Memorex MLT4221P stuck in standby

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  • gb77
    replied
    Re: Memorex MLT4221P stuck in standby

    budm - the rectifier you suggest to change is an ON MBR2045CTG - is it possible that is the only problem? it's about $1 ..

    http://www.mouser.com/Semiconductors...0A+45V&FS=True

    got a decent pic of the 18v area on back of p/s.

    retiredcaps - when i took readings, i used a jumper from the board's ground clip/screw hole to the ground strap screw the power cord plug is grounded to. i'll put it back in and try your suggestion. any ideas for creating leads for the bluepoint?
    Attached Files

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  • retiredcaps
    replied
    Re: Memorex MLT4221P stuck in standby

    Originally posted by gb77
    have a couple MMs left by old roommate - no leads, no battery (9v) so don't know if they even work. if one might be useful, can you point me to some generic manual on how to use it? thanks.
    TWO retiredcaps' bonus points for showing 4 multimeters. The BluePoint would be your "best" multimeter to use. It is mainly geared towards automotive technicians, but can be used for everyday applications.

    I was thinking your fluctuatinig readings may be due to a lack of proper ground? If you have to turn your board upside down to take measurements, you may not have a ground?

    Let's try this.

    1) Put your power board back into the TV and secure it with all the screws in place.

    2) Now measure the DC voltage of the large filter C1.

    3) Put your red probe on the positive leg and black probe on the negative leg. Careful, this is high voltage as it should read about 165V DC.

    4) What is your reading and is it stable?

    5) Try this for your 2 multimeters plus the BluePoint. Before trying the BluePoint on the large cap, try it out measuring some AA batteries first to make sure it works.
    Last edited by retiredcaps; 06-18-2012, 01:27 PM.

    Leave a comment:


  • gb77
    replied
    Re: Memorex MLT4221P stuck in standby

    the 2 9v batts i have measure each other as 9.03v / 8.92v

    have a couple MMs left by old roommate - no leads, no battery (9v) so don't know if they even work. if one might be useful, can you point me to some generic manual on how to use it? thanks.
    Attached Files

    Leave a comment:


  • budm
    replied
    Re: Memorex MLT4221P stuck in standby

    OK, it is a dual Op-amp: http://pdf1.alldatasheet.com/datashe...AS358M-E1.html
    Probably used for comparator circuits of some sort.

    Leave a comment:


  • gb77
    replied
    Re: Memorex MLT4221P stuck in standby

    P/N
    ICS1
    AS358M-E1
    739R84

    2 MMs for the price of 1 - the black has a new(er) batt, yellow is older.
    Attached Files

    Leave a comment:


  • retiredcaps
    replied
    Re: Memorex MLT4221P stuck in standby

    BTW, it is always best to reply directly to a question in a new post rather than edit an old previous post. Most of us usually NEVER re-read the old previous post even if it has been edited.

    Leave a comment:


  • retiredcaps
    replied
    Re: Memorex MLT4221P stuck in standby

    Originally posted by gb77
    (don't know if my cheap multimeter is giving good readings
    Post a picture of it for one retiredcaps' bonus point.

    Leave a comment:


  • retiredcaps
    replied
    Re: Memorex MLT4221P stuck in standby

    What is the part number of that 8 pin IC in budm's marked up diagram where it says P/N?

    Leave a comment:


  • retiredcaps
    replied
    Re: Memorex MLT4221P stuck in standby

    Originally posted by gb77
    starting from pin1 (counterclockwise) the readings go up and down in the following ranges (don't know if my cheap multimeter is giving good readings or i'm doing it wrong, so treat me like a n00b, i don't mind the help)
    Pin1: .39 to .44
    Pin2: 3.81 to 3.88
    Pin3: .01 to -.01
    Pin4: -- with ground/black lead only connected :: .55 to .60
    Pin5: .01 to -.01
    Pin6: 8.56 to 9.22
    Pin7: .28 to .36
    Pin8: 160.9 to 163.3
    I'll have to check the datasheet to see if that is okay or not, but fluctuations are never good.

    Does your multimeter have a fresh new battery in it? An old tired battery might give bad readings.

    i got a bunch of blurry pics - any suggestions for getting clear shots by hand?
    Wait until tomorrow when the sun comes out. Take the board to a window ledge and put your camera on macro mode with no flash.

