Others have pointed to the need to check voltages to try to pinpoint fault areas, and the same advice holds good for any set, be it transistor or valved.
A point worth mentioning which can help quickly pinpoint faults in both valve and transistor sets is that of signal injection and tracing. A signal tracer is nothing more than an amplifier which substitutes for the audio stages of a radio, and when used with a simple RF probe, can trace the signals from the aerial and the mixer/oscillator stages ('frequency changer') of the set, through the IF stages to the audio stages.
In the case of the Bush TR82 (or any similar transistor set), if you place the tracer probe on the base of TR2 and tune the dial across the band and can hear signals in the speaker of the tracer, you know that the mixer/oscillator stage is working on that band. If you then switch to other bands (MW/LW/SW etc) and similarly can tune in signals audible on the tracer speaker, you know that the front end of the radio is working on those bands. If you then apply the tracer probe to the base or (grid in a valve set), of the IF stage transistor and can tune signals, you know the IF stage is working - if only after a fashion, (if for example the IF stages need alignment). In a dead set which works as far as the IF stages, that points to the detector/audio stages being at fault.
If you then inject a signal (1kHz or thereabouts) at the slider of the volume control and hear nothing, the fault(s) lie in the audio stage. In transistor sets if the set has a headphone jack, that is often open circuit, so it's worth checking in that area. In TR82s, it is by no means uncommon for the detector diode to fail (an OA70), which is hiding away inside the can of IFT3. If you can hear signals on the signal tracer at the collector of TR3 you know that the set is working up to that point from the front end. If you inject a signal with the injector at the slider of the volume control and hear a loud tone in the speaker of the set, you know that the audio stage is also working. You have therefore narrowed the location of the fault down to IFT3, and most probably, the detector diode for which more or less any germanium diode will suffice as a replacement - OA90/91 1N34 etc.
It's a bit of a faff to remove IFT3 as you have a few connections to disturb, so it's as well to do these tests to confirm any suspicions that the detector diode may be at fault, rather than just guessing, and perhaps needlessly pulling the IFT can out only to find the diode is fine. You also need to exercise care when replacing the diode that you don't break any of the fine wires of the IFT windings.
I'm not of course implying that the diode is definitely where the fault lies in you case - I'm citing it as an example of how signal tracing/injection can be used to quickly pinpoint faults in a dead set.
A simple signal tracer can be made from any small amplifier such as an external PC speaker-amp often found for a couple of pounds at car boot sales or in charity shops. Similarly, a signal injector can be made from a couple of transistors or a 555 IC, for which circuits abound on internet. However, that takes time to scratch around to gets bits and pieces together and can detract from your primary objective of getting a radio working. A quicker solution could be to buy a signal injector/tracer kit and in that regard, Velleman make an excellent little kit ('K7000'), of which I've made several as gifts for chums. The kit is just under a tenner and can be made in about and hour or so, but you need case of some sort to house it, and some probes and a speaker.
I've attached a few pic of one that I made, and of the simple probe circuits that I used, and some notes I wrote in how to use the injector/tracer.
The notes were written with valve sets in mind, but the same principle apply to transistor sets.
The Kit info is here: http://www.vellemanprojects.eu/downloads..._k7000.pdf
You can buy kit here: http://www.esr.co.uk/products/frame_test-equipment.htm
Hope that's of help and interest.
Good luck with the restoration Laurie!
A point worth mentioning which can help quickly pinpoint faults in both valve and transistor sets is that of signal injection and tracing. A signal tracer is nothing more than an amplifier which substitutes for the audio stages of a radio, and when used with a simple RF probe, can trace the signals from the aerial and the mixer/oscillator stages ('frequency changer') of the set, through the IF stages to the audio stages.
In the case of the Bush TR82 (or any similar transistor set), if you place the tracer probe on the base of TR2 and tune the dial across the band and can hear signals in the speaker of the tracer, you know that the mixer/oscillator stage is working on that band. If you then switch to other bands (MW/LW/SW etc) and similarly can tune in signals audible on the tracer speaker, you know that the front end of the radio is working on those bands. If you then apply the tracer probe to the base or (grid in a valve set), of the IF stage transistor and can tune signals, you know the IF stage is working - if only after a fashion, (if for example the IF stages need alignment). In a dead set which works as far as the IF stages, that points to the detector/audio stages being at fault.
If you then inject a signal (1kHz or thereabouts) at the slider of the volume control and hear nothing, the fault(s) lie in the audio stage. In transistor sets if the set has a headphone jack, that is often open circuit, so it's worth checking in that area. In TR82s, it is by no means uncommon for the detector diode to fail (an OA70), which is hiding away inside the can of IFT3. If you can hear signals on the signal tracer at the collector of TR3 you know that the set is working up to that point from the front end. If you inject a signal with the injector at the slider of the volume control and hear a loud tone in the speaker of the set, you know that the audio stage is also working. You have therefore narrowed the location of the fault down to IFT3, and most probably, the detector diode for which more or less any germanium diode will suffice as a replacement - OA90/91 1N34 etc.
It's a bit of a faff to remove IFT3 as you have a few connections to disturb, so it's as well to do these tests to confirm any suspicions that the detector diode may be at fault, rather than just guessing, and perhaps needlessly pulling the IFT can out only to find the diode is fine. You also need to exercise care when replacing the diode that you don't break any of the fine wires of the IFT windings.
I'm not of course implying that the diode is definitely where the fault lies in you case - I'm citing it as an example of how signal tracing/injection can be used to quickly pinpoint faults in a dead set.
A simple signal tracer can be made from any small amplifier such as an external PC speaker-amp often found for a couple of pounds at car boot sales or in charity shops. Similarly, a signal injector can be made from a couple of transistors or a 555 IC, for which circuits abound on internet. However, that takes time to scratch around to gets bits and pieces together and can detract from your primary objective of getting a radio working. A quicker solution could be to buy a signal injector/tracer kit and in that regard, Velleman make an excellent little kit ('K7000'), of which I've made several as gifts for chums. The kit is just under a tenner and can be made in about and hour or so, but you need case of some sort to house it, and some probes and a speaker.
I've attached a few pic of one that I made, and of the simple probe circuits that I used, and some notes I wrote in how to use the injector/tracer.
The notes were written with valve sets in mind, but the same principle apply to transistor sets.
The Kit info is here: http://www.vellemanprojects.eu/downloads..._k7000.pdf
You can buy kit here: http://www.esr.co.uk/products/frame_test-equipment.htm
Hope that's of help and interest.
Good luck with the restoration Laurie!
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
