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Bush DAC90A

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Bush DAC90A

Post by PYE625 » Sat May 14, 2016 10:46 am

In a desperate attempt to keep the nerves at bay from starting my new job on Monday, I bought a Bush DAC90A from Newmarket yesterday and started a restoration of it last night. It came from an antiques dealer and I got it for £40 after some haggling.... he wanted £50 for it. A bit pricey, but I liked it and wanted one. It came from a local house clearance apparently.
It all looks complete and not messed with, a view inside shows that it may have not been touched for quite some time :bba
There was also inside a doctors appointment card and a magazine clipping for the chance of winning an oriental carpet from 1979.
It was nice to have the original plug and mains lead too.
Attachments
rsz_003.jpg
rsz_1001.jpg
rsz_001.jpg
Last edited by PYE625 on Sat May 14, 2016 10:56 am, edited 1 time in total.

 
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Re: Bush DAC90A

Post by sideband » Sat May 14, 2016 10:56 am

Lovely! That will look superb after a good vacuum. Hopefully the UL41 will be OK but you may have to isolate a couple of pins on the valveholder if it's leaky. Also check the output transformer primary. Common for these to be O/C.

 
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Re: Bush DAC90A

Post by CTV » Sat May 14, 2016 10:59 am

Hi Andrew,

I had six of these at one point, glad to say the habit was kicked and I'm now down to two :bba

As you're a subscriber to the library, don't forget there's lots of service data ready and waiting for you should you need it and dial scans. :thumb

Edit: You may or may not know, the UL46 is a direct swap for the UL41 if you find yours is duff. The UL46 is better in my opinion as its is a ruggerdised version and the other benefit is its cheaper ( for now).

 
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Re: Bush DAC90A

Post by PYE625 » Sat May 14, 2016 11:08 am

Well, after I dismantled the set, a jolly good vacuum out was called for !!
It came up almost like new, and everything proved to be electrically ok apart from the waxies of course.
I spent last night re-stuffing them with modern replacement caps and re-installed them so to keep the chassis looking original.
The wiring sleeve's around the dropper needed replacing, but all the rubber cable to the speaker and lamp-holders is still nice and supple.
The rubber grommets supporting the tuning gang were replaced too, as they were rock hard and crumbly.
Attachments
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rsz_008.jpg
rsz_007.jpg
rsz_006.jpg
rsz_005.jpg
rsz_004.jpg
rsz_002_2.jpg
rsz_001_2.jpg

 
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Re: Bush DAC90A

Post by PYE625 » Sat May 14, 2016 11:10 am

CrustyTV wrote:Hi Andrew,

I had six of these at one point, glad to say the habit was kicked and I'm now down to two :bba

As you're a subscriber to the library, don't forget there's lots of service data ready and waiting for you should you need it and dial scans. :thumb

Edit: You may or may not know, the UL46 is a direct swap for the UL41 if you find yours is duff. The UL46 is better in my opinion as its is a ruggerdised version and the other benefit is its cheaper ( for now).


Blimey Chris...SIX of 'em lol !!
Well, the UL41 is perfect, it's probably been replaced as it is a Brimar type. :aad

PS....The data library is simply brilliant and I would recommend it's subscription as it is well worth it.

 
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Re: Bush DAC90A

Post by CTV » Sat May 14, 2016 11:24 am

I've never stuffed but can see why some do as the authentic look is certainly maintained. Funny thing is I can imagine in a few years when the set has been moved on some poor sod replacing all those old waxies oblivious to the fact its all ready been done. :aaj

You're lucky the old waxy audio coupling had not shoved some +/ve onto the control grid of the UL41. Looking great and yet another great repair from the PYE625 shop. :aad

 
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Re: Bush DAC90A

Post by Cathovisor » Sat May 14, 2016 12:25 pm

Only six 90As... not even trying :qq1 You could easily get six by taking one each of the three scale/knob variations and the two cabinet colours. Then add in all the model variations, export models, Irish models.... you could have a collection made entirely of that cabinet design alone.

For some reason, I think the 90 'sounds' better, dunno why... :aab

What is interesting though is that the caps were re-stuffed successfully. Now, I've tried those in the past and failed miserably so adopted a policy of only re-stuffing pre-war caps. It looks as though I shall have to re-examine that policy now. How did you do it, Andrew?

 
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Re: Bush DAC90A

Post by CTV » Sat May 14, 2016 12:34 pm

Cathovisor wrote:For some reason, I think the 90 'sounds' better, dunno why... :aab

Never heard a 90 version. The 90A can be made to sound better by changing the value of the tone correction cap. No doubt you and others already know that. Others that don't then have a play and you will be surprised how much better they can be made to sound.

 
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Re: Bush DAC90A

Post by Cathovisor » Sat May 14, 2016 12:40 pm

CrustyTV wrote:
Cathovisor wrote:For some reason, I think the 90 'sounds' better, dunno why... :aab

Never heard a 90 version. The 90A can be made to sound better by changing the value of the tone correction cap. No doubt you and others already know that. Others that don't then have a play and you will be surprised how much better they can be made to sound.

