Bush TR82C.

[pwdrive]

It's also worth making sure that the volume control is working ok, ie: not cutting out when turning from min to max.

The approach to fault finding can vary between different folks, with battery operated transistor radios my own approach would be first to check that the battery is up to scratch (I believe you have fitted a new one) my next step would be to check the quiescent current draw from the battery to see if it's within reason.
All above being ok then I would try and ascertain which part of the receiver the fault is in ie: AF or RF then take it from there.

Lawrence.

[Refugee]

The first port of call for a gain fault is the red/black capacitor C22 and C10.
For distorted loud audio C27 first then C21.
For tinny or weak audio C23 and C25.

You will be able to see that C22 and C10 keep the power to the receiver part of the set clean of AC and leakage of the received signal. Any signal lost here does not get to the detector diode.

C21 will make the DC voltages on TR4 bad and part of the audio will get distorter off so that it never gets to the speaker and this will make the set sound awful. C27 will cause buzzing and screeching that can be intermittent or constant that gets worse as the battery ages.

C23 and C25 stop the audio from getting onto the resistors that have to be there to regulate the voltages on TR4 and TR5 the effect of one of these going faulty will start with poor bass and get worse. Faults with these capacitors will be amplified by the transistors.

Most of the buzzing will be from power cables close by and once the gain of the receiver part of the set is restored it should be drowned out by the stations you listen to.

[lol30]

thank you very much for that information,i managed to get a station tuned in but it is so weak
you can just about hear it & it would only tune into one sation,as i bent over the set my chin touched the ferrite aerial rod where the wire is wound round it & it became slightly louder but went quiet again when i moved away,are those capacitors freely avalable at somewhere like maplins ?
regards laurie

[Refugee]

The Maplin ones will do. The values are not critical and can be raised to a higher one if the exact value is not in stock.

I tend to buy them from the main component specialists like RS or Farnell.
There are one or two in valve sets that are best bought from suppliers that batch test them before putting them on sale.
As you read the forum you will see lots of talk about the coupling capacitors in audio amplifiers and these I will always buy from a supplier even more reputable than Maplin along with things like fuses.

[pwdrive]

Obtaining those replacement capacitors should be no problem, note they are all polarized electrolytic and the correct polarity should be observed when replacing them, the 500uf, 8uf, and 4uf are older style values, if you can't get them you can use the nearest value such as 470uf, 10uf and 4.7uf respectively as the production tolerance for the capacity of electrolytics is quite wide.
100uf are still a common production value, the voltage ratings need to be at least the same as the originals or higher, 25v dc working would be ok.
If you should happen to buy on Ebay then be wary of some of the Far East offerings, some of their capacitors are known to have been sub standard.
If you replace them try replacing one at a time and see what improvement there is to the receiver, it will help you to gain an insight as to how they relate to the circuits function. At that age they need replacing anyway as a matter of course for the future reliabilty of the receiver. If C10 (4uf) has lost its capacitance you will have low gain for sure.

Good luck.

Lawrence.

[lol30]

The Maplin ones will do. The values are not critical and can be raised to a higher one if the exact value is not in stock.

I tend to buy them from the main component specialists like RS or Farnell.
There are one or two in valve sets that are best bought from suppliers that batch test them before putting them on sale.
As you read the forum you will see lots of talk about the coupling capacitors in audio amplifiers and these I will always buy from a supplier even more reputable than Maplin along with things like fuses.

thank you very much for your advice i will let you know how i get on

[lol30]

Obtaining those replacement capacitors should be no problem, note they are all polarized electrolytic and the correct polarity should be observed when replacing them, the 500uf, 8uf, and 4uf are older style values, if you can't get them you can use the nearest value such as 470uf, 10uf and 4.7uf respectively as the production tolerance for the capacity of electrolytics is quite wide.
100uf are still a common production value, the voltage ratings need to be at least the same as the originals or higher, 25v dc working would be ok.
If you should happen to buy on Ebay then be wary of some of the Far East offerings, some of their capacitors are known to have been sub standard.
If you replace them try replacing one at a time and see what improvement there is to the receiver, it will help you to gain an insight as to how they relate to the circuits function. At that age they need replacing anyway as a matter of course for the future reliabilty of the receiver. If C10 (4uf) has lost its capacitance you will have low gain for sure.

Good luck.

Lawrence.

thank you very much for your input i will post back on here once i have bought & fitted new capacitors

[Yorkie]

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!

[pwdrive]

Corr....That's a posh one David, mine only had two transistors in it (now long gone)

Lawrence.

[lol30]

Thank you very much yorkie for that piece of information it is really interesting
and really helpfull to me especially the signal tracer kit, i really am gratefull for all the help i have recieved by everyone out there on this site,being a beginner its a bit daunting when i read & hear all the technical jargon & i feel a bit out of my depth but i really am so interested in this that i want to gain as much experiance as i possibly can.i cant believe even after only a few weeks how much i have learnt.
I will keep updating posts untill hopefully i have it working then on to bringing the case up to scratch.
regards laurie