Pye Black Box - Page 4 - UK Vintage Radio Repair and Restoration Discussion Forum

kevinski · 8th Dec 2013, 10:59 am

Can anyone tell me which tags the P/U lead attach to on the tag strip please.

Kevin

matthewhouse · 8th Dec 2013, 2:46 pm

I would think that the screening of the cable would go to tag 2 (I take it that is a stub from the old cable still attached)

Link 5 and 6 together (left and right from the cartridge) and connect the signal wire to one of those.

kevinski · 8th Dec 2013, 2:55 pm

Tags 2 and 4 are linked with a stub on tag 4 so presumably it would be ok to connect screening on either

Kevin

matthewhouse · 8th Dec 2013, 2:57 pm

In that case leave as it was and connect screen to 6 and signal cable to 5.

kevinski · 8th Dec 2013, 3:49 pm

We now have a low hum through the speakers but alas no stylus in the cartridge, Had to rewire the tone arm as the original had got trapped and snapped. Can hear the cartridge when rubbed through the speakers so that's probably a good sign. Next job after the stylus arrives is to strip and relube the deck. Then I will have to try to identify the veneer used because there are little bits missing on the box. After that a good old polish and I should have myself a lovely little player.

Thanks for every ones help again. It is much appreciated. Learned loads again.

Kevin

Radio Wrangler · 8th Dec 2013, 3:57 pm

You have de-Huntsified it, haven't you?

I think you mentioned having a swap session in the capacitor department, but the photos must have been taken from before. This set has two "That capacitor" parts capable of ruining both your transformers.

David

kevinski · 8th Dec 2013, 4:48 pm

Yes, I changed all the capacitors out earlier! No pesky Hunts left.

Kevin

Radio Wrangler · 8th Dec 2013, 7:31 pm

Ah, good. So as the cartridge seemed to have some sensitivity, you've just got the joys of cleaning and re-lubricating a turntable before you can put your feet up with a carefully chosen record and a carefully chosen pint.

David

kevinski · 9th Dec 2013, 5:27 pm

Would a 300v 2a bridge rectifier be a good replacement for the existing one?

Kevin

Steve_P · 9th Dec 2013, 6:40 pm

Well this is more like it....

http://www.maplin.co.uk/p/6a-bridge-rectifier-ar80b

Cheers,

Steve P.

Radio Wrangler · 9th Dec 2013, 8:01 pm

I don't think so. That Maplin page is for a 6 amp 100v PIV bridge, which is going to be rather over-voltaged as an HT rectifier.

Normally you need a PIV of at least double the rectified voltage for a centre-tapped full wave arrangement. With a bridge, the reverse voltage is equal to the output voltage. But you need a comfortable allowance for spikes and de-rating. I'd use a 500-600v bridge at least if I wanted it to be reliable. Bridge failure will easily take out a mains transformer.

David

kevinski · 9th Dec 2013, 9:16 pm

How about this one?

http://cpc.farnell.com/multicomp/cp6...20This%20Range

As you can probably tell I don't really understand the ratings for these items.

Thanks

Kevin

Station X · 9th Dec 2013, 10:10 pm

Quote:

As you can probably tell I don't really understand the ratings for these items.

There are two things you need to consider when choosing a replacement bridge rectifier.

1. Peak Inverse Volts (P.I.V). As Radio Wrangler has suggested, this should be at least twice the applied voltage, so 500V minimum.

2. Forward Current (I.F). I'd have thought 1 Amp would be more than enough for a record player.

So the rectifier you've linked to will be suitable, as will this:-

http://www.maplin.co.uk/p/6a-bridge-rectifier-ar81c

Radio Wrangler · 9th Dec 2013, 10:18 pm

That's the right voltage, and rather generous on current, but it should be fine.

The next issue is that these modern silicon rectifiers are a lot lower resistance than the old Selenium jobs, so to prevent the reservoir capacitor getting a hell of a surge on turn-on, you should add a resistor in series with the bridge… put it in series with the + output of the bridge. About 220 Ohms should do the trick, but get a chunky part rated at about 5W.

David

kevinski · 9th Dec 2013, 10:46 pm

Cheers for the info, will order one up. I have some resistors of that wattage so I'll dig one out.

Kevin

stevekendal · 9th Dec 2013, 10:51 pm

On the tripping the mains question, I had this black box version and it used to trip the mains and the cause was the on off switch shorting out somehow. My cure was to bypass it altogether and install a toggle switch on the rear of the cabinet.

Alistair D · 9th Dec 2013, 11:06 pm

David,I would consider putting the 220 ohm resistor between the transformer and the bridge. It will afford a little extra protection should the rectifier go short circuit. Even a wirewound resistor of say 5 watts would fry very quickly under short circuit conditions.

Al

Radio Wrangler · 9th Dec 2013, 11:25 pm

Good idea! a much better place to put it, and one that might occasionally save someone's transformer if a rectifier ever fails shorted.

David

kevinski · 10th Dec 2013, 12:28 pm

So to get this straight, I put the 220 ohm 5W resistor in line between the transformer and the bridge on the blue wire ie blue wire to one side of resistor, other side of resistor to bridge (if that makes sense!)

Was sure Michael had put a photo of how he did his bridge rectifier/resistor combination up in this thread but it doesn't seem to be here anymore?

Kevin

kevinski · 10th Dec 2013, 5:29 pm

Does anyone got an idea what veneer this box is covered with? Since the electrics are sorted I would like to start on the box itself. Looking very tatty at the moment but nothing a good sanding and revarnish/polish wont put right except for some small pieces where the veneer has come off. So any help identifying what veneer I need would be much appreciated.

