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Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Thu Feb 13, 2014 8:37 pm
by Joe Malone
quantyk wrote:And i suppose if i got hasty and didn't change the jumper back to doubler, then the +48V caps would blow? perhaps because now they're getting way more volts than they're rated for? :oops:
Yes that would definitely happen and the 48v regulator may be fried if the 47R 1w resistor didn't save it. But you might be ok.

Voltages won't adjust on AC/DC

Posted: Thu Mar 27, 2014 10:42 am
by substitute
Boy does this make me feel dumb, I must be missing something really easy...

I'm using the AC/DC version 4 power supply, with a 24vct transformer. My +48v rail is behaving just fine. The +/- rails however are both putting out 17vdc max. I need +24 for two telefunken modules. I measured 18vdc on the input pin of the LM317.

I'll start sleuthing, but any test points or advice are always appreciated. Thanks!

Re: Voltages won't adjust on AC/DC

Posted: Thu Mar 27, 2014 11:42 am
by Joe Malone
substitute wrote:Boy does this make me feel dumb, I must be missing something really easy...

I'm using the AC/DC version 4 power supply, with a 24vct transformer. My +48v rail is behaving just fine. The +/- rails however are both putting out 17vdc max. I need +24 for two telefunken modules. I measured 18vdc on the input pin of the LM317.

I'll start sleuthing, but any test points or advice are always appreciated. Thanks!
The AC/DC is working perfectly. As you should be using a 2 x 24vac transformer or 48vct transformer to get +/-24vdc with 48v set to doubler.

But since you only need +24v the transformer you have will be fine but you need to do the Neve mod written under the PCB.

Note 1 Neve Mod
1.Wire the 24vac between both AC in on the AC/DC like you have already but you must REMOVE the transformer centre tap from the 0v connection as it is not used in the Neve mod.
2.Add the link wire to short out C8
3.And set doubler-tripler jumper to TRIPLER which I think you would have done already since your 48v was working.

You will now we able to set +24v and 48v.

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Thu Mar 27, 2014 11:52 am
by substitute
Well, it sure seems obvious when you put it that way. Thanks Joe.
:lol:

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Fri Jul 04, 2014 10:44 am
by stitchy
Hello!

I have a Powerstation I built and have two quick questions:
ZD39 Is a zener diode? Should it be stuffed on the PS?
I did not have one in my build kit and it is not populated on the powerstation.

Second: I have a Triad F-241U power transformer. Will this work to power the Powerstation?

Cheers and thanks!

-s

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Sun Jul 06, 2014 8:26 am
by Joe Malone
stitchy wrote:Hello!

I have a Powerstation I built and have two quick questions:
ZD39 Is a zener diode? Should it be stuffed on the PS?
I did not have one in my build kit and it is not populated on the powerstation.

Second: I have a Triad F-241U power transformer. Will this work to power the Powerstation?

Cheers and thanks!

-s
Zeners have not been used in powerstation kits for about 10 years. All diodes are 1N4007 these days since the adding of the 47R 1W resistor current limit resistor.

Build powerstation as the PCB overlay shows as it has the correct parts values on it.

That transformer is 18v centre tapped so with centre tapped wired to 0v and each end to AC in it will be good for +/-9vdc max

Or if centre tapped not used and one end wired to 0v and the other end wired to one of the AC in it will be good for +/-18vdc max.

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Mon Jul 07, 2014 3:20 am
by stitchy
Joe Malone wrote:
stitchy wrote:Hello!

I have a Powerstation I built and have two quick questions:
ZD39 Is a zener diode? Should it be stuffed on the PS?
I did not have one in my build kit and it is not populated on the powerstation.

Second: I have a Triad F-241U power transformer. Will this work to power the Powerstation?

Cheers and thanks!

-s
Zeners have not been used in powerstation kits for about 10 years. All diodes are 1N4007 these days since the adding of the 47R 1W resistor current limit resistor.

Build powerstation as the PCB overlay shows as it has the correct parts values on it.

