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Video circuit working but dark
- To: <ukha_d@xxxxxxx>
- Subject: Video circuit working but dark
- From: "Paul" <groups@xxxxxxx>
- Date: Sat, 24 May 2003 10:38:34 +0100
- Mailing-list: list ukha_d@xxxxxxx; contact
ukha_d-owner@xxxxxxx
- Reply-to: ukha_d@xxxxxxx
Having played a lot with the resistor values - I've got a working circuit
b=
ut it still lacks overall brightness (has a 'greyish' quality to the
pictur=
e). Increasing the gain washes out whites but the overall picture is still
=
reasonably dark. Saturation of colours is good though.
Any ideas - Keith?
Paul.
> -----Original Message-----
> From: Paul [mailto:groups@xxxxxxx]
> Sent: 23 May 2003 22:35
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] Heeeeeeeeelp! - got somewhere!
>=20
> Got a picture but it's quite 'grey' and needs to be brighter. How much
of
> this might be down to long lead lengths (as it's on breadboard)? The
> capacitors between the power supply pins of the op amp and GND are
close
> to the IC but have quite long leads to GND - would this make a
difference=
?
>=20
> As to shielding of the incoming/outgoing signal cables - should they
be
> connected to AC GND or the common of the PSU?
>=20
> Should they also be shielded as close to the PCB as possible?
>=20
> Ta,
>=20
> Paul.
>=20
> > -----Original Message-----
> > From: Frank Mc Alinden [mailto:fmcalind@xxxxxxx]
> > Sent: 23 May 2003 22:20
> > To: ukha_d@xxxxxxx
> > Subject: Re: [ukha_d] Heeeeeeeeelp! - got somewhere!
> >
> > Hi Paul
> > What exactly are you making ?? sounds interesting..
(nosey
> > frank) ;-))
> >
> > Frank
> > ----- Original Message -----
> > From: "Paul" <groups@xxxxxxx>
> > To: <ukha_d@xxxxxxx>
> > Sent: Saturday, May 24, 2003 7:17 AM
> > Subject: RE: [ukha_d] Heeeeeeeeelp! - got somewhere!
> >
> >
> > Ahhh - I did have one of the transistors connected wrong - the
datashee=
t
> > from RS was the wrong one!
> >
> > Now I need to fine tune the output which is a bit odd brightness
and
> > colour
> > wise.
> >
> > I've got a tant cap on the input side and a 5K trimmer instead of
2K5 -
> > will
> > this make a difference?
> >
> > Thanks Keith and Dan!!!
> >
> > Paul.
> >
> > > -----Original Message-----
> > > From: Paul [mailto:groups@xxxxxxx]
> > > Sent: 23 May 2003 21:34
> > > To: Dan
> > > Cc: ukha_d@xxxxxxx
> > > Subject: RE: [ukha_d] Heeeeeeeeelp!
> > >
> > > When I disconnect pin 1 (pin6 on the old part) (output) -
it's at
> 10.5V
> > -
> > > is this what you'd expect?
> > >
> > > Paul.
> > >
> > > > -----Original Message-----
> > > > From: Dan [mailto:dtoma@xxxxxxx]
> > > > Sent: 23 May 2003 21:11
> > > > To: Paul
> > > > Subject: Re: [ukha_d] Heeeeeeeeelp!
> > > >
> > > > Hi Paul,
> > > >
> > > > It seems to be a problem with the transistors.
> > > > Disconnect pin 6 of the CI and check if then it is at
0V.
> > > > If yes, then you must check the two transistors.
> > > > Usually they must be pairs (the same beta factor and
the same
> > > > characteristic in order to correctly balance the
push-pull output.
> One
> > > > good
> > > > indication that something is wrong with them is that
the resistance
> > > > bewteen
> > > > E-C is measurable (it must be allmost infinite if the
base is not
> > > > connected).
> > > >
> > > >
> > > > BR,
> > > > Dan
> > > > ----- Original Message -----
> > > > From: "Paul" <paul@xxxxxxx>
> > > > To: "Dan" <dtoma@xxxxxxx>
> > > > Sent: Friday, May 23, 2003 10:55 PM
> > > > Subject: RE: [ukha_d] Heeeeeeeeelp!
> > > >
> > > >
> > > > > Oh, and I'm not sure what you mean by " check
if one of the R6 or
> R7
> > > > resistors is not interrupted"?
