AC/DC & POWERSTATION KIT BUILD THREAD

[band_master]

hello Joe,
i am building an ac/dc kit for a PSU to power 4 channels of a 1290 clone preamp. it seems i might be one of the first to use the v4 PCB boards for this project...the excellent assembly instructions provided by the designer of the 1290 PCBs references using the D coupler setting, while the "neve mod" referenced on the back of the v4 PCB specifies the T coupler setting. I am also uncertain about the transformer wiring to the v4 PCB. here is a link to the assembly instructions, the ac/dc section can be found on page 8 of the pdf.

http://s3.amazonaws.com/EZ1290/assembly4.pdf

this is the toroidal transformer spec:

http://search.digikey.com/scripts/DkSea ... TE62085-ND

i bridged the pins on C8 and set the coupler to the T setting. the toroidal is wired to the IEC socket in parallel, I used the PCB wiring below:

AC: green
0v: red
0v: brown
AC: blue

I tried to power it up last night and blew the fuse in the IEC socket. Can you confirm the"neve mod" with bridged C8, T coupler setting and wiring to the PCB from the transformer are correct for the v4 AC/DC kit PCB?

Also, at first I mounted the +48 regulator in the -V position and had to switch them around. I'm afraid I might have damaged the LM317, could that cause a blown fuse at the IEC socket?

thanks,
BD

[Joe Malone]

hello Joe,
i am building an ac/dc kit for a PSU to power 4 channels of a 1290 clone preamp. it seems i might be one of the first to use the v4 PCB boards for this project...the excellent assembly instructions provided by the designer of the 1290 PCBs references using the D coupler setting, while the "neve mod" referenced on the back of the v4 PCB specifies the T coupler setting. I am also uncertain about the transformer wiring to the v4 PCB. here is a link to the assembly instructions, the ac/dc section can be found on page 8 of the pdf.

http://s3.amazonaws.com/EZ1290/assembly4.pdf

this is the toroidal transformer spec:

http://search.digikey.com/scripts/DkSea ... TE62085-ND

Neve mod is only needed if the voltage between the AC in is only 22 to 25v and nothing goes to the 2 x 0v terminals. You have 44vac with this transformer so no Neve or other mod is needed. Just build normally.

i bridged the pins on C8 and set the coupler to the T setting. the toroidal is wired to the IEC socket in parallel, I used the PCB wiring below:

With 2 x 22vac transformer above no mod needed. Remove short on C8 and set back to Doubler as assembly4.pdf mentions.

AC: green
0v: red
0v: brown
AC: blue

Correct. This is the only change from the assembly4.pdf. 0v on the AC/DC v2 and V3 has been moved from the front left corner to between the ACin's and there is 2 0v terminals on AC/DC v4.

I tried to power it up last night and blew the fuse in the IEC socket. Can you confirm the"neve mod" with bridged C8, T coupler setting and wiring to the PCB from the transformer are correct for the v4 AC/DC kit PCB?

This would have been a dead short as you had wires going to the 2 x 0v terminals and a short across C8. So should have saved everything on the PCB so far.

Also, at first I mounted the +48 regulator in the -V position and had to switch them around. I'm afraid I might have damaged the LM317, could that cause a blown fuse at the IEC socket?

Should be fine due to the input short mentioned above that would have blown the fuse. Remove short on C8 and set to D on front strap and retry. If you have moved the trim pots set them back to roughly half way before power up.

[band_master]

thanks, joe! i put the cap back in C8 and changed the coupler setting to D. fired it up, set the positive probe to the 48v terminal and the black probe to the 0v terminal and blew the fuse again. here are some pics of the build...hopefully an obvious mistake on my part?

http://flic.kr/p/ag76xu
http://flic.kr/p/ag76nY
http://flic.kr/p/ag6WvL
http://flic.kr/p/ag4b5k
http://flic.kr/p/ag4aYz

[Joe Malone]

[quote="band_master"]thanks, joe! i put the cap back in C8 and changed the coupler setting to D. fired it up, set the positive probe to the 48v terminal and the black probe to the 0v terminal and blew the fuse again. here are some pics of the build...hopefully an obvious mistake on my part?

First check that the fuse doesn't blow if the transformer is discounted from the AC/DC?
(This is just to check the fuse is big enough to sirvive the toroid power up surge. Most transformers have a recommended fuse value written on the side for 120v or 240v)
Second check none of the 1N4007 in the centre of the AC/DC PCB has gone short circuit.
(If the 1N4007s are ok then check for a solder short on the bottom of the PCB.)

