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Vivitar 3500 \"zoom thyristor\" flash won\'t whine...

P

Peabody

Guest
I have three of these flashes that I\'ve converted to manual flashes. One
works ok, The second i have to turn on and off several times, but it
finally starts whining, and works perfectly thereafter so long as it stays
on.

The third used to do that too, but now it won\'t whine at all. I\'ve taken
it apart, and the main capacitor checks out good, as does the main power
switch. So I\'m left with tryng to figure out why the boost circuit doesn\'t
start up - doesn\'t oscillate. The smaller electolytics look ok, but I
haven\'t taken them out to check them. And of course there\'s no schematic.

I\'d like to find a fix, but I don\'t want to make a second career out of it
either. Any suggestions on what to check, or how to approach this?

Thanks very much.
 
R

Ralph Mowery

Guest
In article <20200913-210156.50.0@Peabody.ssl-us.astraweb.com>,
waybackNO584SPAM44@yahoo.com says...
I have three of these flashes that I\'ve converted to manual flashes. One
works ok, The second i have to turn on and off several times, but it
finally starts whining, and works perfectly thereafter so long as it stays
on.

The third used to do that too, but now it won\'t whine at all. I\'ve taken
it apart, and the main capacitor checks out good, as does the main power
switch. So I\'m left with tryng to figure out why the boost circuit doesn\'t
start up - doesn\'t oscillate. The smaller electolytics look ok, but I
haven\'t taken them out to check them. And of course there\'s no schematic.

I\'d like to find a fix, but I don\'t want to make a second career out of it
either. Any suggestions on what to check, or how to approach this?
If there are any small electrolytic capacitors I would chanage them.
Many switching supplies have the problem where the capacitors go bad.
One way that may help confirm that is to take the one that sometimes
works and heat the capacitors with a hot air gun or even a hair dryer
and then try starting it. If it starts up faster the capacitors are a
sure bet.
 
S

server

Guest
On Monday, 14 September 2020 01:22:16 UTC+1, Ralph Mowery wrote:
In article <20200913-210156.50.0@Peabody.ssl-us.astraweb.com>,
waybackNO584SPAM44@yahoo.com says...

I have three of these flashes that I\'ve converted to manual flashes. One
works ok, The second i have to turn on and off several times, but it
finally starts whining, and works perfectly thereafter so long as it stays
on.

The third used to do that too, but now it won\'t whine at all. I\'ve taken
it apart, and the main capacitor checks out good, as does the main power
switch. So I\'m left with tryng to figure out why the boost circuit doesn\'t
start up - doesn\'t oscillate. The smaller electolytics look ok, but I
haven\'t taken them out to check them. And of course there\'s no schematic.

I\'d like to find a fix, but I don\'t want to make a second career out of it
either. Any suggestions on what to check, or how to approach this?



If there are any small electrolytic capacitors I would chanage them.
Many switching supplies have the problem where the capacitors go bad.
One way that may help confirm that is to take the one that sometimes
works and heat the capacitors with a hot air gun or even a hair dryer
and then try starting it. If it starts up faster the capacitors are a
sure bet.
Another other way to test them is to piggyback a new one on, see if it springs to life. Another way is to use a component tester.


NT
 
W

whit3rd

Guest
On Sunday, September 13, 2020 at 2:01:59 PM UTC-7, Peabody wrote:
I have three of these flashes that I\'ve converted to manual flashes. One
works ok, The second i have to turn on and off several times, but it
finally starts whining, and works perfectly thereafter so long as it stays
on.

The third used to do that too, but now it won\'t whine at all. I\'ve taken
it apart, and the main capacitor checks out good, as does the main power
switch.
As others have mentioned, that usually is an oscillator-startup problem, and
the entire circuit is ONE feedback loop oscillator; every component is a suspect.
With age, high voltage parts are most susceptible to failure; the HV rectifier
and its associated switch (SCR or transistor) that drive the coil are inexpensive
to replace (except you\'ll have to identify them, and match to modern available
parts, and pay shipping for onesies...).
 
F

Fox\'s Mercantile

Guest
On 9/15/20 1:38 PM, tabbypurr@gmail.com wrote:
Another other way to test them is to piggyback a new one on, see if it springs to life. Another way is to use a component tester.


NT
That ONLY works if they\'re open.
You should know that.


--
\"I am a river to my people.\"
Jeff-1.0
WA6FWi
http:foxsmercantile.com
 
S

server

Guest
On Tuesday, 15 September 2020 23:23:23 UTC+1, Fox\'s Mercantile wrote:
On 9/15/20 1:38 PM, tabbypurr wrote:

Another other way to test them is to piggyback a new one on, see if it springs to life. Another way is to use a component tester.


NT

That ONLY works if they\'re open.
You should know that.
I don\'t know that. Both methods work if they\'re low C, high ESR or open. A component tester also works if they\'re leaky or shorted.


NT
 
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