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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 9th Aug 2021, 10:01 am   #1
David G4EBT
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Default Bush DAC90A Alignment Notes

Having joined the forum shortly after Paul created it back in 2003, a recurring theme has been the Bush DAC90A. (Since June, there have been almost thirty threads). I don't have to elaborate the range of issues - they've been covered many times over. Fortunately, unless the IFTs or RF stage has been twiddled with, on a working DAC90A, the alignment is rarely out, and in any event, many novice restorers won't have the test gear or knowledge that goes with it to successfully complete the alignment.

That said, provided a signal generator is available, the 8-page Bush Datasheet (rather than the 2-page Trader Sheet 1161) gives comprehensive alignment instructions and it's quite straightforward. Until earlier this year, I've never had cause to realign a DAC90A, but then my luck ran out. The first thing I realised was the the green so called 'alignment key' on the rear of the tuning scale is nothing of the sort. It infers that you use that key to set the dial pointer, but you don't. It's purpose is only to show the order in which the various alignment points are arranged.

The Bush Datasheet makes it clear that the actual alignment points are tiny indentations rather like centre punch marks along the top edge of the rear of the (probably rusty or tarnished) metal scale-reflector plate. On the radio I wished to align, they were invisible, but I had two others on the bench and managed to find one where I was just able to highlight the marks. To avoid any ambiguity (and to help in future if I ever again have the misfortune to have yet another DAC90A darken my doorstep), I created a 'proper' alignment key which can be printed and fixed on the rear of the reflector plate between the two upright brackets, with all the alignment points marked.

I won't elaborate further on that as I posted a thread on the topic in January this year, but for anyone who didn't spot it, the thread can be found here:

https://www.vintage-radio.net/forum/...d.php?t=175513

Two points worth mentioning:

Firstly, never directly connect earthed test equipment such as a signal generator, frequency counter or oscilloscope to a DAC90A or any other 'live chassis' radio unless the radio is powered from a mains isolating transformer. (Which in any event is a sensible precaution when doing any live testing on live chassis equipment).

Secondly, for anyone who is enthusiastic about DAC90As, I can highly recommend the 'E-book' download by Yannis Karalis entitled 'Easy Restoration for the DAC90A'. It consists of 51 illustrated pages including very clear coloured diagrams above and below the chassis, and many modifications if desired, such as conversion to capacitive dropper and improved dial lights. It costs £17.95 and is well worth it. It can be bought using Paypal at the link below, where there's more information about the contents. Yannis sends you a password key, and you can open the 'book' and print of pages as often as you might wish:

https://www.yanniskaralis.com/bush-d...sy-restoration

Yannis is Greek, and a professional composer, musician and songwriter who has composed many TV 'jingles'. Quite why he has become an aficionado on the DAC90A is one of life's mysteries. He also supplies replica dials which other forum members have bought and seem to have been happy with.

I hope these notes might particularly help less experienced forum members. As I've passed through life, in the many interests I've pursued, I've often discovered to my cost that my enthusiasm, coupled with inexperience, can be a recipe for disheartening, and sometimes quite spectacular pitfalls.

Happy and safe restorations!
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Old 9th Aug 2021, 10:46 am   #2
Graham G3ZVT
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Default Re: Bush DAC90A Alignment Notes

It might be said that the popularity of the DAC90 & DAC90A is self-fulfilling due to forum threads and articles such as these, but for me, without any of those, I am certain I would still choose these sets as favourites, not because we had one at home, we didn't, but they were so ubiquitous when I was young, and yet had a unique style.
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