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Old 10th Sep 2017, 7:23 pm   #1
Guinnless
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Default Bush DAC90A Rescue

Hi,

I've recently acquired a DAC90A that looks like it had spent the 60s and 70s in a chippy judging by the amount of grease inside the cabinet.

It briefly lit the bulb on my safety lamp but I was only greeted with a fizzing (electrical type!) sound. I wasn't expecting much anyway. The cabinet looks like it's had a regular brush with a Brillo pad - possibly to remove chip fat so I'll have to see just how good I can get it to look with some TLC. On the plus side there are no chips (no pun intended) or scratches.

I'm going through the usual wax cap replacement and had found that the output primary is very high (MegaOhms).

I've searched this forum and I believe forum member Ed Dinning does transformer rewinds, I'd rather do this route than use a Universal from RS if possible.

I already have another DAC90A, VHF62 and an Ekco U353 all in working order and regular use.

Thanks
Steve
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Old 10th Sep 2017, 7:36 pm   #2
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Default Re: Bush DAC90a Rescue

See post number 3, perhaps a PM to Ed.
https://www.vintage-radio.net/forum/...d.php?t=139694
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Old 10th Sep 2017, 8:01 pm   #3
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Default Re: Bush DAC90a Rescue

Thanks, I wasn't sure if it was good etiquette or not to land here as a newbie and PM somebody.

Thanks
Steve
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Old 10th Sep 2017, 8:15 pm   #4
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Default Re: Bush DAC90a Rescue

Hello and welcome, Steve.

These are nice sets and restore easily on the whole, just beware of the potentially live-chassis design.

Quote:
Originally Posted by Guinnless View Post
It briefly lit the bulb on my safety lamp but I was only greeted with a fizzing (electrical type!) sound.
Quite possibly the mains filter cap. Snip it out, no great need to replace IMHO.

N.
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Old 10th Sep 2017, 8:30 pm   #5
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Default Re: Bush DAC90a Rescue

Ed may well post to this thread.
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Old 11th Sep 2017, 9:04 pm   #6
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Default Re: Bush DAC90A Rescue

Hi Gents, seen done and another customer hopefully satisfied.

Ed
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Old 11th Sep 2017, 9:24 pm   #7
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Old 18th Sep 2017, 1:43 pm   #8
Guinnless
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Default Re: Bush DAC90A Rescue

Thanks to Ed Diining there is now a nice refurbed transformer in place. Some of the feed wiring was a bit crusty so I've replaced that too. Looks good now - to me anyway

I'm just waiting for delivery of some 18 SWG heat resistant wire for the connections to the dropper. I'd noticed on the dropper that there is a single take off from the 210v tap going to R16 - is this correct?

I was going to replace both Tone Correction caps with standard items but reading some other threads would suggest different values to reduce HF roll off.
My other DAC90a certainly sounds muddier than my Ekco U353.

Thanks
Steve
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Old 18th Sep 2017, 3:45 pm   #9
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Default Re: Bush DAC90A Rescue

Have a read of this thread: https://www.vintage-radio.net/forum/...ad.php?t=35784
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Old 18th Sep 2017, 5:27 pm   #10
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Default Re: Bush DAC90A Rescue

The modifications suggested by Kaylee make a big difference. I would suggest that you critically examine and listen to the speaker preferably with another sound source first.
They are an odd speaker and do suffer from loose suspension and dirt in the pole gap.
Sam.
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Old 18th Sep 2017, 7:50 pm   #11
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Default Re: Bush DAC90A Rescue

Hi Steve, safest way is to get it working first, then do the mods and be amazed at the difference.

Ed
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Old 18th Sep 2017, 9:17 pm   #12
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Default Re: Bush DAC90A Rescue

If you replace the tone corrector capacitors, you might as well put the modified values in straight away. But anything else - get it working first, and then have a play.

Good luck!
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Old 19th Sep 2017, 10:20 pm   #13
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Default Re: Bush DAC90A Rescue

Thanks very much. I shall return with an update soon.
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Old 27th Sep 2017, 7:31 pm   #14
Guinnless
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Default Re: Bush DAC90A Rescue

Hi

I've replaced the dropper wiring with heat resistant 18SWG.

I've read the thread by Kaylee and I think I understand what I need to do but I'll have to order the correct caps to do the job.

There are some rectangular brown caps C3, C6, C2 etc any special requirements for these?

Once this has been done I think it's just a matter of checking and powering up!!
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Old 27th Sep 2017, 8:08 pm   #15
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Default Re: Bush DAC90A Rescue

Any small value square caps are mica, very rarely defective and replacing them can muck up the alignment, best left alone until proven otherwise.
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Old 27th Sep 2017, 9:14 pm   #16
Guinnless
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Default Re: Bush DAC90A Rescue

Quote:
Originally Posted by Boater Sam View Post
best left alone until proven otherwise.
Brilliant. Thanks for this info.
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