Date   
Re: OT Electrolytic caps

Chris Wilson
 

Hello MIKE,

Tuesday, August 27, 2019

You could put two 25v or more 1000uF caps in series with balancing
resistors, but almost certainly less hassle to just buy the correctly
rated (voltage wise) 470uF ones.


Best regards,
Chris 2E0ILY mailto:chris@...


MW> I am repairing a flickering screen on a Vizio TV. it calls for
MW> 470uf 35v caps. Well wouldn't You know They sent 25v caps. Can I
MW> Parallel 2 470uf 25v and will this give me 470uf 50v? Thank You
MW>
MW>




--
Best regards, Chris Wilson (2E0ILY)

Re: OT Electrolytic caps

Chris Wilson
 

Hello MIKE,

Tuesday, August 27, 2019

If an electrolytic is operated within its rated voltage it should
last the hours the spec sheet states, *ASSUMING* it receives no
sudden voltage spikes and is not operated in a hot environment above
its temperature rating. In some SMPS it's often worth buying higher
temp rated electrolytics and ALWAYS worth buying branded ones. Higher
voltage rtings can certainly do no harm. Specific applications may
demand low ESR ones (a measure of its series resistance at AC) Low
ESR components can probably do no harm if in doubt! Physical size and
lead spacing may be critical on modern tiny PCB's, but often you can
"fiddle" in a bigger one on longer leads and secure it out of the way
with glue.


Best regards,
Chris 2E0ILY mailto:chris@...


MW> Thank You, I assume if I use 25v vs 35v they will just fail sooner, Correct?




--
Best regards, Chris Wilson (2E0ILY)

10w linear, possible improvement? #pa

Nick VK4PP
 

Hi all.
So I came across a post, I was looking for irf510 info and amps, and in this post it mentioned that Alison, had been cutting off the drain pin and using the tab instead.
http://www.n6qw.com/Simple_SSB.html
As said, makes sense to separate input and output.

Now not that there is instability in the QSX 10w linear, but wouldn't it benefit from this treatment?
I see there are a.feq.traces that cross over one another in the ifr510 section of the PCB...

Thoughts? Maybe for rev3?

Cheers Nick.

Re: OT Electrolytic caps

Jerry <wa6owr@...>
 

NO


On Tue, Aug 27, 2019 at 12:19 PM MIKE WILLMAN <aa9aa@...> wrote:

I am repairing a flickering screen on a Vizio TV. it calls for 470uf 35v caps. Well wouldn't  You know They sent 25v caps. Can I Parallel 2 470uf 25v and will this give me 470uf 50v? Thank You

 

Re: OT Electrolytic caps

MIKE WILLMAN
 

24v so 25v would not give a safe margin. Ordered the 35v

Re: 30 Meter QCX WWV

Shirley Dulcey KE1L
 

I have copied the 15 MHz WWV signal on a 20m QCX. The audio is very muffled but it is possible to understand. 10 MHz WWV should sound the same, and will be easier to receive because it won't be attenuated by the low pass filter.


On Tue, Aug 27, 2019, 4:48 PM John Seboldt K0JD <k0jd-l@...> wrote:

Bet it would. The 200Hz bandwidth filter doesn't have super sharp skirts like DSP or crystal filters so you might barely make out the voice. You would surely hear the "tick" tone (1kHz) and the main tone. Tune down to it and try!

John K0JD
Milwaukee

On 8/27/2019 15:39, Don DeGregori wrote:
Would WWV AM voice be readable at all?

Re: U3S + 5 watt PA troubleshooting help needed.

Liam Kingsmill <lumetters1@...>
 

Alan, Update  #2:

Maybe the offending stranded wire revealed itself.  It may have been one strand at the PCB of the 5 volt supply wire (which supplies the U3S)   Anyway, the U3S works again without blowing the 2 amp fuse in its supply.

Another calibration of the U3S PA ought to return us to square one.  After the calibration, I will reconnect the wires hanging off the 5 watt PA to the U3S.  Hoping Update #3 is all good news.

Liam KI7UPZ

Re: 30 Meter QCX WWV

John Seboldt K0JD
 

Bet it would. The 200Hz bandwidth filter doesn't have super sharp skirts like DSP or crystal filters so you might barely make out the voice. You would surely hear the "tick" tone (1kHz) and the main tone. Tune down to it and try!

John K0JD
Milwaukee

On 8/27/2019 15:39, Don DeGregori wrote:
Would WWV AM voice be readable at all?

30 Meter QCX WWV

Don DeGregori
 

Would WWV AM voice be readable at all?

Re: OT Electrolytic caps

Evan Hand
 

Mike,
The short answer is that the life of the caps are not going to change significantly as long as the voltage stays below their maximum working voltage.  If that value is exceeded even once, the cap can fail catastrophically (explode) in that a short circuit will develop across the voltage supply to ground.

I am assuming that these are in the power supply for the TV.

Do you have the schematic, and does it state the voltage on the capacitor?  As Arv stated, as long as the nominal supply voltage is 18 volts or less, you should not have an issue.

Above are my thoughts, you are free to use or ignore as you see fit.
73
Evan
AC9TU

Re: OT Electrolytic caps

Arv Evans
 

If you have a volt meter you can measure the voltage presedt across the cap pads when the circuit is powered.  That should be close to what is present when the circuit is operating.  

