Bush TR82C.

[lol30]

Doing internet diagnosis can be difficult, however from what you describe the receiver is tuning albeit only one station, this would suggest that the mixer is at least working but as to weather the mixer is working as it should it's hard say.
It would be worth checking if Radio 5 Live is tuning in at the correct position of the tuning dial/scale, also a good visual inspection is always worth a try for wires off, broken ferrite rod or loose connection, dry soldered joints can sometimes show up by tapping around gently with the blunt end of a screwdriver or a plastic knitting needle.
Another visual check is the IF transformer cores, don't try and adjust them though, just have look to see if they have been interfered with, same goes for any trimmer capacitors.
As said, it's difficult to give a more accurate diagnoses at the moment, faults in the RF, Mixer/Osc and IF can all give low signal gain/poor performance.
The fact that the signal increases when you touch the tuning coil on the ferrite rod suggests that the RF tracking might be a bit out, maybe linked to the fault, my advice at this stage though is don't go twiddling any adjustments at all.

Lawrence.

thank you for that advice lawrence its apppriciated

[Joe]

I've moved and renamed this thread.

We don't do 'Off Topic' here but it will make it easier to find for people who haven't been following it from the beginning.

- Joe

apologies about that i am a bit new to this & accidently started a new one
laurie

Nothing to apologise for - we let threads wander where they will.

I was a bit concerned that in this case there was a good chance that it would not be noticed by people who may be able to help you.

Good luck with it.

- Joe

[Robert Darwent]

i have replaced the capacitors c10/c22/c23/c25/c27 & has made a minute improvement but it still is very faint

Hi Laurie,

I see you have replaced several capacitors suggested by others with no real improvement, in that case your problem is likely to be with the detector diode.

In the Bush service sheets (found in post #17 of this thread) the diode is labelled CD1 and is housed inside the can of IFT3, which is found roughly in the middle of the chassis at the bottom edge. The service sheets have a couple of images showing its exact location.

it is by no means uncommon for the detector diode to fail (an OA70), which is hiding away inside the can of IFT3... ...more or less any germanium diode will suffice as a replacement - OA90/91 1N34 etc.

As David says above, replacement with an OA90/91 germanium diode is suitable. However, it is not necessary to fit it inside the IFT can, simply soldering it between pins 5 and 6 of IFT3 on the underside of the chassis is just as good.

To do that you will need to remove the chassis from the case which means taking the large clear tuning knob and pointer off first. My method of doing this can be found described in post #18 of the thread; http://golbornevintageradio.co.uk/forum/...p?tid=1558

After removing the knob and pointer you will need to take out the four chassis screws (one at each corner) and take the chassis out by lifting from the bottom edge first.

When refitting the knob and pointer, ensure the tuning capacitor is fully meshed and fit the pointer horizontally. Don't push it too far down the shaft, it needs to sit on the slightly larger diameter section at the bottom of the shaft but not too low it is scrapping against the dial.

Regards

[lol30]

hi & thank you i already have the chasis out.
i have ordered the diode & just waiting for it to come,thats great that i dont have to dismantle ift3 & just solder it on to the pins ,but does it not mater if the old one is still in the circuit ?
regards laurie

[pwdrive]

You have to remove the old one.

Lawrence.

[lol30]

ok thanks i thought i might have to ,sorry if it seemed like a dumb question but i am still learning ,also can a diode be fitted either way round or are they polarised ?
regards laurie

[pwdrive]

No worries Laurie, it's not a dumb question, yes the diode is polarized, one end of the diode will have a colored band or dot at one end, that end is the cathode the other end being the anode, in the context of your receiver the anode is the IF in and the cathode is the AF out. Try and use a pair of side cutters to snip the old diode out if you can unless you are really proficient with a soldering iron as it is easy to strain and break the wires of the IF transformer when applying heat to the connections in a tight space.
I would then do as Robert/David suggested and connect the new diode underneath the chassis, try and use a pair of thin nosed pliers as a heat sink to the diodes wires when soldering as germanium diodes can be sensitive to excess heat.
If you do fit it underneath then it's easy to get at if the new diode happens to be duff or not the correct type.

The detector diode works on the same principles as a rectifier diode as you might find in power supplies etc.

Lawrence.

[Joe]

The end with the stripe goes to pin five of IFT3.

- Joe

[Robert Darwent]

You have to remove the old one.

In fact I never have and I've done this several times now, from personal experience it just hasn't been necessary.

I just solder a new OA90/91 underneath the chassis between pins 5 and 6 of IFT3. In fact, it's the very reason for doing it this way - so you don't have the hassle of removing the IFT can.

However, if you are going to go the trouble of opening up the can and removing the old diode, you may as well solder the replacement in place of it inside the IFT as well.

My advice would be to try the new diode underneath the IFT first and see what happens. Only go inside the IFT if it proves to be required.

Regards

[Refugee]

You should be able to measure it without taking the can off.
Use a diode tester between chassis and the top of the volume control.
Do the test with the volume set to minimum. The control itself should be high enough not to be seen on a diode test.