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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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14th Nov 2020, 7:41 pm | #1 |
Diode
Join Date: Nov 2020
Location: London, UK.
Posts: 5
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Pye PJ501 gram/PU input sockets. Is it safe?
HI guys.
I’m new to the forum so thanks for having me in the community. I have a PYE PJ501 and I’d like to use the gram/pu input at the back to connect my iPod or my computer and I’m wondering is it safe? This is an AC powered radio and it has a mains transformer, but am I right believing this is a live chassis radio? And in that case, even after having checked with a multimeter that the chassis in NOT live, would that be still dangerous to plug anything in the gram/pu socket? And if so, what could I do to make it safe? Replacing all the the capacitors that go to mains with Y class? Cheers |
14th Nov 2020, 8:34 pm | #2 |
Heptode
Join Date: Jan 2009
Location: West Lothian, UK.
Posts: 762
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
Hi,
I had a quick look at the circuit (on the radiomuseum site) and the chassis is marked with an earth symbol and the word "EARTH" so not live. If it has a 3 wire mains lead then you can check with the multimeter that this is true. If so - I would be happy to connect a phone directly to the chassis - if the phone is not connected to a charger. Some (all?) chargers have a voltage on the output enough to give a tingle. I would combine the left and right phone outputs with a couple of resistors and (to be on the safe side) use a capacitor from the resistors to the PU terminal. Just some thoughts before the real experts turn up...
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George |
14th Nov 2020, 8:57 pm | #3 |
Diode
Join Date: Nov 2020
Location: London, UK.
Posts: 5
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
Ho George, I had a look at the schematics too and it does show the Earth sign, although the lead is a two wire cord, no Earth connection. That’s why I’m confused
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14th Nov 2020, 10:29 pm | #4 |
Octode
Join Date: Sep 2017
Location: Bristol, UK.
Posts: 1,659
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
It's clear from the PJ501 circuit diagram that it has a double-wound mains transformer, and that therefore the whole secondary winding circuit is completely isolated from the mains supply (unless there is a serious and pretty unusual fault condition). That means that the chassis can be earthed if you wish and that there will be no risk from connecting external equipment to the Gram socket - it isn't a live-chassis radio. You may not get good signal-level matching, but that's just inconvenient, not dangerous.
The bit of the diagram that I downloaded doesn't show any earth symbol, but even if there is one elsewhere on the diagram, back then I think draftsman often used the earth symbol to signify a connection just to chassis rather than to mains earth. Mike |
14th Nov 2020, 10:39 pm | #5 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
Two wire mains connection with an isolating transformer with (as here) or without a separate earth connection as part of the aerial/earth arrangement was quite common. Most early electrical supplies would have been two wire (lighting and two pin power sockets) anyway. Providing the mains transformer is in good condition using the PU input to connect floating external audio sources should be fine- that's what a gram pickup is anyway.
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14th Nov 2020, 10:58 pm | #6 |
Diode
Join Date: Nov 2020
Location: London, UK.
Posts: 5
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
Thanks for your help guys, much appreciated!
So I’ve been reading about capacitors around the forum, and before I turn this thing on again (last time I did it turned on but didn’t play anything) I thought I’d had a look. I can see one paper cap to be replaced, C43 .001uF (marked in red on the picture) but I can’t find any more. Unless there are other kinds of paper caps that look different from those yellow ones I assume “that capacitor” is C36 .002uF (marked in yellow on the picture) and that I should also replace that, although it looks like it could have been replaced already? Also those red dots on the soldering, would that be some sort of inspection that was done in the factory or by servicing afterwards? Thanks again guys |
14th Nov 2020, 11:26 pm | #7 |
Heptode
Join Date: Jan 2009
Location: West Lothian, UK.
Posts: 762
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
I think there might be some suspect brown caps in the picture but not sure.
Tiny extract of circuit showing earth and PU socket.
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George |
14th Nov 2020, 11:37 pm | #8 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
That yellow ringed capacitor is an old TCC paper type and a prime candidate for replacement!
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15th Nov 2020, 4:33 pm | #9 |
Nonode
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,171
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
That red ringed capacitor looks damaged.
Are there any capacitors on the mains side? If so, you will to replace them with X class capacitors. |
15th Nov 2020, 4:42 pm | #10 |
Diode
Join Date: Nov 2020
Location: London, UK.
Posts: 5
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
Thanks Chris I’ll replace that TCC too
@George, which brown caps are you referring to? The big ones or the small ones that look like a resistor? @silicon I think that’s the only one by looking at the schematics and at the transformer It’s the only one rated AC on the components list from the manufacturer I think I’ll just replace all the “tubular” ones and leave mica, ceramic and electrolytic for now? And ground the chassis too with a 3-wire cord |
15th Nov 2020, 5:22 pm | #11 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
The two brown tubular "Hunts" capacitors (circled in yellow) and any others of the same ilk are definitely prime replacement candidates. The two items circled in red look like 220K 20% resistors- replace them if they're more than about 25% off (probably on the high side).
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1st Dec 2020, 5:06 pm | #12 | |
Diode
Join Date: Nov 2020
Location: London, UK.
Posts: 5
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
Quote:
I finally collected all the bits and today I replaced all the brown hunts and paper capacitors. I’m gonna triple check all the connections and give a nice clean before I try turn it on. Just wanted to check with you Chris , does that mean I can earth the chassis? I also bought a 3wire lead Cheers Luca |
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2nd Dec 2020, 12:13 am | #13 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
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Re: Pye PJ501 gram/PU input sockets. Is it safe?
You can earth the chassis if you wish and this may improve or worsen the radio noise level depending on your local electromagnetic smog situation. It would in principle make the set slightly safer to use though it might cause hum loop problems if fed from another earthed signal source.
For maximum "flexibility" you could terminate the line and neutral cores of the three core cable same as the existing two core cable but bring the earth core back out of the set fitted with a wander plug (1/8" or 3mm banana plug) and connect it to the earth socket as required by noise / hum issues.
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