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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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19th Jun 2017, 5:55 pm | #1 |
Rest in Peace
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
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Roberts R707 batteries
I have been given a faulty R707 to look at by a friend but unfortunately someone has been at it and removed the battery connectors, directly wiring a PSU in their place. I was just wondering what the original battery arrangements were and what the supply voltage should be. The owner says it worked for a short while before going off, after the PSU was fitted by a technical person in a shop. It has Mullard modules inside so I suspect it will have the usual faults associated with those. Any advice welcome. Roberts radios aren't really my strong point.
Alan. |
19th Jun 2017, 6:10 pm | #2 |
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Re: Roberts R707 batteries
According to the service sheet, this set uses two 6V batteries in series with no centre tap.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
19th Jun 2017, 6:53 pm | #3 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
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Re: Roberts R707 batteries
They are lantern batteries, the springs on the battery connect with copper plates in the battery compartment.
Frank |
19th Jun 2017, 7:06 pm | #4 |
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Location: Evesham, Worcestershire, UK.
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Re: Roberts R707 batteries
Does this help?
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19th Jun 2017, 7:06 pm | #5 |
Rest in Peace
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
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Re: Roberts R707 batteries
Ah right, that would explain the gadget in the middle. That must connect with the batteries. For some reason I just assumed it would be some kind of PP3 arrangement. It looks like there was a DC connector on the side for powering the set up. This has been removed for some reason and is now hanging loose on the inside. I will check my CDs and see if I can find the service info. I have just got the set and hadn't got further than a quick look inside to check the damage. Thanks for the help. The original PSU was set for 6 volts so if the set requires 12 volts that wouldn't help with the performance. (PS Just seen the photo.) That's a great help. I see now how it all goes together.
Alan. Last edited by Biggles; 19th Jun 2017 at 7:09 pm. Reason: New post checked. |
19th Jun 2017, 7:34 pm | #6 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,573
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Re: Roberts R707 batteries
Hi.
Mark just beat me to it but attached are a few pics. Note the wood slat that spans across the two lantern batteries. This is not an original but one made from some available plywood, it needs to be stained black as per the original. The R707 is a great radio when working but must be one of the worst sets to work on as it's very labour intensive dismantling everything to gain access to the IF module. Well worth the effort to repair though. Regards Symon. |
19th Jun 2017, 7:38 pm | #7 |
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Join Date: Apr 2012
Location: Wiltshire, UK.
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Re: Roberts R707 batteries
I've retro-fitted my R707 with a couple of 1.2 Amp Hour lead-acid gel-cells wired in parallel; these will happily power it for 3 weeks or so of daily use before needing recharging [i like to turn the volume up to '11'].
Gel-cells make sense in this sort of application - the output-stage design and low-speaker-impedance of the likes of the 707 mean the power-supply needs to be able to deliver high current-peaks without suffering from voltage-sag. |
19th Jun 2017, 8:15 pm | #8 | |
Octode
Join Date: Mar 2006
Location: Co. Durham, UK.
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Re: Roberts R707 batteries
Quote:
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19th Jun 2017, 8:20 pm | #9 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
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Re: Roberts R707 batteries
While the idea is appealing, I have one of these: http://www.sunpower-uk.com/products/...es/default.htm that does the whole condition-and-recharge-thing in four hours.
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19th Jun 2017, 10:24 pm | #10 |
Nonode
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,163
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Re: Roberts R707 batteries
Did you fit a fuse in the supply to the radio?
Lead acid cells can supply high currents, enough to vaporise PCB tracks. |