Corsair SP2500 parts information required

[lexwalker]

Have a Corsair SP2500 power supply board currently under repair, but unfortunately at least two SMD components (R930 resistor and C937 capacitor) has burned to beyond recognition. The main power uses UC3843G I.C with AUK SMK1060 MOSFET driving the transformer. Does anyone here have some information regarding the values of those parts?

The resistor, to my best guess is either around 10K Ohms or 20K Ohms. Could also be either 1k Ohms or 2.2k Ohms as well (from the usual smaller power supplies using UC3843 I.C I've came across but those are around 45W only).

As for the capacitor, it looks like a C0G/NP0 type judging by the grey color and looks to be at least 1kV rating judging by the size (around 1206 metric).

[selldoor]

Re: Corsair SP2500 parts information required

Did you try cleaning the resistor with IPA - sometimes works.


There are a few diagrams in google images for the UC3843 I.C
do any of those help?

[lexwalker]

Re: Corsair SP2500 parts information required

Did you try cleaning the resistor with IPA - sometimes works.

Already done that, unfortunately most of top label area on that resistor has been destroyed. Can only see a tiny bit at one corner, looks the edge of the number "3", although can be another number altogether.

The main cause of the failure is, again, degraded glue which literally fully oxidized some through holes all the way to the bottom (can see clearly from the first picture posted, at the top left there are two solder pads next to each other which were severely oxidized), and literally dissolve leads on the discrete components on the top side. The degraded glue on this board looks shiny with tiny specks of what looks like a sea of crystals or salts, which is very different from usual degraded glue I've came across. To potential buyers, avoid buying this speaker system...

[lexwalker]

Re: Corsair SP2500 parts information required

Here are a few pictures after some degraded glue cleanup (and still in the process of clearing the board of this awful stuff). It ate into the resistor lead, and can see the greenish-blue oxidized stuff in that hole (whatever was left of the lead). Same goes with the lead on the ceramic capacitor in the 3rd picture...

[stj]

Re: Corsair SP2500 parts information required

i may be able to help, but you need to tell me how the parts connect.
i have a 450w supply with the same chip i need to re-cap this week.
same chip, but it's a different board.

[lexwalker]

Re: Corsair SP2500 parts information required

i may be able to help, but you need to tell me how the parts connect.
i have a 450w supply with the same chip i need to re-cap this week.
same chip, but it's a different board.

I've also have lots of schematics for the same I.C, including those around 230W (which is this speaker's power supply's rating). However none look that similar. Anyway, here's a partial schematic, still tracing most of the circuit. Other faulty parts found are a 12V zener diode (with markings "H2" in SOD123 package) and an unknown transistor. This transistor has the marking "CAGR" which I could not find any reference to. Not sure if the "..GR" is the date code either as the letters are together (as a single 4-letter code). The closest would be BCW61AR which has the markings "CA" for SOT23 package. This one is a difficult part to find, and other sites have suggested BCW30, BC860C and BCX71H as replacements...

Those marked in red boxes are all found to be faulty. Those capacitors with "?" is because they are SMD type, and as usual no markings at all. Currently looking for R930 and C937...

[stj]

Re: Corsair SP2500 parts information required

CAG = 2sa1980s-g in my book

[lexwalker]

Re: Corsair SP2500 parts information required

CAG = 2sa1980s-g in my book

As with BCW61AR also. Unfortunately that 2SA1980S-G is not sold on RS Component and Farnell/Newark/element14, thus will be looking for equivalent and/or compatible alternatives. Any recommendations?

As for the burnt resistor and capacitor, any information or make a guess as to the values of those components?

My current guesstimates are...

- R930 is either 10K or 20K
- C937 is either 1nF or 10nF

[lexwalker]

Re: Corsair SP2500 parts information required

My current guesstimates are...

- R930 is either 10K or 20K
- C937 is either 1nF or 10nF

For that capacitor, I found the largest C0G/NP0 with 1206 package and at least 1kV rating, is 1nF in capacitance. As for the resistor, it still un-decided yet...

But for that "CAGR" transistor, will go for BCX71H based on the following datasheet. Unfortunately could not find the A or G version, thus the H version looks to be closest (with overlapping hfe range)...

