APP Studio Ing's products - APP992 - APP14GE Germanium DOA and other kits

[muffy1975]

Hi,

thankyou for my PSU. It's arrived today and looks wonderful.

I am using a 30va 25v transformer and I can't get the + rail down to 24V. The 48V rail is measuring 61V. Is this cos I'm in the UK?

How can I reduce these voltages? I have trimmed them as far back as possible with the trimmers!

Are there a few resistors I can change?

Many thanks

Michael

 

[ppa]

Hi,

thankyou for my PSU. It's arrived today and looks wonderful.

I am using a 30va 25v transformer and I can't get the + rail down to 24V. The 48V rail is measuring 61V. Is this cos I'm in the UK?

How can I reduce these voltages? I have trimmed them as far back as possible with the trimmers!

Are there a few resistors I can change?

Many thanks

Michael

your psu was modified from the original schematic to operate with the neve channels but it can work very fine with a fine trimmer setting. To set well it you should connect a load on the out that you have to fix. The +48V setting should be made with a 6.8k resistor on this out, or a 10k, 12k , 15k resitor. The same resistor can be used for the +24V. To test you can use the resistor used for the led to indicate the on state, it's easy to do: connect the LED- out to the out you have to setting, so for test the 48V out, connect the LED- out to +48V out and after set the voltage of this out at +48V.

 

[ppa]

Hi,

thankyou for my PSU. It's arrived today and looks wonderful.

I am using a 30va 25v transformer and I can't get the + rail down to 24V. The 48V rail is measuring 61V. Is this cos I'm in the UK?

How can I reduce these voltages? I have trimmed them as far back as possible with the trimmers!

Are there a few resistors I can change?

Many thanks

Michael

your psu was modified from the original schematic to operate with the neve channels but it can work very fine with a fine trimmer setting. To set well it you should connect a load on the out that you have to fix. The +48V setting should be made with a 6.8k resistor on this out. The same resistor can be used for the +24V.

However, the psu that I've modified to operate with neve preamps, worked very fine, so I think that there are no problems to fix your PSU. Can you send me a picture with the power trasformer connections?

 

[muffy1975]

HI,

which power transformer did you use?

With both Ez1290s connected the + rail is 25V and the phantom power when on measures 52v at the psu.

here is a picture. The yellow and black are in the centre and the red goes to one side and the orange to the other.

Hope I can pad this voltage down

Michael

 

[ppa]

do not connect the AC power !!!!!!!!!!!!!!!!!!!!!!!!!!!!! danger !!!!!!!!!

THE AC FUSE IS NOT ISOLATED!!!!!!!!!!!!!!!!!!!!!!!!!!!!

DANGER!!!!!!!!!!!!!!!!!!!!!!!

THE PSU PCB IS NOT WELL ISOLATED, THE 4700uF CAP CAN EXPLODE!!!!!!!!!!!!

 

[Sredna]

Michael!

PLEASE, PLEASE, PLEASE!

Mount the fuse holder properly and isolate at least the high voltage cables better!

If the fuse holder comes loose, you´ll have 240V in the case and possibly through your
body as well....

Take care (I mean it),

Anders

 

[ppa]

Mount the fuse holder properly and isolate at least the high voltage cables better!
do not connect the AC power !!!!!!!!!!!!!!!!!!!!!!!!!!!!! danger !!!!!!!!!

DANGER!!!!!!!!

 

[muffy1975]

hey,

thanks for the warning guys!!! The PSU has two layers of electric tape underneath and a thin foam layer. The fuse holder is bolted down there's just no cover on in at the moment.

Back to the PSU. ;D How am I going to pad down the voltage?

Michael

 

[ppa]

hey,

thanks for the warning guys!!! Will redo this section.

Back to the PSU. ;D How am I going to pad down the voltage?

Michael

the dinner went me sideways for the fright.

 

[ppa]

hey,

thanks for the warning guys!!! The PSU has two layers of electric tape underneath and a thin foam layer. The fuse holder is bolted down there's just no cover on in at the moment.

Back to the PSU. ;D How am I going to pad down the voltage?

Michael

What's the voltage across the 4700uF cap's leads? You should measure it after all is well isolated! PLEASE!

 

[muffy1975]

There is 43V DC across the legs of the 4700uf cap! Any good?

Michael

 

[ppa]

There is 43V DC across the legs of the 4700uf cap! Any good?

Michael

the trasformer could be bad connected. Could you send me the trasformer's datasheet by email? please.
There is 43V DC across the legs of the 4700uf cap also with the neve preamps connected?

 

[ppa]

if the power on led (the red led connected to LED- and LED+ outs of the PSU board) sheds light you can use the trimmer to set the +24V out for +24V even if there is 43V on the 4700uF cap.

 

[muffy1975]

Hey,

the trimmer is fully turned and I get 25V! If I go the other way the voltage only increases. The Red LED lights up.

I have sent you the transformer data sheet, it's the 30va 25v model

Michael

 

[ppa]

I've received the datasheet and also cheched the trasformer's connections that're good.
At this point, what's the voltage across R4?
To fix the problem you can use an 4.7K 1/4W resistor for R3 and resetting the trimmer for 24V, I suspect that the LM317 used is a bit out of tollerance but it work well the same.
Have you 25V with the neve preamp on?

However the PSU runs, it is only that LM317 used is a bit out of tollerance and the AC voltage is high.

 

[muffy1975]

The Neve's are both receiving 25V

I have 1.3v DC with my probes either side of the resistor R4

 

[muffy1975]

Cool Cool,

will try changing to 4.7k for R3

Will let you know what happens 8)

Thanks for your help my man ;D

 

[ppa]

I suppose fine, is the LM317 out of tollerance but works fine the same. If you change R3 with a 4.7kohm you can set the trimmer for +24V.

The LM317 heatsink I suspect that's a bit hot, isn't it?

Pay Attention to the heatsink temperature.

 

[muffy1975]

Yeah the LM317 is hot.

But i have 24V ;D So that's now very good

The +48v is reading 60V when not beng used, and when being used with a microphone is measuring 48V Is that correct?

Michael

 

[naths101]

Interested in the APP2050 germanium, do you have an ETA?
Cheers

Scuse me but what means ETA ?

sorry, 'estimated time of arrival'... that is when will they be available?
thanks