Westinghouse 37" LVM37w3 troubleshooting.

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

That certainly sounds like ZD1/ZD3 are shorted. The reading you got on ZD4 (380 ohms) is reasonable.

PlainBill

I think R66 which is 303 resistor is shorted because another 303 at R9 read exactly 303 ohms on 2k setting. Also R34 is shorted too but no matching 121 resistor. 163 is ok, read 15.7 on the 20k setting.

It seems to me everything on the grounded side was damaged. so ZD3, R34, R66, and ZD1 was damaged but D11, R64, and C28 survived. Even the CY3 polymer cap on the other side survived.

Wonders if this board is worth saving?

[PlainBill]

Re: Westinghouse 37" LVM37w3 troubleshooting.

I think R66 which is 303 resistor is shorted because another 303 at R9 read exactly 303 ohms on 2k setting. Also R34 is shorted too but no matching 121 resistor. 163 is ok, read 15.7 on the 20k setting.

It seems to me everything on the grounded side was damaged. so ZD3, R34, R66, and ZD1 was damaged but D11, R64, and C28 survived. Even the CY3 polymer cap on the other side survived.

Wonders if this board is worth saving?

Note that ZD1 and R66 are in parallel. If ZD1 is shorted R66 will also read shorted. Also, a resistor labeled 303 is not a 303 ohm resistor, it's a 30Kohm resistor. The fact that one somewhere else on the board reads 303 ohms is coincidence.

There are a couple of issues here.

First, in my opinion you are fixating on testing the components while ignoring the circuit.

Second, you seem to be unfamiliar with the standards for labeling parts. A 303 ohm resistor, for example would be labeled 301.

Third, there exists a probability tree for likelyhood of damage. Transistors, diodes and zener diodes are likely to short. Resistors are unlikely to short, they might change in value or go open. Most capacitors will give clear physical signs if they short.

More later, I want to review the thread.

PlainBill

[retiredcaps]

Re: Westinghouse 37" LVM37w3 troubleshooting.

"In circuit" readings can be misleading because of surrounding components. If one component is shorted, it can affect readings in the surrounding area.

The only way to know for sure is to desolder them and measure them "out of circuit".

edit: I suggest waiting to see what PlainBill suggests before desoldering these components.

[PlainBill]

Re: Westinghouse 37" LVM37w3 troubleshooting.

OK, I've reviewed the thread. The drop of sweat on the power FET could have done a fair amount of damage.

As retiredcaps said, remove any apparently shorted components. At a guess, ZD1 is clamping the gate voltage on the FET. If ZD1 shorts the SMPS won't operate. There could be other damage.

If you are going to continue, Chip-Quik would be useful. It allows removing SMD components easily.

As far as replacing the power supply, I have mixed feelings. Every day I see TVs listed on Craigslist with the comment 'needs a power supply' or 'probably just a fuse' or 'I'm sure it's something simple'. In most cases, it's something more involved.

Have you checked for availability of the power supply? If I had the TV in my hands I would repair the power supply, but I have the tools, test equipment, and experience to do that. In your case, replacement may be the best option.

PlainBill

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

Well this PSU was kind of working, the Westinghouse light was on but the set would not turn on, no supply voltage to inverter board, one 5v was detected to the logic board but no 3.3 or 12 or 24v was detected.

I can get another PSU for $40 which does not include shipping.

PSU is FSP273-4F01 REV:1

It seems to me that this PSU was worked on before since the heat or protection cover are missing from the main cap.

The set may be worth it since it going for used on amazon for $700 and retail for $1500 when it was released, I'm fine as long it doesn't exceed $300. I paid $80 for it.

I would love to repair the PSU and gain more knowledge on electronics, but if my inexperience is going to be a problem then may be better to replace PSU since I don't know what the original problem was. Could have been bad caps.

If I do get a new PSU then that eliminates the PSU being the problem and we could focus on inverter and logic board.

[retiredcaps]

Re: Westinghouse 37" LVM37w3 troubleshooting.

I'm fine as long it doesn't exceed $300.

Just some thoughts regarding the economics.