That transformer is 18v centre tapped so with centre tapped wired to 0v and each end to AC in it will be good for +/-9vdc max

Or if centre tapped not used and one end wired to 0v and the other end wired to one of the AC in it will be good for +/-18vdc max.
Hi Joe, Thank you for your replies.
I'm building a makeup amp for an EQ (using your Pultec makeup amp schemo) using a pair of your 99V opamps. The schematic I have says 15+/- to the opamps.
Pretty sure it your original opamps and not the new 16+/- version.
Is 15+/-VDC is the voltages I am looking for?

So 30VAC CT PT is what I need to get?

Cheers and thanks again!

-s

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Mon Jul 07, 2014 7:34 am
by Joe Malone
stitchy wrote:
Hi Joe, Thank you for your replies.
I'm building a makeup amp for an EQ (using your Pultec makeup amp schemo) using a pair of your 99V opamps. The schematic I have says 15+/- to the opamps.
Pretty sure it your original opamps and not the new 16+/- version.
Is 15+/-VDC is the voltages I am looking for?

So 30VAC CT PT is what I need to get?

Cheers and thanks again!

-s
If you have original JLM99v best to go for +/-24vdc. So use a 44 to 48vac CT transformer.

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Tue Sep 23, 2014 9:24 am
by sgaudio
HI Joe,
I'm finally getting around to building the powerstation to power and old DBX card. I've built about a dozen 3 rail PS, but this is the first 5 rail i've done, and I've run into a problem. I wanted to see if this transformer is suitable for this build:

http://www.digikey.com/product-detail/e ... -ND/952925

I'm measuring 29VAC across the two AC leads on the secondary, and have attached these to the AC point on the PC board, along with the center tap to the 0V on the board. I have the double strapped, but am only getting a max of about 36Vdc at the 48V point, and all the other V+ and V- read 17V, and the trim pots are making to change to the voltage. I'm thinking there might be a grounding issue? Should the center tap be connected on this particular transformer? I need to see +/-24vdc and +/-15vdc at the outputs. I usually use a torroidal transformer, So I'm thinking it could be something with the way this one is wired.. ANy help would be appreciated!
Thanks
Steve G

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Tue Sep 23, 2014 9:53 am
by Joe Malone
sgaudio wrote:HI Joe,
I'm finally getting around to building the powerstation to power and old DBX card. I've built about a dozen 3 rail PS, but this is the first 5 rail i've done, and I've run into a problem. I wanted to see if this transformer is suitable for this build:

http://www.digikey.com/product-detail/e ... -ND/952925

I'm measuring 29VAC across the two AC leads on the secondary, and have attached these to the AC point on the PC board, along with the center tap to the 0V on the board. I have the double strapped, but am only getting a max of about 36Vdc at the 48V point, and all the other V+ and V- read 17V, and the trim pots are making to change to the voltage. I'm thinking there might be a grounding issue? Should the center tap be connected on this particular transformer? I need to see +/-24vdc and +/-15vdc at the outputs. I usually use a torroidal transformer, So I'm thinking it could be something with the way this one is wired.. ANy help would be appreciated!
Thanks
Steve G
The transformer in the link only has 1 x 24vac which doesn't have a centre tap at all? It is also only 6VA = 6watt which will not drive much as well.

You can try and see if it will work for the power rails you want by moving one end of the 24vac to 0v so the 24vac winding is between one AC in and 0v.t

Not sure want centre tap you have wired to the 0v as there isn't one?

This will give you all the voltages you want but under load I am not sure the 6VA will be enough without knowing the current draw on the different power rails.

Make sure you wind back the 48v trim pot to the middle before repowering. Turn until you here a click over and over and then wind back 12 full turns.

Ideally you should usually be running a 2 x 24vac or 48v centre tap transformer to do the above power rails. And minimum VA is usually 25VA for most jobs.

