Ultra X4 600 ULT-HE620X repair project

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

I think that green band is either the type of resistor or the manufacturer of the resistor.

It would have been much better if they had marked it in a different way.

I found a replacement for the burnt resistor, but the supply still did not turn on. I then discovered that R42 was open. I replaced R42 with another 430 ohm resistor but still no luck. It looks like more probing and troubleshooting are in my future with this supply.

[everell]

Re: Ultra X4 600 ULT-HE620X repair project

This is what I was thinking myself but I was not sure, the green band was throwing me off.

I think that green band is either the type of resistor or the manufacturer of the resistor. Some of those low ohm resistors are flame resistant and others are not.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

It's pointing towards a 0.18 ohm +/- 5% resistor (meaning of the 5th band is unknown in this case). That is with the second possible orientation. The first is completely invalid, as the first or second band cannot be silver or gold.

This is what I was thinking myself but I was not sure, the green band was throwing me off.

[cheapie]

Re: Ultra X4 600 ULT-HE620X repair project

It looks to me like the the colors are:

Green - Gold - Silver - Grey - Brown

or

Brown - Grey - Silver - Gold - Green

Either way these colors in these orders do not make any sense so any input would be appreciated.

It's pointing towards a 0.18 ohm +/- 5% resistor (meaning of the 5th band is unknown in this case). That is with the second possible orientation. The first is completely invalid, as the first or second band cannot be silver or gold.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

I think I may have found the reason this supply is not turning on. The "current sense" resistor between the the FET and common was blown. Normally I do not have a problem determining the value of a resistor if I can make out the color bands but this one is confusing me so I am hoping for some input as to its' value.

It looks to me like the the colors are:

Green - Gold - Silver - Grey - Brown

or

Brown - Grey - Silver - Gold - Green

Either way these colors in these orders do not make any sense so any input would be appreciated.


I have also ordered a Blue Ring Tester, I have wanted one for a while so I went for it.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

The same company that sells the Blue ESR Tester sells a Ring Tester. I wasn't sure where I would use it, but I bought one to play with. One thing I found is that using a DVM ohmmeter will not tell you much about a booster coil. Whether good or shorted the resistance is about the same. Putting the ring tester on it gives an immediate indication of short, substandard performance (probably some windings shorted, or a good ring. So....I am glad I bought it, and checking the booster coil with the ring tester is one of the first things I do when troubleshooting APFC circuits. I have already found a few shorted booster coils along with the shorted transistors.

Is there a way to use a scope to do the same thing as the ring tester? I had considered buying a ring tester before, but I thought I would use a scope more often. My tool/toy buying is high on the wife's radar for now so I am trying to keep it to a minimum for a while.

[everell]

Re: Ultra X4 600 ULT-HE620X repair project

I was able to take some pictures last night. Just to make sure I am understanding you correctly, when you say booster coil you are talking about the one the arrow is pointing at in the first attached image, correct?

Yes, that is the booster coil. Visually, I could not see any difference between a good coil and a shorted coil. Only the ring tester could verify a problem. Also, temperature is a factor. The hotter the coil runs the more likely a short. Use a temperature gun to try to determine operating temperature. If the mfg. uses a cheap core, the coil will run hotter and cause problems with time.

[everell]

Re: Ultra X4 600 ULT-HE620X repair project

The same company that sells the Blue ESR Tester sells a Ring Tester. I wasn't sure where I would use it, but I bought one to play with. One thing I found is that using a DVM ohmmeter will not tell you much about a booster coil. Whether good or shorted the resistance is about the same. Putting the ring tester on it gives an immediate indication of short, substandard performance (probably some windings shorted, or a good ring. So....I am glad I bought it, and checking the booster coil with the ring tester is one of the first things I do when troubleshooting APFC circuits. I have already found a few shorted booster coils along with the shorted transistors.

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

I was able to take some pictures last night. Just to make sure I am understanding you correctly, when you say booster coil you are talking about the one the arrow is pointing at in the first attached image, correct?

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

I replaced all the components that I could determine were bad. I do not have any good pictures of the primary side, the one I attached is the best I could find. I will take some better ones when I get a chance. It is possible that the booster coil is damaged however I could not see any indications to support it. Time will tell I suppose if I can eventually get it to turn on.

[everell]

Re: Ultra X4 600 ULT-HE620X repair project

So............what all did you do to get the APFC working again? In my experience if the transistors are blown up, the booster coil is shorted (or intermittently causing problems which will blow up the transistors again).

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

The APFC is now working on this supply. The supply still will not turn on and I have not yet bothered to troubleshoot the problem. Hopefully it is only a minor issue, but with my luck it will be something off the wall.

[shovenose]

Re: Ultra X4 600 ULT-HE620X repair project

The caps in those power supplies suck... hopefully you will replace with quality caps

[LDSisHere]

Re: Ultra X4 600 ULT-HE620X repair project

I have decided to replace Q10 with a MMBT3906 and Q8 with a MMBT3904. These transistors have a higher voltage rating than the original which I think is beneficial. How well they will work remains to be seen. I am just hoping I have correctly identified the original transistors in the first place, if not my testing may get very interesting at least for a few seconds. Identifying surface mount components is a real pain in the rear and somewhat of a crap shoot IMO.

[LDSisHere]

I am attempting to repair this Ultra X4 supply but I am not sure what my best option is on replacing a couple of surface mount transistors and I am hoping I can get some helpful input from the forum.

I think I have identified them, but of course I am not 100% certain. One I can easily find a replacement, the other one is not in stock at Digi-Key so I am not sure what part of its' specs are the most important when trying to source a replacement.

These two transistors are the only ones on this supply with these particular markings and of course they are not complete due to the transistors being blown. Q10, I believe is marked ZC which I think is a MMBT4124. The MMBT4124 is the transistor in stock at Digi-Key. Q8 appears to be marked ZD which I think is a KST4125. Digi-Key does not stock this transistor and it is the one for which I need to find a suitable replacement. I could be completely wrong on both identifications and if anyone has a better idea on what they really are I would appreciate the input.

These transistors are connected to the CM6068A PWM pin. The CM6068A controls both the APFC and the primary side PWM functions. It appears that these transistors act as the driver between the chip and the main FETS.