Bush MB60, TR82, VTR103 and other variants

[Mike Watterson]

Check out pound shop etc toy & craft beads.
I've also used nail varnish to make wooden ones look plastic.

[Refugee]

I have got quite a bit to do on it as it is very crackly. The bead could come from almost anywhere.

[Old Sparky]

I am repairing a TR82C from which the tuning knob was missing & the pointer badly bent.  Having managed to straighten the pointer, i now have the dilemma of replacing the tuning knob, and I know these are as rare as hen's teeth!  All that was left of the original was the broken off boss and retaining clip.  The pointer won't locate on the shaft without the knob.  Any suggestions as to how to overcome this problem welcome.
The tuning gang has intermittent short circuits, which hopefully can be cured, but, having set it fully closed whilst working on the radio, it's reluctant to open again by turning the shaft, so a replacement may be needed. I may have  a suitable 2-gang airspaced gang somewhere, and can probably measure the capacitance of the original once the s/cs have been sorted, so a replacement knob/lens is the main requirement.

[Terry]

The pointer won't locate on the shaft without the knob.

It should do! The pointer is made from a single piece of sheet metal. The part that grips the spindle is cut to resemble teeth that can then be bent almost at right angles to the pointers. The circle they form, with a slight inward bias due to the bend being slightly less than a right angle, enables the circle of teeth to grip the spindle. (The teeth point downwards, toward the gang.)

As for the gang jamming, has anyone over tightened the rear bearing nut? This could also be responsible for the shorting problem.

Otherwise, there is no need to measure the capacitance - it is 500 + 500pF. If you have another that is mechanically identical, that will do for a replacement as it was a commonly used component at the time these sets we made.

[Old Sparky]

Thanks for the info., Terry. I sould be able to carefully bend the gripping part of the pointer so that it does grip, and i can easily remove the tuning gang - at least that involves simply desoldering a few connections and undoing 3 screws - the grommets have hardened, so i may have to replace those. The radio is otherwise working, despite it being the version with AF117s!, so if the mechanical faults can be fixed all will be well.

[Refugee]

I have had the same problem on the same set as yours.
On mine the tuning dial survived leaving me with the fixings between the chassis and cabinet to rebuild.
The tuning cap had gone intermittent short.
First I got the moving vanes running true to the frame using the adjuster nut.
Then I added paper between the vanes and warmed the solder holding the fixed vanes to the frame and moved them about a bit to settle them in there new position. It worked well.
The photo shows the cap with the left hand vanes about to be adjusted. You can see that the fixed vanes need to move to the left a bit.
The set is now a good one.

[Old Sparky]

I found the fault to be caused by the adjuster being incorrectly set, so, by careful adjustment, I was able to get the tuning gang working correctly, and, by checking with a DMM on a resistance range, cleared the intermittent short circuits without having to resort to heating & noving the fixed vanes. I've also adjusted the pointer so that it fits snugly on the tuning cap. shaft, although it turns maybe 360 deg. when the VC is turned from Max. to Min.(or vice-versa), which is surely not right. It's a long time since I've worked on a TR82, but I'd expect the pointer to rotate 180 deg. between max & min, so what's happening here?

[Terry]

Have you got the pointer on the right section of the shaft?

The TR82 gang has an integral reduction drive - you should be able to see where the shaft is divided. The movement of the tuning knob is greater than that of the gang which, as you say, is restricted to 180°.

Remember that I said that the teeth of the pointer point downwards, toward the gang. If you put it on upside down, it won't work properly!

In your first post on this subject you said that the pointer won't locate on the shaft without the knob.  

Have you got confused here?

[Old Sparky]

Thanks for the further info, Terry. The reason the pointer wouldn't locate on the shaft was because it had opened up so that the teeth weren't gripping anything - the pointer was badly bent when I received the radio. I've now rectified that problem, and, on closer inspection, I can see where the tuning shaft is divided, so it's problem solved. The original grommets had hardened and were breaking up, so I've remounted the gang with three new black rubber grommets, the only ones I could find which would fit. However the centre holes of the new grommets are too small in diameter to accomodate the metal sleeves into which the bolts should be inserted, but, short of attempting to slightly enlarge the holes, there's nothing I can do about that. The gang is now securely mounted and has a small amount of 'float', so it should be OK. IMHO, someone had 'had a go' at this radio, hence the gng being out of adjutment, the pointer being badly bent, and the tuning knob not being present, but nothing electronc appears to have been touched, and the radio works well.

[Refugee]

The reason I had to heat the solder and move the fixed vanes was due to the set having been dropped.
The chassis fixings were broken and it was propped up with rolled up paper so that the controls could be accessed.
The fixed vanes at the knob end of the capacitor were correct so it was certainly mechanical damage.