Hi Guys

I have 3 receivers (bought 2 hoping hoping to fix the first), the same resistor has failed on all 3 receivers (the resistor ballooned 3 times it's size), replacing the resistor hasn't fixed the auto-reboot issue.

Any help would be appreciated.

Thanks in advance.

 

Better pictures will help, you have a switchmode psu, ...... start praying...

 

Which model receiver are they? I recognise the board but what is the model and revision number?

 

Hi Guys

I'll get some better pictures up as soon as I can. It's a Spiderbox 7000.
Just to add the printed circuit board has a few components missing.
In theory they should be there, but for some reason they are not.

 

Ok, take a picture of the box, and also one with the case removed and the power supply in place. The missing components are probably because the manufacturer uses the same psu in different equipment which needs them. Save them having to have too many pcb designs.
Look on the boards for revision numbers and I will see if I have the schematics for them.

 

Hi,
You mentioned 3 receiver but the pictures is a smps power supply.
Do you have a knowledge if the output of the power supply is giving proper voltages.
Because the resistor in the receiver will blown if the supply output in the power supply is higher than the receiver voltage needed.
What is the value of the resistor and its wattage? Resistor will only be burned but not a ballooned.

 

Model: 25WS
Revision: 1.0
2010 02.08

 

Hi the pictures are too blurred to help, Try turning off the flash and take the picture in good daylight, outdoors if necessary. Also try and get the whole boards in, upload them as jpeg files then I can open them in Adobe photo shop.

 

Downloaded as JPG.

 

That's much better, give me a little bit of time and I will ask my ex business partner if we have a service manual or schematic. I don't see a "Ballooned" resistor, I wasn't too sure what you meant by that. Also I will look up the i.c and you can then check a couple of things. Be Very careful as you really need an isolating transformer when working on smp's. have a look at a thread I'm in the process of compiling. Bear with me and I'l see what I can do to get you going again.
Switch Mode Power supplies, My experience

The i.c marked Q2 is usually used to provide a separate supply for standby etc. and often damaged due to high esr capacitors, s/c diodes, etc

 

Hi,
You mentioned 3 receiver but the pictures is a smps power supply. - I've got 3 x Spiderbox 7000, The picture is of a power supply of one of them.

Do you have a knowledge if the output of the power supply is giving proper voltages. - No knowledge of that, I presume so, the receiver is auto booting and freezing.

Because the resistor in the receiver will blown if the supply output in the power supply is higher than the receiver voltage needed.
What is the value of the resistor and its wattage? It was R8 - orange, orange, red, gold, as it ballooned, oozed, it was unrecognisable. I think it was 3.135k. - 3.465k

Resistor will only be burned but not a ballooned.

 

That's much better, give me a little bit of time and I will ask my ex business partner if we have a service manual or schematic. I don't see a "Ballooned" resistor, I wasn't too sure what you meant by that. Also I will look up the i.c and you can then check a couple of things. Be Very careful as you really need an isolating transformer when working on smp's. have a look at a thread I'm in the process of compiling. Bear with me and I'l see what I can do to get you going again.
Switch Mode Power supplies, My experience

The i.c marked Q2 is usually used to provide a separate supply for standby etc. and often damaged due to high esr capacitors, s/c diodes, etc

O.K. Many Thanks, the ballooned resistor has been replaced in this unit (pictures), the other 2 resistors show the blown resistors.

 

Downloaded as JPG.

O.K. Many Thanks.

Have a look at the data sheet to give you an idea of how they are used. you will have to start checking a few voltages, and as I pointed out, Dangerous without an isolating transformer! just have a look at what I use when working on them!
Switch Mode Power supplies, My experience

Have you checked the fuse (the brown thing top left in pic three and four)? marked as T2al 250v

 

Have a look at the data sheet to give you an idea of how they are used. you will have to start checking a few voltages, and as I pointed out, Dangerous without an isolating transformer! just have a look at what I use when working on them!
Switch Mode Power supplies, My experience

That sheet looks difficult to understand. I've bought an auto-range multimeter.

 

This is the PSU from one of the other receivers, you can see the blown resistor. In all three receivers the same resistor has blown in the same manner.