In Canada, you can get a name brand (Samsung, LG, etc) 42 inch plasma for about $400. Depending on where you buy and what credit card is used, it will come with a 2 year warranty.

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

Down here in Florida, you can get 32" LED backlit LCD for $425, But this is just a basic tv, 1x hdmi, A/V, Comp, VGA or DVI input and hybrid tuner. Go any higher like 42" and you can pay about 500 or $600 and if you want features like PIP, cable card, "internet TV gimmick" or a better resolution it can hit $800.

I understand economics thing about this. Frankly I only bought this tv as project thing, like recapping and getting my solder skill up and learn about electronics. I'm disappointed that events have unfolded the way it did, and not achieving anything. I think I'll sit on it for awhile and think about it. Maybe buy a new PSU and try it, if it doesn't work, part it out and get rid of it.

[PlainBill]

Re: Westinghouse 37" LVM37w3 troubleshooting.

Down here in Florida, you can get 32" LED backlit LCD for $425, But this is just a basic tv, 1x hdmi, A/V, Comp, VGA or DVI input and hybrid tuner. Go any higher like 42" and you can pay about 500 or $600 and if you want features like PIP, cable card, "internet TV gimmick" or a better resolution it can hit $800.

I understand economics thing about this. Frankly I only bought this tv as project thing, like recapping and getting my solder skill up and learn about electronics. I'm disappointed that events have unfolded the way it did, and not achieving anything. I think I'll sit on it for awhile and think about it. Maybe buy a new PSU and try it, if it doesn't work, part it out and get rid of it.

These supplies are actually two power supplies on one board. The standby supply (typically 5 volts) is on whenever the TV is plugged in. The second is controlled by the standby processor on the main board. When the power button on the remote is pushed the standby processor turns on the main supply. No output from the main supply could indicate a power supply problem or a main board problem. And until you get the standby supply working, you can't find out.

Ordinarily I would say try to fix this supply, but the piece of metal that is missing is part of the heat sink. Unless you have access to the facilities to cut and drill a replacement, you might as well replace the power supply.

PlainBill

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

These supplies are actually two power supplies on one board. The standby supply (typically 5 volts) is on whenever the TV is plugged in. The second is controlled by the standby processor on the main board. When the power button on the remote is pushed the standby processor turns on the main supply. No output from the main supply could indicate a power supply problem or a main board problem. And until you get the standby supply working, you can't find out.

Ordinarily I would say try to fix this supply, but the piece of metal that is missing is part of the heat sink. Unless you have access to the facilities to cut and drill a replacement, you might as well replace the power supply.

PlainBill

Well I do have the tools to do a replacement piece. I got bench grinder, dremel, jigsaw and/or router, variable speed corded drill, metal work drill bits, a tap and die kit.

But considering that I have to recap which is the least of my worries; I would have to replace the damaged transistor and other SMD components. Which I have no problem removing them with my pencil iron and de-soldering braid. Unless these SMD are heat sensitive therefore I would need chip-quik?

Once I get them off where do I get replacements assuming they are shorted?

What else could be damaged?

After all that and the PSU still doesn't work, I would just end up buying a new one anyways?

I'm all for trying to repair this one if you think it's worth it. I'm inexperience but I don't mind being taught new things. I've gotten pretty good with my iron considering I have recapped 3 displays and I'm currently working on two more not including this one.

[PlainBill]

Re: Westinghouse 37" LVM37w3 troubleshooting.

What is the part number for ZD1? OK, let's do a little circuit analysis. ZD1 limits the maximum gate voltage, ZD3 appears to do the same for the source voltage. By the datasheet for Q4, the FET switches on fully at a gate voltage above 5-6 volts, and the gate can tolerate any voltage up to 30V.

Googling, I found this page. Using the color codes you mentioned earlier, that says the zeners are either 13 or 16 Volt. They appear to be a match for Rohm RLZ series (500 mw, glass package). The closest match I could find quickly is KDZTR13BCT-ND from Digikey at $.41 each. That still leaves the issue of the FET itself. By the way, what is the part number of IC2 (the SMPS controller)?

