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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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6th Apr 2009, 11:26 pm | #1 |
Pentode
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National DE-631 any info?
Just wondering if anyone has any info on this radio, how old etc. I picked it up on Freecycle and it was complete but completely dead. Got it to power up by retensioning the jaws of the internal fuse holder and cleaning some corrosion off the fuse but it is silent apart from a very faint hum from the speakers. As I turn the tuning control the magic eye responds so I'm hoping there's nothing too seriously wrong.
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6th Apr 2009, 11:39 pm | #2 |
Dekatron
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Re: National DE-631 any info?
Well, it's Japanese and I can't find anything either. But given a valve data book you should be able to coax it into life. If the Magic Eye is showing stations then we can't have much wrong.
Is the O/P Valve - the one by the Transformer alight? Are the wires to the controls in place? The first part to look at is the capacitor that feeds the grid of the O/P valve from the Anode of the one before it. Cheers, Steve P.
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6th Apr 2009, 11:49 pm | #3 |
Pentode
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Re: National DE-631 any info?
Thanks for the tip Steve. I'll be taking a closer look over the next few days.
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6th Apr 2009, 11:56 pm | #4 |
Retired Dormant Member
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Re: National DE-631 any info?
Yes, with the info you've given I too would focus on and around the o/p valve. I note it's not sitting vertically in its socket; try moving it gently to see if the radio splutters into life - there may just be a poorly connecting pin or two on that valve.
Dating is very difficult; frontal appearance suggests 1960-ish but the wooden cabinet and MW plus 2 x SW coverage may mean it's 1956/7. There may be a date stamped inside the cabinet or on certain components (the smoothing/Res cap, for example). The knobs don't appear original - note the wavechanger is sitting midway between two bands. |
7th Apr 2009, 12:13 am | #5 | |
Pentode
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Re: National DE-631 any info?
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7th Apr 2009, 10:07 am | #6 |
Rest in Peace
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Re: National DE-631 any info?
Wasn't National a Panasonic trade name?
Mind you, I couldn't find anything under that either. Alan |
7th Apr 2009, 10:17 am | #7 |
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Re: National DE-631 any info?
It all stems from the rather unfortunately titled Matsushita Electric Co. To save this, essentially repair, thread from drifting too OT, there's something of a historical explanation here on Wikipedia.
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7th Apr 2009, 10:54 am | #8 |
Dekatron
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Re: National DE-631 any info?
Absence of LW and two SW bands suggests it's of non UK origin, or originally destined for somewhere other than the Uk.
U.S? Have you tried looking for info on some American sites, as I believe National was used as a brand name by Matsushita over there.
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7th Apr 2009, 10:00 pm | #9 |
Pentode
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Re: National DE-631 any info?
I have trawled through some U.S. sites, Tim, but haven't found it. I've found some close relatives on this japanese site though. The AH-700 on there from 1958 makes darren_uk's guess of 1960 look pretty good. It now looks likely that the knobs are original as the shafts have splines allowing the wavechanger to be aligned correctly. they also have their felt discs behind.
As Steve_P suggested the O/P valve doesn't light up so I know where to start looking when I've got the chassis out. I'll also be able to upload a photo of the circuit diagram that's pasted on the inside of the cabinet. A cursory check with a terminal screwdriver told me that the chassis is live. Can anyone confirm that this is a live chassis model? |
7th Apr 2009, 10:04 pm | #10 |
Nonode
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Re: National DE-631 any info?
From the image in your first post it appears to have a hefty looking mains transformer and thus it shouldn't have a live chassis.
You should cast a suspicious eye towards any mains filter / suppression capacitors as they are probably leaky. It's a very nice looking set in my opinion. Regards,
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Brian |
7th Apr 2009, 10:08 pm | #11 |
Pentode
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Re: National DE-631 any info?
Thanks Brian. I did think it a little odd that the shafts of the controls were live as well.
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7th Apr 2009, 10:15 pm | #12 |
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Re: National DE-631 any info?
Do you have the rear panel? It should say on there about the mains supply, but as Brian says it looks like an AC set to me.
I'm surprised there's a splined shaft on the wavechanger; risk of stripping rather high I'd have thought. |
7th Apr 2009, 10:53 pm | #13 |
Pentode
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Re: National DE-631 any info?
I do have rear panel and it says the power source is AC. Does this mean that it definitely shouldn't have a live chassis?
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7th Apr 2009, 11:00 pm | #14 |
Dekatron
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Re: National DE-631 any info?
In theory Yes, but practice is different. Always keep one hand out of the way when going inside live equipment.
Anyway, if the O/P valve does not light up, and the rest do and you have HT, then there are no heater volts to the O/P valve or the valve has gone. It might be some Japanese type though. What does it say it is? Cheers, Steve P.
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7th Apr 2009, 11:25 pm | #15 |
Pentode
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Re: National DE-631 any info?
It's a 6AR5. The others are 6BE6, 6BA6, 6AV6, 6DA5 (magic eye) and 6X4 (rectifier).
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7th Apr 2009, 11:57 pm | #16 |
Dekatron
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Re: National DE-631 any info?
6BE6 - EK90
6BA6 - EF93 6AV6 - EBC91 6DA5 - EM81 6X5 - EM35 There does not seem to be an equivalent for the 6AR5. http://www.radiomuseum.org/tubes/tube_6ar5.html The heater goes between pins 3 and 4. Hold the valve with the pins toward you, gap at the bottom. Count the pins round from the left of the gap. Pins 3 and 4 are the ones you want. I think an EL90 would work here. Cheers, Steve P.
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If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...? |
8th Apr 2009, 12:25 am | #17 |
Pentode
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Re: National DE-631 any info?
That's great Steve. Thanks for all the help.
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8th Apr 2009, 1:12 am | #18 |
Dekatron
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Re: National DE-631 any info?
Murphy strikes again.
It would be the rarest valve that's gone wouldn't it! Good luck Derminator, I look forward to reading a "Success Story"..... You might find some on E-bay.Check your PM box. Such as http://cgi.ebay.co.uk/VACUUM-TUBE-6A...3286.m63.l1177 (No connection with seller) (Apologies if not allowed. Have also sent PM)
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"Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly." Last edited by Tim; 8th Apr 2009 at 1:17 am. |
8th Apr 2009, 7:24 am | #19 | |
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Re: National DE-631 any info?
Quote:
It's most likely that there's just some leakage, perhaps through a Y-mode capacitor or just parasitic coupling. A neon screwdriver will light with less current available than you can feel (obvious when you think about it). If the set runs OK from a "PowerBreaker"-type ELCB adaptor with the chassis earthed, then fit a proper 3-core power lead.
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8th Apr 2009, 10:55 am | #20 | |
Dekatron
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Re: National DE-631 any info?
Quote:
It's very common for neon screwdrivers to light up when touched to old, non-earthed (Class 0) equipment, even when it's not faulty. Nick. |
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