Memorex MLT3221 - No Power

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Hopefully my replacement caps will be in very soon. Thanks again PlainBill for hanging in there with me.

[PlainBill]

Re: Memorex MLT3221 - No Power

I had to take a nerve pill after I measured the voltages...do you know how many IC's I've blown trying to measure voltages on pins on IC's 3X that size...Whew!

Anyway:

resistance from hot ground to pin 1 of the SMPS controller (IC2) -zero
voltage from hot ground to pin1 = 0vdc
voltage from hot ground to pin2 = 0-5vdc
voltage from hot ground to pin3 = 0-2vdc
voltage from hot ground to pin4 = 0vdc
voltage from hot ground to pin5 = 9-14vdc
voltage from hot ground to pin6 = 0-.4vdc

I didn't see or smell smoke, hope that's a good sign!

I hear you. I'm working on 4 Mindstorm NXTs soldering parts much smaller than a grain of rice.

Well, the voltages indicate there is some activity on the SMPS controller. Possible causes are a bad startup cap or problem with the tertiary winding. Because of the lack of activity on pin4, it's probably not a shorted output diode.

PlainBill

[johnnieboy2]

Re: Memorex MLT3221 - No Power

I had to take a nerve pill after I measured the voltages...do you know how many IC's I've blown trying to measure voltages on pins on IC's 3X that size...Whew!

Anyway:

resistance from hot ground to pin 1 of the SMPS controller (IC2) -zero
voltage from hot ground to pin1 = 0vdc
voltage from hot ground to pin2 = 0-5vdc
voltage from hot ground to pin3 = 0-2vdc
voltage from hot ground to pin4 = 0vdc
voltage from hot ground to pin5 = 9-14vdc
voltage from hot ground to pin6 = 0-.4vdc

I didn't see or smell smoke, hope that's a good sign!

[PlainBill]

Re: Memorex MLT3221 - No Power

this may be the datasheet you need.



hope this help

ecking767

ecking, Thanks. It'll be fairly easy to verify the pinout.

johnnieboy2, I've marked up the picture of the bottom of the power supply. The point circled in black is the negative terminal of the large cap. It is also the 'hot' ground. I've also marked pins 1, 3, 4, and 6 of the SMPS controller.

With the TV disconnected from AC power, measure the resistance from hot ground (circled in black) to pin 1 of the SMPS controller (IC2). It should be very low - essentially zero.

Next, plug in the power cord and carefully measure the voltage from hot ground to pins 1 through 6 of IC2. Report the readings.

PlainBill

[ecking767]

Re: Memorex MLT3221 - No Power

this may be the datasheet you need.



hope this help

ecking767

[johnnieboy2]

Re: Memorex MLT3221 - No Power

[QUOTE=johnnieboy2;193033]I managed to get a pic of the IC in question, excuse the quality please. It's got a 'blue star' just below the IC, number is definitely correct...maybe a 'house' number...unless the '6' is a 'G'? Sorry for the triple post.

[johnnieboy2]

Re: Memorex MLT3221 - No Power

I managed to get a pic of the IC in question, excuse the quality please. It's got a 'blue star' just below the IC, number is definitely correct...maybe a 'house' number? Sorry for the double post.

[johnnieboy2]

Re: Memorex MLT3221 - No Power

I managed to get a pic of the IC in question, excuse the quality please.

[johnnieboy2]

Re: Memorex MLT3221 - No Power

If I had to bet, I'd stick with that number...but, possibly the '6' could be a '5'. It's not hard to read with a 'glass', but there is a small dot to the lower left of the first number that could make a 5 look like a 6. The only other number that could be confusing is the '7' which could be a '1', but it's slanted so I highly doubt that.

[PlainBill]

Re: Memorex MLT3221 - No Power

IC2 (six pin IC up from the IC I circled in blue) is probably the SMPS controller. What is it's part number (yes, time to get a magnifying glass).

number on this is...62739

Nope, that crosses to a 3 pin IC. Sometime is you look at them at an angle the numbers are easier to read.

