Tecnoware FAL501FS12 does not turn on

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

can you tell me if this transistor can be problematic?

[R_J]

Re: Tecnoware FAL501FS12 does not turn on

I do not know if there is a problem with the transistors, If they were shorted they usually burn the 10Ω (next to the driver transformer) or the 1.5K (next to the small diode near the white plug and fuse)
The KA7500 has vcc but also needs to be turned on, If it is turned on and working, it will output drive waveforms to the two small transistors connected to the T2, these small transistors drive T2 which drives the two primary transistors.

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

so what do I do? of course I try to change them, if that is not the problem how do I proceed?

[R_J]

Re: Tecnoware FAL501FS12 does not turn on

so what do I do? of course I try to change them, if that is not the problem how do I proceed?

Change what? the transistors? the ic? Have you tried reinstalling ALL the parts and see if the power supply works? The power supply might not try to turn on because it does not see any voltage on the +12v or +5v supplies.
While you have the main primary transistors removed I would change those 2 small electrolytic caps near Q7 and Q8 They are the same ones listed on the schematic as C7 and C6or8? (10µf/50v)

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

of course I tried, every time I change some component I put everything back and try again, I am making attempts, otherwise I was not here to ask you for help, my knowledge stops at bad capacitors and burnt schotty mosfets and diodes, at the bridge rectifier, in short those common things, since I can't go further I'm asking for help, maybe my culture on switching power supplies will be wider

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

already done, the capacitors have all been changed, they are all new, later I try to change the npn transistors, if it doesn't work it could be one of the ics?

[R_J]

Re: Tecnoware FAL501FS12 does not turn on

Do you get any voltage on the +5 or +12 (even 1or2v) when you turn on the power supply?
There is 16 volts on the KA7500 pin 12 which is good. There should also be part of that voltage (10~12v) going to the drive transformer, I traced the path so can you check the small diode next to the 1.5k and the 1.5k and the 100Ω (in green square) I also marked the schematic

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

no, I don't have a minimum voltage in the outputs even on the 3.3v ... then summing up, I have to check the goodness of those components that you reported to me and see if I have 12v on that yellow track? sorry if I ask you but I'm using the translator and it's not always clear

[R_J]

Re: Tecnoware FAL501FS12 does not turn on

Is there any other voltage on the KA7500? I know pin 12 has 16 volts but what about the other pins?

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

I only checked pin 12 as it was recommended to me, what other pins should I check?

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

about post # 68 you didn't reply to me if I understood what to do or not

[R_J]

Re: Tecnoware FAL501FS12 does not turn on

I only asked if there was a small amount of voltage on the 12 volt line to see if the power supply tried to start and maybe shut down. It is not that important now.

It is important to have voltage on the drive transformer. That voltage supplies the collectors of the two 2sc945.
On the KA7500, check pins 16 and 15

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

ok in a while I reassemble everything and check, I want to change the two transistors now that I have disassembled them and there is one that does not convince me

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

I reassembled everything, I replaced the transistors but did not want to know how to turn on, on pin 15 we have 4.99 volts on pin 16 2.80 volts

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

I have practically changed all the components, it is driving me crazy

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

but now on the transformer I have 6.50 volts when it is on, 1.50 volts in standby

[R_J]

Re: Tecnoware FAL501FS12 does not turn on

but now on the transformer I have 6.50 volts when it is on, 1.50 volts in standby

That is good, It could be that the KA7500 was damaged when the transistor failed.
Do you see any voltage on the +12 or the +5 when you first turn on the power supply?

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

no, I don't see anything but nothing, there is no shadow of tension, I tried to replace the ka7500 with a tl494 taken from a working power supply but nothing does not start, could it be lm339?

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

i tried to change also lm339 nothing moves, tell me what i can try now it has truly become a mystery

[CapLeaker]

Re: Tecnoware FAL501FS12 does not turn on

I have practically changed all the components, it is driving me crazy

maybe mark on the picture or schematic what you changed. Just by trying to catch up on this thread it makes my head spin!