Let me know how you get on

[band_master]

hey joe,
thanks again! i tested just now and the fuse does indeed blow when the transformer is not connected to the AC/DC PCB. here is a picture of the label on the xformer...where should i look for the fuse rating?

http://flic.kr/p/agD8gt

i am using 1A fuses...

http://search.digikey.com/scripts/DkSea ... e=F2419-ND

i found this on the digikey page for the xformer...since i am wiring in parallel i need 2A fuses?

Series Output Voltage @ Current 44 VAC @ 1.14A
Parallel Output Voltage @ Current 22 VAC @ 2.28A

http://search.digikey.com/scripts/DkSea ... &x=23&y=20

BD

[Joe Malone]

hey joe,
thanks again! i tested just now and the fuse does indeed blow when the transformer is not connected to the AC/DC PCB. here is a picture of the label on the xformer...where should i look for the fuse rating?

http://flic.kr/p/agD8gt

i am using 1A fuses...

http://search.digikey.com/scripts/DkSea ... e=F2419-ND

i found this on the digikey page for the xformer...since i am wiring in parallel i need 2A fuses?

Series Output Voltage @ Current 44 VAC @ 1.14A
Parallel Output Voltage @ Current 22 VAC @ 2.28A

http://search.digikey.com/scripts/DkSea ... &x=23&y=20

BD

Main thing with toroids is to use slow blow fuse that is as small enough in value that it will not blow on power up surge. So I would try 1A slow blow and see if it holds first. If it doesn't then 2A fast.

[band_master]

i got some 2A fast fuses and they will hold when the ac/dc is not connected, however when i connect the PCB the fuse still blows. i used a digital meter to check the diodes in the center of the board, the first and second diode looking from left to right in both rows was measuring just under 600 in both directions. when i removed the two diodes in the lower left corner near the "T" both diodes then read normally outside of the circuit?

also, once the two lower left diodes were removed the two left diodes in the upper row then measured normally as well. after I inserted a new 4007 into the lowest left position it read 600 in both positions and the far left diode in the upper tow started reading 600 in both directions too.

hope this info helps narrow it down? thanks again for your help!!!

thanks,
BD

[band_master]

hi joe,
just an update...i had another AC/DC board i bought for another project and decided to try it out with this toroidal. everything went smoothly dialing in 48v and 24v, so the PSU for my neve 1290 project appears to be all set. since the 4007s i pulled out of the old board were reading normally out of the circuit but I was getting just under 600 in both directions in the circuit I guess I must have burned a trace or something.

cheers,
BD

[Joe Malone]

hi joe,
just an update...i had another AC/DC board i bought for another project and decided to try it out with this toroidal. everything went smoothly dialing in 48v and 24v, so the PSU for my neve 1290 project appears to be all set. since the 4007s i pulled out of the old board were reading normally out of the circuit but I was getting just under 600 in both directions in the circuit I guess I must have burned a trace or something.

cheers,
BD

You need to use a diode test function on your multimeter not ohm setting to test diodes in circuit. If diodes are ok then can only be the regulators that are faulty if none of the capacitors have puffed up.

[alistair]

Hi Joe,

I've got a couple of AC/DC and Powerstations in operation in my studio, and all running great. Thank you! They get used everyday and have given me no dramas (maybe a couple that were my fault when building, but once I got them correct they've been great).

I was wondering if you thought a Powerstation would be able to be used a power supply for guitar pedals? I've got an odd collection that require 9v, 12v and 24v and I can't seem to find an off the shelf supply that will do all this easily. I've got a spare Powerstation board at home and thought that might work well.
I'm assuming I could just use a 12-15v transformer and the 48v line to achieve 12v, but I'm wondering if I will get any problems if I choose to go via this route. The marketing spin for guitar stuff seems to carry on about isolated outputs etc, but I know the Powerstation has been whisper quiet in the past.

Would there be problems with getting a steady voltage if I was plugging in/out pedals? I know in the past I've had to readjust the trimmer resistors for correct voltage under load. I'd hate to do that, unplug a pedal and have the voltage jump up higher and fry something.

[Joe Malone]

Hi Joe,

I've got a couple of AC/DC and Powerstations in operation in my studio, and all running great. Thank you! They get used everyday and have given me no dramas (maybe a couple that were my fault when building, but once I got them correct they've been great).

