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Old 12th Oct 2015, 12:59 pm   #1
Martin Bush
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Default Bush DAC70 melted dial

Hello all

Is there such a thing as a replacement dial for a Bush DAC70?

Mine is melted, although not to a great degree. The plastic surround that it's stuck to is also a bit melted, but I can imagine repairing that by sanding and filling.

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Old 12th Oct 2015, 3:12 pm   #2
Half a Mullard
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Default Re: Bush DAC70 melted dial

Hi Martin

I have three of these sets (one is 70a).

As far as I can see the dial is clamped between the front panel and the speaker baffle. The latter appears to be fixed with barbed metal clamps pushed over thin plastic pillars. I'm not sure if these can be released without damaging them. I think unfortunately this may be the only way the dial can be replaced but I could be wrong of course.
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Old 12th Oct 2015, 3:43 pm   #3
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Default Re: Bush DAC70 melted dial

Thanks Howard.

I was doing other jobs yesterday and only had a quick look. I managed to get the perspex tuning dial off easily and presumed that the red dial would come off as part of that process - or at least that the method for removing it would be obvious.

Thinking about it now, that's a bit naive...

It's not a major issue as the set needs some electrical work anyway, but it's a shame as the set is in reasonable condition otherwise.
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Old 12th Oct 2015, 5:24 pm   #4
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Default Re: Bush DAC70 melted dial

This sort of damage is very common. It happens when people change the dial bulb and don't reposition the bulb holder correctly.

It's a while since I dismantled one of these, but I think everything comes away with the chassis when you remove it.
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Old 12th Oct 2015, 6:15 pm   #5
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Default Re: Bush DAC70 melted dial

Thanks Paul.

This is a set that I got almost by accident while picking up another set. I thought it would be a simple job until I noticed the melted dial... That's going to really annoy me!

Oh well
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Old 12th Oct 2015, 6:48 pm   #6
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Default Re: Bush DAC70 melted dial

I've just dug out the DAC 70's and will post some pictures shortly. Strangely two of the dials look OK whereas one is melted by the misplaced lampholder exactly as Paul described. I imagine many owners did a DIY replacement with the lamp too close to the dial.
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Old 12th Oct 2015, 7:28 pm   #7
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Default Re: Bush DAC70 melted dial

As promised these are the 3 sets with one dial melted but the others seem OK.
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Old 12th Oct 2015, 7:31 pm   #8
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Default Re: Bush DAC70 melted dial

DAC70s are actually nice sets and very much late 50s icons, just as the DAC90 typified the late 40s a decade previously. They are good performers and easy to work on, though the sound has too much top cut for many modern ears. It's easy enough to modify them to produce a brighter sound if that's what you want.
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Old 12th Oct 2015, 7:46 pm   #9
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Default Re: Bush DAC70 melted dial

The white reflector plate which Paul mentioned is fixed to the main chassis with 3 screws. The slot can be seen at the top or the reflector where the lamp fitting is attached with a knurled nut. There is a fair degree of adjustment with this and in particular the lamp can be swung nearer the dial scale which no doubt results in the melted plastic.

A plastic lens forms the tuning dial itself. I found this quite tricky to remove and eventually managed it with the aid of 2 loops of thin wire and much patience and wiggling.

I think the problem that Martin has highlighted is that the tuning scale appears to be sandwiched between the front panel and the speaker baffle board. The baffle board is held by the barbed metal clips which I referred to earlier. These are pushed over thin plastic pillars very close to the top of the cabinet. This gives very little room for manoeuvre even if the clips can be gently prised off. If the plastic pillars where to be broken I can't see any obvious way of re-securing the baffle board.

Having examined the set I think this is how the tuning scale is fixed unless I am missing something. Any comments would be appreciated!
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Old 12th Oct 2015, 7:48 pm   #10
David G4EBT
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Default Re: Bush DAC70 melted dial

The DAC70 is notorious for having melted dials. It isn't simply the positioning of the bulb, but the fact that its a mains voltage 15 Watt pigmy bulb. Far too large, both physically and in Wattage terms. Really quite bizarre considering that in contrast, the DAC90A is noted for being as dim as a Toc H lamp - from one extreme to the other!

