Switching power supply repair

[KeepItSimpleStupid]

Wow! you get parts fast.

I lost my registration there and I always have trouble with the questions and I really shouldn't. The time before today, the questions were non-English. At least they were English this time. It said, I think that I got 1 right. Well, I know I got one wrong, but I accidentally clicked the wrong answer.

The site doesn't use cookies or the email for retry attempts, That leaves IP address or MAC address. I tried a different email and it said i took the test, so it's either IP or MAC address. Changing the IP address of the router is definitely possible by turning it off. I don't know how long it takes.

The MAC address is probably the modem's or the routers. I have the means of trying stuff, but don't feel like it.
e.g new modem IP (turn off & check); new modem MAC (switch modems or possibly go non-bridge); New PC mac (switch PC's).

I don;t understand the protocols enough to know what MAC is affected by the outside world in bridge mode. I think an html page can read the MAC address of the computer that i am on.

 

[lynx]

Wow! you get parts fast.

I lost my registration there and I always have trouble with the questions and I really shouldn't.

hi

last monday i ordered the IC yesterday evening i had it...costed 2.90 euros

you don't need registration to download 1-2 schematics...(i haven't registered) also probably they use cookies
to trace if you're the same person trying to download from a different IP. if you can't manage to get the pdf then
tell me and i'll try to download it from my mobile phone, but why you can't see the png photo i uploaded?
i know it's not super clear but that's what i also have so i can check the board.

P.S guys.. i need help to troubleshoot thank you.

 

[KeepItSimpleStupid]

OK, here is the PDF. Thanks. The site doesn't use cookies. I deleted them all.

The first thing to check would be rectified mains across the the big cap which is also pin 9 with respect to pin 8 of the regulator.

Note that there are three grounds (commons) in that power supply, so be careful.

Check the resistances of the transformer in both directions. The primary will be difficult. I'd also look for shorts on any of the voltage supplies it's supposed to generate. Resistances in both directions.

See, what voltage you get between pins 7 & 8 of the IC.

 

[lynx]

The first thing to check would be rectified mains across the the big cap

the voltage at that point it is 320VDC

Check the resistances of the transformer in both directions.

can you give me more details? which pins and what values i should expect?
(i have L meter in case it is useful)

See, what voltage you get between pins 7 & 8 of the IC.

pin 7-8 for a short time i think it was 11VAC now shows no voltage
but probing between the one leg of the R101 and the pin 8 of the IC
it is around 110VDC

 

[KeepItSimpleStupid]

Between IC pins 7 & 8 , I would expect a DC voltage rectified by D105. So check D105 for shorts. If it's shorted, then look at the components nearby for changes in value. If D105 is shorted, the IC may be toast again. D105 being toast might make some sense.

==

Transformer:
e.g. Resistance in-circuit transformer pins 7&8 with probes one way and then the other. Repeat for all windings. 7&8 would be influenced by the FET body diode whereas transformer pins 18 & 14 would be different if the secondary was open because of D107.

 

[lynx]

I would expect a DC voltage rectified by D105. So check D105 for shorts.

D105 doesn't look shorted it is replaced and i also checked now on circuit. (the pcb is very delicate and it's easy to lift pads)

Transformer:
e.g. Resistance in-circuit transformer pins 7&8 with probes one way and then the other.

pins 7 & 8 ??

measuring pin 1 & 3 of the trasformer it is 18uH on circuit and 1 ohm resistance

7 & 9 it's 4 ohm and 402uH

 

[KeepItSimpleStupid]

Mistake on my part reading: 7 & 9 of the transformer.

Per the 2A65 datasheet http://www.datasheetcatalog.com/datasheets_pdf/I/C/E/_/ICE_2A165.shtml Vcc should be between 8.5 and 21 VDC. The VCC pin looks like a rectified, and filtered voltage divider. It should be DC.

