Pye transistor portable PE12TBQ SW3 not working - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 23rd Jun 2020, 8:39 pm

A TV rental customer gave me this Pye radio set forty years ago. Got thinking it was about time I took a look at it. The set is a made for export Pye PE12TBQ, a four waveband all transistor portable radio receiver.
There might have been a version for the UK, 1138?
The set has cleaned up nicely and works well on medium waves and two of the short wavebands. However, the set is dead on SW3 (15 to 22Mhz).
The 'scope was connected to the emitter of the frequency changer transistor, V1 (OC171). This has proved that the oscillator is active on all wavebands except SW3. Note that the waveform on MW is not a pure sine wave, slightly better waveforms on SW2 and SW3.
Switches check out OK so the prime suspect is the OC171.

DFWB.

poppydog · 23rd Jun 2020, 10:51 pm

If you didn't have the scope, how else could you have sorted this problem? (If T1 is the problem)

Regards Poppydog

FERNSEH · 24th Jun 2020, 12:46 am

Quote:

Originally Posted by poppydog

If you didn't have the scope, how else could you have sorted this problem? (If t1 is the problem)

Regards Poppydog

A simple diode probe can be made up. This device will detect any RF or if the local oscillator is working.

Tried different transistors but the fault persists.

DFWB.

crackle · 24th Jun 2020, 8:22 am

Circuit for the PYE PE12TBQ is in the Radio Museum. https://www.radiomuseum.org/r/pye_pe12tbqpe_12_tb.html
V1 is listed as an AF115.
It doesn't feel right advising you, but did you try an AF125?

Mike

FERNSEH · 24th Jun 2020, 12:46 pm

Hi Mike,
two HF transistors were tried, a Mullard AF114 and a TFK AF134, no improvement so the original OC170 has been refitted.
The reason for the no SW3 fault has been found. The aerial coil L7 did not have a earth connection to the tuning capacitor.
A wire link has now been soldered in between the coil and capacitor frame. Now the local oscillator is active on SW3 but there is still another fault to sort out. The tuning range is limited to the HF end of the waveband. On SW3 a 180pF capacitor C19 is inserted between the tuning capacitor and oscillator coil L8. it might be faulty.

DFWB.

23rd Jun 2020, 8:39 pm	#1
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Pye transistor portable PE12TBQ SW3 not working A TV rental customer gave me this Pye radio set forty years ago. Got thinking it was about time I took a look at it. The set is a made for export Pye PE12TBQ, a four waveband all transistor portable radio receiver. There might have been a version for the UK, 1138? The set has cleaned up nicely and works well on medium waves and two of the short wavebands. However, the set is dead on SW3 (15 to 22Mhz). The 'scope was connected to the emitter of the frequency changer transistor, V1 (OC171). This has proved that the oscillator is active on all wavebands except SW3. Note that the waveform on MW is not a pure sine wave, slightly better waveforms on SW2 and SW3. Switches check out OK so the prime suspect is the OC171. DFWB. Attached Thumbnails

23rd Jun 2020, 10:51 pm	#2
poppydog Banned Join Date: Oct 2015 Location: Cornwall, UK. Posts: 849	Re: Pye transistor portable PE12TBQ SW3 not working If you didn't have the scope, how else could you have sorted this problem? (If T1 is the problem) Regards Poppydog

24th Jun 2020, 8:22 am	#4
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Pye transistor portable PE12TBQ SW3 not working Circuit for the PYE PE12TBQ is in the Radio Museum. https://www.radiomuseum.org/r/pye_pe12tbqpe_12_tb.html V1 is listed as an AF115. It doesn't feel right advising you, but did you try an AF125? Mike Last edited by crackle; 24th Jun 2020 at 8:33 am.

24th Jun 2020, 12:46 pm	#5
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pye transistor portable PE12TBQ SW3 not working Hi Mike, two HF transistors were tried, a Mullard AF114 and a TFK AF134, no improvement so the original OC170 has been refitted. The reason for the no SW3 fault has been found. The aerial coil L7 did not have a earth connection to the tuning capacitor. A wire link has now been soldered in between the coil and capacitor frame. Now the local oscillator is active on SW3 but there is still another fault to sort out. The tuning range is limited to the HF end of the waveband. On SW3 a 180pF capacitor C19 is inserted between the tuning capacitor and oscillator coil L8. it might be faulty. DFWB. Attached Thumbnails