Thanks John
L. Board:
26,1 volt on Emitter of Q3
20,2 volt on Base of Q5
R18-R21 are 10K
I think that the Q3 is "dead" because yesterday I checked 24,6 on Emitter and 17 volt on Base of Q5
R. Board:
24,6 volt on Emitter of Q3
18 volt on Base of Q5
R18-R21 are 10K
Yes, I used 10k on R18 and R21
Regards
Okay, well, the voltages you get at the base of Q5 on both boards doesn't make sense because it should be very close to 1/2 the voltage of the emitter voltage of Q3. The voltages you measure are much higher than 1/2 that voltage.
So, that's why I suggested you actually measure the resistances R18 & R21 with an ohmmeter, cause there maybe be a problem with a solder connection there or a problem with the Q3 transistors.
Anyway, that's very strange. Hope you can get that solved.
I agree, it looks like Q5 on the left board is damaged.
So, that's why I suggested you actually measure the resistances R18 & R21 with an ohmmeter, cause there maybe be a problem with a solder connection there or a problem with the Q3 transistors.
Anyway, that's very strange. Hope you can get that solved.
I agree, it looks like Q5 on the left board is damaged.
An externally hosted image should be here but it was not working when we last tested it.
Well now I would like add a Led on board. Can I used the Pad 4?
Thanks to all for your patience
Regards
No ! Pad4 is intended to use a 9V battery in place of the zener if you want ... It's a reference place for the regulation. Don't use that spot or you would add problems !
If you experience too much noise (hiss) in case of low gain cart, you can remove the zener and try to use 9V battery instead. It should be a tad quieter in high gain cases.
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I would use a Led + series resistor between V+ and Ground pads. You can use unreg DC if you're suspicious about adding a Led on regulated audio V+. It can be done too, as you wish.
Best,
nAr
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Depends if you use a high efficency one or standard.
Range between 10k and 68k should be ok. For my high eff white ones I use about 137k 0,25W on 48V
Best,
nAr
Attachments
Hello guys!
I added a 10K resistor to the LED and the result is very good, but when I turn off the LED takes a long time off. I guess adding greater resistance than take off.
I've been testing the masses and how best to go is as I have now (safety Earth).
On the other hand, wanted to ask if the voltage on Q8-12 zone is crucial. I have a voltage of 0.1 V in this area.
Regards
I added a 10K resistor to the LED and the result is very good, but when I turn off the LED takes a long time off. I guess adding greater resistance than take off.
I've been testing the masses and how best to go is as I have now (safety Earth).
On the other hand, wanted to ask if the voltage on Q8-12 zone is crucial. I have a voltage of 0.1 V in this area.
Regards
Thanks Zen
I can use +-37 or +-18 volt DC and the LED is a WP7104QBC/G (3.3 volt/20mA)
I would like the LED turns off slowly fod this I was think on a cap
Regards
LED resistor calc
say that you're going to use +/-18 ; that's 36Vac ;
say that you're going for max 3mA (plenty for any signal LED)
say that you're going for just one diode in series - that's half rectifier , so you'll have (roughly , but precise enough for purpose ) 36/2 x 1.41 volts DC after diode , with modest cap ; say that 10uF/50V is sufficient
so - we have around 25Vdc
R=U/I
R=(25-3,3)/0,003
R=21,7/0,003
R=7233 Ohms
use first standard value - say 7K5
without recalc of current with altered value , we assume that we still have near 3mA
so - dissipation in resistor is :
P=I^2 x R = 0,003^2 x 7500 = 67mW , so any small metal film resistor is good enough ( factor 3 is always min in my book)
so - secondary - just one diode - cap for smoothing - resistor - LED
easypeasy
if LED is still blinding ya from listening position , you can solve that in 3 ways :
1- turn case for 90 degs , so you can't see LED
2- glue something diffuse across LED (foil or something)
3 - increase value of resitor
say that you're going to use +/-18 ; that's 36Vac ;
say that you're going for max 3mA (plenty for any signal LED)
say that you're going for just one diode in series - that's half rectifier , so you'll have (roughly , but precise enough for purpose ) 36/2 x 1.41 volts DC after diode , with modest cap ; say that 10uF/50V is sufficient
so - we have around 25Vdc
R=U/I
R=(25-3,3)/0,003
R=21,7/0,003
R=7233 Ohms
use first standard value - say 7K5
without recalc of current with altered value , we assume that we still have near 3mA
so - dissipation in resistor is :
P=I^2 x R = 0,003^2 x 7500 = 67mW , so any small metal film resistor is good enough ( factor 3 is always min in my book)
so - secondary - just one diode - cap for smoothing - resistor - LED
easypeasy
if LED is still blinding ya from listening position , you can solve that in 3 ways :
1- turn case for 90 degs , so you can't see LED
2- glue something diffuse across LED (foil or something)
3 - increase value of resitor
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Thanks for your good reply Zen.
I keep your post, since it is very interesting and helpful.
I used the 18 volt (DC) and added thanks to your recommendation a cap 10 uF but I used a 10K resistor.
According to my calculations, the result would be: (18-3.3)/0.003= 4900 Ohm; 5K
The result is very good, turning off with a slow.
An externally hosted image should be here but it was not working when we last tested it.
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