4th Apr 2019, 2:49 pm | #1 |
Retired Dormant Member
Join Date: Mar 2019
Location: Bournemouth, Dorset, UK.
Posts: 1
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Roberts 505
Hello,
my first post, a question please I have just recently bought a Roberts 505, which I am cleaning and tidying up externally, I can only receive VHF, and there is a humming sound, which is tolerable, but can anything be done inside the radio to make the humming sound go? |
4th Apr 2019, 3:05 pm | #2 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,943
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Re: Roberts 505
Do you mean an R505? https://www.radiomuseum.org/r/roberts_r505r_50.html
This is a battery transistor radio so it's not clear why it would be humming. |
4th Apr 2019, 3:48 pm | #3 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
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Re: Roberts 505
There is a DC input skt on the radio, are you using an adapter to power the radio. If so try batteries as Paul suggests.
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Frank |
6th Apr 2019, 2:03 pm | #4 |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,761
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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.
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David. BVWS Member. G-QRP Club member 1339. |
25th May 2019, 10:17 am | #5 |
Hexode
Join Date: Jun 2011
Location: Glossop, Derbyshire, UK.
Posts: 487
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Re: Roberts 505
I have just bought a R505 for the vast cost of £8 and as David said C40 was indeed S/C ( quick easy repair thanks ) now I have cleaned it up it looks and sounds great only fault is the caps on the volume/tone knobs . Has anyone got a clue where I can get new ones?
Thanks Dave L
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