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Old 23rd Mar 2009, 4:23 pm   #1
howard
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Default 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Hello again,

I waited a long time before acquiring one of these ivory coloured urea-formaldehyde cased Bush DAC90As, cos it is very difficult to find one which is free from cracks and chips, indeed very often a long hairline crack appears in the top of the case on these above the dropper due to heat. I even went up to Cowbit last year, a long trip from Surrey, to bid on a couple of ivory DAC90As as they were described as good and mint, but one was cracked in the top, and the other was slightly chipped around the back edge (it was still very good) but I was determined to find a totally undamaged example so I left them, but I did buy some other very nice sets there though. These appear on Ebay regularly but are much rarer than the brown ones, occasionally with rather optimistic 'buy it now' prices of £200. I bought this one on Ebay for under £35 including postage and it arrived intact - it was double boxed which is essential for the safe transit of early plastic cased radios.

On arrival, I checked it over, no cracks, chips or even scratches were found on its case, it had obviously had been in a smokey home as underneath it was caked in brown nicotine, but the rest of the case had already been cleaned up apart from around the knobs. Inside it was very dusty and again brown from nicotine but it was all original and complete, and the set came with its original Bush mains lead. This set serial number 73/217295 is one of the last DAC90As built in 1957, as it has shiny metal trims embedded in its knobs and a gold dial. I got on with restoring the set as soon as it arrived, and less than 72 hours later, it's all done. I used Trader Service sheet 1161 for the Bush DAC90A which is on Paul Stenning's DVD, or is available online for £1.99 here .....

http://www.service-data.com/section.php/951/1

Dismantling

- The worst job on this late DAC90A was the removal of the front knobs which pull off, no grub screws. They really were stuck on tight so I sprayed a little switch cleaner onto them via the holes under the case, left that to soak in for about 10 minutes and then spent around 20 minutes tugging and rocking them around before they eventually came off intact ..... phew ! (don't ever be tempted to prise knobs off bakelite sets with a screwdriver as there's a real risk of breaking them, or worse, cracking the case).
- I took off the back cover (4 screws)
- The waveband switch on the side was removed (its securing screw is accessible inside the case)
- The two screws either end of the chassis were removed and the chassis then slid out the back of the case.
- To separate the chassis from the case, the two wires on the tags on the loudspeaker were unsoldered.
- Finally I removed the loudspeaker and trim (four screws and clamps) and then the dial, (two screws and clamps).

Chassis restoration

- All the dust was brushed off the chassis and then cleaned with white spirit.
- The valves were removed one by one, their pins cleaned with a soft copper brush and their bases cleaned with Servisol 10 switch cleaner.
- The off/on/volume potentiometer, the waveband switch and the earth springs in the tuning capacitor were also cleaned with switch cleaner.
- The dial bulbs were removed, both were good so they were cleaned and put back
- A spot of oil was dropped onto each of the dial cord pulleys and a little grease worked into the tuning capacitor ball bearings and along the dial pointer rail
- DAC90As are full of wax capacitors all of which really should be replaced. This is the list ...

1 x 0.003uf
3 x 0.01uf
5 x 0.05uf
1 x 0.1uf

I used new Vishay 0.01uf 630v polyester caps from Farnells, 0.003uf and 0.05uf 630v polyester caps from Justradios in Canada and a 0.1uf 275v AC class X2 metallised paper safety capacitor from Maplins.

- Before switching on the set, I replaced the two 0.01uf AF coupling capacitors, the 0.01uf tone corrector capacitor on top of the output transformer and removed the 0.1uf mains RF bypass capacitor which sits on the top of the chassis.
(I managed to remove all the original capacitor wiring from all the solder tags, which took some time cos as usual with Bush sets all the wires were wrapped round and round the tags and under and over the wiring from other components).

- I switched it on and checked if the chassis was live with my test screwdriver, it was so I switched it off, turned the Bush plug over and switched it back on, and about 50 seconds later it started to work.
- I ran it for a few minutes and found that it was working well on both MW and LW, but eventually it started to become distorted. I had noticed that the UL41 had become very hot very quickly so I fitted a NOS Mullard UL41 (my only one) and good sound quality was restored.

I then took the set over to Ron Bryan for evaluation.

- The original UL41 was tested in the set and the grid voltage was found to be a staggering 7 volts. That was definitely knackered and so it was binned and the new one refitted and that was fine, its grid voltage just 30 millivolts.
- Ron noticed that the voltages in the set were on the high side, but he soon spotted the cause, the mains wire on the dropper was connected to the 210 volt setting and not the 240 volt setting ! That's how the set arrived (see the before pic below) and I hadn't spotted the mistake, I always check Philips and continental sets cos several times I've found them set to 220 volts even when there's a 240 volt setting but it didn't dawn on me that anyone would mess around with the voltage setting on a UK built Bush. So that was corrected, there was nothing wrong with the top stages of the dropper and the voltages in the circuit then measured OK, just a touch on the low side.

