UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Cracklemaster · 10th Aug 2022, 7:41 pm

Hello everyone my first post here!

I’ve been working on a friends car with a Radiomobile 1070XB. The radio had not been used for quite a while and the tuning knob “slipped” and only moved in the central section on the indicator. The preset buttons were also very stiff and the bulb had expired. I decided to remove it and service it as best as I can. All of the above problems were sorted out and I ran the set for several hours on a bench with 12v car battery supply, connected to a spare car aerial and to the original 4 ohm speaker. The reception was poor but that was expected with no proper earthing and trimming. It all worked fine for hours on end and over several days.

Refitted the set to the car and the reception was excellent. I moved the car several times of the next few days and tested the radio as much as possible. Then all of a sudden it just went very quiet when switching between MW & LW, you can just about make out radio 4 on LW, but that is on full volume.

Removed the set again. If you introduce an audio input via the volume knob, the audio is perfect meaning the output side of the radio is fine. Looking inside there is no visible damage or burnt components, I noticed if you fiddle or even gently tap transistor VT3 you get a crackle relative to the volume knob setting.

Reading the excellent posts elsewhere on this forum it would appear these transistors change through the 70s each time with a minor change to the model number.

1070 has AF117 Germanium Transistors
1070X has BF184 & BF185 Silicon Transistors
Also having the metal cap with the fourth leg to shield it

My 1070XB has quite modern looking transistors with three legs (there is the hole in the circuit board for the fourth leg unused) I have downloaded the schematics for the 1070X and although it has a Radiomobile Service Bulletin about 1070XB and 1070XS differences it does not mention the transistors.

I have included the best photo I can get and the text on the transistor looks like E5465 or E5485, but wondered if anyone has any idea?

Thanks!

10th Aug 2022, 7:41 pm	#1
Cracklemaster Diode Join Date: Aug 2022 Location: Uttoxeter, Staffordshire, UK. Posts: 3	Radiomobile 1070XB Transistors Hello everyone my first post here! I’ve been working on a friends car with a Radiomobile 1070XB. The radio had not been used for quite a while and the tuning knob “slipped” and only moved in the central section on the indicator. The preset buttons were also very stiff and the bulb had expired. I decided to remove it and service it as best as I can. All of the above problems were sorted out and I ran the set for several hours on a bench with 12v car battery supply, connected to a spare car aerial and to the original 4 ohm speaker. The reception was poor but that was expected with no proper earthing and trimming. It all worked fine for hours on end and over several days. Refitted the set to the car and the reception was excellent. I moved the car several times of the next few days and tested the radio as much as possible. Then all of a sudden it just went very quiet when switching between MW & LW, you can just about make out radio 4 on LW, but that is on full volume. Removed the set again. If you introduce an audio input via the volume knob, the audio is perfect meaning the output side of the radio is fine. Looking inside there is no visible damage or burnt components, I noticed if you fiddle or even gently tap transistor VT3 you get a crackle relative to the volume knob setting. Reading the excellent posts elsewhere on this forum it would appear these transistors change through the 70s each time with a minor change to the model number. 1070 has AF117 Germanium Transistors 1070X has BF184 & BF185 Silicon Transistors Also having the metal cap with the fourth leg to shield it My 1070XB has quite modern looking transistors with three legs (there is the hole in the circuit board for the fourth leg unused) I have downloaded the schematics for the 1070X and although it has a Radiomobile Service Bulletin about 1070XB and 1070XS differences it does not mention the transistors. I have included the best photo I can get and the text on the transistor looks like E5465 or E5485, but wondered if anyone has any idea? Thanks! Attached Thumbnails