P8-1D STC rectifier - selenium?

[6SN7WGTB]

Sorry for not having a picture but don't have the device to hand yet.

Is the above a selenium rectifier?

The circuit (a Taylor 127A) shows two in series with centre-tap - so may be a 'double diode'. On the AC circuit obv.

Does 'leave it alone if it works' apply to a 1,000V measuring device? Current will be small I appreciate, but if it goes up in smoke, so will the movement.

If I have to replace with 4007s then I assume I'll need to adjust the meter shunt resistor to get back to 1,000Ω/V else the scale will be out?

[factory]

Some data here: https://www.vintage-radio.net/forum/...ad.php?t=53213

The second scan has the P type selenium data (easy to miss as a hole is punched through the P), 8 is the size of the plate, the 1 indicates only 1 plate and the D is a doubler arrangement.
The volt drop shouldn't be too high, as it's only using a single diode plate, each plate only has a low voltage rating, hence the stacks of many plates for high voltage use, which would have a much higher volt drop as a result.

Can't imagine it going up in smoke, unless the meter is set in the lowest AC voltage range and it gets severely overloaded, in which case the meter movement probably wouldn't survive anyway.
Possibly add some modern diodes in reverse parallel, to limit the voltage across the meter movement would be a good idea.

As for the reputation of smoke & selenium rectifiers, I suspect this is more due to power supply use, where a short-circuit in something like a smoothing capacitor would overload the rectifier and make it smoke if the fuse didn't blow first.

David

[6SN7WGTB]

Originally Posted by factory

Some data here: https://www.vintage-radio.net/forum/...ad.php?t=53213

The second scan has the P type selenium data (easy to miss as a hole is punched through the P), 8 is the size of the plate, the 1 indicates only 1 plate and the D is a doubler arrangement.
The volt drop shouldn't be too high, as it's only using a single diode plate, each plate only has a low voltage rating, hence the stacks of many plates for high voltage use, which would have a much higher volt drop as a result.

Can't imagine it going up in smoke, unless the meter is set in the lowest AC voltage range and it gets severely overloaded, in which case the meter movement probably wouldn't survive anyway.
Possibly add some modern diodes in reverse parallel, to limit the voltage across the meter movement would be a good idea.

As for the reputation of smoke & selenium rectifiers, I suspect this is more due to power supply use, where a short-circuit in something like a smoothing capacitor would overload the rectifier and make it smoke if the fuse didn't blow first.

David

Thanks David, great bit of reconnaissance and very helpful.

I intend to use the meter, but can't see it being abused so think I will leave as is. It's also reading pretty accurately so as it is a sealed PO unit, might leave it all alone.