National DE-631 any info? - UK Vintage Radio Repair and Restoration Discussion Forum

Derminator · 6th Apr 2009, 11:26 pm

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.

Cheers

Steve_P · 6th Apr 2009, 11:39 pm

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.

Derminator · 6th Apr 2009, 11:49 pm

Thanks for the tip Steve. I'll be taking a closer look over the next few days.

Darren-UK · 6th Apr 2009, 11:56 pm

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.

Derminator · 7th Apr 2009, 12:13 am

Quote:

The knobs don't appear original - note the wavechanger is sitting midway between two bands.

Yes, I did notice that. I've been trying to find an image of one online but haven't as yet.

AlanBeckett · 7th Apr 2009, 10:07 am

Wasn't National a Panasonic trade name?
Mind you, I couldn't find anything under that either.
Alan

Darren-UK · 7th Apr 2009, 10:17 am

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.

Tim · 7th Apr 2009, 10:54 am

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.

Derminator · 7th Apr 2009, 10:00 pm

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?

Brian R Pateman · 7th Apr 2009, 10:04 pm

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,

Derminator · 7th Apr 2009, 10:08 pm

Thanks Brian. I did think it a little odd that the shafts of the controls were live as well.

Darren-UK · 7th Apr 2009, 10:15 pm

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.

Derminator · 7th Apr 2009, 10:53 pm

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?

Steve_P · 7th Apr 2009, 11:00 pm

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.

Derminator · 7th Apr 2009, 11:25 pm

It's a 6AR5. The others are 6BE6, 6BA6, 6AV6, 6DA5 (magic eye) and 6X4 (rectifier).

Steve_P · 7th Apr 2009, 11:57 pm

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.

Derminator · 8th Apr 2009, 12:25 am

That's great Steve. Thanks for all the help.

Tim · 8th Apr 2009, 1:12 am

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)

julie_m · 8th Apr 2009, 7:24 am

Quote:

Originally Posted by Derminator

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?

Depends whether it's a "proper" transformer with separate windings or an autotransformer (just one tapped winding; more commonly used for higher voltages e.g. 110V from 230V UK mains than 6.3V for parallel heaters, since the low-voltage section needs to be would with thick wire to avoid voltage drop at the current it is going to be expected to carry, but the high-voltage section needs to be wound with thin wire so it will fit in the space available; and if you have to change the wire on the winding machine anyway, then it's hardly any less effort to make a separate winding). Check the wiring carefully, and test for continuity between chassis and the plug pins.

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.

Nickthedentist · 8th Apr 2009, 10:55 am

Quote:

Originally Posted by ajs_derby

If the set runs OK from a "PowerBreaker"-type ELCB adaptor with the chassis earthed, then fit a proper 3-core power lead.

Yes. Run it via a plug-in RCD adaptor (like you might use with an electric lawnmower). Then temporarily connect the chassis to the earth pin in the mains plug and try again. If the RCD doesn't trip, you have an isolated chassis, and may want to earth it permanently for safety's sake.

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.

6th Apr 2009, 11:26 pm	#1
Derminator Pentode Join Date: Feb 2009 Location: Crystal Palace, London, UK. Posts: 118	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. Cheers Attached Thumbnails

6th Apr 2009, 11:39 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	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. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

6th Apr 2009, 11:49 pm	#3
Derminator Pentode Join Date: Feb 2009 Location: Crystal Palace, London, UK. Posts: 118	Re: National DE-631 any info? Thanks for the tip Steve. I'll be taking a closer look over the next few days.

6th Apr 2009, 11:56 pm	#4
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	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, 10:07 am	#6
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	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
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	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.

7th Apr 2009, 10:54 am	#8
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,307	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. __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

7th Apr 2009, 10:00 pm	#9
Derminator Pentode Join Date: Feb 2009 Location: Crystal Palace, London, UK. Posts: 118	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
Brian R Pateman Nonode Join Date: Jun 2005 Location: Western Lake District, Cumbria (CA20) - UK Posts: 2,136	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, __________________ Brian

7th Apr 2009, 10:08 pm	#11
Derminator Pentode Join Date: Feb 2009 Location: Crystal Palace, London, UK. Posts: 118	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.

7th Apr 2009, 10:15 pm	#12
Darren-UK Retired Dormant Member Join Date: Apr 2003 Location: Blackpool, Lancashire, UK. Posts: 4,061	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
Derminator Pentode Join Date: Feb 2009 Location: Crystal Palace, London, UK. Posts: 118	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?

7th Apr 2009, 11:00 pm	#14
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	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. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

7th Apr 2009, 11:25 pm	#15
Derminator Pentode Join Date: Feb 2009 Location: Crystal Palace, London, UK. Posts: 118	Re: National DE-631 any info? It's a 6AR5. The others are 6BE6, 6BA6, 6AV6, 6DA5 (magic eye) and 6X4 (rectifier).

7th Apr 2009, 11:57 pm	#16
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	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. __________________ 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
Derminator Pentode Join Date: Feb 2009 Location: Crystal Palace, London, UK. Posts: 118	Re: National DE-631 any info? That's great Steve. Thanks for all the help.

8th Apr 2009, 1:12 am	#18
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,307	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) __________________ "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.