It's suggested that half that wattage would be plenty, and I guess one possible mod would be to add another series resistor to calm it down a bit. The ones with melted or distorted plastic may have been used for prolonged periods at a time perhaps? Pigmy bulbs seem mostly for use in 'fridges, ovens, cooker hoods etc. Not sure what the lowest Wattage is.

(Same case as the VHF70 - don't know if that suffers from the same design shortcoming).
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Old 12th Oct 2015, 8:08 pm   #11
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Default Re: Bush DAC70 melted dial

I think I still have a spare DAC70 you can have for the cost of postage. The O/P transformer will be O/C and I will probably have used the UL41 elsewhere but from what I remember the rest was OK.
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Old 12th Oct 2015, 8:20 pm   #12
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Default Re: Bush DAC70 melted dial

If anyone has one of these sets with an undamaged dial, might I suggest replacing the dial lamp with an LED equivalent.
These are widely sold and give almost no heat. Not original of course but easily changed back to original if desired.
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Old 12th Oct 2015, 9:15 pm   #13
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Default Re: Bush DAC70 melted dial

Quote:
Originally Posted by David G4EBT View Post
It isn't simply the positioning of the bulb, but the fact that its a mains voltage 15 Watt pigmy bulb. Far too large, both physically and in Wattage terms.
No, the bulb won't melt the plastic if it's positioned correctly, but it's certainly brighter than it needs to be and it generates a lot of heat. There's actually a small resistor in series with it to reduce the brightness and heat somewhat.

It's easy for an innocent bulb replacement to result in a misaligned bulb though.
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Old 13th Oct 2015, 12:11 am   #14
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Default Re: Bush DAC70 melted dial

Thanks to all who have helped so far... It's amazing what can come from a bit of poking round in the shed! Yesterday I managed to part repair a soldering transformer and clean up an old portable... Minor stuff for you guys, but quite a buzz for a novice like me.

As regards the bulb, which I know in mine has blown, could I ask about the LED option.

My thoughts are that I am still new to this and know the chances of me making a mistake and getting a replacement bulb in the wrong place are high - and the world doesn't need another melted dial. So is it the case that I can get an LED version that will fit the old holder and be correct in terms of the rating?
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Old 13th Oct 2015, 12:57 am   #15
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Default Re: Bush DAC70 melted dial

The dial bulb is essentially a mains light bulb so any LED bulb that will physically fit will work, though the colour temperature may make the dial look a bit odd. All the cheap LED bulbs I've seen are bigger than a traditional pygmy bulb, presumably for marketing reasons. I'm sure correctly sized LED bulbs are now available though.

If you have a DAC70 with a melted tuning scale then the primary problem is to fix that. A conventional pygmy bulb will be fine as a replacement if you take care to fit it correctly.
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Old 13th Oct 2015, 6:51 am   #16
Martin Bush
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Default Re: Bush DAC70 melted dial

Cheers Paul.

I know what should happen... But I just know I will get everything right and a day later I will spot I've gone and melted a nice new dial!

At this stage I think I need to try to play safe.
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Old 13th Oct 2015, 7:00 am   #17
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Default Re: Bush DAC70 melted dial

I wonder if this would be any good? The smaller glass envelope could be an advantage?


http://www.homebase.co.uk/en/homebas...-2-pack-814344
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Old 13th Oct 2015, 6:01 pm   #18
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Default Re: Bush DAC70 melted dial

Just a thought but how about adding a BY127 or similar diode in series with the 15w mains lamp? this would reduce the brightness and the heat generated.

Steve
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Old 13th Oct 2015, 11:50 pm   #19
Martin Bush
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Default Re: Bush DAC70 melted dial

I started to dismantle the set tonight. I was intrigued to see how the dial was attached. Anyway, now I know... No dramas, just some logical steel clips. All the bits I'm keeping are OK and cleaned up nicely.

The reason for this update is that in taking it apart I noticed that the bulb wasn't there.

So I dont have one to take to the shop to make sure I get the right size fitting. Is it safe to say that the bayonet end sizes haven't changed over the years (is. If it looks the right size, is it likely to fit?).
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Old 14th Oct 2015, 12:01 am   #20
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Default Re: Bush DAC70 melted dial

Bayonets haven't changed.

Common ones are

BA22 ordinary light bulb size
BA15 SBC fridge lamps etc
BA9 MBC Instrument bulb size

number is diameter in mm.

DAC70 bulb is SBC.
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