I was wondering if you thought a Powerstation would be able to be used a power supply for guitar pedals? I've got an odd collection that require 9v, 12v and 24v and I can't seem to find an off the shelf supply that will do all this easily. I've got a spare Powerstation board at home and thought that might work well.
I'm assuming I could just use a 12-15v transformer and the 48v line to achieve 12v, but I'm wondering if I will get any problems if I choose to go via this route. The marketing spin for guitar stuff seems to carry on about isolated outputs etc, but I know the Powerstation has been whisper quiet in the past.

I have made several of these type of custom boxes for silverchair and wolfmother but you need to know your pedals very well as you have to be sure if there phone jack sheild connections on the pedal are all direct to 0v and then is the power is used as a positive or negative rail or is it vertically half rail split. Hench why it is easier if the all DC outputs are electrically isolated as you not need to think about it.

Would there be problems with getting a steady voltage if I was plugging in/out pedals? I know in the past I've had to readjust the trimmer resistors for correct voltage under load. I'd hate to do that, unplug a pedal and have the voltage jump up higher and fry something.

No the regs will keep the voltage regulated over a large current range as long as they are well heatsinked. If you are getting variations under different load then look at your heatsinking.

[alistair]

Hi Joe,

Thanks for the reply. The board was halfway stuffed, so I knocked it up quickly last night and was having a test earlier today. You're spot on with both bits of your advice, these are the problems I'm having!
All pedals are working well when used one at a time, except for one, a Deluxe Memory Man which claims to be positive tip 24v, 100ma. After having burnt out a few resistors on the board it turns out it's actually positive tip going to ground, with -24v on the shield. A bit of a pain, but as you suggested, not something that you need to know when using isolated outputs or separate power supplies.
Is there a way to achieve -24v with the Powerstation if I'm using a 15v transformer? I'm assuming -V1 and -V2 won't get there and the 48v can't be converted to negative?


Also, voltage drop is quite significant when plugging pedals in. If I plug in one pedal that has a high current draw (12v, 300mA), it drops both the 9v and 24v lines by 3v each. Even small current pedals (9v, 30mA) affect the other lines by 0.2v or there abouts. Thanks for the thoughts on heatsinking, at the moment the tabs are just attached to the metal case, so I'll try some heatsinks and hopefully that will cure this issue.

For what it's worth, at the moment I have the -V set to around 9v each, with nothing attached. I assume this is fine.

[alistair]

Hi Joe,

Still battling with these problems. I initially had the voltage regs remote mounted to the side of the case, but was getting fluctuating voltages when plugging/unplugging pedals so I mounted them directly onto the board, and attached heatsinks. This hasn't fixed the issue, so I've replaced the voltage regs but I still can't stop the voltage from fluctuating. Are there any other parts of the circuit that I could investigate to stabilise this?

[Joe Malone]

Hi Joe,

Still battling with these problems. I initially had the voltage regs remote mounted to the side of the case, but was getting fluctuating voltages when plugging/unplugging pedals so I mounted them directly onto the board, and attached heatsinks. This hasn't fixed the issue, so I've replaced the voltage regs but I still can't stop the voltage from fluctuating. Are there any other parts of the circuit that I could investigate to stabilise this?

The regs if they have enough unreg voltage into them to regulate and as long as the unreg volts can supply the current without sagging will not fluctuate at all. Small separate heatsinks are not what I call real heatsinking. So the thing to look at is the unreg voltage across the 1000uF 50v caps is staying at least 5v or more highert than the reg voltage you need when under full load or check the ac volts coming in isn't sagging. As thew fluctuating voltage can only be due to overheat, not enough current or volts from the transformer.

So have you worked out the size and voltage of the transformer you are using with the JLM Calculator on the build thread to make sure it is big enough?

[alistair]

Thanks for your reply Joe.

Yes, I used your calculator to VA needs. I'm using a 15v 50VA transformer, as your calculator suggested I needed 41VA when I entered very overspec'd values. I'm getting a voltage dip even if I just plug in one 50mA draw pedal, but I used values of 600 and 700mA for the 12v and 9v taps, and 400ma for the 24v.

I've done as you suggested and checked values at the AC points on the board, and also the caps 1000uF caps. The voltage is sagging at the AC points if I plug in a single pedal- from 16.42v to 16.28v when drawing about 300mA of current, and from 16.42v to 16.39v when about 50mA is drawn. I'm not sure if this is within reasonable amounts of if it should remain steady regardless.

Also, I've checked under the board, and only C1 and C2, and the Bridge rectifier are giving me 16v, the other caps are significantly lower and fluctuating. I'm guessing this could be the issue and I should replace them??