We use cookies to provide our visitors with an optimal site experience. View our privacy notice and cookie notice to learn more about how we use cookies and how to manage your settings. By proceeding on our website you consent to the use of cookies.
I was using an off-camera flash in an office environment when out of the blue, it sounded like a gun went off. Before I get into the damage, i’ll explain the flash so you have some background. This type of flash has a “pack” that houses the controls and battery, and two “heads” that each connect to the pack with cords. Each head has a flash tube (quick burst of light like a strobe light), and a modeling light (continuous LED, which can be used for aiming lights or video work).
After the loud pop, one modeling light is stuck on, and the other modeling light wont turn on at all. The actual flash part still works fine though. I opened the heads up and they’re comprised of one main circuit board, and another board that mainly holds the modeling light. On one of the main boards there’s an obviously blown resistor (R603), and a thru-hole pad looks burned (next to M600). However, it doesn’t look like a component was there. I tried swapping the LED boards with each head and those are fine so the problem is in the head’s main board and/or the pack. Can you tell what value R603 is or do you need a better pic?
That one resistor obviously needs to be replaced, but what else could be the issue since I’m having issues with both heads? And what do you think caused it?
I opened up the pack and the components seem good, nothing obviously blown and no swollen caps. The pins of the cord socket have dark around them but I’m not sure if it’s just dark flux or some kind of burn.
I can read schematics and have been soldering a long time, but I’m no electrical engineer so any help is appreciated!
Suspecting that the trigger voltage of one of the flash xenon tubes leaked to the LED side circuitry and destroyed the LED drivers. That is, the main damage is probably in the battery pack unit, although you could not see anything alarming there. Can you take some photos (also the bottom side of the head’s PCB)?
Cheers, heke
Thank you for contacting DigiKey , I am not seeing any real visible damage on the other main boards other than the discoloration on hhat looks to be the circular connectors . here is a link to those style resistors 100 ohm 1% .
Thank you for the excellent photos.
First you’d replace the retired resistor R603 to the one @Craig_2048 provided a link (if you happen to have some other type of 100ohm resistors around, you can try with them).
You stated:
Try plugging each head to each connector to see if the problem depends on the head or the socket where the head is plugged in.
Note that the problematic part may be a cable as well. Try swapping the cables to see if the problem follows.
Note: Be careful with the bare boards. Some tracks and exposed metal parts may contain hundreds of volts, if the boards are powered up, and for a while even after the boards are powered down.
Cheers, heke
I swapped head parts and the problem seems to be within the board shown in the second picture in the first post (the board with the blown resistor). The other head doesn’t show any obvious damage, but the modeling light is stuck on. What could be causing that?
Also, there appear to be heat marks on the two inducers in the pic below. Is that normal? That board appears to be working OK though.
In case it helps with diagnosing, I took apart the cable ends and noticed the cables have 3 burnt pins.
Does Digikey sell those amphenol connectors, and cable?
That you for the additional picture. Now it makes sense. I was wondering while staring the earlier photos that where is the LED driver…
At first, you should replace the blown out resistor. Then, on the modeling light that is always on, you could replace the MOSFET (referenced as T1).
(is obsolete, replace with recommended options)
Cheers, heke
