RCA 1T5J transistor radio. - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 27th May 2020, 4:01 pm

The two RCA 2N408 output transistors were found to be faulty and have been replaced with a pair of silicon PNP BC327s. Adjustment to the biasing was necessary to compensate for the characteristics of the replacement transistors.
So far so good and then the final IF transformer developed a short circuit between the windings. Can't fix the transformer so I'm going to try a "Toko" transformer which was removed from a trash can radio set.

DFWB.

FERNSEH · 28th May 2020, 12:09 pm

The replacement IF transformer was fitted yesterday. It works OK but now the there is the biasing for the output transistors to attend to.

DFWB.

FERNSEH · 28th May 2020, 5:32 pm

Decided the silicon PNP BC327 transistors was not a good idea and a pair of Siemens & Halske germanium 4160 transistors have been fitted instead.

Type 4160 = AC128?

DFWB.

FERNSEH · 29th May 2020, 9:51 pm

The 1N34 detector diode was found to be faulty and a suitable replacement couldn't be found in my isolation workshop.
My solution was to make a "NTK155" diode. Newmarket Transistors Ltd. didn't make signal diodes and to satisfy the requirement for such a device a general purpose transistor was used instead. The base and collector connected together which then becomes the diode's cathode. An AC126 was chosen to make the detector diode.
The RCA "Globe Trotter" now works very well indeed. Because it has a tuned RF amplifier it's a very sensitive receiver.
However, after final assembly the set developed another fault, intermittent operation. I didn't relish the thought that the receiver will have to dismantled again and then having to go through that dial cord stringing procedure again.
Thankfully, a wire link between the tuning capacitor frame to a convenient ground connection solved the problem.

DFWB.

vinrads · 30th May 2020, 8:19 am

Nice one that man ,I rather like the early American transistor radio's ,as with there valve sorry, tube sets they seem to work better than the should . Mick.

27th May 2020, 4:01 pm	#1
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	RCA 1T5J transistor radio. The two RCA 2N408 output transistors were found to be faulty and have been replaced with a pair of silicon PNP BC327s. Adjustment to the biasing was necessary to compensate for the characteristics of the replacement transistors. So far so good and then the final IF transformer developed a short circuit between the windings. Can't fix the transformer so I'm going to try a "Toko" transformer which was removed from a trash can radio set. DFWB. Attached Thumbnails

28th May 2020, 12:09 pm	#2
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA 1T5J transistor radio. The replacement IF transformer was fitted yesterday. It works OK but now the there is the biasing for the output transistors to attend to. DFWB. Attached Thumbnails

28th May 2020, 5:32 pm	#3
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA 1T5J transistor radio. Decided the silicon PNP BC327 transistors was not a good idea and a pair of Siemens & Halske germanium 4160 transistors have been fitted instead. Type 4160 = AC128? DFWB. Attached Thumbnails

29th May 2020, 9:51 pm	#4
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RCA 1T5J transistor radio. The 1N34 detector diode was found to be faulty and a suitable replacement couldn't be found in my isolation workshop. My solution was to make a "NTK155" diode. Newmarket Transistors Ltd. didn't make signal diodes and to satisfy the requirement for such a device a general purpose transistor was used instead. The base and collector connected together which then becomes the diode's cathode. An AC126 was chosen to make the detector diode. The RCA "Globe Trotter" now works very well indeed. Because it has a tuned RF amplifier it's a very sensitive receiver. However, after final assembly the set developed another fault, intermittent operation. I didn't relish the thought that the receiver will have to dismantled again and then having to go through that dial cord stringing procedure again. Thankfully, a wire link between the tuning capacitor frame to a convenient ground connection solved the problem. DFWB. Attached Thumbnails

30th May 2020, 8:19 am	#5
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,763	Re: RCA 1T5J transistor radio. Nice one that man ,I rather like the early American transistor radio's ,as with there valve sorry, tube sets they seem to work better than the should . Mick.