    Leave a comment:


  • gb77
    replied
    Re: Memorex MLT4221P stuck in standby

    i checked thread 16434 & that looks the same as mine. IC2 is
    230D6
    PALS
    so 2nd part of label is different. following that thread, using pin4 as ground/black, starting from pin1 (counterclockwise) the readings go up and down in the following ranges (don't know if my cheap multimeter is giving good readings or i'm doing it wrong, so treat me like a n00b, i don't mind the help)
    Pin1: .39 to .44
    Pin2: 3.81 to 3.88
    Pin3: .01 to -.01
    Pin4: -- with ground/black lead only connected :: .55 to .60
    Pin5: .01 to -.01
    Pin6: 8.56 to 9.22
    Pin7: .28 to .36
    Pin8: 160.9 to 163.3

    removing the 18v load brings the readings up to 11.88 from 11.83

    i got a bunch of blurry pics - any suggestions for getting clear shots by hand? the pic in that other thread is accurate
    Last edited by gb77; 06-17-2012, 11:58 PM.

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  • budm
    replied
    Re: Memorex MLT4221P stuck in standby

    From what I can see, there 3 feedback signals in the 18/24VDC outputs that are used to regulated the output, since I do not have the diagram for this power supply, I would try replacing the rectifier for the 18V section, the whole thing does not clear yet why it is regulating the 24Vdc OK but not the 18Vdc, one possibility is that the 24Vdc is not loaded due to the backlights are not running, it may drop under load.
    What happen if you remove the 18V connector so it will not have the load? Do you get 18v?
    Attached Files

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  • retiredcaps
    replied
    Re: Memorex MLT4221P stuck in standby

    Originally posted by gb77
    let me know if the one posted above is clear enough, thanks
    I think we need a clear shot of the section in yellow.
    Attached Files

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  • gb77
    replied
    Re: Memorex MLT4221P stuck in standby

    let me know if the pics posted above are clear enough, thanks
    Last edited by gb77; 06-17-2012, 11:31 PM.

    Leave a comment:


  • budm
    replied
    Re: Memorex MLT4221P stuck in standby

    Spec:
    http://www.fspgroupusa.com/fsp2714f02/p/764.html
    Looks like we are going to need good clear pictures of the bottom side of the board to look at the area of the 18Vdc section.
    Last edited by budm; 06-17-2012, 10:11 PM.

    Leave a comment:


  • retiredcaps
    replied
    Re: Memorex MLT4221P stuck in standby

    Another TV as budm alluded to uses this same power supply. See

    https://www.badcaps.net/forum/showthread.php?t=16434

    Is IC2 the same part number as the Memorex?

    If yes, measure the DC voltage IC2 for all pins wrt to its ground pin. I just want to verify some readings.

    Leave a comment:


  • gb77
    replied
    Re: Memorex MLT4221P stuck in standby

    the center lead of the dual diode also reads 11.8v - the outer leads vary when contacted but seem to settle on -.04v after a bit. the + leads from the caps (both 25v 680uF) are also 11.8v (measure from the back side of the board.
    Attached Files
    Last edited by gb77; 06-17-2012, 10:15 PM.

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  • retiredcaps
    replied
    Re: Memorex MLT4221P stuck in standby

    I don't have schematic for this power supply so I'm guessing based on your picture.

    If CN2 is the middle connector, then I'm guessing that the dual diode is mounted onto the heat sink just to the left.

    If correct, try measuring the output from the diode and see if it is 18V. The two caps just to the right of the diode may be on the 18V rail. If yes, see if the voltage across those two caps (which might be 25V or 35V rated caps) are 18V or not.

    Leave a comment:


  • gb77
    replied
    Re: Memorex MLT4221P stuck in standby

    yes, cns1 labeled 5v @ yellow wire, the red wire is labeled 0/F. cns2 - 18v (got 11.8 3 times measured), cns3&4 24v - all the red and blue leads show the same 24v.

    Leave a comment:


  • budm
    replied
    Re: Memorex MLT4221P stuck in standby

    Are the connectors labeled with voltages? this chassis is the same as used in Polaroid TV.
    So the 18V output is reading 11.84V? That will be strange since the 24Vdc supply is generated by the same transformer as the 18Vdc supply section, so I expect the 24Vdc output will be low also.
    Last edited by budm; 06-17-2012, 12:51 AM.

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  • gb77
    replied
    Re: Memorex MLT4221P stuck in standby

    i found my other multimeter (both are cheap $15 models, but this one has new 9v battery, while other one has older battery, but no batt warning) - but nearly the same result - i used 20vDC scale for 3 of them.

    readings this time were:
    cns1 - yellow 5.06v - red 4.63v (0/F)
    cns2 - brown 11.84v (18v)
    cns3 - blue & red 24.1v
    cns4 - red 24.1v

    Leave a comment:

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