A first for me...

[Herald1360]

Believe it or not, in all my years I have never had my hands on a DAC90(A). This has just changed as I now have a DAC90A to fix. Described as "Very hummy and weak sounding 15 years ago and not touched since" it sounds like it's almost a cliche.

It was brought round along with "Another one for spares" but that turned out to be a white DAC90- no back, speaker, tuning knob or scale but the case looked perfect. Pity it's not compatible with the A. It's gone back home with a suggestion that it might well be worth offering for sale "as is".

I'll make a start later in the week when the sun goes back in........

[sobell1980]

Great news, Chris.
I will follow your thread with great interest. I would love to own one of these too one day, i' ve a keen following for these. I have not yet got round to one yet as i have to justify keeping all the ones in my to do pile that I am slowly working through. Best of luck with it.
Dave.

[kalee20]

I'll follow with interest too, particularly with what faults you find.

Guess the back of the DAC90 has crumbled to dust, as they do - but an undamaged white case must be unusual. Maybe the back was removed deliberately to let it run cool?

[Herald1360]

I must confess to not really fancying one- they may be iconic but I prefer art deco and some of the more outrageous French sets to look at.

Fixing one for someone else with a sentimental reason for it is fine, though.

[Tractionist]

Mmmmm ... I've got a mint 90 and 90A [prefer the former] well-built with steel drive cords etc. Make sure that the rectifier is up to scratch, and of course renew the RF by-pass [if it hasn't already exploded].

My place is getting like 'Bush City'. I picked-up yet another TR82 today - that makes five + a VTR too! However, this one's filthy but perfect and working nicely with a new battery thrown-in. It's also an early model featuring OA/OC series glass envelope Mullards, so there's no screen can lead for 'anything that grows inside' to short to!! (I've seen those tin whiskers on the outside of the AF series too!!). Anyway this thing is amazingly selective [better than all my other TR's] and as loud as a 103!! Maybe the later AF series were something of a Bush cost-cutting exercise?

And I accuse my ninety-year old Mother of being 'obsessive', but I couldn't leave it on the car boot for the others to have away could I? !!

I shall watch your DAC90A travails with interest, you never know - by the end of this repair you may become a 'convert' !!

Cheers,

D.

[paulsherwin]

I'm sure everything will be fine if you change the usual waxies, though there's always the risk of a bad UL41.

[electrogram]

and an open circuit o/p transformer primary

[Techman]

Believe it or not x2!

I've also never had my hands on one of either of the 90 types. Two wave bands, live chassis and series heater chain with dropper don't really do it for me when it comes to radios. That's not to say that I wouldn't have one if one were to float my way for a couple of quid at the local auction house, though.

[Nickthedentist]

These are lovely sets. Access is easy, construction quality excellent, and they sound good because of the the large Celestion speaker used. They're also very usable thanks to the frame aerial. I thought I had about half a dozen of them, but more and more keep turning-up the harder I look.

[Tractionist]

I think you and I may be being 'Bush'ed To Death' !!! (Every find these days seems to be a Bush ...)

[MurphyNut]

Originally Posted by paulsherwin

I'm sure everything will be fine if you change the usual waxies, though there's always the risk of a bad UL41.

My first two restorations were DAC90A's and even at that time with my limited knowledge I got them both working very well.
All the wax capacitors were changed, luckily the UL41 valves were good the only tricky bit was changing the output transformer in one of the sets, it was shorting inside and causing the radio to crackle very badly.
Lovely radios, I listen to mine often.

[Nickthedentist]

There's one (well-hidden) C that can be omitted or vastly reduced in value to give a much less muddy sound. The mains filter cap can be replaced by a modern equivalent tacked straight onto the back of the mains switch.

N.

[Skywave]

My first encounter with a DAC90A was way back in the early-1970s. A relation presented me with one with the comment "I use it in the garden shed - or used to: it now doesn't work. You know about radios: can you fix it, please?"

His understanding about my alleged "knowledge about radios" was largely based on his awareness that I was an avid short-wave listener who 'knew how radios work'. My knowledge and experience then was largely based on typically-available ex-WD receivers of that time. When I looked at the inside of the DAC90A and saw the type of construction and parts within it - and its relative crudity - I was amazed at just how little was in it! The fault turned out to be an open-circuit winding in an IFT. A replacement item could not be sourced. The DAC90A had no particular value to its owner. In those days, "It's just another old radio" was the current sentiment of such things. The fate of the radio I never discovered; I suspect it was simply thrown out with the rubbish.

Al.

[Mike. Watterson]

Originally Posted by Herald1360

Believe it or not, in all my years I have never had my hands on a DAC90(A).

I've never managed to get one. They and the KB "toaster" seem too expensive for what they are. I did get a DAC10, which is really a deluxe DAC90a, for £12. It's quite good now, though one preset had me baffled for ages. Snapped wire on coil.

