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Old 14th Nov 2019, 9:47 pm   #1
Michael Maurice
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Default Bush DAC90A

I have nearly finished restoring this lovely radio but I have two questions:

1. One of the lamps has failed, they are rated at 3.5V 0.15A but I cant find anything like this type. RS sell 200mA ones or the more common 300mA.

How do I go about modifying the circuit for a different bulb?

2. Having thoroughly cleaned the cabinet, it is still very very dull. How do I go about getting it shiny again? Should I use T-cut or should i just spray a shiny laquer?
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Old 14th Nov 2019, 9:53 pm   #2
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Default Re: Bush DAC90A

Send me a PM with your address and I'll send you one of the correct lamps FOC.
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Old 14th Nov 2019, 10:05 pm   #3
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Default Re: Bush DAC90A

For a brighter finish, Mr Sheen can work wonders, but you need to build the layers up as it'll likely soak in for the first few go's. Spay on a coat, buff, spray another or two and buff, leave a week and repeat.

For a toffee-apple finish, t-cut until the cabinet feels smooth and finish with proper car or furniture wax (not polish) and build those layers up. The more you buff, the shinier the set.

Cotton cloth/old t-shirts work well, especially the final buff.

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Old 14th Nov 2019, 10:20 pm   #4
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Default Re: Bush DAC90A

I've just repaired one too. I now always use 6v 100ma bulbs and change the shunt to 180 ohms. This gives improved illumination of the scale but not too bright. I know some people go to the trouble/expense of fitting a dedicated transformer for the bulbs. As for bakelite cabinets, I've been messing about with old radios for decades and still don't know how to clean/polish them. If they are not very good to start with they will never look too good whatever you do to them imhe. Cleaning with water often makes them worse.

Last edited by electrogram; 14th Nov 2019 at 10:35 pm.
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Old 14th Nov 2019, 10:44 pm   #5
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Default Re: Bush DAC90A

I found furniture wax (bees wax) to be best for Bakelite..as suggested above you need to build the layers up. I use Bakobrite to clean of the initial grime....don't use water on Bakelite although on really bad cases I have used a foam cleaner....it turns brown as it soaks up the gunge! Once the initial surface is cleaned it will probably look quite dull and that is when you build up the layers of bees wax using a clean soft cloth between each layer.
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Old 14th Nov 2019, 11:34 pm   #6
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Default Re: Bush DAC90A

I understand 'Greygate Paste Polishing No 5' is used for restoration of Bakelite telephones. Some more suggestions on polishing Bakelite can be found from an Internet search of this polish.
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Old 15th Nov 2019, 3:12 am   #7
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Default Re: Bush DAC90A

Quote:
Originally Posted by pip5678 View Post
I understand 'Greygate Paste Polishing No 5' is used for restoration of Bakelite telephones. Some more suggestions on polishing Bakelite can be found from an Internet search of this polish.
I use Silvo Wadding, used to be called Duraglit.

Brasso is probably equally effective.
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Old 15th Nov 2019, 8:46 am   #8
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Default Re: Bush DAC90A

When I restored my DAC90A I used 200mA bulbs and changed the shunt resistor to 180 ohms. This gives a nice warm glow that is a big improvement over the original glow worm effect that barely illuminates the tuning scale.
Also care needs to taken over cleaning the case as many of these cleaning products are mildly abrasive and the surface can be easily damaged by too enthusiastic application of these products - some cleaners such as metal polish also tend to leave an oily film.
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Old 15th Nov 2019, 10:37 am   #9
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Default Re: Bush DAC90A

Quote:
Originally Posted by pip5678 View Post
I understand 'Greygate Paste Polishing No 5' is used for restoration of Bakelite telephones. Some more suggestions on polishing Bakelite can be found from an Internet search of this polish.
Another vote here for 'Greygate Paste Polishing No 5' - use sparingly and buff to a shine.

http://www.greygate.com/product/paste-polishing-no-5/

I'm wary of adding anything to the surface finish, especially a shiny lacquer.
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Old 15th Nov 2019, 11:30 am   #10
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Default Re: Bush DAC90A

Quote:
Originally Posted by rambo1152 View Post
Quote:
Originally Posted by pip5678 View Post
I understand 'Greygate Paste Polishing No 5' is used for restoration of Bakelite telephones. Some more suggestions on polishing Bakelite can be found from an Internet search of this polish.
I use Silvo Wadding, used to be called Duraglit.

Brasso is probably equally effective.
Brasso is nowhere near as abrasive as the Paste Polishing No 5 which is quite gritty.
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Old 15th Nov 2019, 11:51 am   #11
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Default Re: Bush DAC90A

Quote:
Originally Posted by DonaldStott View Post
Quote:
Originally Posted by pip5678 View Post
I understand 'Greygate Paste Polishing No 5' is used for restoration of Bakelite telephones. Some more suggestions on polishing Bakelite can be found from an Internet search of this polish.
Another vote here for 'Greygate Paste Polishing No 5' - use sparingly and buff to a shine.

http://www.greygate.com/product/paste-polishing-no-5/

I'm wary of adding anything to the surface finish, especially a shiny lacquer.
I agree with Donald entirely.