[ouroboros]

Re: Corsair SP2500 parts information required

R930 has 103 written on it and C937 has no markings on my board. If i was to measure that cap, wouldn't i have to remove it from the board first? If not then i'll measure it for you tomorrow with my ESR60

[ouroboros]

Re: Corsair SP2500 parts information required

I tried to measure C937 for you, but i would have to remove it from the board. Which i won't be able to do.

[lexwalker]

Re: Corsair SP2500 parts information required

R930 has 103 written on it and C937 has no markings on my board. If i was to measure that cap, wouldn't i have to remove it from the board first? If not then i'll measure it for you tomorrow with my ESR60

10K was one of my guesses and looks like I was right. Thanks a bundle, mate..

I tried to measure C937 for you, but i would have to remove it from the board. Which i won't be able to do.

If you do not have any hot air soldering equipment, then you could try de-soldering one of the transformer pins (as this capacitor is parallel to the transformer).

[ben7]

Re: Corsair SP2500 parts information required

10K was one of my guesses and looks like I was right. Thanks a bundle, mate..

If you do not have any hot air soldering equipment, then you could try de-soldering one of the transformer pins (as this capacitor is parallel to the transformer).

The capacitor probably is in the pF range, as the transformer operates at a high frequency, so I wouldn't expect it to have significant capacitance.

In the picture "C32", You should also check the large resistors which are standing near the heatsink. Also, it looks like one of the through hole resistors has a burnt spot on the top. (The one next to the 220K resistor)

(Oh, and is that a yellow Lelon capacitor?! Never seen a yellow one before!)

[ouroboros]

Re: Corsair SP2500 parts information required

If you do not have any hot air soldering equipment, then you could try de-soldering one of the transformer pins (as this capacitor is parallel to the transformer).

Did that and my meter showed 0,2nF for the C937.

[ben7]

Re: Corsair SP2500 parts information required

Did that and my meter showed 0,2nF for the C937.

Did you zero your meter first? just having the probe wires closer together, when measuring this low of a capacitance, can have quite an effect on the reading you get.

[budm]

Re: Corsair SP2500 parts information required

C937 and C? are part of the snubber circuit so the value have to be so that the ringing voltage will exceed the break down voltage of the MOSFET.
Typical value for the Gate-Source resistor is 10K.

[ouroboros]

Re: Corsair SP2500 parts information required

Did you zero your meter first? just having the probe wires closer together, when measuring this low of a capacitance, can have quite an effect on the reading you get.

I used 37XR-A and i followed it's manual and it didn't say anything about zeroing. But i did put the leads together before measuring...

[lexwalker]

Re: Corsair SP2500 parts information required

Did that and my meter showed 0,2nF for the C937.

Thanks! Sounds like 220pF, a little smaller than expected (for high power output unit) but will try that value.

The capacitor probably is in the pF range, as the transformer operates at a high frequency, so I wouldn't expect it to have significant capacitance.

C937 and C? are part of the snubber circuit so the value have to be so that the ringing voltage will exceed the break down voltage of the MOSFET.
Typical value for the Gate-Source resistor is 10K.

Yups, I did use 10K. However for the capacitor, I used 1nF instead. Was working very well, but then it suddenly blew again after about an hour. Took out the PWM I.C (again) and one 10 Ohm resistor driving the MOSFET, plus possibly a signal diode as well (that 1N4148). Not sure if the MOSFET has failed though as there are no shorts detected between the pins. I think the current sense resistor survived since it measured OK, and was using a 5W one instead of following the original 2W resistor (that failed)...

In the picture "C32", You should also check the large resistors which are standing near the heatsink. Also, it looks like one of the through hole resistors has a burnt spot on the top. (The one next to the 220K resistor)

(Oh, and is that a yellow Lelon capacitor?! Never seen a yellow one before!)

Already known that. Check one of my earlier posts above, the one with the schematics.

Pretty busy at the moment (repair work overload), thus some delays in replies (and also did not post much here lately)...

[ouroboros]

Re: Corsair SP2500 parts information required

Could you measure the resistance between positive and negative of connector CN101 for me? it's on the amplifier board...

[ouroboros]

Re: Corsair SP2500 parts information required

nevermind the above, found the short that caused the problem and got it working.