8th Dec 2013, 10:59 am	#61
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box Can anyone tell me which tags the P/U lead attach to on the tag strip please. Kevin Attached Thumbnails

8th Dec 2013, 2:46 pm	#62
matthewhouse Octode Join Date: Jul 2006 Location: Willand, Devon, UK. Posts: 1,023	Re: Pye Black Box I would think that the screening of the cable would go to tag 2 (I take it that is a stub from the old cable still attached) Link 5 and 6 together (left and right from the cartridge) and connect the signal wire to one of those.

8th Dec 2013, 2:55 pm	#63
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box Tags 2 and 4 are linked with a stub on tag 4 so presumably it would be ok to connect screening on either Kevin

8th Dec 2013, 2:57 pm	#64
matthewhouse Octode Join Date: Jul 2006 Location: Willand, Devon, UK. Posts: 1,023	Re: Pye Black Box In that case leave as it was and connect screen to 6 and signal cable to 5.

8th Dec 2013, 3:49 pm	#65
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box We now have a low hum through the speakers but alas no stylus in the cartridge, Had to rewire the tone arm as the original had got trapped and snapped. Can hear the cartridge when rubbed through the speakers so that's probably a good sign. Next job after the stylus arrives is to strip and relube the deck. Then I will have to try to identify the veneer used because there are little bits missing on the box. After that a good old polish and I should have myself a lovely little player. Thanks for every ones help again. It is much appreciated. Learned loads again. Kevin

8th Dec 2013, 3:57 pm	#66
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: Pye Black Box You have de-Huntsified it, haven't you? I think you mentioned having a swap session in the capacitor department, but the photos must have been taken from before. This set has two "That capacitor" parts capable of ruining both your transformers. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

8th Dec 2013, 4:48 pm	#67
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box Yes, I changed all the capacitors out earlier! No pesky Hunts left. Kevin

8th Dec 2013, 7:31 pm	#68
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: Pye Black Box Ah, good. So as the cartridge seemed to have some sensitivity, you've just got the joys of cleaning and re-lubricating a turntable before you can put your feet up with a carefully chosen record and a carefully chosen pint. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

9th Dec 2013, 5:27 pm	#69
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box Would a 300v 2a bridge rectifier be a good replacement for the existing one? Kevin

9th Dec 2013, 6:40 pm	#70
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Pye Black Box Well this is more like it.... http://www.maplin.co.uk/p/6a-bridge-rectifier-ar80b Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

9th Dec 2013, 8:01 pm	#71
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: Pye Black Box I don't think so. That Maplin page is for a 6 amp 100v PIV bridge, which is going to be rather over-voltaged as an HT rectifier. Normally you need a PIV of at least double the rectified voltage for a centre-tapped full wave arrangement. With a bridge, the reverse voltage is equal to the output voltage. But you need a comfortable allowance for spikes and de-rating. I'd use a 500-600v bridge at least if I wanted it to be reliable. Bridge failure will easily take out a mains transformer. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

9th Dec 2013, 9:16 pm	#72
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box How about this one? http://cpc.farnell.com/multicomp/cp6...20This%20Range As you can probably tell I don't really understand the ratings for these items. Thanks Kevin

9th Dec 2013, 10:18 pm	#74
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: Pye Black Box That's the right voltage, and rather generous on current, but it should be fine. The next issue is that these modern silicon rectifiers are a lot lower resistance than the old Selenium jobs, so to prevent the reservoir capacitor getting a hell of a surge on turn-on, you should add a resistor in series with the bridge… put it in series with the + output of the bridge. About 220 Ohms should do the trick, but get a chunky part rated at about 5W. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

9th Dec 2013, 10:46 pm	#75
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box Cheers for the info, will order one up. I have some resistors of that wattage so I'll dig one out. Kevin

9th Dec 2013, 10:51 pm	#76
stevekendal Heptode Join Date: Mar 2004 Location: Kendal, Cumbria, UK. Posts: 625	Re: Pye Black Box On the tripping the mains question, I had this black box version and it used to trip the mains and the cause was the on off switch shorting out somehow. My cure was to bypass it altogether and install a toggle switch on the rear of the cabinet. __________________ Knobs and tubes rule ok

9th Dec 2013, 11:06 pm	#77
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Pye Black Box David,I would consider putting the 220 ohm resistor between the transformer and the bridge. It will afford a little extra protection should the rectifier go short circuit. Even a wirewound resistor of say 5 watts would fry very quickly under short circuit conditions. Al __________________ I won't tell you how I discovered that.

9th Dec 2013, 11:25 pm	#78
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: Pye Black Box Good idea! a much better place to put it, and one that might occasionally save someone's transformer if a rectifier ever fails shorted. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

10th Dec 2013, 12:28 pm	#79
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box So to get this straight, I put the 220 ohm 5W resistor in line between the transformer and the bridge on the blue wire ie blue wire to one side of resistor, other side of resistor to bridge (if that makes sense!) Was sure Michael had put a photo of how he did his bridge rectifier/resistor combination up in this thread but it doesn't seem to be here anymore? Kevin Last edited by kevinski; 10th Dec 2013 at 12:35 pm.

10th Dec 2013, 5:29 pm	#80
kevinski Retired Dormant Member Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 330	Re: Pye Black Box Does anyone got an idea what veneer this box is covered with? Since the electrics are sorted I would like to start on the box itself. Looking very tatty at the moment but nothing a good sanding and revarnish/polish wont put right except for some small pieces where the veneer has come off. So any help identifying what veneer I need would be much appreciated. Attached Thumbnails