Memorex MLT3221 - No Power

[mattmarkgo]

Re: Memorex MLT3221 - No Power

need help!!!good day i have mlt3221 when i plug it i see red led light after a second it goes blank....

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Thanks, already looked there

[Dgtech]

Re: Memorex MLT3221 - No Power

If you feel like searching through schematics... here is a polaroid site that has some service manuals. A few of these sets have the same IPOS 150 power board, I think.

http://www.polaroidsupport.com/polaroid/en_us-sm.html

If you search around, you'll find out that this IPOS 150 power supply is found in many sets.

Memorex, Polaroid, Element, and a couple others.

This service manual is for one of the sets with this type of power supply but as you'll see... it does not have details on the board.

[johnnieboy2]

Re: Memorex MLT3221 - No Power

If I had any indication of life in this thing, I'd probably continue on. I bought the capacitor kit at ebay and nothing but 5v. Then I saw another kit there that said..."if you bought the cap kit and only get 5v now, buy 'this' kit...for more money than the first one. I thought that was pretty funny...this thing could easily be a money pit. Nothing ventured nothing gained, but this venture has gone far enough. Thanks again.

[Dgtech]

Re: Memorex MLT3221 - No Power

If it's the power board that is giving you problems, try to find it on ebay. I just found one for $40 for a similar set. I've been messing with this set for about 6 months now, off and on. It finally came down to a transformer that I found was arching and making an audible arching sound.

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Think I'm throwing in the towel, without a schematic this is just a shot in the dark. Thanks for all the help, much appreciated.

[PlainBill]

Re: Memorex MLT3221 - No Power

Any suggestions?

Hopefully you can wing this one on your own. The logical assumption is there is an excessive load on the 5 volt rail on the main board. Try to verify this. Then it becomes a matter of tracing the 5V rail on the main board.

Also, earlier I had noted that there are a pair of power FETs on the cold (output) side of the power supply. Presumably these control the missing voltages. If I recall, there was an obvious control line to turn on these voltages. Do that by pulling the line to 5 volts through a 3.3K resistor.

PlainBill

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Any suggestions?

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Well, I disconnected the CON3 plug to the board and I get the 5vdc solid as can be. The connector has other voltages listed but since the set is not turning on maybe that's the reason, anyway no other voltages present. ARGGGGGGGG! Maybe my power supply board was good all the time!

[PlainBill]

Re: Memorex MLT3221 - No Power

Thanks, I'll check it...can you tell me what transformer it is...where? I didn't know if I might damage anything ELSE if I unloaded the P/S and powered on. Again, anybody need any parts if this doesn't work out in the end...which might be soon approaching?

I've marked up the picture. The lines in yellow indicate the path.

PlainBill

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Thanks, I'll check it...can you tell me what transformer it is...where? I didn't know if I might damage anything ELSE if I unloaded the P/S and powered on. Again, anybody need any parts if this doesn't work out in the end...which might be soon approaching?

[PlainBill]

Re: Memorex MLT3221 - No Power

All the EC 's were replaced on this board except for the large one which was ruled out early on as the problem. Can I check the transformer windings with an ohm meter in circuit, AND is the possible shorted load on this same board or another one? I'll check pin 5 voltage again.

You can check the transformer windings in circuit. They will all read a very low resistance. The 'shorted load' can be anywhere. This design is a little unusual; there is only 1 SMPS which is always on. Disconnect the other boards and see if the power supply works.

PlainBill

[johnnieboy2]

Re: Memorex MLT3221 - No Power

All the EC 's were replaced on this board except for the large one which was ruled out early on as the problem. Can I check the transformer windings with an ohm meter in circuit, AND is the possible shorted load on this same board or another one? I'll check pin 5 voltage again.

[PlainBill]

Re: Memorex MLT3221 - No Power

what should my voltage be? Earlier I reported 9-14vdc on this pin.

There are several parameters to consider. The absolute maximum voltage allowed on that pin is 30 volts. The normal operating range is 10 - 30 volts. The controller starts when the voltage on that pin rises above 15 volts and stops if it drops below 7.5 volts (+- 1 volt on the last two parameters).

Those readings suggest the controller is starting, but the run power is not maintaining operation. There are a number of possible causes. One is if the startup cap is bad. If you replaced it, that is unlikely to be the cause. Another (rare) cause is a bad winding on the smps transformer. A bad diode, either on the run power circuit (open) or on one of the outputs of the SMPS transformer (shorted), or a shorted load would also cause the problem.

PlainBill

[johnnieboy2]

Re: Memorex MLT3221 - No Power

what should my voltage be? Earlier I reported 9-14vdc on this pin.

[PlainBill]

Re: Memorex MLT3221 - No Power

Control - Print Screen didn't work, but MWSnap did the trick.

The area circled in yellow is the run supply for the SMPS controller. The coil is actually part of the main SMPS transformer.

PlainBill

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Hit the Alt and Printscreen (copy screen into buffer) key at the same time while the pdf is displayed. Then bring up your favourite graphics program and press Ctrl-V (paste).

Out of curiosity I tried this and it did not do anything to bring up any of my graphics programs. I use a free program MWSNAP3 to capture any screen area and it works great. I can save the snapshot and load it into my graphics program.

[retiredcaps]

Re: Memorex MLT3221 - No Power

Darn!!! I wish I had a way to edit PDFs - or at least convert a page to a jpg.

Hit the Alt and Printscreen (copy screen into buffer) key at the same time while the pdf is displayed. Then bring up your favourite graphics program and press Ctrl-V (paste).

[PlainBill]

Re: Memorex MLT3221 - No Power

Well, after about an hour of careful soldering...looks like I got a 'trick' this Halloween night...seems to have changed nothing. No LED lit on P/S board, steady blinking lED on lower right front of TV, no 'noise' of any kind. Sort of disheartening, but I do appreciate your help and advice given...all caps replaced. I did have two 10uf @ 450v and a 10uf @ 50v caps left over from the kit I ordered, but no place on the board for them, curious, but I guess they applied to a different revision board.

You mentioned tertiary winding, where and can it be checked easily?

Darn!!! I wish I had a way to edit PDFs - or at least convert a page to a jpg.

Pin 5 of the SMPS controller is Vcc. It gets power via two paths - through avery high resistance from the + side of the mains filter cap (the big one), and from a winding on the SMPS transformer. For some reason I'm unable to download the datasheet; and while your pictures are very good, I can't see traces that run under ICs. All I can suggest is to identify where pin 5 comes out from under IC2.

PlainBill

[johnnieboy2]

Re: Memorex MLT3221 - No Power

Well, after about an hour of careful soldering...looks like I got a 'trick' this Halloween night...seems to have changed nothing. No LED lit on P/S board, steady blinking lED on lower right front of TV, no 'noise' of any kind. Sort of disheartening, but I do appreciate your help and advice given...all caps replaced. I did have two 10uf @ 450v and a 10uf @ 50v caps left over from the kit I ordered, but no place on the board for them, curious, but I guess they applied to a different revision board.

You mentioned tertiary winding, where and can it be checked easily?