My parents had the "Toaster" for ages which was replaced by GEC transistor 7 with fabric front.

[Herald1360]

Originally Posted by Nickthedentist

These are lovely sets. Access is easy, construction quality excellent, and they sound good because of the the large Celestion speaker used.

I don't doubt it, but I just don't go for the appearance. There's something not quite right about it for me.

[Herald1360]

OK, I'm inside it now. There's a bit of phantom bodgery around the mains input and dropper and the LS wires have been cut, resoldered and taped up.

Started by rewiring the mains lead- a classic example of how not to wire a mains plug- no strain relief, inner cores trailing out the back, 13A fuse (what else?), at least the colours went to the right pins. This was matched only by the state of the 5A connector the other end- no strain relief of any sort and the neutral bare end actually hanging out the back. Since it also had solid tubes that were too tight on the set pins it's been replaced by a better fitting one from then rummage box. The cable outer was sleeved to allow some semblance of strain relief when the two halves were screwed together.

On to the chassis- rewired pretty much the whole mains input and replaced a 500V Metalmite hanging between blobby joints in the wiring with a 22n X class radial across the output side of the mains switch.

Next up, checked the output transformer . Open circuit primary. Not quite the show stopper it might have been, I found an old Radiospares midget output tranny on the speaker of a scrap portable set chassis with intact windings. It's only 30mA rated so it looks like I'll be biassing the UL41 back somewhat, but it should work OK. I'm not about to start rewinding, though maybe the output tranny from the white DAC90 might be OK- I'll ask the owner to check......

One more interesting bodge- there's a couple of yards of single flex attached to a loop of tinned copper wire mounted inside the aerial coil former, presumably as an attempt at an isolated aerial coupling. I'd have been quite impressed if that loop had been properly insulated wire, but it wasn't

That's all for now, folks

[Herald1360]

Right, had a solid session on this set tonight. First up- replace the dead output TX with the Radiospares midget. Interestingly they are exactly the same size, so no need for any drilling. Did some artistry with a couple of 2+E tag strips soldered to each other and to the top of the TX clamp to terminate the flying leads from the new TX and mount the tone correction cap, now reduced to 4.7 nF.

Next up the recap. Evicted all the waxies and replaced with a mixture of BVWS axials and a few modded short lead radials (this is definitely a repair, not a restoration!).

Time to see whether the magic smoke had been safely corked in the bottles.....

On with the lamp limiter. No sign of life from the bulb, heaters gradually reddened but total silence. Not even a volume control or wavechange switch crackle.

Rectifier getting AC OK. DC on its cathode, though not as much as expected. Looked at reservoir capacitor- minus a few mV. ***? Wonder why Bush thought it was a good idea to mount it as far away from the rectifier as possible and wire it up with complete disregard for any ripple current loops? Anyway, resisted the temptation to "improve" it on the basis that thousands of the sets worked just fine regardless and went looking for the missing volts. Eventually I found them hiding behind a break in the sleeved tinned copper wire from the rectifier cathode to the output TX primary, about an inch and a half away from the TX tagstrip. That sorted, there was now life

Quite a lot of it in fact. Yes the DAC90A is a good performer!

Bearing in mind the fragile nature of the diddly output TX, I checked the cathode volts expecting to see trouble, but no, cathode current under 30mA, so no overload there.

Finally looked at grid volts- half a volt or so, not brilliant. Remembered pin4. Chopped the wires to pin 4 and rewired grid stopper direct to tagboard. No need even to extend the resistor leg. Grid volts now down to <50mV. That'll do.

Soooo..... not converted to the looks, but definitely impressed by the performance. Wonder if I could fit a chassis in a French extravaganza cabinet

[crackle]

Polished up I think the DAC90A is a very cute looking radio, and being as it is self contained and can be used anywhere in the house, with no external aerial, makes it very versatile. I think this is one of the reasons why the DAC90A and the KB FB10 seem to have been adopted as the de facto icons for a vintage radio.
I have never recorded how many DAC90A radios sell on Ebay over the course of a year, I wonder if they outsell the KB "Toaster", which according to my records regularly sells over 30 times in a year.
Does anyone keep records of these?
I have now sold my 2 examples of this radio to make room for more KB or ITT radios, but I still have a chassis and reasonable cabinet lurking somewhere.

Mike

[D Cassidy]

Hello.
The DAC90A is an excellent receiver considering it is a straight forward design.
I was advised some time ago to replace the heat emitting mains dropper with either a diode or capacitor. I opted for the capacitor option as mine is a cream cabinet and I'm told they do not like heat and can crack.
The radio runs so much cooler since then and is used every day and the cabinet still looks like new!

[Nickthedentist]

Glad you liked it in the end, Chris.

It's looks may well grow on you, especially if yours has a good cabinet which can be polished up nicely. Some nice pics of such a set here: http://steamradio.tripod.com/


Nick.