Fluorescent Light YZ-236EAA T8/PLL Ballast fault - Page 1
Forum section: electronics / repair

author: Bsas3
author_rank: Newbie
timestamp: November 12, 2024, 01:33:01 am
content: Hi all,I've been trying to track down a circuit board diagram for this Ballast, from a 2 X 36w Fluro light. It has 2 resistors with obvious damage. However, both are still reading resistance. I have marked them with blue arrows. The first Inductor (labelled LC 25094 2.65mH) after these, is showing signs of overheating, as is the MJE13007 Transistor before them. If anyone could point me in the right direction, I would be very grateful.John(Bsas3).

author: benj38
author_rank: Frequent Contributor
timestamp: November 12, 2024, 11:34:26 am
content: I would be surprised if you will find a schematic for this.Given that the board has so few components, even without knowing how such circuits work you can get very far simply by testing all the individual components for obvious faults.

author: Bsas3
author_rank: Newbie
timestamp: November 12, 2024, 09:22:09 pm
content: Thanks for your input. I was thinking the same. One of the damaged resistors, now looks to be a fuse resistor. Which helps to explain the weird colour code.

author: MathWizard
author_rank: Super Contributor
timestamp: November 13, 2024, 12:21:36 am
content: If it's something like this schematic, it would be R1/2, power resistors, used to limit the current to some reasonable level, when the transistor's are fully on. Sometimes they are the fusable type too, those might be just modern carbon resistors.Does it still light up tubes any more ? Resistors like that and even the PCB and caps near them, can get a bit cooked over time.Is this just maintenance or did something else fail ??

author: Bsas3
author_rank: Newbie
timestamp: November 13, 2024, 12:29:26 am
content: Thanks for your reply. Unfortunately, it doesn't power the tubes at all, but there is still some voltage getting to them. It's a work light in my garage, which suddenly just stopped working. I bought two new tubes, but nothing. I hate throwing things out, if they can be fixed.

author: MathWizard
author_rank: Super Contributor
timestamp: November 14, 2024, 02:50:32 am
content: Do you have an oscilloscope ? Some part is probably just gone a bit bad, or fully bad. Was there any controller IC? Was it a double sided PCB with stuff on the bottom too ?If not and that's all the parts, there's not much to goes wrong. What voltages do you measure around the board ? Watch out for dangerous levels, I usually clip on a few wires, or solder on wires, to make testing easy/safe.Most of these parts could be checked to some degree, unpowered, in circuit, with a DMM.What voltage do you get right after those 4 diodes, left of the giant electrolytic caps ? The diodes would probably be a full-wave rectifier, so you'd probably get about 1.42x the VAC there.In the schematic I posted, that would be the voltage between the top of C1 and bottom of C2

author: Bsas3
author_rank: Newbie
timestamp: November 15, 2024, 05:20:12 am
content: Sorry for the delay, I was mowing the lawn, before a storm. All Diodes on the board are measuring between .55 - .6v drop in diode mode, & OL the opposite way. The only two components that I've found to be bad are R10 & R12. R10 is the same as R11, which test at 11.8-12Ω, whereas R12 is the same as R13. This one measures 1.825MΩ on board & about .9-1.0MΩ out of the board???The back of the board has a few SMD resistors & capacitors & two Zener diodes next to each of the MJE13007 Switch-mode NPN Bipolar Power Transistors. Board view attached.Thanks again for your knowledge & experience. I'm just struggling along, trying to learn something new in my retirement. I need all the help I can get.

author: MathWizard
author_rank: Super Contributor
timestamp: November 18, 2024, 09:35:01 am
content: I've never worked on 1 of these, so I'm trying to make a model of it in LTSpice. Did you ever get the voltage from those 2 giant black caps ? It should be up around 340V if there's no real load on it.I'm having trouble seeing the colours on these resistor's, like R3, R10-R13. So what do you think they were/ and what are they now that's wrong ? IDK the max allowable drift, but yeah it's probably like the tolerance and only a few percent like %5-10%.What is Q3, I'm not sure yet if it's something like a TL431, is R3 feeding it, a 51K ?. But overall the main 2 transistor's, should be oscillating. If you're not sure they are running, you could take them out and check them with a DMM.Some of those caps around there, like in the base drives, would be prime suspects for wearing out too, like those big red ones, even if they still work some. So I'd want to check them out of circuit (or unsolder 1 leg ) with a normal capacitance meter. Cap C3, I'd also check it's ESR with an meter, since I own 1. And I'd check the ESR of those main bulk caps too.Here's omse of the schematic if it helps, I never really labelled it tho

author: Bsas3
author_rank: Newbie
timestamp: November 22, 2024, 08:22:55 am
content: Finally had time to identify most parts on the board, starting from the 3 wire 240v inlet, J1 Jumper, L1 JHD19006 60-120mH, R1 Glass fuse JF3, C4CE102M 1nf 240v,C5 MPX/MPK x2 SR-CAP .22uf 280v,L2 BXRJJ16002 4.1mH, D3-D6 IN4007, C6 SR-CAP .047uf 250v, C7 & C8 473J 47nf 630v, D9-D12 FR107,D7 & D8 IN4007, C1 & C2 22uf 350v, R3 51.3Ω .5%, D13 FR107, D1 DB3 C531 DIAC, Q3 X0619 Gate SCR, D2 DB3 C531 DIAC, Q4 S8050 NPN Tran, J2 Jumper, Q2 MJE 13007 Switch Mode NPN Bipolar Trans, R11 12Ω 0.5%, R13 1.8MΩ ?, D16 FR107,C12 10uf 50v, J3 Jumper, D17 FR107, L7 ?, R10 12Ω 0.5%, R12 ?, D18 & D19 FR107, C15 & C16 8.2nf 630v, Q1 MJE 13007, L3 & L4 LC25094 2.65mH, C13 & C14 15nf 1250v, D21 Blank, K2 6 wire outlet, D20 Blank,Back SideR16 - R21 1203, D14 ?, C10 ?, R22 & R23 5602, R14 & R15 224, R24 334,R25 1001, C11 ?, D15 ?, R26 4701, R28 0, R27 4701, C17 ?, R9 510, R5 - R8 224, C9 ?,D14 & D15 are small SMD Zener Diodes as per picture, appear to be Black /Silver & SMD Caps I have no idea of the values. Appreciate any help on these.