National Panasonic transistor radio unknown model - UK Vintage Radio Repair and Restoration Discussion Forum

MALC SCOTT · 11th Jan 2009, 2:58 pm

Hi, can anyone please tell me the model of this old National Panasonic radio. It has MW and 3 short wave bands. Someone has replaced the audio output transistors with an AD161/162 pair and have mounted them (glued!!) on the underside of the cabinet top. Rather a neat job they have done. The radio works but the sound goes low and distorted when the volume is increased.
I need a circuit diagram to figure out what the proper output transistors are.
Cheers, Malc.

Paul_RK · 11th Jan 2009, 3:19 pm

Hi Malc,

I've one just like it, and there's an inner back cover identifying the model as R-441LB.

Regards,
Paul

Nickthedentist · 11th Jan 2009, 3:33 pm

Apparently covered in the 71/2 volume of R&TVS. And scanned for Paul's discs

Paul_RK · 11th Jan 2009, 3:42 pm

So it is

Listed as R-441B under National (rather than National Panasonic) from the service here: the R-441LB is the same except for band coverage and is included in the data. The original output transistors are two 2SB178.

Regards,
Paul

MALC SCOTT · 11th Jan 2009, 4:45 pm

Hi, thanks to Paul and Nick for their help. I have found the circuit in my R&tvs book. The sound has a good right to be distorted as the output transistors which are fitted are NPN/PNP pair. The circuit shows them as both being PNP. I will try a couple of AC128 in. I looked 2sb178 on the net and one joker advertising them wants £4.95p each!!

paulsherwin · 11th Jan 2009, 4:54 pm

My Towers Update 4 gives the AC128 as an equivalent. You might even get some medium power silicons to work if you adjust the bias.

Paul

11th Jan 2009, 2:58 pm	#1
MALC SCOTT Octode Join Date: Aug 2006 Location: Willington, County Durham, UK. Posts: 1,499	National Panasonic transistor radio unknown model Hi, can anyone please tell me the model of this old National Panasonic radio. It has MW and 3 short wave bands. Someone has replaced the audio output transistors with an AD161/162 pair and have mounted them (glued!!) on the underside of the cabinet top. Rather a neat job they have done. The radio works but the sound goes low and distorted when the volume is increased. I need a circuit diagram to figure out what the proper output transistors are. Cheers, Malc. Attached Thumbnails __________________ Malc Scott

11th Jan 2009, 3:19 pm	#2
Paul_RK Dekatron Join Date: Nov 2003 Location: Fakenham, Norfolk, UK. Posts: 4,255	Re: National Panasonic transistor radio unknown model Hi Malc, I've one just like it, and there's an inner back cover identifying the model as R-441LB. Regards, Paul Attached Thumbnails Last edited by Paul_RK; 11th Jan 2009 at 3:43 pm.

11th Jan 2009, 3:33 pm	#3
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,841	Re: National Panasonic transistor radio unknown model Apparently covered in the 71/2 volume of R&TVS. And scanned for Paul's discs

11th Jan 2009, 3:42 pm	#4
Paul_RK Dekatron Join Date: Nov 2003 Location: Fakenham, Norfolk, UK. Posts: 4,255	Re: National Panasonic transistor radio unknown model So it is Listed as R-441B under National (rather than National Panasonic) from the service here: the R-441LB is the same except for band coverage and is included in the data. The original output transistors are two 2SB178. Regards, Paul Last edited by Paul_RK; 11th Jan 2009 at 3:57 pm.

11th Jan 2009, 4:45 pm	#5
MALC SCOTT Octode Join Date: Aug 2006 Location: Willington, County Durham, UK. Posts: 1,499	Re: National Panasonic transistor radio unknown model Hi, thanks to Paul and Nick for their help. I have found the circuit in my R&tvs book. The sound has a good right to be distorted as the output transistors which are fitted are NPN/PNP pair. The circuit shows them as both being PNP. I will try a couple of AC128 in. I looked 2sb178 on the net and one joker advertising them wants £4.95p each!! __________________ Malc Scott

11th Jan 2009, 4:54 pm	#6
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,932	Re: National Panasonic transistor radio unknown model My Towers Update 4 gives the AC128 as an equivalent. You might even get some medium power silicons to work if you adjust the bias. Paul