PlainBill

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

What is the part number for ZD1? OK, let's do a little circuit analysis. ZD1 limits the maximum gate voltage, ZD3 appears to do the same for the source voltage. By the datasheet for Q4, the FET switches on fully at a gate voltage above 5-6 volts, and the gate can tolerate any voltage up to 30V.

Googling, I found this page. Using the color codes you mentioned earlier, that says the zeners are either 13 or 16 Volt. They appear to be a match for Rohm RLZ series (500 mw, glass package). The closest match I could find quickly is KDZTR13BCT-ND from Digikey at $.41 each. That still leaves the issue of the FET itself. By the way, what is the part number of IC2 (the SMPS controller)?

PlainBill

ZD1 component has no writing on it unless it's on the bottom side of the zener, which I would have to remove and look. I can do it but not today, I have to help a friend put the lower control arm back on his 1970 olds 98. Also I ran out of desoldering braid and waiting patiently for UPS to deliver my order from digikey.

Also the band colors are RED RED GREEN.

The chip at ic2 is inorder, topdown.
EA1532A <-- TEA1532AT GreenChipII SMPS control IC
M1E002
inS5511 <--- this last one is bit hard to read not engraved as well as others, if I shine the light from the side it could be S55, SSS, or 555. If I shine it directly down it shows 355, or G55, hard to determine if "S" are "5"

[PlainBill]

Re: Westinghouse 37" LVM37w3 troubleshooting.

ZD1 component has no writing on it unless it's on the bottom side of the zener, which I would have to remove and look. I can do it but not today, I have to help a friend put the lower control arm back on his 1970 olds 98. Also I ran out of desoldering braid and waiting patiently for UPS to deliver my order from digikey.

Also the band colors are RED RED GREEN.

The chip at ic2 is inorder, topdown.
EA1532A <-- TEA1532AT GreenChipII SMPS control IC
M1E002
inS5511 <--- this last one is bit hard to read not engraved as well as others, if I shine the light from the side it could be S55, SSS, or 555. If I shine it directly down it shows 355, or G55, hard to determine if "S" are "5"

Sorry, I wasn't clear. The identity of ZD1/ZD3 was the question I was attempting to answer. There are three approaches - look at the specs on the part being driven (Q4), which placed the maximum voltage of ZD1 at 30 Volts, try to identify the value by interpreting the color bands (Red, Red, Green is 15 volts), or look at the specs on the driving circuit. Strangely enough, the application note for IC2 (TEA1532A) does not indicate any such zener is required!! Still, I'm comfortable with the results.

PlainBill

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

My package came a day early, so I can start work. YAY!

So whats the first order of business?

[PlainBill]

Re: Westinghouse 37" LVM37w3 troubleshooting.

My package came a day early, so I can start work. YAY!

So whats the first order of business?

I'd remove both ZD1 and ZD3 and verify they are shorted. If they are, the next step would be to replace them. After that I think I would replace the input fuse with a 40 watt light bulb, disconnect the output cables, and apply power. If everything is working correctly the light bulb will glow briefly and you will see the proper voltage (5V) out of the standby supply. At that point, reinstall the fuse, hook up the output cables, and start testing.

Usually on one of the output connectors is a pin labeled On/Off or PS_ON, or something like that. Once the standby supply is working check the voltage on that pin. If it is 3 volts or higher, the main board is trying to turn on the supply.

PlainBill

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

SO I destroyed ZD1 with my pliers, I squeezed little too hard and crush it, it was glued. ZD3 on other hand I was successful in the extraction, but testing it with my meter, I get a reading before going no continuity on *started low* the highest ohm setting. So that leaves the Q4 and D11 and ZD1.

I think I'm going to replace both zeners, since it looks like I either removed the paint or fracture ZD3, because some of it is still glued to the board except I have the whole ZD3 intact including contact end points. This thing is tiny. Would have chip quick work better?

The 40 watt bulb sounds OLD SCHOOL!
But how is a 40watt bulb going to act as a fuse? I assume it suppose to be indicator that circuit is complete? I assume incandescent bulb is needed?

I have screw in incandescent socket, an electrical box and some 14awg solid copper wire, all I need is some alligator clips and I would have a safe way of attaching it to the input fuse holders.

[PlainBill]

Re: Westinghouse 37" LVM37w3 troubleshooting.

