[JohnerH]

Hi all,
 
I've got a pair of Stax SR-X in which the right driver takes a while to "charge".
 
Has anyone every tried to fix a Stax pair, or dismantle them?
 
J

 

[AmarokCZ]

If "while" means less then few minutes than my recommendation is: get over it!  

 
I have almost the same problem with SR-3N - I tried to do something with it, but there is not much to do with two metal plates with piece of plastic foil between them (if cable is OK - mine cable is OK).
So I accepted that there is nothing to do with it (no surprise considering its age). But it took approximately 5 hours to fully charge, so I made myself a "pocket charger" so I can turn amplifier off without loosing charge (especially useful if I'm away for few days).
 

 

[JohnerH]

Yeah my cable is perfect....
 
Where/how did you get charger? From what you said I'm assuming you made yourself? (I have never seen one b4)
 
Care to share how? 

 
J

 

[AmarokCZ]

I built it myself, but for home use you can use "energizer" (SRD-5 and others ... if you have one) - it consumes only 0.2W, but it's not portable ... 

 
Here is schematic of charger - it is really very simple design. R2 adjust output voltage to point when LED (high luminosity blue - even with this one it barely emits light) starts to shine with supply voltage approx 3V. Consumption from battery is approximately 400uA. 555 is cmos version (low quiscent current).

 
"Stax connector" is made from two cheap 3pin XLR connectors (it uses same pins).

 
 
BTW ... for home use you can made yourself mains powered "charger" (just 230V DC PSU), but it could be little dangerous, battery powed charger is extremely safe.

 

[JohnerH]

Quote:

I built it myself, but for home use you can use "energizer" (SRD-5 and others ... if you have one) - it consumes only 0.2W, but it's not portable ... 

 
Here is schematic of charger - it is really very simple design. R2 adjust output voltage to point when LED (high luminosity blue - even with this one it barely emits light) starts to shine with supply voltage approx 3V. Consumption from battery is approximately 400uA. 555 is cmos version (low quiscent current).

 
"Stax connector" is made from two cheap 3pin XLR connectors (it uses same pins).

 
 
BTW ... for home use you can made yourself mains powered "charger" (just 230V DC PSU), but it could be little dangerous, battery powed charger is extremely safe.

First of all, thank you for sharing...
Secondly, I'm still a noob electronics person, I'm slowly learned, so chances are I'm going to have to "deeply" analyse your schematic, in order to completly understand it.
 
I would ask, (given my noobness) if you could expand on your last sentence? R2.....
 
R2, is that name you've given it?
 
Again, thank you...
 
J
 

 

[AmarokCZ]

Well, it is just better to replace resistor R2 with resistive trimmer (5Mohm) and adjust this trimmer to point when LED starts to shine with supply voltage approx 3V ... this adjustment is to lower power consumption and to adapt charger for particular inductor L1.
 
R2=2.7M was OK for me, but if you use another L1 you'll have to change R2 (so use trimmer 5Meg for easier adjustment)...

 

[JohnerH]

Ok, I'm going to see if I can build this...
 
Is there a safe way to test it before actually putting my headphones in it?
 
J

 

[AmarokCZ]

This is quite a problem. Only way to test it is by looking at LED - it is OK when LED shines and current consumption is less than approx 1mA.
Output voltage drops almost to zero if you touch output with finger or ordinary mutimeter. You would need high impedance multimeter (mine has 1giga ohm) to measure output voltage properly.
 
You can add 470Kohm resistor in series with diafragm output pin to be on the safe side.