The other thing is that the 2A165 oscillates at 20 kHz which may be too low. The circuit may oscillate and generate much lower voltages if the frequency is lower than expected.

Are the supply voltages generated low by chance or non-existant?

In a bit, I'll have to go out for a while.

EDIT: Blurb about frequency lower

 

[lynx]

Mistake on my part reading: 7 & 9 of the transformer.

no problem.. as i said previously... 7 & 9 it's 4 ohm and 402uH

Per the 2A65 datasheet http://www.datasheetcatalog.com/datasheets_pdf/I/C/E/_/ICE_2A165.shtml Vcc should be between 8.5 and 21 VDC. The VCC pin looks like a rectified, and filtered voltage divider. It should be DC.

i don't understand why i don't see that voltage (or maybe i thought i saw that voltage for a short period of time)
do you think a shorted capacitor could make that mess? there are two decoupling capacitors C102 and C103
as i said before i shouldn't desolder parts for no reason because the pcb it's very delicate. but do you think i
should do it so i can check atleast one of these caps?

that power supply line VCC/GND for the IC doesn't have many stuff that i can think they might failed.

The other thing is that the 2A165 oscillates at 20 kHz which may be too low. The circuit may oscillate and generate much lower voltages if the frequency is lower than expected.

no...as far as i can understand it oscillates at 100KHz but what i bought it is the 2A265 not 2A165 although probably
the board had the 165 which is lower watt version.

 

[lynx]

guys any help pls?

 

[MrAl]

Hi,

Did you check the snubber diode and cap and resistor?

You'll probably have to check many of the parts in this thing to see if any went bad.

Is that the right chip, the 2A165?

 

[lynx]

Hi,

Did you check the snubber diode and cap and resistor?

You'll probably have to check many of the parts in this thing to see if any went bad.

Is that the right chip, the 2A165?

the ICE2Axxx IC differences inly wattage and oscilation frequency what i bought is higher wattage same frequency with the 2a165

 

[tvtech]

Hi Guys

SMPS transformers rarely fail...

Unlike Line Output Transformers that do. Regularly.

Regards,
tvtech

 

[MrAl]

the ICE2Axxx IC differences inly wattage and oscilation frequency what i bought is higher wattage same frequency with the 2a165

Hi,

Well i asked you if you checked the snubber circuit, did you ?
These things could cause it to fail and possibly not right away but after being on for a little while or a long while.

 

[KeepItSimpleStupid]

You still haven't measured any of the DC supplies to see if they are barely functioning or dead.

tvtech said that the SMPS transformer rarely fails and he's probably right, but you still can check all of the windings.

I'll print the schematic and look at it some more/

 

[KeepItSimpleStupid]

Without DC at pins 7 & 8, I think we have problems. You said you had about 11 VAC there.

So take a look at D101, D103 (most likely)
C102, C103 - not likely
R101, R102 and R103
D105 has already be covered.

D103 and D103 - Not likely

In circuit tests should be fine.

The diodes have to be responsible for rectification.

Bet R101, D100 and D102, C102 and C103 are responsible for startup. Then it's up to C102, D105, R102 and R103 to sustain Vcc.

 

[alec_t]

Check for a dry joint either end of R104. Excessive resistance there would probably shut down the IC.

 

[lynx]

Hi,

Well i asked you if you checked the snubber circuit, did you ?

you mean the diode on the heatsink? ...the SMPS IC doesn't even start, so
i guess right now that diode it's the least concern maybe?