SO I destroyed ZD1 with my pliers, I squeezed little too hard and crush it, it was glued. ZD3 on other hand I was successful in the extraction, but testing it with my meter, I get a reading before going no continuity on *started low* the highest ohm setting. So that leaves the Q4 and D11 and ZD1.

I think I'm going to replace both zeners, since it looks like I either removed the paint or fracture ZD3, because some of it is still glued to the board except I have the whole ZD3 intact including contact end points. This thing is tiny. Would have chip quick work better?

The 40 watt bulb sounds OLD SCHOOL!
But how is a 40watt bulb going to act as a fuse? I assume it suppose to be indicator that circuit is complete? I assume incandescent bulb is needed?

I have screw in incandescent socket, an electrical box and some 14awg solid copper wire, all I need is some alligator clips and I would have a safe way of attaching it to the input fuse holders.

There are various methods for removing SMD components. I've see a variety of heated tweezers, special tips for soldering irons, hot air rework stations, etc. The best seems to be a hot air 'wand' with various tips to match the components. The station runs over $100, tips run about $5. This can represent a major investment for a hobbyist, but is reasonable for someone doing this professionally.

Chip-Quick is a low melt alloy (Woods metal) in wire form. It blends with the solder, as a result solder at both ends of the part stays molten, making removing the part easy. It has two chief disadvantages. 1. It is somewhat messy; you have to remove the left over Chip-Quick with solder braid before installing the new component. 2. It is expensive, a small coil costs $15. Fortunately that can last years.

The point of using a light bulb is it represents a fairly high resistance on the AC line. Few things are quite as disconcerting as spending several hours troubleshooting a power supply, being certain you have found the problem, replacing the defective parts, then watching your work go up in smoke when you plug in the power cord. I speak from experience. A light bulb will limit the current. If the bulb glow brightly for a fraction of a second, then gets dimmer there is an excellent chance it is working. Voltage measurements will confirm that. If it continues to glow brightly, at least you can make voltage measurements to locate the problem. I've been known to use a variac, a light bulb, and an isolation transformer when I don't have any confidence that I have identified the problem. I've noticed when I do this the item decides to cooperate and work properly. Crossing my fingers and just plugging in the power cord sometimes results in the odor of burnt plastic.

PlainBill

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

Ok that makes sense, thanks plainbill for explaining that.

I'm gonna need new zeners. Are the ones you suggested in your previous post still recommended for use?

BTW should I order new caps, just in case if I do get this thing working again? Even if I don't use them I will still have them on hand.

[PlainBill]

Re: Westinghouse 37" LVM37w3 troubleshooting.

Ok that makes sense, thanks plainbill for explaining that.

I'm gonna need new zeners. Are the ones you suggested in your previous post still recommended for use?

BTW should I order new caps, just in case if I do get this thing working again? Even if I don't use them I will still have them on hand.

Digikey MMSZ5245BFSCT-ND would be a better choice. It's a different package, but identical electrical ratings. As closely as I can determine, it will fit in the same space.

I don't recall the brand of caps currently in the power supply. If they are one of the 'crap' brands (Capxon, Elite, Lelon, etc) listed in the badcaps FAQ, replace them.

PlainBill

[Mad_Professor]

Re: Westinghouse 37" LVM37w3 troubleshooting.

Digikey MMSZ5245BFSCT-ND would be a better choice. It's a different package, but identical electrical ratings. As closely as I can determine, it will fit in the same space.

I don't recall the brand of caps currently in the power supply. If they are one of the 'crap' brands (Capxon, Elite, Lelon, etc) listed in the badcaps FAQ, replace them.

PlainBill

Capxon KF and GL
Teapo A3, other one I can't identify due to being next to a heatsink.
Taicon M
2x Rubycon YXG
There's another one with no name but it's 35V 470uF has KZH, color is brown.

I'll buy zener and the caps, it might be week or two if I use USPS.

[retiredcaps]

Re: Westinghouse 37" LVM37w3 troubleshooting.

There's another one with no name but it's 35V 470uF has KZH, color is brown.

Brown and KZH means United Chemi-com. They usually have a "crown" symbol.