Capacitor voltacge ratings are the safe maximum operating voltage for that capacitor.  Paralleling capacitors will double the effective capacitance but does not affect the maximum safe voltage.  Putting capacitors in series hill decrease the effective capacitance and can increase the safe operating voltage, but only if you also add voltage dividing resistors calculated to hold the voltade across each capscitor within its safe range.  

Fuses cannot be paralleled or seriesed.

Are you a licensed ham radio operator?  If yes, you may be able to find a local ham operator  who can help you with the basics of electronics.





On Tue, Aug 27, 2019, 1:43 PM MIKE WILLMAN <aa9aa@...> wrote:
I am not sure how much voltage the caps. are subjected to

Re: OT Electrolytic caps

MIKE WILLMAN
 

I am not sure how much voltage the caps. are subjected to

Re: OT Electrolytic caps

MIKE WILLMAN
 

Thank You, I assume if I use 25v vs 35v they will just fail sooner, Correct?

Re: OT Electrolytic caps

Arv Evans
 

What is the voltage that those caps will be subjected to?  If less than 18 volts or so the 25 volt caps might work fine.  

Arv. K7hkl
_-_


On Tue, Aug 27, 2019, 1:30 PM Evan Hand <elhandjr@...> wrote:
The short answer is no.  You  would need 4 caps, 2 in parallel and then two more parallel in series with the first two.  You also should add bleeder resistors to balance the voltage across them.  The value needs to be high enough to not be a load on the system, yet low enough to maintain proper voltages.  2 1 meg should work.

Better answer is to get the correct part.

73
Evan
AC9TU

Re: OT Electrolytic caps

Evan Hand
 

The short answer is no.  You  would need 4 caps, 2 in parallel and then two more parallel in series with the first two.  You also should add bleeder resistors to balance the voltage across them.  The value needs to be high enough to not be a load on the system, yet low enough to maintain proper voltages.  2 1 meg should work.

Better answer is to get the correct part.

73
Evan
AC9TU

Re: OT Electrolytic caps

Viktors Miske KC8CKZ
 

Nope, you will end up with 940uf at 25volts....

OT Electrolytic caps

MIKE WILLMAN
 

I am repairing a flickering screen on a Vizio TV. it calls for 470uf 35v caps. Well wouldn't  You know They sent 25v caps. Can I Parallel 2 470uf 25v and will this give me 470uf 50v? Thank You

 

Re: QCX 3 Trimmers can't find minimums

Arv Evans
 

In the "bad-old-days" we had to contend with brown-body resistors (brown is one of the color code bands).
Then it was gray resistors (gray is a color code band).  Seems that most of the popular colors are already
taken, so what color should resistor bodies actually be?   Oh, yes we do have an easy fix...just use SMT
components which have the value printed on each component.  Us old timers have to use a 10X magnifier,
but that seems a small price to pay for knowing exactly what the value might be.

8-)

Arv  K7HKL
_._


On Tue, Aug 27, 2019 at 12:47 PM James Daldry W4JED <jim@...> wrote:

Hi, Don

I ran into blue body resistors when repairing Pioneer CD/tape/FM integrated systems in the '90's. One of the interesting design details was a circuit that detected excessive output current and would turn on - saturate - all the output transistors at once, blowing the AC fuse. Guess what - as designed, it would blow out all the output devices, then blow the fuse. So - when you repaired one of the "cube" amps (ask any stereo tech about "cube amps") you had to change a bunch of resistors in the sense circuit to recalibrate it. Some of the replacement resistors had blue bodies. I've also run into blue body resistors in the "600 resistors for $2" packages on Ebay. When I use them I don't even try to read them - I use an ohmmeter.

Jim

On 8/27/19 11:55 AM, Don DeGregori wrote:
You never know. Maybe the blue LED I've seen has skewed my color perception of blue body resistors. But I have a blue body Elantra car. No problem seeing the colors of the day.

Anyway Ron WA7GIL, the fixer of 13 boards, has my board. He knows all about blue body resistors and hates it too!

Don

Re: QCX 3 Trimmers can't find minimums

James Daldry W4JED
 

Hi, Don

I ran into blue body resistors when repairing Pioneer CD/tape/FM integrated systems in the '90's. One of the interesting design details was a circuit that detected excessive output current and would turn on - saturate - all the output transistors at once, blowing the AC fuse. Guess what - as designed, it would blow out all the output devices, then blow the fuse. So - when you repaired one of the "cube" amps (ask any stereo tech about "cube amps") you had to change a bunch of resistors in the sense circuit to recalibrate it. Some of the replacement resistors had blue bodies. I've also run into blue body resistors in the "600 resistors for $2" packages on Ebay. When I use them I don't even try to read them - I use an ohmmeter.

Jim

On 8/27/19 11:55 AM, Don DeGregori wrote:
You never know. Maybe the blue LED I've seen has skewed my color perception of blue body resistors. But I have a blue body Elantra car. No problem seeing the colors of the day.

Anyway Ron WA7GIL, the fixer of 13 boards, has my board. He knows all about blue body resistors and hates it too!

Don

Re: U3S + 5 watt PA troubleshooting help needed.

Liam Kingsmill <lumetters1@...>
 

Alan.  Here;s the first update:
With power supply disconnected the resistance measured between the 5 volt and ground at the PCB remains  3100 ohms.

Possibly, my fooling around hooking up the 5 watt PA shorted something that wasn't shorted when the U3S, GPS and receiver worked.

Your suggestion to get the U3S working alone is the next step here. (soon as my nap is done)  I will check the BS170 and re-read section 5.2 (Bias adjustment)

Liam KI7UPZ