- I brought the set home and replaced the remaining wax capacitors
- Some of the wiring around the dropper had lost its insulation so that was all replaced using silicone sheathed cable in the original colour.

Then back to Ron for its final testing.

- The 0.1uf mains bypass capacitor was fitted directly onto the tags on the back of the on/off switch
- Voltages in the set were rechecked now that all the old wax capacitors had been replaced, still a bit low, 190 volts from the rectifier valve into the smoothing capacitor (should be around 205 volts) and 88 volts output from the smoothing capacitor (should be around 98 volts). In fact these slightly low voltages are fine and within tolerances.
- A NOS Mullard UY41 rectifier valve was fitted and that increased the voltages by less than 1 volt so the original UY41 was reinstated.
- The UL41 150 ohm cathode resistor was checked, that measured 159 ohms so that was fine.

Restoration of the case and trim

- The case inside and out was cleaned with B&Q upholtery cleaner
- The outside of the case was polished up with Brasso
- The edges of the front knobs were scrubbed clean with a scrubbing brush
- The knob trims fell off so they were cleaned and stuck back on with superglue
- The dial platform was removed from the chassis, the white PVC backplate removed and all parts cleaned with upholstery cleaner and then reassembled. A little Evostick was used to reattach the PVC backplate to its frame.
- The face of the glass dial was very carefully wiped clean
- The two front spindles were cleaned with a Brillo pad and then lighly coated with plastic grease

The DAC90A was then reassembled.

I am really pleased with this Bush DAC90A, it works exceptionally well (better than my older brown one) needing no realignment and it's the nicest example in ivory that I have seen to date so it was well worth the wait. My thanks again to Ron for his help.

Howard
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Last edited by howard; 23rd Mar 2009 at 4:51 pm.
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Old 23rd Mar 2009, 6:21 pm   #2
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

With its tag board, that has to be the drop-dead-easiest radio to re-cap. Must be an absolute pleasure to restore, as opposed to a 1937 Philco.
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Old 23rd Mar 2009, 6:32 pm   #3
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Lovely condition Howard.

Have you ever wondered why the tag board has a square hole in it? I found out today quite by accident.
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Old 23rd Mar 2009, 6:33 pm   #4
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Hello Bill.

Not so sure about easiest. As Howard says, the way that the leads are threaded through holes and then wrapped around the tags several times is not exactly childsplay

An excellent looking set Howard, well done (and Ron)
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Old 23rd Mar 2009, 6:37 pm   #5
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Nice job as always, Howard. Not as easy as they look as Tazman says.

Cheers,

Steve P.
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Old 23rd Mar 2009, 6:51 pm   #6
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Quote:
Originally Posted by David Tilley View Post
Have you ever wondered why the tag board has a square hole in it? I found out today quite by accident.
I'm assuming it is to allow better airflow around the resistor mounted directly across it.

Nice condition Howard! Incidentally, has the bin that you put the UL41 in been emptied yet? I'd like to try and zap the offending internal leakage! There aren't too many UL41'a about, and if one can be given a new lease of life, so much the better!
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Old 23rd Mar 2009, 7:12 pm   #7
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Nice work and an amazing bargain, Howard!

As others have said, these sets are a real pleasure to mend with no nasty access issues whatsoever.

I too tend to mount the mains filter cap on the back of the switch now. Much easier, neater and it won't be roasted by the dropper.

Nick.
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Old 23rd Mar 2009, 7:41 pm   #8
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Hello again,

When this set arrived on Friday afternoon I said to myself, this is my lucky day ! It is a lovely set but I like the look of the brown one just as much.

The old capacitor wiring on the tags on the central board does take some time to remove cos the women workers in the Chiswick factory who assembled these sets were very thorough, winding the wires round and round the tags, and the worst ones to remove are those where two or more wires are wound over one another. One has to admire the neat design of the Bush DAC90A chassis though, with most of its capacitors in a neat row on that central tag board ..... so unlike some Philips chassis I've worked on !

OK David, we're all dying to know, why has the tag board got a square hole in it ?

Howard
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Old 23rd Mar 2009, 8:09 pm   #9
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Quote:
Originally Posted by howard View Post
OK David, we're all dying to know, why has the tag board got a square hole in it ?

Howard
OK but sorry to hijack your thread....

I was looking through the junk box looking for something to rebuild a burnt up TV22 panel with and it dawned on me how similar an old DAC90A board was to the burnt TV one. When I'd stripped the DAC panel it seemed obvious to me that the square hole was cut out to hold a blocking transfomer.

