Bush DAC10

[defender]

Decided to get myself an old valve radio described as working but humming, it arrived today.
I opened the parcel and it had survived Hermes and arrived in one piece.
I plugged it in and it still worked with a hum even with the volume down.
After looking in the back I reckon it should stay unplugged
looks like it needs a rewire and there are a lot of wax capacitors in it and a large tagged on new capacitor but still old.

It still picks up lots of stuff on MW and LW but with a hum, hoping it's just capacitors and not a faulty valve.
It's my first valve radio I need to make a list of parts needed.
I just felt I had the need to tinker with one

[Ed_Dinning]

Looks quite clean and tidy. The tacked on cap is an attempt to reduce hum I think.
It has had a repaire to the dropper with an RS "polo mint" and appears to have had a new FC valve.
Waxies should be easy to replace and with luch you will then have a nice set

Ed

[pip5678]

In common with the similar DAC90A the UL41 valve can be a cause of hummimg, lots of info on the forum on this.

[60 oldjohn]

Not sure if Bush used a spare tag (Pin 4) on the UL41 in the DAC10, but it was used in the similar DAC90A. Some of the newer UL41 valves have this pin internally connected, one to be wary of.

John.

[defender]

Loads of bare wire as the insulation has fallen off the old wire

[mark pirate]

Loads of bare wire as the insulation has fallen off the old wire

It is a common issue with these sets, but not a difficult job to replace the old wiring. Just replace one wire at a time to avoid any mistakes, do the same with the wax capacitors.

Obviously do not use the set until this work has been carried out, also be aware this is a live chassis set, make sure that the mains plug is wired correctly (Red to the Live terminal, Black to neutral).
Avoid touching the chassis while plugged in.

Mark

[Silicon]

Heat resistant wire or heat resistant sleeving is recommended for the mains dropper resistor connections.

[mark2collection]

Reckon it'll turn out nice this set.

Looks as though the mains has been set to 220V(?)

The wire I used last came from scrap equipment, which was full of PTFE sleeved cabling. Where the sleeving had fallen away on solid-cored wiring, I stripped the PTFE sleeving from my 'new' wires, unsoldered one end of the sets wire(s) and slid the PTFE sleeve in place.

Luckily some of the PTFE stuff was the right colour too, but not critical.

Mark

['LIVEWIRE?']

It's a while since I've seen one, but doesn't the DAC10, in common with the DAC90 & 90A have the Reversible 2-pin mains connector on the chassis? AFAIK all Bush products, including TVs (we had a TV53 back on the day) used those chassis plugs. If so, the OP should make doubly sure that the mains lead is connected the correct way round.

[defender]

It's got two core brown blue, a non safety plug and a 13A fuse fitted
The wire goes in through a round hole in the rear case.
Its also missing it's little Christmas tree badge
I was wondering if it wasn't set for the correct voltage.
Very wary not to touch the insides.

[Mike. Watterson]

I've a DAC10. However no matter how it's wired you are best to assume such a design of set is live. An isolation transformer is a must if working on "live chassis" sets regularly.

I've also used Silicone insulated wire for hotter parts of sets. Mine did have a UL41 with a screen grid to control grid leak that would appear as the valve warmed up. That can burn out the audio transformer.

Also a wire was snapped on one of the coils for preset tuning. That was hard to spot. I think these are nicer than the similar DAC90a, having a Bakelite rear and only small card underneath.

The current rating is more important than the voltage for the scale lamps as it's series.
It was the first time I'd seen an inverted speaker.

P.S. I never plug in a valve set without first doing some checks including capacitor on mains, between anode and next grid and capacitor on final anode or audio transformer. Leaky caps on the screen grids won't do much harm but will dramatically reduce gain (RF, IF or AF).

[Boater Sam]

Its been got at then. fit a 1 Amp (a 3 if you can't find 1 ) but be sure that the chassis is connected to the neutral mains NOT the line.

[Herald1360]

Having done one recently, I can say that changing the waxies on the main tagboard is both messy and a bit awkward to get at the far end connections.

There's also a mains filter cap to replace with an X-class type and ISTR that the output grid coupling cap hangs in the wiring by the UL41 and the tone correction cap is on the output transformer.

[defender]

It had already been plugged in before I got it so didn't have anything to lose.
It looks like the cap on top has been used to bypass one of the sections of the two section cap.
The case looks solid possibly just needing a polish, and the 13A fuse has been removed. When I saw it and after I saw the bare wires inside I decided not to plug it in again.
It sounded nice and warm apart from the hum.

[electrogram]

It doesn't have a reversible mains connector like the 90/90a, though strangely the multi shortwave export version does, looks like the grid coupling cap has been replaced in your set, possibly by a Mullard mustard

[Boater Sam]

I see that the valve retaining springs have been lifted out of the grooves and parked on the skirts, a good idea. These spring rings can snap the locating pip off the valve = dead valve.
That smoothing capacitor need sorting, consider re-stuffing the electrolytic can with new caps, much neater and safer than hanging extras on.

[Graham G3ZVT]

I tend to re-stuff smoothing blocks in old radios even if they seem OK.

Actually, I find it a quite satisfying chore.

Here, for the OP, are some images of how I do it, and note with modern components there is always ample room in the can, even when an extra one is used in parallel to make up the required value with what I had to hand.

[defender]

When I see it done re stuffing it looks easy thanks for that.

I need to create a shopping list of parts capacitors, silicone wire, resistors and anything else that's needed and also where to source parts and what values.
Anyone have any pointers?

I might be lucky and have some parts already in amongst the bits I've bought from radio rallies, but not sure if I'll have high voltage ones.

To start with I'll have to get it on a table where it can stay laid out so nothing gets lost

[Boater Sam]

Lots of little boxes, lots of photographs before, one at a time, seems the best.
X type cap across the mains, or none at all. Y type as isolators for aerial and gram if you have sockets.
The rest can be 400v or 650v DC except the tone cap across the output transformer primary, 1000v for that, 650v at a real pinch.
The BVWS sell all the caps you would need, modern values eg. 0.047uf (47nf) replaces 0.05uf.
Well worth joining but membership runs January to January.

Don't change any silver mica caps, flat rectangular waxed, the are almost always fine, and changing them can muck up the alignment, don't twiddle any cores or IF transformers, leave as they are .

[pip5678]

Originally Posted by Boater Sam

The rest can be 400v or 650v DC except the tone cap across the output transformer primary, 1000v for that, 650v at a real pinch.

Out of interest please could I ask why this particular capacitor needs to be so highly rated? Thanks