Vivitar 365 flash unit

I have an old 365 that I still use. Lately the capacitor has been getting hot. Cap is rated 1800uf 400V
The flash works fine except for the heat.

On checking I found that there is 465V on the cap. Even hooking it to a "dead" battery that only had 8V during charging, the cap still had 430V on it. I believe the cap is getting hot from the overvoltage. I've checked the cap on a Sencore Z meter, an ESR meter and with an ohm meter and all indicate that it is ok. The Z meter showed a little dielctric absortion but not bad for a cap 30 yrs old and that size. Ohm meter tests in the 50meg I ran over all the diodes, resistors and semis that I could recognize. I found one semi in a TO-220 type package that reads 94 ohms between the outside leads. It reads .09 in both directions on a diode test. The tab-center lead reads around 5meg to the other 2 leads and counts up like a capacitor charging. I have searched extensively on the net for info on this device and have found nothing. Anyone know what this is and if it's good or bad? My thoughts are that it is used to regulate the voltage applied to the cap and is not working. Any and all advice is apprecaited.

 

[N_Cook]

<bhawkes926@gmail.com> wrote in message
news:8c750d38-89b2-46a8-b8ce-a438b06c505a@googlegroups.com...
I have an old 365 that I still use. Lately the capacitor has been getting
hot. Cap is rated 1800uf 400V
The flash works fine except for the heat.

On checking I found that there is 465V on the cap. Even hooking it to a
"dead" battery that only had 8V during charging, the cap still had 430V on
it. I believe the cap is getting hot from the overvoltage. I've checked the
cap on a Sencore Z meter, an ESR meter and with an ohm meter and all
indicate that it is ok. The Z meter showed a little dielctric absortion but
not bad for a cap 30 yrs old and that size. Ohm meter tests in the 50meg I
ran over all the diodes, resistors and semis that I could recognize. I found
one semi in a TO-220 type package that reads 94 ohms between the outside
leads. It reads .09 in both directions on a diode test. The tab-center lead
reads around 5meg to the other 2 leads and counts up like a capacitor
charging. I have searched extensively on the net for info on this device
and have found nothing. Anyone know what this is and if it's good or bad? My
thoughts are that it is used to regulate the voltage applied to the cap and
is not working. Any and all advice is apprecaited.

++++


What is the normal temperature for these caps , presumably when used near
continuously.
What does a thermometer tell you is the temp of you're one in use. As users
don;t experience the heat of these caps , as they're enclosed, maybe its
normal. As the volume of these caps is critical to the aesthetics/ergonomics
I would not be surprised if they used underated caps, as the way they are
used is different to the usual specified application.

 

[William Sommerwerck]

There's no question the capacitor is being overcharged. This is almost
certainly due to failure of the "monitor" circuit that shuts off charging at
a particular voltage. This guarantees consistent light output in /manual/
exposure.

You're headed in the right direction, but you're probably going to need a
schematic to track down which component or components are defective.

I had this problem with several Polaroid 360 cameras -- but the charging
circuit had a pot you could adjust. You might look for one.

 

[Cydrome Leader]

bhawkes926@gmail.com wrote: > I have an old 365 that I still use. Lately
the capacitor has been getting hot. Cap is rated 1800uf 400V > The flash
works fine except for the heat. > > On checking I found that there is 465V
on the cap. Even hooking it to a "dead" battery that only had 8V during
charging, the cap still had 430V on it. I believe the cap is getting hot
from the overvoltage. I've checked the cap on a Sencore Z meter, an ESR
meter and with an ohm meter and all indicate that it is ok. The Z meter
showed a little dielctric absortion but not bad for a cap 30 yrs old and
that size. Ohm meter tests in the 50meg I ran over all the diodes,
resistors and semis that I could recognize. I found one semi in a TO-220
type package that reads 94 ohms between the outside leads. It reads .09 in
both directions on a diode test. The tab-center lead reads around 5meg to
the other 2 leads and counts up like a capacitor charging. I have
searched extensively on the net for info on this device and have found
nothing. Anyone know what this is and if it's good or bad? My thoughts are
that it is used to regulate the voltage applied to the cap and is not
working. Any and all advice is apprecaited.

the to-220 is probably a SCR for the quench circuit, if this flash has
one.

it would be connected to a inductor.

 

[William Sommerwerck]

There is a pot on the one circuit board. It is not labeled. I turned it
1/8 turn,
fired the flash and let it recharge and the voltage was the same. I will
do
some more checking in that area to see if I can find anything. I wasn't
sure
what the pot would be for.

It might be calibration for the auto flash. Can't hurt to experiment.

 

[Bruce Hawkes]

On Tuesday, December 11, 2012 3:18:39 PM UTC-5, Bruce Hawkes wrote:

I have an old 365 that I still use. Lately the capacitor has been getting hot. Cap is rated 1800uf 400V

The flash works fine except for the heat.