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Tue Sep 23, 2014 10:01 am
by sgaudio
Thanks Joe. I was going off this diagram which looks like there's a CT on the secondary:
http://media.digikey.com/pdf/Catalog%20 ... _SCHEM.jpg

I used your calculator and it looked like 6va was enough, I'm powering one DBX 902 deesser card which doesn't have much curent draw. I'll go ahead and order a new transformer though, i've always used the torroidal ones with good results anyways, no sense experimenting now! Thank you!
SG

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Tue Sep 23, 2014 10:13 am
by Joe Malone
sgaudio wrote:Thanks Joe. I was going off this diagram which looks like there's a CT on the secondary:
http://media.digikey.com/pdf/Catalog%20 ... _SCHEM.jpg

I used your calculator and it looked like 6va was enough, I'm powering one DBX 902 deesser card which doesn't have much curent draw. I'll go ahead and order a new transformer though, i've always used the torroidal ones with good results anyways, no sense experimenting now! Thank you!
SG
Ok the description and diagram don't line up. But either way if it is centre tapped and you wire it the way you have it is only 12vac - 0v - 12vac so the highest voltage you will get for +/-V is only 15vdc. So do as I said in the previous post but make sure the centre tap is not connected to anything at all. That way you will have 1 x 24vac between 0v and one of the AC ins which will give you all the voltage you want but if they sag to lower voltages when you connect the DBX it is because there is not enough current available from the transformer as its max ac current is 250mA which in dc terms is only 150mA total for all DC rails (so about 38mA per rail).

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Mon Sep 29, 2014 1:19 pm
by sgaudio
Hi Joe,
Ok... i'm know i'm doing something obvious, but for a sanity check:
I took your advice and picked up a triad torodial transformer, ive used about a dozen of these with good results

http://www.mouser.com/ProductDetail/Tri ... OQIg%3d%3d

I have the secondary wired in series for 24V CT
I have the center tap connected to 0V and the black and yellow wire connected to AC. I'm measuring 27VAC across the black and yellow lead, but the output of the PS is only reading 16.5V across all the rails, and 34V for the 48V rail. Adjestments to any of the pots makes no change to the output DC voltage.

Should I have the 0V CT disconnected??

Like I said, i'm sure i'm missing the obvious, thanks for your help!
image.jpg

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Mon Sep 29, 2014 1:42 pm
by Joe Malone
sgaudio wrote:Hi Joe,
Ok... i'm know i'm doing something obvious, but for a sanity check:
I took your advice and picked up a triad torodial transformer, ive used about a dozen of these with good results

http://www.mouser.com/ProductDetail/Tri ... OQIg%3d%3d

I have the secondary wired in series for 24V CT
I have the center tap connected to 0V and the black and yellow wire connected to AC. I'm measuring 27VAC across the black and yellow lead, but the output of the PS is only reading 16.5V across all the rails, and 34V for the 48V rail. Adjestments to any of the pots makes no change to the output DC voltage.

Should I have the 0V CT disconnected??

Like I said, i'm sure i'm missing the obvious, thanks for your help!
image.jpg
Yes as explained in the post above. That is all working correctly then. 24v CT = 2 x 12vac so peak unregulated +/-V will be about 12vac x 1.4 = 16.8v (so 48v rail would see 2 x this = 33.6v unreg). So max well regulated rail would be +/-12vdc.

I think you might of wanted to buy a 2 x 24vac or 48v CT transformer to get 48v CT = 2 x 24vac so peak unregulated +/-V will be about 24vac x 1.4 = 33.6v. So max well regulated rail would be +/-28vdc (so 48v rail would see 2 x this = 67.2v unreg to make 48vdc)

You can as also explained in my last post disconnect the centre tap and not use it at all and connect one end of the 24vac to 0v and one end to AC in which will work like a 48v CT except with only be 50Hz half wave rectified so is only recommended for small current loads.

MAKE SURE YOU WIND ALL TRIM POTS BACK 12 TURNS BEFORE RECONNECTING THE POWER TRANSFORMER.

Re: AC/DC & POWERSTATION KIT BUILD THREAD

Posted: Mon Sep 29, 2014 1:46 pm
by sgaudio
Thanks Joe. After i reread my post I figured that was the case. Not sure why it didn't sink in the first time! I remember your old AC/DC boards only having two connections, and I left the center tap unconnected, so I think I was just confused with the newer version boards, with the two AC and 0V connections.

Anyways, thanks again!