A wax polish will impart an extra shine, but at the expense of being more prone to fingermarks etc. I avoid waxing cabinets, unless they're very dull indeed even after a good polish with the Greygate bakelite polish.

The worst culprits for destroying the shine seem to be prolonged exposure to sunlight, damp and also washing in hot water with strong detergents. If I wash at all, I tend to use tepid water with just a dash of washing up liquid. If the case is just a bit grubby, then some baby wipes work as well as anything, prior to polishing.

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Old 15th Nov 2019, 12:16 pm   #12
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Default Re: Bush DAC90A

As I understand it, Bakelite was made from a mixture of phenolic resin and inert filler such as wood flour. The outer polishable skin has a higher proportion of resin, something like the gel coat with fibreglass. The danger with polishing too enthusiastically is that it can cut through this skin and expose the filler fibres, which will then impart a dull finish. I imagine that they could also absorb water if left in contact with it for too long.
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Old 15th Nov 2019, 12:41 pm   #13
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Default Re: Bush DAC90A

You would have to really go for it with something much harsher than Bakelite polish to do that though IMHO, but it's a valid point that only the top layer is capable of being polished.
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Old 15th Nov 2019, 12:58 pm   #14
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Default Re: Bush DAC90A

Quote:
Originally Posted by Mr 1936 View Post
As I understand it, Bakelite was made from a mixture of phenolic resin and inert filler such as wood flour. The outer polishable skin has a higher proportion of resin, something like the gel coat with fibreglass. The danger with polishing too enthusiastically is that it can cut through this skin and expose the filler fibres, which will then impart a dull finish. I imagine that they could also absorb water if left in contact with it for too long.
I agree entirely, that's why they're always shiny on the inside. Exposure to sunlight has a massive detrimental effect on bakelite as well. So many times I hear of owners scrubbing away at bakelite, washing away years of nicotine when in all probability its the actual surface being washed away.


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Old 15th Nov 2019, 2:37 pm   #15
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Default Re: Bush DAC90A

Quote:
Originally Posted by Nickthedentist View Post
You would have to really go for it with something much harsher than Bakelite polish to do that though IMHO, but it's a valid point that only the top layer is capable of being polished.
Agreed, which is why I said " ...use sparingly and buff to a shine."
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Old 15th Nov 2019, 8:32 pm   #16
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Default Re: Bush DAC90A

I have restored plenty of Bakelite telephones, in many cases I have 'reprofiled' chipped edges with a file and progressively smoothed off with wet and dry paper and then machine polished using special buffing compound and it will come back to a very shiny finish (probably better than new). Similarly deep gouges can be removed with wet and dry and machine polished.
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Old 15th Nov 2019, 8:43 pm   #17
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Default Re: Bush DAC90A

Regarding the dial bulbs, I leave the circuit unmodified and keep the current the same using 0.15 amp bulbs, but 6.5 volt types, mainly due to the fact that I've already got a stock of them. The glow from the dial is nice and gentle and the bulbs are likely to last forever. However, there's nothing wrong with altering the parallel resistor value and using different bulbs if so desired, or even the original types if you happen to have them to hand.
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Old 15th Nov 2019, 11:58 pm   #18
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Default Re: Bush DAC90A

Graham, thank you for the offer, but I'm going to use 6.5V 150mA as they're available from RS and I'll need two as I always replace all the bulbs.

I'll order some Greygate compound as well.
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Old 18th Nov 2019, 3:54 pm   #19
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Default Re: Bush DAC90A

For over five decades I have cleaned TV and radio cabinets of all types. Some have been incredibly filthy, mostly cigarette tar, food, human grot and the like! Anyone who has been in the service trade will know exactly what I mean and will probably have their own ideas about dealing with it.

In the case of dirty dull 'sticky' Bakelite I remove all cabinet fittings usually screwed into brass inserts. I then wash the case in dilute detergent such as washing powder or 'FLASH' in warm water.

It is then rinsed and dried with a cloth in a warm atmosphere.

The case is then gently polished with 'T CUT' in circles with a soft cloth. Not attacked with force like someone possessed.. You don't want it to look like a toffee apple.

It is then buffed up with a soft fluffy duster. This will give a very nice natural shine. I have never had a problem with this method. If 'T CUT' is not available, BRASSO is a good substitute and appears to be of a very similar make up.

I finish the case with a simple polish with MR SHEEN or any propriety non beeswax furniture polish, TESCO value aerosol being a good example.

I have never had a problem with this my own method and have many examples of Bakelite receivers that I restored many years ago still in very good order and they have never been polished since their restoration.

The picture shows a Bush DAC90A I have just pulled off the shelf and given it just a dust. As you can see it is still nice and natural, not too bright. Many of these receivers have been in collections for a lot longer than they were in service!
Hope this helps and I can assure you I have never had any deterioration of the Bakelite. Regards, John.
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Old 18th Nov 2019, 5:54 pm   #20
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Default Re: Bush DAC90A

Re DAC90a dial lamps. There was some discussion on the forum regarding this method of dial illumination https://www.ebay.co.uk/itm/6-x2-Elec....c100903.m5276 a couple of years ago.
Did anybody try this idea, and what success (if any) was had with it?
A.F.I.R. the topic just fizzled out. Tony.

Last edited by boxdoctor; 18th Nov 2019 at 6:00 pm.
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