Repair of International Tower Lighting ITL-4740 Timing and Trigger Board Out of Flash Technology PC310-4 Strobe Controller and Power Supply Unit – October 9, 2021

International Tower Lighting ITL-4740 Timing and Trigger Emulation Board. This board is manufactured and sold by ITL as replacement for Flash Technology Corporation’s original timing and trigger board and can be set to emulate a variety of Flash Tech board configurations, depending on the lighting system configuration. The ITL-4740 has proven to be a very reliable board for my client’s, but like any electronics there might be the occasional failure. This one was possibly damaged by lightning hitting the tower, but there’s no real way to confirm that.

This failed International Tower Lighting ITL-4740 Emulation Timing & Trigger Board was part of the reason the top strobe on a client’s tower had stopped working recently. I got the strobe working again after temporarily replacing the failed ITL-4740 board and the burst resistor in the client’s Flash Technology PC310-4 Controller / Power Supply unit with a loaner Flash Tech board from one of my spare/emergency PC310-4i units and replacing the burst resistor with a new one.

Reference photo of board model number.
ITL factory software version number markings on logic IC.
Solder side view of ITL-4740 Timing and Trigger Board.
Inspecting and testing the board under the stereo microscope in the Alabama Broadcast Services, LLC Repair and Service Lab.

Inspection and Troubleshooting Findings

Troubleshooting revealed that the IRF740 MOSFET had short-circuited. The 220 Ohm / 2 Watt resistor connected in series with the MOSFET had also burned out, causing noticeable heat damage to the circuit board, although that was primarily a “cosmetic” issue — no traces or pads were damaged.
On the solder side of the ITL-4740 board, there was notable “blistering” and some charring from the intense heat which was produced when the MOSFET shorted and overheated the 220 Ohm / 2 Watt resistor seen in the previous photo. Again, the damage was essentially cosmetic with no trace or pad damage.

Performing the Repairs On The ITL-4740 Board

View of the area with the original IRF740 MOSFET and 220 Ohm resistor desoldered and removed. I did some cleanup in this area, although some of the charring is within the substrate of the board, so it’s there for posterity. It won’t present any problem functionally, however.
Failed components after removal from the circuit board. They obviously suffered some serious overheating.
Replacement components consisted of an NTE2397 MOSFET (to replace the IRF740) and a 220 Ohm / 2 Watt flameproof resistor.
View of board after some cleanup and installation of the replacement NTE2397 MOSFET and 220 Ohm / 2 Watt flameproof resistor.
Inspecting the solder joints at the MTE2397 on the component side. I always do a microscopic inspection of my soldering work, as I like to know the connections are solid, clean, and meet IPC-A-610 Standards as much as possible.
Microscopic inspection of the solder joints for the NTE2397 on the component side of the board looked good as well.
Microscopic inspection of solder joint at leg #1 of R35 (the replaced 220 Ohm / 2 Watt resistor.)
Inspecting the solder joint at R35 leg #1 on the solder side of the board.
Component side solder joint at leg #2 of R35 being inspected.
Solder joint at leg #2 of R35 on the solder side of the board looked good and solid as well. All solder joints checked out well.

Time To Test the Repaired ITL-4740 Timing and Trigger Board Under Actual Working Conditions

The repaired ITL-4740 Timing and Trigger Board installed in a known good Flash Technology Corporation PC310-4i Controller/Power Supply unit in my collection of “spare/emergency” strobe and tower lighting units.

The following video shows the board performing flawlessly in my spare/emergency Flash Technology PC310-4i controller/power supply unit. Both day and night modes are functioning as they should, with correct strobe intensity and flash rate. The flashes of the strobe in medium intensity (day mode) are a bit hard to see in the video because the flashes are so fast and so bright that the video camera has a hard time capturing them — they are much easier to catch on video in the low intensity/night mode.

Cost of the repair (not including my labor) was around $7.00 in parts, which sure beats having to purchase a new board. I certainly have nothing against the purchase and installation of new boards for clients, but why toss out a board which I can repair for the client (labor included) for roughly 20% of the cost of a new board? ITL offers repairs on the boards, but that would also have incurred shipping costs and going to the trouble of packaging the board for shipping. In this case, it made more sense to just repair it here in the lab.