Dustiest DAC90A ever?

[Pete_kaye]

I bought this set last week , in 'working' condition .I let them show me before parting with my cash. It worked well for 3 minutes so I paid up.
When I opened it up it was as dusty as can be seen .The mains cap is buried in the photo and the output TRX too. All valves are Mullard and looked original as did the whole set. All stations were in correct place , no hum. Only the bulbs were gone.. Original plug and back. Looks like it has never ben touched.

[mark pirate]

That is relatively dust free, you should see some of the DAC90's I have restored
I am not surprised it is all original, as these are a very reliable set. Having said that, I would replace all the wax caps ASAP. Not forgetting the mains filter cap!

Mark

[ColinTheAmpMan1]

Now here's a thought....If those wax capacitors have been there since 1959 at least and the radio is working fine, what does that say about their reliability? There is also the comment on this website

http://www.classicwireless.co.uk/Bush_DAC90A.htm

where it is stated that "routine replacement of all capacitors is not generally needed on these sets." This has me doubting my own sanity.
Colin.

[paulsherwin]

There's a distinction to be made between 'working' and 'working properly'. UL41s don't come cheap.

[mark pirate]

Quote from the website concerned :

Routine replacement of all capacitors is not generally needed on these sets.

I have restored over a dozen of these sets (and the DAC10) and have found ALL the wax caps had some degree of leakage when tested.
Although the main electrolytic cap is normally fine.
An absolute must is 'that cap', as it could kill the output transformer.

Mark

[Paul_RK]

I don't think I've ever carried out "routine replacement of all capacitors", which for me at least means that any such operation would be exceptional and by definition not routine

That's not to say that no set exists in which I've eventually changed all the tubular waxies and electrolytics. The more a radio is likely to be in regular and prolonged use the further it's worth going in the way of changing components, but still there are circuit positions in which readily measurable leakage neither threatens to harm any other part of the radio nor is likely perceptibly to degrade performance.

[Phil G4SPZ]

Going back to 'dusty' radios, I once restored a pre-war Marconi 559 which was so full of dust that I could only conclude that it had operated for years in a carpet factory. The chassis was covered by a solid 1/4" thick layer of what resembled carpet underfelt, and the bottom third of the speaker was choked solid with dust.

[Dave757]

Hi Phil,

I once was given a radio just like that, - I think it was an Etronic RA640.

Taking the back off revealed a solid carpet of dust which you could actually lift!

But the nice thing was that under the 'carpet' were a good few small coins -
sixpences, threepences and the like, which some kiddie must have fed in
like a money box, before the carpet formed!

Kind regards

Dave

[mark pirate]

As there are only eight capacitors to replace, it is well worth doing them all while you have it apart. It costs less than a fiver and takes about 25 minutes, you then have the peace of mind that the set will work as well as Bush intended.
Here are some photos of a couple of mine in 'as found' condition, and before and after a recap.

Mark

[lesmw0sec]

Wot no mice or spiders

[mark pirate]

Ok, not a DAC90A. But an DAC11. this set had an actual carpet covering the chassis
I was the first person to remove the back since it left the factory in 1949, and yes it was still working!

Mark

[Nickthedentist]

That's more like it, Mark! My grandad's Hacker Mayflower was the same when I inherited it in about 2010; no repairs ever required, set still working, 45 years of dust in a thick blanket, but a super-clean shiny chassis after a quick vacuum.

Nick.

[G6Tanuki]

It certainly looks better after an internal clean!

Worst radio I ever had to deal with was an old Cossor (model-number forgotten) that had spent at least a decade in a sawmill. There was hard, black carbonised sawdust and wood-flour at least an inch deep round the output-valve.

[60 oldjohn]

Contrary to popular belief. I believe most of these dirty radios would have come from clean houses, My theory regular vacuuming (early vacuums in particular) agitates to dust and release some into the air, it is then attracted to the sets especially if set is switched on.

John.

[mark pirate]

It seems to me that Bush sets attract dust the most, just look at the two chassis below
The first two show my PB22, the second two show my AC34.
Maybe we should have a competition to find the dustiest Bush!

Mark

[Nickthedentist]

Originally Posted by 60 oldjohn

Contrary to popular belief. I believe most of these dirty radios would have come from clean houses, My theory regular vacuuming (early vacuums in particular) agitates to dust and release some into the air, it is then attracted to the sets especially if set is switched on.

I would agree with that. My grandparents' house was immaculate, and got vacuumed and dusted fastidiously every day. Nobody smoked, no open fire.

Nick.

[Herald1360]

And a reliable set will get dustier than one needing regular mending when it's likely that at least a cursory brushout will be done just to make the job less mucky.

[Phil G4SPZ]

Having owned dogs for the past 37 years (sadly not at the moment though) I can confirm that an animal-free house gets far less dusty!

Left to its own devices and assuming minimal air movement, dust eventually settles on horizontal surfaces due to gravity. It's therefore interesting to speculate how dust accumulates inside a radio. My theory is that dust particles, suspended in the ambient air, are drawn into the radio by a combination of thermally-induced air flow and the piston effect of the speaker. Once inside the cabinet, when the radio is switched off the dust particles that have been sucked into the cabinet fall onto the top of the chassis, where of course they aren't removed by normal household dusting. The cycle repeats every time the radio is used, leading to a gradual build-up of dust.

Dust is also attracted by electrostatic forces to regions of high potential. I don't think this is a big factor in domestic radios, where perhaps 250 volts is the highest potential that could be encountered, but in TV sets it was certainly the case that the most dust tended to collect around the focus and final anode connections.

I've never found much dust inside 'sealed' radios such as attache-case style portables.

Herald makes a good point that the most reliable radios will, by definition, spend more time playing and trapping dust, and hence a reassuring layer of dust is definitely a Good Thing when considering buying an old radio.

[Pete_kaye]

Well that was a good set of replies . I can see I am in good company! I am cleaning mine and the case has come up very well. The chassis looks full of potential as the dust seems to have protected it - as suggested earlier.
I will replace all 10 caps but the 2 important ones first ,before I switch on again .

you then have the peace of mind that the set will work as well as Bush intended

I wonder? bet they wanted 5 years at most, or am I being cynical?