Studio Light 320 watt-hour unable to achieve full power

[sherwinubaldo]

I have this old Chinese brand Jin Hui Fy-320 that cannot reach full power. Upon checking individual components and replacing some major parts like swapping the capacitors (3pcs 1800uf/350v in parallel) from a working studio light, new BTA12-600R Triac and a new BT152-800R Thyristor.

Here is the mystery of the repair adventure; when putting the new BT152-800R it can only reach 120 volts (across the main capacitors for a full minute of recycling) but with the old thyristor it can reach 260 volts in 4 seconds but never the 300 volts expected to give full power. Can someone shed light on the matter? I am attaching images of the board and the thyristor in question. Thanks in advance for the help.

Component side: https://drive.google.com/file/d/1oXA1KEtswnAMNjDJwdpBo-28s9TAYkaX/view?usp=sharing

Connection side: https://drive.google.com/file/d/1t8muHizl6wWNZ0DFuza-yf8Xkq4LsxZ_/view?usp=sharing

Old thyristor on top https://drive.google.com/file/d/1TuQ1v07tgFijxyqCSavlXArvM9M9WWUp/view?usp=sharing

[Cyberdragon]

Where did you get the thyrister from? It could be fake or faulty. Just leave the old one in for now.

Second, did you do that to the board, or was it already in bad condition? We have soldering advice in the beginner's section as bad soldering can also damage components.

It was probably never the triac or thyrister, they usually fail noticably, not with a small voltage drop. Without a schematic, the numbers on the chips would help figure out the circuit.

[sherwinubaldo]

I got the thyristor from RS Ph component online https://ph.rs-online.com/web/. They sent me 5 pcs. in a pack. About the soldering job, I had this repaired from where I bought it (3 years ago but it got same problem after just a few months of use) and I was in horror to see the condition of the board upon trying to analyze it myself. I cannot find any schematic diagrams online but my first suspect was the voltage multiplier that is why i had doubts with the thyristor. My friend has the same model and make that is why I was able to swap  the capacitors and the voltage readings on his reaches 330 volts in just 6 seconds. Could it be the 6A10 diodes at fault as well?

[sherwinubaldo]

I will try my best to trace out the schematic and will post it here. The triggering works perfect via sync cord or optical. What value of the resistor should I place between the gate and cathode of the BT152? Oh by the way, i am getting a reading of 80 volts dc on the gate via common wire (black wire going to the negative side of the capacitors) Thanks in advance.

[sherwinubaldo]

i will look for a resistor then within the 20k ohm range in my bin. Will report back in when I get home to do it.