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David G4EBT · 6th Apr 2019, 2:03 pm

It's a good idea to check the current being drawn because it's not uncommon in my experience for C40 - a 680µF cap, to go short circuit. When testing a 505, it's as well to insert a meter on say the 10Amp range or whatever, in series with the battery, switch on briefly and if the consumption is more than a few mA, and the output pair of transistors get hot very quickly, it's more likely C40 that's the culprit. If C41 and/or C42 are leaky they can increase battery drain and lower the voltage so are also worth checking.

Even if all seems well or the set has other faults, given the hassle they can cause, it's as well to change those caps after almost six decades since they left the factory.

See this thread:

https://www.vintage-radio.net/forum/...t=Roberts+R505

Also, Post #8 here:

https://www.vintage-radio.net/forum/...t=Roberts+R505

Hope that might help a bit.

6th Apr 2019, 2:03 pm	#4
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,760	Re: Roberts 505 It's a good idea to check the current being drawn because it's not uncommon in my experience for C40 - a 680µF cap, to go short circuit. When testing a 505, it's as well to insert a meter on say the 10Amp range or whatever, in series with the battery, switch on briefly and if the consumption is more than a few mA, and the output pair of transistors get hot very quickly, it's more likely C40 that's the culprit. If C41 and/or C42 are leaky they can increase battery drain and lower the voltage so are also worth checking. Even if all seems well or the set has other faults, given the hassle they can cause, it's as well to change those caps after almost six decades since they left the factory. See this thread: https://www.vintage-radio.net/forum/...t=Roberts+R505 Also, Post #8 here: https://www.vintage-radio.net/forum/...t=Roberts+R505 Hope that might help a bit. __________________ David. BVWS Member. G-QRP Club member 1339.