[TechAssist] Re: Toshiba CF3054J,TAC8950 still vert lin troublesafter C301 & C305 repl.]
- From: "J Silverman" <greentron@xxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Tue, 10 Sep 2002 01:52:25 -0400
There is a practical side to the making of the lower value capacitors that
gives you more than you realize you are getting. There is a minimum size of
anode that can be handled. A given raw anode is characterized by a CV
product. In short, the higher the voltage it is formed to, the lower the
capacitance value. There is also a limit to the voltage that a given anode
can be formed to without breaking down.
For example, when I worked for a capacitor manufacturer, we could not make a
low value capacitor with a voltage rating of less than 125 volts. This was
formed at about 250 volts, although our formation supplies could go up to
500 volts. If somebody ordered 1 ufd, 35 volt caps, we took the 125 volt
unit and marked it 1/35 to avoid a hassle with the buyer, who might only
note that we did not give them what they ordered. Some distributors bought
the caps unmarked and printed the C and V after they got an order. If you
want to tell what voltage an electrolytic was formed to you need to connect
it to a adjustable power supply (through a resistor or fuse for safety) and
slowly increase the voltage while monitoring the current. As the formation
voltage is approached, the leakage current will increase rather abruptly. We
used to do that in the lab when examining competitive products to see if
they had a good product or were just reducing the formation voltage safety
margin to get a smaller package or lower materials cost.
Jerry Silverman
Greentron Inc
4 Newland Ave
Greenville SC 29609
864 232 3889
Fax 271 2080
mailto:greentron@xxxxxxx
----- Original Message -----
From: "Wayne Vanaman" <Wayne@xxxxxxxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Monday, September 09, 2002 7:18 PM
Subject: [TechAssist] Re: Toshiba CF3054J,TAC8950 still vert lin
troublesafter C301 & C305 repl.]
>
> In the military, at least in the Hi reliability circuits, the design
> requirements (specifications) are that a capacitor on a line be 2x the
> maximum possible voltage. In other words, a 5v line regulated down from
24v
> would require a 48 volt cap to be 2x24 in the event the regulator would
> short. Furthermore, the mil-spec caps require that they be able to
> withstand 24 hours at 100 centegrade at 100% OVER voltage and not change
5%.
> Which means that the cap on our theoretical 5 volt line would be rquired
to
> withstand (2x24)x2, or 96 volts.
>
> The problems I see with using a higher voltage rating cap is the added
> expense of the higher voltage device, and the physical size.
>
> Wayne Vanaman
> Omega Electronics
> 6904 W Fairfield Dr
> Pensacola, Fl. 32506-3310
>
> 850-456-5995 voice
> 850-458-6369 fax
>
> Mailto:Wayne@xxxxxxxxxxxxxxxxxxxxx
> WWW.PensacolaTVRepair.Com
>
>
> ----- Original Message -----
> From: "Kevin" <kevinstv@xxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Monday, September 09, 2002 5:49 PM
> Subject: [TechAssist] Re: Toshiba CF3054J,TAC8950 still vert lin
> troublesafter C301 & C305 repl.]
>
>
> >
> > If you use a cap with, lets say a voltage of 4 times the original, you
> could
> > run into problems with the cap failing prematurly depending on the type
of
> > circuit. The voltage should be the same or higher but not too much
> higher.
> > A capacitor likes to work close to its rated voltage. But, does the
> higher
> > voltage have anything to do with timing? I don't think so either. I
have
> > noticed that 105 degrees C caps do have higher ESR values than 85
degrees
> C
> > ones.
> >
> > Kevin Wilks
> > Kevin's TV and Video Repair
> > Penticton BC Canada
> > kevinstv@xxxxxxx
> >
> > ----- Original Message -----
> > From: Wayne Vanaman <Wayne@xxxxxxxxxxxxxxxxxxxxx>
> > To: <techassist@xxxxxxxxxxxxx>
> > Sent: Monday, September 09, 2002 3:12 PM
> > Subject: [TechAssist] Re: Toshiba CF3054J,TAC8950 still vert lin
> > troublesafter C301 & C305 repl.]
> >
> >
> > >
> > > I don't believe the voltage rating has anything to do with discharge
> time.
> > > That is a factor of capacity, esr, and possibly dialectric absorbtion
> > > ("memory").
> > >
> > > Check for ANY not-black caps, I believe that most of the Toshibas, but
> not
> > > all, need three- c301, 305, 308, and sometimes the the 100uf or 220uf.
> > >
> > > Wayne Vanaman
> > > Omega Electronics
> > > 6904 W Fairfield Dr
> > > Pensacola, Fl. 32506-3310
> > >
> > > 850-456-5995 voice
> > > 850-458-6369 fax
> > >
> > > Mailto:Wayne@xxxxxxxxxxxxxxxxxxxxx
> > > WWW.PensacolaTVRepair.Com
> > >
> > >
> > > ----- Original Message -----
> > > From: "Ed Gaidies" <teltek2@xxxxxxxxxxxx>
> > > To: "TechAssist" <techassist@xxxxxxxxxxxxx>
> > > Sent: Monday, September 09, 2002 4:05 PM
> > > Subject: [TechAssist] Re: Toshiba CF3054J, TAC8950 still vert lin
> > > troublesafter C301 & C305 repl.]
> > >
> > >
> > > >
> > > > Phil......
> > > > Always....always.......C308......220ufd/35volts.
> > > > Due to the fact that these 2.2ufd/35 volts are timing
> > > capacitors.....should
> > > > never use higher than 50 volts.....discharge time is too great with
a
> > > > 250volt cap. I have never tried to go higher for that
> reason,,,although
> > > you
> > > > may be lucky.
> > > > BTW...you may have to change the vertical O/P IC too.
> > > >
> > > > -Ed-
> > > > Tel-Tek Electronics
> > > > Midland, Ontario
> > > > Canada.
> > > >
> > > > teltek2@xxxxxxxxxxxx
> > > > teltek3@xxxxxxxxxxxx
> > > > teltek@xxxxxxx
> > > >
> > > > "Quality will be remembered....long after Price is forgotten"
> > > >
> > > >
> > > >
> > > > Phil Bader The above is the reply to your message dated 9/9/02
> 2:33
> > PM
> > > >
> > > > >
> > > > >
> > > > >
> > > > > 31" Toshiba TV CF3054J: Orig. symptom was very narrow vert.
> deflection
> > > > > and fold over.
> > > > > ESR'd C301 and C305, both 2.2/50V red electrolytics.Both very
high,
> > > > > almost infinate ESR. Replaced both with 2.2/250v @105 deg. (all I
> > had).
> > > > > Increased vert. heigth but still narrow by 4 inches top and bottom
> > with
> > > > > a top fold over. These two caps always do it. I measured the caps
> > before
> > > > > install and are exactly 2.2 mfd. What else am I overlooking here?
> > > > > Phil Bader
> > > >
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