| Author |
Message |
    
Cnit
Tinkerer
Username: Cnit
Post Number: 1
Registered: 08-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 12, 2011 - 06:06 am: | 
|
Hello,
I have bought a Olympus T32 flash. When turned to on it starts to make a sound when it charges. But there is still a continuous high pitch sound heard as long as the flash is turned on. The flash seems to operate correctly other than that. I have tried it both on my OM-10 and E-400 cameras. But is this noise expected? Or is it an indication that something is going wrong? I would hate to have it blow up in my face! And in any case its not the best thing to have to work with that noise in your ears all the time. Does anyone have any experience with this particular unit? Thanks. |
Br1078lum
Tinkerer
Username: Br1078lum
Post Number: 131
Registered: 11-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, August 12, 2011 - 10:55 am: |
|
I used flashes many years ago that would whine the whole time they were on. Though it didn't bother me, I had a nephew with sensitive hearing that would go nuts whenever I was taking pictures indoors. I think with the later technology, such as Thyristor circuitry, a lot of that went away.
PF |
Cnit
Tinkerer
Username: Cnit
Post Number: 2
Registered: 08-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 13, 2011 - 03:01 am: |
|
Seems I 'm stuck with the noise then. Pity. At least the flash is working fine. Thanks for the reply. |
Ron_g
Tinkerer
Username: Ron_g
Post Number: 84
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 13, 2011 - 01:20 pm: |
|
When the capacitor starts getting old they tend to leak between the plates therefore they are unable to reach a full charge so they are always drawing current while in the charge mode.
Eventually they won't even charge enough to light the ready light.The sound that you hear is an oscillator driving a transformer that creates the high voltage which is then rectified and stored in the flash capacitor.Ron G |
Cnit
Tinkerer
Username: Cnit
Post Number: 3
Registered: 08-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 14, 2011 - 01:24 am: |
|
Cheers Ron.
So its just the charging sound going on. Is there something I can do besides finding another unit that doesn't sing? |
Ron_g
Tinkerer
Username: Ron_g
Post Number: 85
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 14, 2011 - 04:10 am: |
|
The only cure is replacing the capacitor.
They can sometimes be hard to find because one of the parameters will be the physical size which is less of a consideration in larger equipment.
In many cases with real old equipment technological advances will produce the proper capacitance at the required voltage in a smaller size which will be in your favor.
I find that getting the rechargeable batteries can sometimes be a hassle as some of those batteries are no longer available and there is no room for the equivilent cells that you need for a replacement.Ron G |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 229
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 14, 2011 - 08:17 am: |
|
Okay, I have to chime in :D
There's a inverter design used very often in flash charge circuits.
[you can skip from here on if you are not interested in the background]
For those interested in the background: There are two challenges inherent to building a flash charger:
1) You start with an empty capacitor of a large capacity, essentially it is a short circuit. So you have to build a charger that can work shorted for a prolonged time (charging time is measured in seconds and overloaded semiconductors die within hundredths of a second, so for a semiconductor device there's little difference between five seconds and eternity).
2) You have to boost the voltage by a factor of 100 or more. This is harder to explain. To boost voltage you can use a transformer. A transformer is essentially two coils on one core. To rise voltage twice you need one of the coils to have twice more turns than the other. The thing is, that every coil has some parasite effects, that make certain designs better than others. Specifically, the number of turns is important. So if you have a coil core and bobbin that will work well with a coil of 100 turns, it seldom will work as easily with a coil of 10.000 turns. And to boost voltage 200x (from 2AA = about 2,5 Volt under load to 500V) you need to make a transformer that has secondary winding with over 200x more turns than the primary.
To build a good transformer with such a turn ratio is extremely challenging and contradicts requirement #1 (it has to be immune to short circuit).
Okay, long story cut short, there are two simple designs, that can get all the problems solved, however come with a share of their own quirks.
The first idea is to use the transformer as a storage coil. The work cycle consists of two phases: in the first one energy goes from the battery into the transformer. In the second phase the stored energy from the transformer is delivered to the flash capacitor. The TIME to store or release the energy is depending on the VOLTAGE. Since batteries keep their voltage the storage part of cycle keeps constant time. The flash capacitor voltage increases as it is getting charged and so cycle-by-cycle the time needed to *discharge* the transformer energy gets shorter. This is why in modern electronic flashes the whine gets higher and higher. Now, this method can always add a little charge each cycle so charging would never stop. There has to be some circuitry to measure the output voltage and to stop the circuit when there's enough. This solution is employed in modern flashguns and that's why they "whine" only while charging and the whine stops as soon as they're ready. Also, the whine does not go to very high frequency before it stops.
Now, the solution is real good, has good efficiency and charges the flash fast, but it is not without fault. A storing transformer needs bigger core and is more expensive, also the control circuitry has to be somewhat smart. In older flashguns, about from the time when TVs advertised "7 Transistors inside!", this was not a feasible solution. They used a different approach: The transformer is loaded with simple DC voltage from the battery and the transformed voltage goes directly to the flash capacitor. The secondary (HV) winding is made with really thin wire, so the resistance of the winding limits the charging current for an empty capacitor. DC voltage means, the current in the primary winding increases steadily till the core saturates. As soon as it saturates, the current is interrupted and core demagnetized, then the cycle repeats. Any energy stored in the transformer gets wasted, as well as all the energy lost in the resistance of the secondary winding. Overall efficiency is about 25-50% on a good day, but the circuit needs only ONE transistor and the transformer is small. This circuit oscillates with an increasing frequency because as the secondary voltage increases less and less energy can be transferred per cycle and so the cycles get shorter. Well designed circuit of this kind will increase the switching frequency indefinitely, but the output voltage will approach a definite final value: the voltage that comes from the winding proportion of the transformer. This way there's no need for any output voltage limiting or control, a simple neon light is enough to keep the voltage from any runaway.
This flash charger whines all the time, the whine frequency increases as the charge current drops. That's why an old and leaky capacitor can make these annoying: with leakage current high enough the whine frequency will not rise above hearing limit and will stay audible. Usual cure is to let the flash whine for an hour or so, the capacitor will get somewhat formed and the leakage will drop.
[end of background]
Most old flashes will whine indefinitely, you can help by putting a new *flash*grade* capacitor in, or you may try reforming the old one by letting it sit under charge for longer time: let the flash charge and let it on for some time, then don't fire it but let the cap full. Repeat a few times over the course of few days. the situation should improve if the reason was a leaky main cap. Some designs did whine all the time in audible range even new, nothing will help these. Mind it, they draw power from the batteries all the time, albeit noticeably less when full. Still, they will take but few, maybe few-teen hours to drain a set of batteries, this is normal.
Marek |
Cnit
Tinkerer
Username: Cnit
Post Number: 4
Registered: 08-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 21, 2011 - 11:38 am: |
|
I 've been trying the capacitor reforming and it does not seem to help. So it will have to be a capacitor change. Will post any further developments. |
Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 144
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 24, 2011 - 11:48 pm: |
|
I have an old Vivitar 283 that took about 2 days hooked up to an SB-4 A/C adapter before it finally reformed the capacitor. Works fine now. But I wonder how long it'll last.
I have a Canon 430EZ that I would love to get working but it has an auto-off feature, so there's no way to leave it on to reform its capacitor. So I guess I'll need to get a new one for it. |
|
