what would cause an open screen resistor?

randalp3000 · Post by **randalp3000** » Fri Oct 18, 2013 7:40 pm

Had a Morgan SW50(single channel dumble type) come back that sounded like poo.

anyhoo I found out there was no bias on one OP tube and traced it to an open 470R screen resistor.

I'm figuring it was caused by a bad OP tube? So is this the most likely cause?

thanks mucho
rp

Firestorm · Post by **Firestorm** » Fri Oct 18, 2013 8:21 pm

What was the wattage rating on the 470R? A screen short will take it out, but some historical amps used small watt resistors, almost like a fuse, and they might open up in "normal" use.

randalp3000 · Post by **randalp3000** » Fri Oct 18, 2013 8:26 pm

It was some big black, fancy, wire wound something I'd say at least 3-5 watts

randalp3000 · Post by **randalp3000** » Sat Oct 19, 2013 1:25 am

the resistor was a Pacific 500r.

all fixed and sounds pretty good.

Firestorm · Post by **Firestorm** » Sat Oct 19, 2013 3:42 am

Screen short probably. Tube is gone, right?

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what would cause an open screen resistor?

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