The TV one is slightly longer as it has a couple more holes. I suspect they all started off life the same length and were cut down as needed.

That's what I thunk anyway. A bit of cheap skatery on the part of Bush. One board fits all. Worth remembering if you ever need to rebuild a burnt up board and have a scrap DAC chassis. It should be fairly easy to glue an extra bit on for the extra holes.

Dave
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Old 23rd Mar 2009, 8:17 pm   #10
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Quote:
Originally Posted by Tazman1966 View Post
Hello Bill.

Not so sure about easiest. As Howard says, the way that the leads are threaded through holes and then wrapped around the tags several times is not exactly childsplay

Remind me to read a little more carefully. Someone slipped me a Ritalin placebo today....
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Old 23rd Mar 2009, 11:45 pm   #11
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Quote:
Originally Posted by kalee20 View Post
Nice condition Howard! Incidentally, has the bin that you put the UL41 in been emptied yet? I'd like to try and zap the offending internal leakage! There aren't too many UL41'a about, and if one can be given a new lease of life, so much the better!
Sorry it's gone, but I daresay others here have suitably knackered UL41s for you to experiment with.

Quote:
Originally Posted by Nickthedentist View Post
I too tend to mount the mains filter cap on the back of the switch now. Much easier, neater and it won't be roasted by the dropper.
Nick.
It does look tidy attached to the back of the switch, but it doesn't look original and as I removed the original capacitor there's a small hole in the chassis where the clip screw used to be. I couldn't find a suitably sized 0.1uf capacitor to replace the old wax cap in its original position so that was the best solution.

Howard

PS: I've just noticed that I put the loudspeaker back in upside down ..... I'll fix that tomorrow !
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Old 24th Mar 2009, 2:40 pm   #12
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Hello again,

I've turned the loudspeaker around now so that the tags are at the top as they were in the set on its arrival. I assume that's the way these were fitted when built ? I also replaced the grille on my other brown one this morning as it had a scratch on it, that looks a little better now. They're nice little sets and they both work well

Howard
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Old 24th Mar 2009, 2:43 pm   #13
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

What have you polished the brown ones case with Howard?

Ps if the wires to the loudpseaker are unsoldered they need to be refitted with yellow to the left looking from the rear otherwise the phase will be wrong.
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Old 24th Mar 2009, 2:55 pm   #14
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Hello David,

I did that one in Safecut which is a light rubbing compund made for use on car paint. It didn't need anything more abrasive as it has retained most of its original gloss. I had to use Brasso on the white one cos it had nicotine on it, but it all came off and is just as glossy.

The wires to the loudspeaker are as found, I always put a small drop of Snopake on one wire and another next to its speaker tag.

Howard

The write up on the brown one is here ...

https://www.vintage-radio.net/forum/...ad.php?t=30397

Last edited by howard; 24th Mar 2009 at 3:01 pm.
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Old 24th Mar 2009, 3:36 pm   #15
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Howard,
I suppose it's sacrilege to say so, but the fascination with these escapes me utterly .
What you need is acouple of nicely polished wooden Pyes.
Alan
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Old 24th Mar 2009, 7:38 pm   #16
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Hello Alan,

I have PYEs as well, in fact I put a new potentiometer in a P43 today.

The Bush DAC90A was the best selling UK radio set of the 1950s and rightly so cos they're well built, quite cute looking, sound very good for their modest size and were reasonably priced. They're still popular, you won't see one on Ebay go unsold unless too much money is being asked for it .... still, each to their own !

Howard
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Old 24th Mar 2009, 7:46 pm   #17
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Howard,
It's good to see you're maintaining your sense of humour.
Alan
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Old 24th Mar 2009, 7:59 pm   #18
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Quote:
Originally Posted by David Tilley View Post
Ps if the wires to the loudpseaker are unsoldered they need to be refitted with yellow to the left looking from the rear otherwise the phase will be wrong.
Is the "phase" important though, as this set only has one LS?
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Old 24th Mar 2009, 8:12 pm   #19
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

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Is the "phase" important though, as this set only has one LS?
lol - I was waiting for a bite Nick! I often have 2 sets going so yes phasing is important to me.

I have an AMT3000 and missed another a while back. I wanted to run a pair of DAC90A's in stereo.
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Old 24th Mar 2009, 8:35 pm   #20
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Default Re: 1957 Bush DAC90A AC/DC 5 valve MW/LW compact table radio in ivory

Hello again,

Just one last thing about these late DAC90As, don't get the perspex trims under the front knobs wet ! I did that once on a perspex trim from another Bush set and it immediately crystallised. Just polish them with mildly abrasive polish.

Howard
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