On checking I found that there is 465V on the cap. Even hooking it to a "dead" battery that only had 8V during charging, the cap still had 430V on it. I believe the cap is getting hot from the overvoltage. I've checked the cap on a Sencore Z meter, an ESR meter and with an ohm meter and all indicate that it is ok. The Z meter showed a little dielctric absortion but not bad for a cap 30 yrs old and that size. Ohm meter tests in the 50meg I ran over all the diodes, resistors and semis that I could recognize. I found one semi in a TO-220 type package that reads 94 ohms between the outside leads. It reads .09 in both directions on a diode test. The tab-center lead reads around 5meg to the other 2 leads and counts up like a capacitor charging.. I have searched extensively on the net for info on this device and have found nothing. Anyone know what this is and if it's good or bad? My thoughts are that it is used to regulate the voltage applied to the cap and is not working. Any and all advice is apprecaited.

The handle of the flash unit where the cap is housed gets so hot you can't hang on to it. That's what prompted me to take it apart.

I have put the cap back on the Z meter and one an intensive leakage test on it. The meter has 396V across the cap (measured with an external DVM) and is only showing 440 microamps of current through the cap and it's cool after 15-20 minutes of this voltage applied. No signs of heating at all. It appears the cap survived being over heated/charged drastically. I have no idea how they monitor/regulate the voltage. The circuitry is pretty simple with no processors or logic involved that I have found. I'm beginning to doubt if the 3JM device is involved in that control, but I still don't know.

 

[Bruce Hawkes]

On Tuesday, December 11, 2012 3:18:39 PM UTC-5, Bruce Hawkes wrote:

I have an old 365 that I still use. Lately the capacitor has been getting hot. Cap is rated 1800uf 400V

The flash works fine except for the heat.



On checking I found that there is 465V on the cap. Even hooking it to a "dead" battery that only had 8V during charging, the cap still had 430V on it. I believe the cap is getting hot from the overvoltage. I've checked the cap on a Sencore Z meter, an ESR meter and with an ohm meter and all indicate that it is ok. The Z meter showed a little dielctric absortion but not bad for a cap 30 yrs old and that size. Ohm meter tests in the 50meg I ran over all the diodes, resistors and semis that I could recognize. I found one semi in a TO-220 type package that reads 94 ohms between the outside leads. It reads .09 in both directions on a diode test. The tab-center lead reads around 5meg to the other 2 leads and counts up like a capacitor charging.. I have searched extensively on the net for info on this device and have found nothing. Anyone know what this is and if it's good or bad? My thoughts are that it is used to regulate the voltage applied to the cap and is not working. Any and all advice is apprecaited.

There is a pot on the one circuit board. It is not labeled. I turned it 1/8 turn, fired the flash and let it recharge and the voltage was the same. I will do some more checking in that area to see if I can find anything. I wasn't sure what the pot would be for. It would stand to reason that it would be a voltage control, but it didn't see to do much when I turned it.

 

[klem kedidelhopper]

On Dec 13, 4:19 pm, "William Sommerwerck" <grizzledgee...@comcast.net>
wrote:

There is a pot on the one circuit board. It is not labeled. I turned it
1/8 turn,
fired the flash and let it recharge and the voltage was the same. I will
do
some more checking in that area to see if I can find anything. I wasn't
sure
what the pot would be for.

It might be calibration for the auto flash. Can't hurt to experiment.

Did you measure the voltages on either side of the TO220 device? I'm
thinking that if it were some type of regulator , (with an "in" or
"out") then you might get a clue from seeing what that looks like.
Maybe the pot controls gate current. Lenny

 

[Cydrome Leader]

klem kedidelhopper <captainvideo462009@gmail.com> wrote:

On Dec 13, 4:19?pm, "William Sommerwerck" <grizzledgee...@comcast.net
wrote:
There is a pot on the one circuit board. It is not labeled. I turned it
1/8 turn,
fired the flash and let it recharge and the voltage was the same. I will
do
some more checking in that area to see if I can find anything. I wasn't
sure
what the pot would be for.

It might be calibration for the auto flash. Can't hurt to experiment.

Did you measure the voltages on either side of the TO220 device? I'm
thinking that if it were some type of regulator , (with an "in" or
"out") then you might get a clue from seeing what that looks like.
Maybe the pot controls gate current. Lenny

I checked a manual for a 365. it is a "thyristor" model.

Any beefy device on the HV side will be a SCR as I said earlier, and in
series with an inductor. The voltage across it will match that of the
storage cap.

 

[William Sommerwerck]

I checked a manual for a 365. it is a "thyristor" model.

TO-220 device is almost certainly the thyristor. It sits between the storage
capacitor and the flash tube. It's normally "on". When the auto-exposure
circuit determines that correct exposure has been obtained, the thyristor is
shut off, killing the flash tube's output.