 

Ok, in the other pictures I was not sure what you meant. Tell me the number on the device marked ic2, looks like a transistor near the resistor, also have a look underneath and tell me if the resistor connects to the opto coupler marked pc2 to the left of it in the picture where you replaced it.
Did you check the fuse? is it blown. if it is, don't just replace it and switch on or you may have more problems. just let me know before you connect it back to your mains supply.
Well it's nearly sleeping time for me now so will look in again tomorrow.

 

Ok, in the other pictures I was not sure what you meant. Tell me the number on the device marked ic2, looks like a transistor near the resistor, also have a look underneath and tell me if the resistor connects to the opto coupler marked pc2 to the left of it in the picture where you replaced it.

ic2 = KIA, 431A, 951
tell me if the resistor connects to the opto coupler marked pc2 = Yes it does.

Fuse as in the plug, no haven't checked that, but it powers up, so should be fine.

O.K. speak tomorrow, take care.

 

How to build an isolation transformer:

I have several transformers out of microwave ovens. Every unit I have starts with 120 VAC. The secondary is something you DON'T want to mess with, so don't even think of powering up one of those just to see all the colorful sparks and smoke. That said, you have to find the weld that secures the core together and cut the weld just deep enough to break through the weld and allow you to remove one end of the core. Carefully drive the high voltage winding off of the transformer core being careful not to nick the 120 primary winding. Once you have the secondary removed you'll need a second transformer the same size and rating. Go ahead and cut that one apart too, being just as careful not to damage any of the windings. Using some hard wood dowels you can usually drive the coil off of the core by tapping on it with a hammer and the dowel on one side then the other. Eventually you'll have the 120 volt primary free.

Using every bit of care possible, and being sure to use the insulating paper that came from one of the transformers carefully slip the second winding onto the core. When you initially took the transformer apart you found some steel tabs in between the primary and secondary windings. DON'T DAMAGE THEM AND DON'T NEGLECT TO PUT THEM BACK IN THE WAY YOU FOUND THEM. They limit the current. Without them you can over burden the transformer and over heat it.

Now that you have the two coils of the same size and rating onto one core, check EVERY contact to the core to make sure you didn't expose the core to any high voltage. That's why it's very important to keep the insulation paper in tact and do not damage it. You need to be SURE you don't have stray voltage on the core where someone can get a good shock.

What you've just built is a 1:1 (One to One) transformer. It retains most of the line voltage with some slight loss, but it's 100% isolated from main power, which is exactly what you want.

How does this help you? Well, you're working with a Switch Mode Power Supply (SMPS). They're dangerous because they're running directly from the mains. Don't be fooled into a false sense of security, 120 volts can still be quite deadly, so your SMPS STILL needs to be handled very very carefully.

I am hoping you can identify which component is the ballooned resistor. Looking at the pictures I saw no signs of any resistors overheating. I DID see some measling on the board, but that can be anything. Good photos too, by the way. All the capacitors look good. But you can't judge a component by looks alone. Sometimes it's obvious what has failed, like when part of the body is missing because it exploded through the casing. Other times a component may show signs of melting in one small location where the smoke leaked out. But often a component can be dead with no visible signs. To be sure, you're going to have to troubleshoot the system carefully. ALWAYS REMINDING YOURSELF THAT EVEN THOUGH IT PRODUCES A LOW VOLTAGE IT IS WORKING WITH HIGH VOLTAGE. We'd like to get to know you better when you ask questions, and eventually offer advice to someone who's encountering the same things you've already experienced.

Hope this is helpful. Keep in mind you don't MUST build an isolation transformer, but if anyone does, old microwaves are a good source of materials.

[edit] Forgot to mention I welded my core closed again. Which means I have a welder.

 

The fuse I was referring to is the one in the picture above. T2AL 250v. just let me know if it is blown, don't be tempted to wire it out and turn on if it is. After you have let me know if it is blown or not, I will see if we can identify the problem WITHOUT you having to connect it to the mains, but it will need very specific answers to a list of question I will ask. I've got a few things to do today, but will check back when I can.

 

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View attachment 133171

The fuse I was referring to is the one in the picture above. T2AL 250v. just let me know if it is blown, don't be tempted to wire it out and turn on if it is. After you have let me know if it is blown or not, I will see if we can identify the problem WITHOUT you having to connect it to the mains, but it will need very specific answers to a list of question I will ask. I've got a few things to do today, but will check back when I can.

O.K. will check the fuse and let you know.