You ought to, if you get a chance. The sound has a different character to it, and a better bass performance. Probably a lot to do with the rather larger output transformer on the 90. I never liked Bush's tendency to fit what were in my view rather small transformers for the job: their only pre-war set with push-pull - the PB55 - always seems to have either one or both halves of the primary o/c when found all these years later. Couple that (no pun intended) to the very large output valves they used in that set - Mullard PENB4s - and it seems to be a fault in waiting.

 
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Re: Bush DAC90A

Post by sideband » Sat May 14, 2016 1:45 pm

PYE625 wrote:Well, the UL41 is perfect, it's probably been replaced as it is a Brimar type. :aad


...so does that mean you've already powered it up?....and there was me eagerly awaiting the 'first switch-on' moment.....

 
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Re: Bush DAC90A

Post by PYE625 » Sat May 14, 2016 1:51 pm

sideband wrote:
PYE625 wrote:Well, the UL41 is perfect, it's probably been replaced as it is a Brimar type. :aad


...so does that mean you've already powered it up?....and there was me eagerly awaiting the 'first switch-on' moment.....


Erm, yes I have and it's working very nicely.
I was ready to check the alignment, but noticed the IF on this one is 470kc's and not 465 in the trader info.
(There is a note in R&TV servicing that units above a certain serial number have 470 kc IF).

 
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Re: Bush DAC90A

Post by PYE625 » Sat May 14, 2016 2:08 pm

Cathovisor wrote:What is interesting though is that the caps were re-stuffed successfully. Now, I've tried those in the past and failed miserably so adopted a policy of only re-stuffing pre-war caps. It looks as though I shall have to re-examine that policy now. How did you do it, Andrew?



Well, re-stuffing wax capacitors is fairly simple but can be rather messy. However, with practise, a neat job can be done.
This is how I do it in pictures below....
Attachments
rsz_001.jpg
Here is an old cap as removed from a unit.
rsz_002.jpg
Heat both ends with a soldering iron and melt the wax.
rsz_003.jpg
Pull out both ends with pliers.
rsz_004.jpg
Push out the internal foil and paper with a screwdriver.
rsz_005.jpg
The old foil and paper removed.
rsz_006.jpg
A cleaned empty tube ready for a new capacitor to be inserted.
rsz_007.jpg
Select a suitable replacement capacitor, extending the lead-out wires if needed.
rsz_010.jpg
Place the new cap inside the tube, fold over the ends of the tube and use a candle to provide new wax.
rsz_011.jpg
Use a soldering iron on a LOW temperature and melt the wax from the candle into the capacitor tube.
rsz_012.jpg
Once allowed to cool, the completed capacitor can be cleaned and is ready for use.

 
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Re: Bush DAC90A

Post by PYE625 » Sat May 14, 2016 6:15 pm

Well, after a good polish with Bake-o-bright, the case is looking rather smart.
Just need to sort out the knobs now.
Attachments
rsz_004.jpg

 
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Re: Bush DAC90A

Post by Cathovisor » Sun May 15, 2016 12:10 am

Andrew,

I've found that after polishing the case with Bakelite polish, giving it a good going-over with an appropriately matching colour of Cherry Blossom shoe polish not only brings it up to a brilliant shine, but it helps the shine to last.

What interested me about your cap re-stuffing was that you didn't seem to refit the brass discs that go in the ends of the cardboard tubes. This was always the problem for me: pre-war caps from some manufacturers (e.g NSF) had a bowl-like pressing that was easy to refit and thread the new leads through, but post-war caps - like TCCs - seemed to have a flat disc that was difficult to re-fit, which was why I didn't really try and do it.

I used to use a small length of metal tube to push the contents of the old caps out: it avoided screwdrivers making a bid for my hands... :aai

 
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Re: Bush DAC90A

Post by crackle » Sun May 15, 2016 6:57 am

I have found that many of the 50's waxy caps have a tightly wound flat coil made out of the same wire forming the connecting terminals.
You can solder the new cap lead to the inside edge of the flat disk and push the lot back into the card tube, using the original capacitor leads if required, and if still long enough.

To remove the old foil I use a small flat screwdriver, work it around the lip to open up one of the rolled over ends of the cap then slide out the old innards, a little heat from a heat gun will help. Then when re-stuffed I use a soldering iron to warm and bend back the card to trap the disk and new capacitor in the tube, finish off with a little wax.

Mike

 
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Re: Bush DAC90A

Post by PYE625 » Sun May 15, 2016 8:52 am

Cathovisor wrote:Andrew,

I've found that after polishing the case with Bakelite polish, giving it a good going-over with an appropriately matching colour of Cherry Blossom shoe polish not only brings it up to a brilliant shine, but it helps the shine to last.




I will try that.....thanks :aad

 
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Re: Bush DAC90A

Post by nuvistor » Sun May 15, 2016 12:32 pm

Best wishes for tomorrow Andrew, hope it all goes well

Frank
ps the radio looks good

 
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Re: Bush DAC90A

Post by PYE625 » Sun May 15, 2016 12:35 pm

Bless ya Frank,
many thanks :bba

 
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Re: Bush DAC90A

Post by PYE625 » Thu May 19, 2016 7:50 pm

The shoe polish as suggested by Catho arrived today and after a session on the cabinet, has come up with a lovely deep shine and depth, like new on the bakolite. I am very pleased with it. Just have to fit the knobs when they are ready.
Thanks Mike, a well worth-while suggestion. :aad
Attachments
rsz_001.jpg


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