Tecnoware FAL501FS12 does not turn on

[CapLeaker]

Re: Tecnoware FAL501FS12 does not turn on

216 what? ohms, k ohms, M ohms...
just a 216 of something doesn't mean anything. When you measure Ohms, the power supply is off, correct? If you have the PSU on while doing measurements in Ohms, you get false readings.

Find some resistors in different known values, like 100 ohm, 1 kOhm, 100kOhm, 1 MOhm etc and see if your DMM can read them correctly out of circuit. Also make sure the battery is good. Some meters don't show correct readings when the battery is almost dead.

Reading components in circuit can be tricky as it depends on the circuit if a component can be read properly or not.

So when you come across a component that has a questionable reading, always take it off the circuit and retest.

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

yes it is exactly what I said, I have another one and that I believe is with the measurement of the ohms in automatic, but that also signals me. 216, so this measurement is wrong? what should the multimeter measure with that resistance?

[CapLeaker]

Re: Tecnoware FAL501FS12 does not turn on

Are you saying that you have to measure everything with your DMM in the 2M Ohm position? The other Ohm settings don't work? If that's the case, you want to invest into a new DMM, maybe even a auto ranging one.

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

This is my multimeter, the only value I can see is when I put the knob on ohm 2m with everyone else it doesn't give me anything, I repeat one of the resistances signals me .216, the other with the same colors gives me 0 in all positions in ohms (naturally out of the circuit)

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

the test I did it off the track of course but the one that looked bad did not mark anything, now I don't have the strength to prove if the problem is because here is a holiday, tomorrow I will replace it, in a while I send a photo of mine multimeter to understand if I measured exactly

[CapLeaker]

Re: Tecnoware FAL501FS12 does not turn on

A usual, if you find something questionable, take it out of circuit and measure it again.
Damaged resistors go 99.9% either higher in value or open. I guess you found a bad bleeder resistor. Resistors are measured in Ohm, measure them again out of circuit.

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

it's this one

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

Good morning,
The resistance in question is this, there are two equal ones among the large capacitors, of which one marks me about .218, the other identical marks nothing

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

perfect tomorrow i will do what you told me, now it's night here thanks for the moment

[momaka]

Re: Tecnoware FAL501FS12 does not turn on

They are the pictures let me understand what are the resistances to check

First, see that red polypropylene film cap between one of the big input caps and the main transformer? This is the H-bridge coupling cap. Remove it for now.

Next, see the small resistor between the two big input caps? This is one of the two discharge resistors placed across each cap. Find the other one - it should be close to the big caps also and have the same value. Take both out of circuit and measure their resistances. If they are in spec (i.e. no more than +/- 5% of their printer value, which should be somewhere around 100+ KOhms... looks like 510 KOhms if I'm reading the bands correctly), the unbalanced voltage could be coming from the switching transistors on the primary side.

So again, if the "bleed" discharge resistors across the big input caps measure proper resistance out of circuit, then the problem could be from the switching transistors for the main PS. In that case, remove transistors Q7 and Q8, along with the two bigger diodes in front of them. Put Q6 back in, as that is for the 5VSB circuit. Now try running power to the PSU and check again the voltages across the two big primary caps. It should be balanced and more or less equal. Please post back your findings in regards to what I mentioned above so we can confirm step by step what is good and what isn't.

sorry, maybe I didn't explain myself well, there are two integrated similar to the tl494 but neither of them has this abbreviation, which six are I to check? one of the two if I'm not mistaken is an lm339

LM339 is a quad op-amp. This is likely used for handling the protections (short-circuit, under-voltage, and over-voltage.) This is NOT the PWM chip we are looking for.

TL494 = DBL494 = KA7500
So really look for anything with *494 or *7500
.
.
.
Unless the PWM IC is a AT2005b or ATX2005 or some other custom IC (please post info what it is.)

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

sorry, maybe I didn't explain myself well, there are two integrated similar to the tl494 but neither of them has this abbreviation, which six are I to check? one of the two if I'm not mistaken is an lm339

[CapLeaker]

Re: Tecnoware FAL501FS12 does not turn on

without a way to measure ESR, just change them both. Or trace pin 12 from TL494 back.

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

if I'm not mistaken there are two in, one seen in the photo, the other is under the heatsink, which of the two?

[CapLeaker]

Re: Tecnoware FAL501FS12 does not turn on

yes, we know... but the circuit is similar. Check that pin 12 and see how much Vcc you get.

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

that's not the schematic of this power supply, and that component isn't there

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

no unfortunately I don't have this tool, I noticed that the unbalanced capacitor charges up to 130 volts then slowly drops to about 95 volts while the other starts from 160 and reaches 220

[CapLeaker]

Re: Tecnoware FAL501FS12 does not turn on

so the main filter caps are still not balanced? Hmm... can you measure how much current the power supply draws from the power mains? something like a watt meter?
check Vcc on pin 12 on the TL494 IC. In the schematic there is a C21 that supplies pin 12 on that TL494. Change C21.

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

I replaced the rectifier bridge but nothing to do, same problem, I also put the new capacitors to scruple, we hope to understand what's going on

[falcontech]

Re: Tecnoware FAL501FS12 does not turn on

it's one of the old ones, but it's working I tried it on another power supply, however even with the new ones it does the same problem, now I try to change the bridge

[CapLeaker]

Re: Tecnoware FAL501FS12 does not turn on

the big 200V capacitor next to the bridge rectifier looks bloated to me.