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Old 10th Aug 2018, 3:49 pm   #1
Half a Mullard
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Default Bush TR82B

As this is the first time I have attempted a transistor restoration, I would be grateful for some expert advice!

I have managed to remove the tuning lens without mishap by careful use of some thin wire and gentle persuasion. The chassis is then very easy to remove. However I had hoped to remove the volume and tone control knobs so that I could give them a good soak in some washing liquid. I have tried pulling them gently but they will not budge. I donít want to apply too much pressure for fear of damaging them or the ferrite rod. I wondered if anyone has experience of removing these knobs and if so, what is the best approach to use?

I am also considering replacing C33 before powering up the set as I have read that this can cause problems. I have noticed that the set contains a number of Plessey electrolytic capacitors as well as quite a few Mouldseals. I wondered if these are best replaced as in a valve set or are they more reliable operating at a lower voltage and best left alone? Anything else I should look out for?

Any advice would be very much appreciated!
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Old 10th Aug 2018, 3:58 pm   #2
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Default Re: Bush TR82B

The knobs just pull off. If they are stuck, some Plus-Gas or WD40 may help. Can you ease the metal compression ring open with a small screwdriver?

I wouldn't change any caps initially, even the Mouldseals if they haven't disintegrated. Obviously Mouldseals and Plessey electrolytics are the first place to look if a fault is present, but these sets often fire up without problems once the pots and switch contacts have been cleaned.

These are a good first transistor set to work on. The construction is very open and forgiving, and it's easy to take voltage measurements and change components. The transistors are particularly easy to change, though the B uses the OC series so this shouldn't be necessary.
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Old 10th Aug 2018, 4:13 pm   #3
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Default Re: Bush TR82B

The aerial might get in the way of taking the knobs off.
I cleaned mine with a brush loaded with fresh foam cleaner.
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Old 10th Aug 2018, 5:03 pm   #4
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Default Re: Bush TR82B

Thanks for the replies folks. I've sprayed a little WD40 on the knobs, I'll give it a while to soak in but if that fails I think an old toothbrush is the way to go

Paul, good advice, thank you. I'll connect a battery and do some voltage checks before replacing anything.
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Old 10th Aug 2018, 6:19 pm   #5
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Default Re: Bush TR82B

Hi Howard, has it the OC44/45 or the AF1xx series of transistors ? If the former it will have a very good chance of working after the W/C switch and Volume control have been cleaned.


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Old 10th Aug 2018, 6:19 pm   #6
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Default Re: Bush TR82B

Prise the metal ring apart slightly with a flat screwdriver and work the metal ring off the plastic knob shaft. Once the metal ring is removed the plastic knob should lift off easily.
When refitting smear a little wax from an old capacitor over the control shaft, and in the hole in the knob, refit the metal compression ring to the knob and slide the knob back on the shaft.
You will need to unscrew the ferrite rod brackets before removing the knobs, do one end at a time to help hold the aerial in place.
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Old 10th Aug 2018, 8:47 pm   #7
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Default Re: Bush TR82B

Hi John, thanks, it is the OC series so fingers crossed!

Mike, good advice, I'll give that a try. I didn't want to damage the knobs or inadvertently catch the ferrite rod. Thanks for that. I'll report back!
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Old 10th Aug 2018, 11:07 pm   #8
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Default Re: Bush TR82B

Easy way to remove knobs as Mike says remove the clips and the knobs will slide off, I would not use WD40 on any plastic as it slowly over a period of time it will perish. making the plastic crumble like broken toughened glass.
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Old 11th Aug 2018, 7:54 am   #9
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Default Re: Bush TR82B

John

Many thanks for the advice re WD 40
I tried a small amount around the spindle. I'll have a go at the clips today as Mike suggested and give the knobs a thorough clean.
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Old 11th Aug 2018, 8:58 am   #10
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Default Re: Bush TR82B

I'm a bit baffled by post #8

I wanted to find out if it was "safe" to coat entire PCB's with WD-40.

About 5 years ago I conducted an experiment with WD-40. I placed about 1/4 of a can of it in a jar and placed about 20 objects in it, all types of components found on PCB's different plastic coated capacitors, resistors, IC sockets and all the plastics I could find in my junk box and engineering materials, thermoplastics , Bakelite and others that I could not identify the chemistry of.

I left all this in the jar for a few days. Then I removed the objects and washed off the WD-40 with circuit board cleaner and looked at the surfaces of all the plastics with my binocular microscope. I could not find any evidence at all of any form of chemical attack or surface melting .

Though WD-40 will soften & melt sticker glue, it did nothing I could find to any resin cured or thermoplastics. Including polished acrylic, For example, WD-40 will clean sticker glue off polished acrylic and leave no damage to the polished surface.

I would guess that if WD-40 appeared to melt any plastic knob, the plastic must already have been disintegrating and turning to powder anyway.

