AKG N6128/23 power supply
« on: February 12, 2017, 07:06:53 AM »
Hi Folks, I bought a Philips badged AKG C12a with AKG N6128/23 power supply from a japan store.
Because the unit was operated with a step up converter, I opted to open the supply first.
Inside looks clean with 2 newer 2200 uF caps for the heater.
Mains ground pin is open, and there's no fuse.
The bottom side of the PCB looks like someone did a modification once.
The front shows heater setting for either the C12a/C61 or C28/C12, which is puzzling me.
The C12 needs an extra bias voltage and the supply has only a 6pin connector.
 
Does anyone have a schematic of this AKG N6128/23 power supply?
Cheers,  Erik


Khron

Re: AKG N6128/23 power supply
« Reply #1 on: February 12, 2017, 09:19:10 AM »
The different heater settings make a certain amount of sense - the schematics for the C12 and C12A show a 5v heater voltage for the C12A, and 6.3v for the C12.

That being said, the whole system is a bit different - the pattern selection for the C12 was a separate box, while the C12A seems to have the pattern selector included in the power supply.

http://www.filmsoundsweden.se/voxbilder/filmhist/akg-c12-schema1.jpg
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Re: AKG N6128/23 power supply
« Reply #2 on: February 12, 2017, 01:14:54 PM »
Here's a pic of the inside, as its a single layer, it would not be difficult to trace back to a schematic. But better would be the official one.

Re: AKG N6128/23 power supply
« Reply #3 on: February 12, 2017, 01:58:37 PM »
Front

Re: AKG N6128/23 power supply
« Reply #4 on: February 12, 2017, 01:59:31 PM »
Back view

Re: AKG N6128/23 power supply
« Reply #5 on: March 06, 2017, 11:47:39 AM »
Finally had some time to do some examination:
Much of the components are from the N24S supply, so summing up the differences:
The heater caps were changed, now 2200uF. I cannot say which value was used originally.
To get the heater voltage down resistors in line and as load have been added.
GND pin from the IEC mains connector was not connected to casing.
The lamp has a resistor inside, don't know if its a GF21 but it does not affect functionality.
Diode for the 120V is a BY142.
So attached is the schematic of how I found it. This is not in any way meant to be an original schematic.

Cheers, Erik

Khron

Re: AKG N6128/23 power supply
« Reply #6 on: March 06, 2017, 07:52:58 PM »
As long as the output voltages are what they should be, and the power supply is capable of providing the needed current, i couldn't care less about the exact values of the components used :P
 If anything, i might even be inclined to replace / upgrade the electrolytics (stock ones being old, etc).

... But that's just me :)
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pucho812

Re: AKG N6128/23 power supply
« Reply #7 on: November 07, 2019, 11:33:32 PM »
This is an old thread but we have a couple of those supplies at our studio.

It's hard to get in there but one of ours is wired for 220V,   As we are in the U.S. what needs to change to make it run on 110V?
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

Re: AKG N6128/23 power supply
« Reply #8 on: November 09, 2019, 07:37:28 AM »
Although the type label says 110/220 V~, they do not have 2 sets of primaries, only 1.
Either you'll need new transformers in there or a step-up transformer.

analogguru

Re: AKG N6128/23 power supply
« Reply #9 on: November 09, 2019, 09:38:34 AM »
Although the type label says 110/220 V~, they do not have 2 sets of primaries, only 1.
Either you'll need new transformers in there or a step-up transformer.
If it is like in the schematic then you only need to rewire the two (110V) primaries in parallel (which are now in series).


Re: AKG N6128/23 power supply
« Reply #10 on: November 09, 2019, 10:04:32 AM »
It's not the original schematic, I photoshopped it from the N24 schematic.
That is drawn with 110V/220V switch

analogguru

Re: AKG N6128/23 power supply
« Reply #11 on: November 09, 2019, 10:13:56 AM »
It's not the original schematic, I photoshopped it from the N24 schematic.
That is drawn with 110V/220V switch
I was talking about your photoshopped schematic.
Quote
If it (the reality) is like in the (photoshopped) schematic then you only need to rewire the two (110V) primaries into parallel (which are now in series).

Re: AKG N6128/23 power supply
« Reply #12 on: November 09, 2019, 11:20:55 AM »
I have a set of Philips badged AKG C60's (1966 vintage) with a similar power supply.  The fuse is a thermal link in the power transformer.  Might be worth modifying the incoming AC with a 150 ma (or closest value) fuse so the fuse will go before the transformer in the event of a rectifier short, etc.

Look carefully inside the power supply for a link for 110/220 volt operation.  It should be labeled.  Move or connect the link for the incoming AC voltage and put a label near the power cord/socket.