to put this: TV (SCART output), Audio (RIAA), Modern (STB), Tips (useful, I hope) . . . so I ended up here having put stuff together. A relative needs a turntable: I "found" a Pioneer belt-drive with mag cart in the loft and for this, bought a cheapish pre-amp off ebay - about £15. All tested fine with a new belt bought online from Maplins. But the pre-amp uses PP3s so I searched the workshop for a powered box to put it in. I'd bought several obsolete FreeView boxes without remotes at a rally a few years ago, costing only pennies. Prodding around inside I found 14 volts DC at the end of a fairly chunky rectifier. I built a little LM317 regulator (240 R o/p to adj, 1k3 adj to gnd giving 8.3 volts). Actually this was unstable 'til I used the recommended input and output decouplers. By snipping out the little RF tuner I found space for the RIAA PCB and fitted a DIN socket in a reamed-out aerial socket-hole. This was to match the cable out of the Pioneer. I took the output to Left out and Right out of the TV SCART, snipping the original connections. I also used the audio gnd, taking it directly to the RIAA PCB. So now it plays through the TV and the original FreeView video output keeps the TV happy in case it objects to no video on its AV input. There was bad hum, even with the Pioneer earth wire connected. I found that it mattered which of my SCART leads I used - with a decent quality one it is silent. Makes me want to build other useful stuff inside some of the other gash FreeView boxes. Graham __________________ Half my stuff is junk - trouble is, I don't know which half!

21st Sep 2014, 4:10 pm	#2
Guest Guest Posts: n/a	Re: RIAA in FreeView box Making homebrew stuff pretty can be a bit of a pain at times, those freeview boxes can look quite good.

21st Sep 2014, 7:10 pm	#3
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,932	Re: RIAA in FreeView box Yes, they're a useful size for project boxes. Old router boxes are also good.