You still haven't measured any of the DC supplies to see if they are barely functioning or dead.

but i did...and and i have already told you about it, (last post on page #2)

i took some measurements and the voltages don't seem right.

now that i have the schematic i took some more measurements at the output of the transformer and i saw none of the voltages
listed at the schematic...either the pins show no voltage or far more less, usually 2-3 volts which fluctuates!

also...i've changed multimeter and tried to measure again at the pin 7-8 of the 2A265 and i've noticed that the voltage
also fluctuates at these pins usually it's 11-12VDC but it is going going up and down i've also saw 2VDC.

also measured all the diodes and the resistors around the IC in circuit and everything looked fine, i've also
tried to measure the resistors from nearby pads to see for broken joints or maybe for faulty results because
of the in circuit measurement, but again everything looked fine, now i'll try to measure the capacitors in
circuit but i don't know if i can manage to have accurate results (as i said i should avoid desoldering because
of pad lift danger).

i want to ask...can i remove the IC and power the board so i can check pin 7-8 or it may damage something?
i have the IC in a socket so i can remove it easily.

 

[MrAl]

you mean the diode on the heatsink? ...the SMPS IC doesn't even start, so
i guess right now that diode it's the least concern maybe?

Diode D104, resistor R105 and cap C108 in the schematic.

The diode shorted could stop the circuit from starting up, as well as the resistor and cap.
If the diode is open the circuit could easily destroy itself after a few seconds running, or maybe a longer run time.
If the resistor is open it could take out the diode which could then prevent startup, or destruction after a few seconds of operation.
If the cap is open the circuit could start and then destroy itself after a few seconds running (or longer).
If the cap is shorted it could stop the circuit from starting.

So the failed operating mode depends on what is bad and how it actually went bad: short or open.

When my scanner power supply blew up (smoked) i did not attempt to fix it because it had a transformer in it and various other parts which are hard to identify. Instead i just designed a new power supply which took about 30 minutes. Took about a week to get all the parts in, then after another couple hours it was up and running and ran ever since.
One thing nice about building your own power supply is that you know exactly what all the parts are and what they do, and usually you build it so it can handle more current than it actually has to so it lasts a long time.
You've got more voltages here than i had with that supply, but that's not too much of a problem as you just build several supplies rather than one single one. Some voltages can be gotten from others too, like the 3.3v can be gotten from the 5v line with a simple cheap regulator IC chip.[/quote]

 

[lynx]

measuring again the components around the IC i found that R104 was blown...it wasn't obvious until i
looked at it from the sides and i've noticed the coating from the bottom side of the resistor was missing,
from the schematic i can see it goes to the pin that says ISENSE i guess it senses current...but since i
don't know much about switching power supplies i don't know if that resistor is the cause that the
previous IC got blown and now the new one is not functioning.

it's value must be 0.47ohm (yellow, blue or purple? and silver) and now it measures 7Mohm and it is 0.5W
which i don't have because it is rare number...with what else i could substitute that resistor?

do you think i should power up the supply after i change the resistor or it might blow the IC again?

thank you guys.

 

[lynx]

When my scanner power supply blew up (smoked) i did not attempt to fix it because it had a transformer in it and various other parts which are hard to identify. Instead i just designed a new power supply which took about 30 minutes. Took about a week to get all the parts in, then after another couple hours it was up and running and ran ever since.
One thing nice about building your own power supply is that you know exactly what all the parts are and what they do, and usually you build it so it can handle more current than it actually has to so it lasts a long time.
You've got more voltages here than i had with that supply, but that's not too much of a problem as you just build several supplies rather than one single one. Some voltages can be gotten from others too, like the 3.3v can be gotten from the 5v line with a simple cheap regulator IC chip.

recently i've built an LM350K power supply i had an old stabilized 13.8v power supply with three 7812 i kept the box and the pcb
i've changed the diodes to 6A6, did some holes for the heatsink of the lm350 and for the potentiometer, replaced some cables with
thicker ones and it's ready...now i can take advantage of the huge tranformer the PSU had and i can regulate from 23VDC to 1.25VDC at 3A
(i guess below 13volts it's not giving 3A, but still it's ok!!!) but this has nothing to do with thedesigning of a new power supply for the DVD-R!!

don't forget thes witching outputs also negative voltages and it is also supplying the VFD desplay!! also the currents for all these rails are unknown as you can see the schematic doesn't even give the values for the components.