Apart from sticker glue, does anybody know of a specific plastic type which is melted by WD-40 ?? I would like to know and conduct another experiment to verify it.
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Old 11th Aug 2018, 9:06 am   #11
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Default Re: Bush TR82B

As I understood it, the problem with WD40 and ilk is not dissolving or melting of plastics but the degrading of some polymers leading to embrittlement. It's the white spirit I think, which certainly causes some paints to curl and strip.
But what do I know?!
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Old 11th Aug 2018, 9:07 am   #12
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Default Re: Bush TR82B

I've found WD40 to be damaging to some plastics over the long term. A few hours or days is fine as long as it is washed off afterwards, but long term exposure (as in months/years) will have exactly the effect Jonnybear describes in post 8.
We had a TV in the workshop which had been treated with WD40 (for a crackly volume control) over a period of years, and the plastic in the area of the V/C was crumbling quite badly.
This may be an extreme case, but I'd advise that all traces of WD be carefully cleaned off after it has done its job.
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Old 11th Aug 2018, 9:30 am   #13
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Default Re: Bush TR82B

Quote:
Apart from sticker glue, does anybody know of a specific plastic type which is melted by WD-40 ?? I would like to know and conduct another experiment to verify it.
I did not say WD40 melts plastic I said it can perish some plastic and cause it to crumble, as Andrew has come across, it can take years in some cases. you may notice transistor radio printed circuit chassis supports disintegrating when undoing screws when volume/wave change switches have been sprayed in the past. any way we are getting off the subject of knob removal.

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Old 11th Aug 2018, 10:01 am   #14
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Default Re: Bush TR82B

There are lots of myths about WD40, encouraged by the secretive nature of the company over decades. It is just white spirit and mineral oil. When applied, the white spirit evaporates within a few days leaving the mineral oil.

Different people will have different opinions about WD40 and their beliefs aren't going to change, so there's not much point in arguing about it.

As John suggests, back on topic please.
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Old 11th Aug 2018, 10:32 am   #15
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Default Re: Bush TR82B

Thanks Paul for clarifying that. It probabably explains why in the short term at least little trouble is seen with it as the white spirit disappears fairly quickly and in the long run, it is possible the mineral oil could cause some difficulty, but that certainly would be a very long term experiment to verify. Though for the most part, mineral oils are fairly non reactive.

The devil with plastic parts like post 1950's vintage radio & TV knobs etc is the plastic always seems to harden and crack with time. Bakelite knobs and even wooden knobs are much longer lasting. I was interested to see some replica Hacker knobs for sale on eBay recently. So for any radio restoration it's worth looking to see if they have been replicated.
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Old 11th Aug 2018, 10:46 am   #16
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Default Re: Bush TR82B

1950s plastics do seem to be relatively unstable. We will all have experience of knobs, buttons and grilles becoming fragile or brittle, but there doesn't seem to be a clear pattern to it. I haven't known the knobs on the TR82 series deteriorate in this way, but that doesn't mean it never happens, so the OP is right to be careful.
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Old 11th Aug 2018, 10:02 pm   #17
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Default Re: Bush TR82B

Some of the hard plastics are naturally too hard, to the point of brittleness which has to be moderated by the use of plasticisers. Plasticisers tend to go walkies over time, and old plastics lack the advantages of modern plasticisers.

Some plastics like polycarbonates are also diabolically sensitive to fluorocarbon solvents like freons which used to be used as aerosol cleaners and also some other cleaners. I was shown some HP plastic moulded board extractor, one quick spritz of 'Inhibisol', count to ten and then try to use them.... breaks every time! Those solvents are long outlawed but do trace amounts accumulate?

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Old 12th Aug 2018, 6:26 am   #18
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Default Re: Bush TR82B

Sunlight is one of the worst things that can effect plastics, wood and fabrics. Plastics can go chalky and brittle, and change colour in a remarkable short time, especially the plastic of a Bush TR82.
I polished some marks out of the back of the case on one leaving a pale colour where the bleached surface had been rubbed away. After 6 months on the window sill the mark had almost disappeared. But there was a horizontal line across the back where the bottom of the window frame had cast its shadow.
So keep your treasured radios out of the sun light.
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Old 12th Aug 2018, 4:48 pm   #19
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Default Re: Bush TR82B

Success! I took Mike's advice with a slight variation. I was afraid of damaging the knob by prising the ring apart. However I tried another approach. I used a small screwdriver inserted in the slot under the ring and pushed upwards. Each ring flew off circlip style but was soon retrieved. As Mike suggested the knobs then lift off easily although ferrite rod brackets need loosening to give sufficient clearance. I will lubricate before refitting as suggested. Now destined for a good soak in wash liquid.

The various comments re WD40 make very interesting reading. I think perhaps my conclusion is to use sparingly and perhaps be very cautious with cherished items!

Thanks again. Will try applying power tomorrow.
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Old Yesterday, 9:55 pm   #20
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Default Re: Bush TR82B

Following a temporary diversion I was finally able to get on with the Bush today.

The knobs cleaned up very well in the wash liquid. I found it easiest to refit them by sliding the spring clips on first, then easing them over the shafts which had been cleaned and a touch of wax applied as suggested. The tuning lens is still a little cloudy but quite usable. I cleaned up the cabinet using foam cleaner and polished up the brass work. The set has come up very nicely.

The wave change switch was treated with switch cleaner as were the volume and tone pots which were very crackly. I just replaced C32 and C33 (Trader sheet) connected a battery and switched on. The radio worked very well with good volume. The tone control is very effective too. I was very pleased with the sound quality, certainly beats any modern transistor set!

Taking Paulís advice (#2) I left the remaining capacitors alone. The current draw hovered around the 20ma mark on mid volume. Voltage checks were pretty much spot on as per the service sheet. On a valve set the Mouldseal capacitors would probably be replaced on sight but given that the set is working well would I be best advised to leave well alone? The Bush is very easy to work on and makes an ideal first transistor set.

The only drawback with being AM only is the lack of stations to listen to, so with this in mind Iíve ordered a couple of the FM modules and hope to have a go at the FM/AM converter. No doubt Iíll be back asking for help with that looking at the instructions!!

Many thanks for the advice so far.
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