wad hd83

davebms · Post by **davebms** » Sun Sep 12, 2010 10:40 pm

hello all . i have a wad hd83 i have the circuit diagram but due to me being computer illiterate i cannot put it on here !! (you can leave the word computer out if you wish) cilin.hepburn has given me some advice (other forum) as i have the wrong power supply caps in ,and a choke would help the power supply . transformer diodes 205v 470uf 100r 200v 470uf 4.7k 100uf 190 v .. i have A E CHOKE that looks like an ideal candidate i think ita a mk 1.5 first board there was a change of resistor and some other part and i think it needs another resistor on the input . so if someone can help and put up the circuit dia mike h poss can help where to put the E CHOKE, polite its answers on her rude suggestions on a post card

dave

davebms · Post by **davebms** » Mon Sep 13, 2010 9:24 pm

http://www.world-designs.co.uk/acatalog/hd83.pdf

that i think is a link to the curcuit info i have juat done some voltage checks i dont think i have enough spare volts to put a choke in

dave

Post by **Nick** » Mon Sep 13, 2010 9:58 pm

Not entirely sure what you meant about wrong caps, but replacing r1 with a hammond 159Q choke should work fine.

davebms · Post by **davebms** » Mon Sep 13, 2010 10:16 pm

Nick wrote:Not entirely sure what you meant about wrong caps, but replacing r1 with a hammond 159Q choke should work fine.

wrong caps. as in it has been built 250volt caps for c1/c2 i think more safety margin is req ? i was hoping to use my E CHOKE as i have a couple of them but i think they drop volts by 20 i think that can be changed and a big plus it will fit in the case its a mk1 small steel case

thanks dave

Mike H · Post by **Mike H** » Mon Sep 13, 2010 10:26 pm

This is "our" E-choke is it?

If so then presume the 220k is reduced to 100k (as supply seems to be about 250V or less (?)

And yes needs a 10R 1 - 2W resistor adding in series with the input. The module will drop 24V

Finally found the connection diagram:

http://www.audio-talk.co.uk/phpBB2/view ... 4864#34864

Post by **Nick** » Mon Sep 13, 2010 10:28 pm

If you were buying them now, I would suggest 300v or above, but 250v will be fine, 205v across 250v caps is ok, 12% below max, so not worth fretting about IMHO.

Do you have a hum problem the echoke is to fix? As you say, I think you need more than 5v margin. I could be possible if the ripple at that point is only a volt or so P/P

davebms · Post by **davebms** » Mon Sep 13, 2010 11:18 pm

Nick wrote:If you were buying them now, I would suggest 300v or above, but 250v will be fine, 205v across 250v caps is ok, 12% below max, so not worth fretting about IMHO.

Do you have a hum problem the echoke is to fix? As you say, I think you need more than 5v margin. I could be possible if the ripple at that point is only a volt or so P/P

This is "our" E-choke is it? yes mike it is. 30v is to much !

yes nick the thing is 1980s , so i am going to re cap it ,prob better diodes and resistors etc . but i can hear Maine's type hash, and all other post on this amp indicate that improved power supply helps

MICK H do you do an equvilant to hammond 159Q choke ! thiS is prob the simple answer to improve the amp

Mike H · Post by **Mike H** » Mon Sep 13, 2010 11:38 pm

Well there's what was the old Maplin ST28F, 10H, 100mA, 150 Ohms

Now coded VT495

davebms · Post by **davebms** » Tue Oct 19, 2010 9:54 pm

[quote="Mike H"]Well there's what was the old Maplin ST28F, 10H, 100mA, 150 Ohms

hello all. i fitted new power supply caps and fast diodes ,i a little better
then i put the choke in, i thought poss its resistance may be a bit high but no its all good, ht ok no smoke or fire ,and its made a BIG improvement
i think shielding the mains transformer from the output transformers
will also help( its all in a small steel shoe box )will aluminium sheet be ok ?

Post by **Nick** » Tue Oct 19, 2010 10:15 pm

Ali will be good to shield static fields. Is it a toroidal mains tx, if so, its always worth if you can to rotate it till the lowest him is produced. They tend to "spray" field from where the leads come out.

davebms · Post by **davebms** » Tue Oct 19, 2010 10:47 pm

Nick wrote:Ali will be good to shield static fields. Is it a toroidal mains tx, if so, its always worth if you can to rotate it till the lowest him is produced. They tend to "spray" field from where the leads come out.

thanks nick. yes its a toroidal mains, with long leads so i can try rotating it

Mike H · Post by **Mike H** » Wed Oct 20, 2010 12:42 am

FWIW I tend not to like steel cases as I've found it "conducts" the magnetic fields all over the place

Aluminium is preferred

little mick · Post by **little mick** » Wed Oct 20, 2010 3:05 am

Hello

In my experience you will need to isolate the mains trany to reduce hum

Mike H · Post by **Mike H** » Wed Oct 20, 2010 12:48 pm

If you mean remove it away from the amplifier, that's what I've discovered too.

little mick · Post by **little mick** » Thu Oct 21, 2010 2:44 am

Well shield the O/P transformers from the mains transformer i.e. with an insulation plate (metal)

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