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Vivitar 3500 "zoom thyristor" flash won't whine
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Peabody
Sep 13, 2020, 5:01:59 PM9/13/20
to
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.
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.
Ralph Mowery
Sep 13, 2020, 8:22:16 PM9/13/20
to
In article <20200913-2...@Peabody.ssl-us.astraweb.com>,
waybackNO...@yahoo.com says...
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.
waybackNO...@yahoo.com says...
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.
tabb...@gmail.com
Sep 15, 2020, 2:38:22 PM9/15/20
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NT
whit3rd
Sep 15, 2020, 4:09:03 PM9/15/20
to
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
> 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.
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...).
Fox's Mercantile
Sep 15, 2020, 6:23:23 PM9/15/20
to
On 9/15/20 1:38 PM, tabb...@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.
> 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
You should know that.
--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
tabb...@gmail.com
Sep 17, 2020, 7:45:03 PM9/17/20
to
On Tuesday, 15 September 2020 23:23:23 UTC+1, Fox's Mercantile wrote:
NT
> 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.
> > 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.
NT
Peabody
Sep 20, 2020, 4:54:34 PM9/20/20
to
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
Peabody
Sep 20, 2020, 5:06:12 PM9/20/20
to
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.
is a germanium PNP transistor. I'd guess I won't find a direct replacement
for that.
dansabr...@yahoo.com
Sep 21, 2020, 7:18:24 AM9/21/20
to
Send me a private message so we can connect.
Dan
Cydrome Leader
Oct 12, 2020, 12:28:53 AM10/12/20
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old stock. I doubt the chinese would even fake those.
abrsvc
Oct 12, 2020, 8:57:31 AM10/12/20
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Dan
Peabody
Oct 12, 2020, 6:03:16 PM10/12/20
to
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.
>> > 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.
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.
Peabody
Oct 14, 2020, 5:04:43 PM10/14/20
to
> 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
> 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.
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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