> > > > >
> > > > > Paul.
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Dan [mailto:dtoma@xxxxxxx]
> > > > > > Sent: 23 May 2003 19:40
> > > > > > To: ukha_d@xxxxxxx
> > > > > > Subject: Re: [ukha_d] Heeeeeeeeelp!
> > > > > >
> > > > > > Hi Paul,
> > > > > >
> > > > > > Check the following points:
> > > > > > - IC1-pin 2, 3 and 6 to be as near as 0V as
possible (without
> any
> > > > input
> > > > > > signal)
> > > > > > - direct voltage on each of the two diodes(D1
and D2)... it mus=
t
> > be
> > > > around
> > > > > > 0.6V
> > > > > > - check if one of the R6 or R7 resistors is
not interupted
> > > > > > - check the polarity of the two diodes.
> > > > > > If something different, send me a mail.
> > > > > >
> > > > > > I don't know EL2244C... you're sure that it
is compatible with
> > > CA3100
> > > > ?
> > > > > > The rest of the substitutions are not
important.
> > > > > >
> > > > > > BR,
> > > > > > Dan
> > > > > >
> > > > > > ----- Original Message -----
> > > > > > From: "Paul" <groups@xxxxxxx>
> > > > > > To: <ukha_d@xxxxxxx>
> > > > > > Sent: Friday, May 23, 2003 8:39 PM
> > > > > > Subject: RE: [ukha_d] Heeeeeeeeelp!
> > > > > >
> > > > > >
> > > > > > > I'm building the following circuit:
> > > > > > >
> > > > > > > http://home.maine.rr.com/randylinscott/jan98.htm
> > > > > > >
> > > > > > > But with the following substitutions:
> > > > > > >
> > > > > > > IC1 CA3100 (single opamp) changed to
EL2244C (dual opamp
> > package)
> > > > > > > Q1 2N3053 (Gen purpose NPN transistor)
changed to BC182L
> > > > > > > Q2 2N4037 (Gen purpose PNP transistor)
changed to BC212
> > > > > > > D1 1N914 (small signal Diode) changed to
1N4148
> > > > > > >
> > > > > > > R3 is a 5K trimmer rather than 2K5
specified (is this a
> > problem?)
> > > > > > >
> > > > > > > I'm using an ATX PC PSU as the +12V and
-12V source with the
> > > common
> > > > > > connection connected to the ground points on
the circuit (is
> this
> > > > right?).
> > > > > > The PSU has slightly different voltages (+12V
is something like
> > > +11.4V
> > > > > > and -12V is actually -11.04V).
> > > > > > >
> > > > > > > When I connect up the circuit, it
doesn't work and the
> > transistors
> > > > and
> > > > > > IC
> > > > > > get very hot!
> > > > > > >
> > > > > > > I'm treble checking the circuit. Any
thoughts?
> > > > > > >
> > > > > > > Thanks,
> > > > > > >
> > > > > > > Paul.
> > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: Dan [mailto:dtoma@xxxxxxx]
> > > > > > > > Sent: 23 May 2003 18:14
> > > > > > > > To: ukha_d@xxxxxxx
> > > > > > > > Subject: Re: [ukha_d] Heeeeeeeeelp!
> > > > > > > >
> > > > > > > > Hi Paul,
> > > > > > > >
> > > > > > > > Transistor from what???
> > > > > > > > Or ...just a simple transistor?
> > > > > > > > :-)
> > > > > > > > Dan
> > > > > > > > ----- Original Message -----
> > > > > > > > From: "Paul"
<groups@xxxxxxx>
> > > > > > > > To: <ukha_d@xxxxxxx>
> > > > > > > > Sent: Friday, May 23, 2003 7:46 PM
> > > > > > > > Subject: [ukha_d] Heeeeeeeeelp!
> > > > > > > >
> > > > > > > >
> > > > > > > > > Anyone with electronics
experience =96 I need help (pleas=
e!)
> > > > > > > > >
> > > > > > > > > My transistors are cooking!
> > > > > > > > >
> > > > > > > > > Anyone?
> > > > > > > > >
> > > > > > > > > Paul.
> > > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > ** UKHA2004 BE THERE! ** -
start planning now.
> > > > > > > > >
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>=20
>=20
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>=20
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