PlainBill

[johnnieboy2]

Re: Memorex MLT3221 - No Power

IC2 (six pin IC up from the IC I circled in blue) is probably the SMPS controller. What is it's part number (yes, time to get a magnifying glass).

number on this is...62739

[PlainBill]

Re: Memorex MLT3221 - No Power

Gosh, I need a microscope! Best I can tell...

blue...very hard to read, guesstimate...ST (?) C2747 or CZ747
yellow...top one in pic is 78074 and STM4410A
yellow...6675A (Extremely hard to read accurately)
orange...SG3525AN
Red...D78F9222CX

OK, time to regroup. After looking this over carefully, I missed a LOT of clues, and misidentified the function of some components.

IC2 (six pin IC up from the IC I circled in blue) is probably the SMPS controller. What is it's part number (yes, time to get a magnifying glass).

The IC circled in blue is almost certainly the PFC controller; we aren't going to sweat the identification.

PlainBill

[PlainBill]

Re: Memorex MLT3221 - No Power

I guess I was wrong to think that chip was the main PWM for this power supply. I could not find any schematic to go by. How would I identify this as the main PWM in this circuit (for furture ref.)?

Aww, crap!!! It looks like I was wrong. I'm going to have to look over this again. One of the ICs I identified as an SMPS controller is a power FET, the other isn't identifiable, both are on the cold side of the power supply. The one I thought was an inverter controller is an SMPS controller. No, it's worse than that. The SG3525AN is definitely the controller for the high voltage (inverter) output. And the SMPS controller must be on the hot side of the power supply

PlainBill

[Dgtech]

Re: Memorex MLT3221 - No Power

I guess I was wrong to think that chip was the main PWM for this power supply. I could not find any schematic to go by. How would I identify this as the main PWM in this circuit (for furture ref.)?

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Well, since you were nice enough to provide good pictures, I'll return the favor.

These identifications are tentative; if you supply the part number of the first three I an confirm them.

Blue circle - PFC Controller.

Yellow circles - Standby and Main SMPS controllers

Orange circle - Inverter controller.

Red circle - unknown, but possibly a 'power good' sensor.

PlainBill

Gosh, I need a microscope! Best I can tell...

blue...very hard to read, guesstimate...ST (?) C2747 or CZ747
yellow...top one in pic is 78074 and STM4410A
yellow...6675A (Extremely hard to read accurately)
orange...SG3525AN
Red...D78F9222CX

[johnnieboy2]

Re: Memorex MLT3221 - No Power

If that's the pinout for IC8 then what voltave do you have on you pin 13 VCC?

.024 to .029 volts fluctuating

[PlainBill]

Re: Memorex MLT3221 - No Power

This is what I was referencing in my last the comments on voltages. I'm assuming your advice relates to a different IC which I cannot seem to find. Feeling like a clutz!

Well, since you were nice enough to provide good pictures, I'll return the favor.

These identifications are tentative; if you supply the part number of the first three I an confirm them.

Blue circle - PFC Controller.

Yellow circles - Standby and Main SMPS controllers

Orange circle - Inverter controller.

Red circle - unknown, but possibly a 'power good' sensor.

PlainBill

[Dgtech]

Re: Memorex MLT3221 - No Power

If that's the pinout for IC8 then what voltave do you have on you pin 13 VCC?

[johnnieboy2]

Re: Memorex MLT3221 - No Power

As you know, your 5V DC standby voltage is most likely your problem. With that being said, the problem rests on the power board. There are only a few components that make up the 5VDC. I dont have a schematic, and I'd give my left pinky toe for one, but I think the PWM might have something to do with the standby 5V. Check to see if that main chip, near the main output connector, has 13 volts on one of the pins. I can't remember what pin it was. I'm gonna try to find a thread with more info to help out.

This is what I was referencing in my last the comments on voltages. I'm assuming your advice relates to a different IC which I cannot seem to find. Feeling like a clutz!

[PlainBill]

Re: Memorex MLT3221 - No Power

All I got was some low levels of pulsating voltages, millivolt range. Definitely replacing those startup caps when I get them. Short on the output, can you elaborate, what part... another board?

Wrong controller. That's the inverter controller. The SMPS controllers would be the two 8 pin ICs near oneanother on the bottom of the board.

PlainBill