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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
 
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.

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...).
I removed all of the electrolytics, and all but one tested
good on my scope. I replaced the dubious one, but the flash
still doesn\'t work. The oscillator whine doesn\'t start up.

But I did find one thing that gets really hot when the power
switch is turned on. It is a pair of three-pin parts
(triange pattern footprint) that look like cylinders, and
they are enclsed in a U-shaped heatsink. They are each
marked with the Mitsubishi triagle logo, and \"B324ST\", with
\"12\" on the second line. I assume they are transistors or
thyristors, but searching for them comes up with nothing.
This is all from the 1980s, so I guess it\'s not surprising
that the parts aren\'t active anymore, but it would be nice
to at least find a datasheet.

By the way, the dubious cap was right next to the mystery
pair.

Any ideas?

https://www.eevblog.com/forum/repair/repair-vivitar-3500-speedlight/?
action=dlattach;attach=1070818;image
 
P

Peabody

Guest
Someone on the EEVblog forum says the part number is actually 2SB324, which
is a germanium PNP transistor. I\'d guess I won\'t find a direct replacement
for that.
 
D

dansabr...@yahoo.com

Guest
On Sunday, 20 September 2020 at 17:06:12 UTC-4, Peabody wrote:
Someone on the EEVblog forum says the part number is actually 2SB324, which
is a germanium PNP transistor. I\'d guess I won\'t find a direct replacement
for that.
If you need 2SB324 transistors, I have them in stock. They don\'t have the heatsink attached, but I have heat sinks as well.
Send me a private message so we can connect.

Dan
 
C

Cydrome Leader

Guest
Peabody <waybackNO584SPAM44@yahoo.com> wrote:
Someone on the EEVblog forum says the part number is actually 2SB324, which
is a germanium PNP transistor. I\'d guess I won\'t find a direct replacement
for that.
NTE still sells crosses for stuff like that. Looks like NTE102A. Must be
old stock. I doubt the chinese would even fake those.
 
A

abrsvc

Guest
On Monday, 12 October 2020 00:28:53 UTC-4, Cydrome Leader wrote:
Peabody <waybackNO584SPAM44@yahoo.com> wrote:
Someone on the EEVblog forum says the part number is actually 2SB324, which
is a germanium PNP transistor. I\'d guess I won\'t find a direct replacement
for that.

NTE still sells crosses for stuff like that. Looks like NTE102A. Must be
old stock. I doubt the chinese would even fake those.
OP may provide details, but I supplied transistors to him and as of this writing, one is working by changing transistor and some caps.

Dan
 
P

Peabody

Guest
abrsvc says...

Someone on the EEVblog forum says the part number is
actually 2SB324, which is a germanium PNP transistor.
I\'d guess I won\'t find a direct replacement for that.

NTE still sells crosses for stuff like that. Looks like
NTE102A. Must be old stock. I doubt the chinese would
even fake those.

OP may provide details, but I supplied transistors to
him and as of this writing, one is working by changing
transistor and some caps.
Yes, thanks very much, Dan. I found that one of the two
ganged transistors had failed short. So I replaced that one
with one of Dan\'s 2SB324 transistors, and I replaced the two
electrolytic capacitors, one of which tested bad for ESR.
And now it works.

I have two more of these flashes which still work, but don\'t
always spin up when I first turn on power. I\'m going to
make sure their transistors are good, but I\'m going to
replace their capacitors. The existing ones are 35 years
old, so it\'s not too soon to replace them. They are
Panasonic CE series, which don\'t appear to have been
anything special.

Thanks for bailing me out, Dan. I was thinking of trying to
switch over to silicon transistors, but at least for now I
don\'t have to do that. These flashes run on two NiMH AAs,
so about 2.4V, so the lower base drop of germanium may
actually be important. Anyway, I was not looking forward to
making that transition.
 
P

Peabody

Guest
I have two more of these flashes which still work, but
don\'t always spin up when I first turn on power. I\'m
going to make sure their transistors are good, but I\'m
going to replace their capacitors. The existing ones
are 35 years old, so it\'s not too soon to replace them.
They are Panasonic CE series, which don\'t appear to have
been anything special.
I did the capacitor replacements, and now all three flashes
seem to be working nominally. The high-ESR capacitor on the
first flash also measured bad on the other two. But the
replacements tested fine. I guess the old ones could have
been bad from the beginning, but other CE series caps of
that vintage don\'t have high ESR. So maybe the way they are
used in the circuit tends to kill them. They are just 10uF,
16V. Nothing special.
 
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