Pye PJ501 gram/PU input sockets. Is it safe?

[Hoborizla]

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

[buggies]

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...

[Hoborizla]

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

[Boulevardier]

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

[Herald1360]

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.

[Hoborizla]

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

[buggies]

I think there might be some suspect brown caps in the picture but not sure.
Tiny extract of circuit showing earth and PU socket.

[Herald1360]

That yellow ringed capacitor is an old TCC paper type and a prime candidate for replacement!

[Silicon]

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.

[Hoborizla]

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

[Herald1360]

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).

[Hoborizla]

Originally Posted by Herald1360

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.

Hi guys!

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

[Herald1360]

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.