bias issues
Hi
I have F5 (V3) powered up, 24,4V on the rails, started with a variotrafo and no smoke...
But i cant bias R7 / R8 above 200mV.
Now I have meassured idss on my sk170 /sj74 (9v battery, no resistors) to 4,1mA. I have searched threads and found that I have to increase R5/R6. How much?
Or is there a way to calculate "right" value for drain resistors, now knowing idss????
(I actually started out with all resistor wrongly placed regarding V2/V3 labeling - sigghh, all replaced and pretty sure nothing is roasted.)
baek47
Hi
I have F5 (V3) powered up, 24,4V on the rails, started with a variotrafo and no smoke...
But i cant bias R7 / R8 above 200mV.
Now I have meassured idss on my sk170 /sj74 (9v battery, no resistors) to 4,1mA. I have searched threads and found that I have to increase R5/R6. How much?
Or is there a way to calculate "right" value for drain resistors, now knowing idss????
(I actually started out with all resistor wrongly placed regarding V2/V3 labeling - sigghh, all replaced and pretty sure nothing is roasted.)
baek47
If you run at half Id you need double the resistance.
That Id*R gives the voltage drop across the gate/source of the output device.
That Id*R gives the voltage drop across the gate/source of the output device.
Hi AndrewT
Working! Thanks so much.
I have ~0,59V on all R//R8 - well it is drifting from 0,588V to 0,6V - is that normal?
I have dc offset - also drifting a bit - between 1 and 8 mV.
Time for music?
the best
baek47
Working! Thanks so much.
I have ~0,59V on all R//R8 - well it is drifting from 0,588V to 0,6V - is that normal?
I have dc offset - also drifting a bit - between 1 and 8 mV.
Time for music?
the best
baek47
Isolation Transformer
I've been trying to solve a problem with my F5 (no inputs connected) having a slight hum with my ear a few inches away from the speaker. Also a louder hum with the BA-3FE and Pearl II connected (ground loop), which can be heard from the listening position. I've tried different ways of grounding with no success.
I installed two Jensen JT-11P-1 isolation transformers (Thanks vdi_nenna) on the inputs of the F5 and the system is quite as a church mouse. The F5 still has a slight hum with no input connected but when the inputs are connected it's silent.
No downside so far, I've only listened to a few songs but I can't tell any difference from before other than the dead quite background.
As you can see one transformer is higher than the other. I let my 7 year old son drill the holes in the chassis. It got away from him a little. Hey anything to get the kids involved, right?
I've been trying to solve a problem with my F5 (no inputs connected) having a slight hum with my ear a few inches away from the speaker. Also a louder hum with the BA-3FE and Pearl II connected (ground loop), which can be heard from the listening position. I've tried different ways of grounding with no success.
I installed two Jensen JT-11P-1 isolation transformers (Thanks vdi_nenna) on the inputs of the F5 and the system is quite as a church mouse. The F5 still has a slight hum with no input connected but when the inputs are connected it's silent.
No downside so far, I've only listened to a few songs but I can't tell any difference from before other than the dead quite background.
As you can see one transformer is higher than the other. I let my 7 year old son drill the holes in the chassis. It got away from him a little. Hey anything to get the kids involved, right?
Ha! Even the brackets came in handy! Glad they are being used! I originally got them to solve a hum problem in my F5 in an active two-way.
Cool! 😉
Vince
Cool! 😉
Vince
I still haven't connected speakers or signal.
F5 has benne powered for hours....
There is continuity between "out" on the 2 F5 boards???????
F5 has benne powered for hours....
There is continuity between "out" on the 2 F5 boards???????
Do you mean infinite continuity (no resistance)
I just checked my F5 at the + speaker terminals and there is continuity but ~60Ω resistance.
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There is music.....succes!
Thanks for all your help............I'm very grateful.
I will upload picture of my baby playing, just a little trouble uploading now.
The best from
baek47, Copenhagen
Thanks for all your help............I'm very grateful.
I will upload picture of my baby playing, just a little trouble uploading now.
The best from
baek47, Copenhagen
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Please forgive me if I am being blind but I can't find this anywhere.
What are the spec on the Thermistors for an F5 power supply using the universal boards?
One shown on mains input for 240v
And one to ground.
Thanks.
What are the spec on the Thermistors for an F5 power supply using the universal boards?
One shown on mains input for 240v
And one to ground.
Thanks.
Maybe. I used both.
Generic ps schema say cl-60
See upper right corner of ps schmatic for small bold print.
http://www.diyaudio.com/forums/pass-labs/241729-aleph-j-illustrated-build-guide.html
Generic ps schema say cl-60
See upper right corner of ps schmatic for small bold print.
http://www.diyaudio.com/forums/pass-labs/241729-aleph-j-illustrated-build-guide.html
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CL60 suits big transformers rated for 110/120Vac mains power.
A CL60 does NOT suit 240Vac mains power.
Your transformer soft start needs a much higher resistance, than the 10 to 15ohms of a CL60.
Even two CL60 in series (for 240Vac) does not reduce the starting current enough to enable close fuse rating.
Papa used the CL-60 in the factory-built Firstwatts, so it's safe to assume it works.
If you think there is a better part, and there certainly may be, please suggest it instead of just announcing (and yelling via caps) that the recommend part is not appropriate.
If you think there is a better part, and there certainly may be, please suggest it instead of just announcing (and yelling via caps) that the recommend part is not appropriate.
CL60 is good enough for both 120 and 240Vac , in most cases , with fuse sized by simple rule A=VA / V