[Ronja] nebulus test points don't match

[Gullik Webjörn]

Put one or two diodes in series with the zener, each diode
will give you 0.6-0.7 V, i.e. 6.2 + (2*0.6) = 7.4.
Any small si diode will do. (check correct polarity!)

Gullik


On Sun, 2009-08-02 at 19:58 +0300, mohamad al-jamal wrote:
> thanks a lot , that was really helpful , i think where my problem is ,
> the zener i used isn't neither 7.5 nor 7.3 , it's 6.2 !! my supplier
> has gived me the wrong zener . as for P6 , actually now it reads
> 4.96 . the previous reading - the wrong one = 4.21 - was due to
> misplacing the prope of my multimeter . 
> so everything adds up now .now my question is : will my nebulus work
> with this zener ? fiding the 7.5 wasn't easy !! 
> 
> On Sun, Aug 2, 2009 at 2:20 AM, Gullik Webjörn
> <gullik.webjorn at corevalue.se> wrote:
>         
>         On Sun, 2009-08-02 at 01:17 +0300, mohamad al-jamal wrote:
>         > come on guys , i need help here
>         >
>         >
>         > On Sat, Aug 1, 2009 at 2:28 AM, mohamad al-jamal
>         > <mohammadaj at gmail.com> wrote:
>         >         Hi
>         >
>         >         I've just finished building my nebulus Tx ,
>         following the
>         >         exact instructions in the guide to the last detail ,
>         except
>         >         for the zener , where i used a 7.3V instead of 7.5
>         >         as i couldn't find one  . but the "DC - no signal"
>         test points
>         >         didn't  match , i rechecked the connections , and
>         tested the
>         >         parts before placing them , and afterwords,
>         >         but there are differences , 1.3 V for P7 for
>         example !! here
>         >         are my results :
>         >         P1   1mV
>         >         P2    5.55 V
>         >         P3    4.88
>         >         P4    5.58
>         >         P5    9.88
>         >         P6    4.21
>         >         P7    5.00
>         >         P8    0
>         >         P9    1mV
>         >         any help is highly appreciated
>         >
>         >
>         
>         
>                P1 = 1 mV ?? Do you have a proper AUI connected at coax
>         input?
>                P2 = 5.55 V, well, 7.3 - 0.7 = 6.6V, do you have 7.3 at
>         D2?
>                P3 = 4.88 V, well 5.55 - one VBE 0.7 V, seems OK
>                P4 = 5.58 V, derived from P2, higher than P2 ???? with
>         or without
>         signal ??
>                P5 = 9.88 V, reasonable, 9.88n - 4.88 = 5 V over Q2 VCE
>                P6 = 4.21 V, I should have expected same as P7,
>         something taking
>         current, broken IC U1, U2 or U3???
>                P7 = 5.00 V, 7.3 - 1.4 ( 2 * VBE) = 5.9, a little low,
>         how much current
>         does nebulus take?
>                P8 = 0, very reasonable with P6 at 4.21 V
>                P9 = 1mV, well, if P8 is at 0, then P9 should also be 0
>         V,
>                        since P9 is voltage drop over R17, and with no
>         voltage
>                        out of the driver ICs you do not get any
>         current, thus
>                        no voltage drop.
>         
>         In all, your circuit looks good, BUT, it looks like your U1-U3
>         are
>         taking input current, which they should not, (P6=4.21 V) so
>         maybee you
>         broke one of them. I would have expected P6 = P7 (+/-) 50 mV,
>         with no
>         signal. IF you have a signal, the difference might be OK,
>         depending
>         on signal duty cycle....
>         
>         So, with input signal disconnected P6 = (almost) P7, WITH
>         signal
>         lower, i.e. 4.21 V might be OK.
>         
>         Hope this helps
>         
>         Gullik
>         >
>         >
>         >
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