Terbly PT-160B Shutter Issue

[partyanimallighting]

Hi all!

I ran into an issue will one of my Terbly PT-160B 5R beams (Golden Sea) recently and I thought it best to post the issue to find a solution. Please don't knock me too harshly but upon checking back, the last time these units came out of their flight cases was in 2017 but they have been stored in cases in a safe dry environment and the reason they were out of use was because I moved onto smaller lighter LED spots for all my smaller jobs. Anywayssss, I finally pulled them out for a job and surprisingly, all worked fine (except for the ONE). I was fully expecting lamp or ballast failures but I encountered no issues throughout the night that they were used (except for the ONE). Onto the ONE in question. The unit started up fine with no issues and no RESET errors but the shutter refused to open so I simply did not use it that night. I did some testing on the unit and the SHUTTER motor resets fine but refuses to open under DMX command or in AUTO function. I checked the harness wires from the motor to the PCB and there are no breaks, full continuity. I then swapped out the driver PCB in question with one from a working unit and the unit functioned fine so the problem is the driver PCB. So I lifted the heatsink off the driver IC that feeds the terminal to the shutter and it's L6225. So I had some of these lying around so I swapped out the IC and reinstalled but the issue was not resolved, in fact, it's completely different now. Before I was getting a glitch in the gobo wheel and no shutter control and the shutter was closed. Now I'm getting no color and no shutter but the shutter remains open. I would think that, if the issue was not the L6225 and it was replaced, the problem would not change. So now I'm thinking that maybe it's a microcontroller issue or issue with the 20 pin 74HC73D IC?? The working unit, although it's the identical model, has an additional terminal going into the third red input at the top of the PCB but the problematic unit does not have this terminal. However, the working PCB works fine in the problematic unit. I'm considering swapping out the 28 pin microcontroller to see if this is the cause of the problem but I DO NOT want to screw up this functioning PCB before I get some advice/guidance. Any feedback or assistance would be great.

The shutter motor terminal is top left white.

 

 

[indyld]

Regarding the change during diagnostic steps, I go back and check the work hasn't introduced a new issue. Assume you've done that, but still worth mentioning. Bridges, pins not properly connecting, cracked traces etc. Including at all connections/joints involved in removing the board. Every invasive diagnostic carries risk and I've caused plenty of new issues for myself over the years. 

Could also remove the driver IC completely to try to get certain functions back and verify what it's doing. 

I understood that during reset the motor could be seen to move but cannot be operated using manual control in the menu. This is puzzling as usually it either works or doesn't, unless there is an issue with firmware that prevents the manual control completely. If the driver has issues, they will be consistent. 

I would avoid lifting the MCU at the moment. Not convinced enough by verification given the info so far. 

Still feels like an issue around the drive circuit. Sense, drive, control. etc. 

Forgot to mention. You didn't state such, but the common way to verify driver issues is to first swap connections with another similar function nearby. 

 

 

Edited March 6, 2023 by indyld

[KevinE]

These are also sold under the ADJ brand, so I assume they will suffer similar problems. First I would change the capacitor on the secondary side of the dc-dc converter, this supplies the logic on the board, the capacitors are not the best quality. It's the small electrolytic below the inductor in the picture and any ripple can confuse the micro. Secondly as rob has already said, do check your work. It's always suspicious when a repair attempt makes something worse! It's easy for example to get the plugs in the wrong headers because they all look the same. There should be tiny inkjet-printed numbers on each plug matching the pcb markings.

I have a vague recollection of a blown stepper driver IC killing one of the micro output lines, so your suspicions of the micro may be right 😕 

 

[partyanimallighting]

Here's the update. As suggested, I pulled the PCB and retested all traces from the 4 pin shutter terminal to the relevant pins on the L6225 and continuity was fine. I retested this PCB in the working unit and double checked the homing of the motors (from top to bottom, SHUTTER, COLOR and FROST and the issue still exists and the unit takes forever to home as it continuously resets trying to clear the error codes. So I swapped around the terminals as you suggested (COLOR into SHUTTER etc) and there were the obvious error messages in the display and no tension in either of the three motors. I then put the terminals back in their correct positions and restarted and monitored for motor movement during the homing process. There is no movement except for the FROST and that is caused by gravity during the homing process and not motor movement. When the unit eventually resets all three motors can be moved by hand with no tension and every other function not performed by this PCB (PAN, TILT, GOBO, PRISM) works fine. I do recall that on the night that the units were used, I did open up this unit to check and the shutter was in a closed position and when I opened the shutter by hand, the unit went into a lengthy reset process but never functioned via DMX but I believe that the color wheel was functioning at that time. So now I'm thinking my poking around fried the microprocessor that was faulty to begin with.

[indyld]

If other motors are controlled by that board are fine, that removes the possibility of an issue with the motor supply but I would remove the IC you replaced completely and retest, having cleaned up the pads. 

Don't forget that removing the board flexes the joints on every connection, not just the faulty one. 

[partyanimallighting]

Hi indyld, all three motors controlled by the PCB are non-functional. As I mentioned above, when the unit eventually resets after trying to clear the error messages, all motor functions (SHUTTER FLAGS, FROST, COLOR WHEEL) can be easily turned by hand without any motor tension so I believe the problem is the microprocessor and not the driver IC but I will wait for your advice on this. I can't recall if I checked the FROST initially via DMX when the problem first occurred because I was focusing on the obvious problem, the closed shutter but this was over 3 weeks ago so I can't really recall. I did find another PCB in the warehouse today with a date of 2019 so I'll try this PCB in a bit to see if it's functional. Even if this found PCB is functional, I would still like to get the problematic PCB repaired and stored away as a spare so I'm going to continue troubleshooting.

[partyanimallighting]

Well, I just put in the found PCB and the unit is fully functional. Now it'll be packed away with the other working units probably for another 4 years. However, I'm still interested in getting the defective PCB working again and packing it away for later use.

 

[indyld]

I know that the faulty board isn't now a primary task at the moment, but:

It could be the controller, but also could be a lot of other things that have not been properly discounted. At present, it seems like perhaps none of the motors/attributes that run from this board are actually functioning. And maybe haven't since the first look. This is because the full initial fault state and the problem wasn't properly verified before making the first diagnostic change. The reason I mentioned removing the IC fitted during this change was to roll things back to nearer the starting point. Also, stepper drivers are sometimes used for two different attributes and if this isn't known, it can be helpful to find out which ones you lose when removing. (On older fixtures, the drivers were sometimes socketed making this easier.)

If it turns out none of the attributes are working from this board, the issue can still be pretty much anything. This includes any power supply made, regulated, or protected on that board.

The lesson for the future is improving the initial stages of diagnosis. I teach others in repair with the premise that "Never take the cover off anything without already knowing what is wrong with it and how to verify that". In this case, testing the unit with the lamp off and the cover off would be appropriate but hopefully the point holds up. Today, I have a customers' PS5 that at some point I am going to have to take the motherboard out BUT before that I will use every trick in the book to diagnose it intact. Not least because removing the board is not a fast process and, as always, comes with risks. Given the described symptoms, I even have a pretty good idea of where to start looking, and a test/verification strategy for much of that system. But. I'm not replacing a £70 IC in a tricky spot on a difficult board until the last possible moment.

Keep them coming, I enjoy thinking about these boards. 🙂

Edited March 8, 2023 by indyld

[partyanimallighting]

Hi indyld, I fully understand where you're coming from. I really did not fully check all the issues and I really should have check all of the PCB's attributes before assuming that it was only a shutter driver issue and changing out the driver. If I make some time, I'll do as you suggested and remove the new driver and see how the PCB responds and continue probing from there.