Phillips / Magnavox-26MF605W/17 - bad PS

[ahickman]

Looking at a PS that came from a Magnavox 26MF605W/17. Not getting voltage at any of the outputs. Looked up the schematic and am trying to muster my way through it. Getting kind of lost though and hoping for pointers. With AC on, I get 165 VDC on the main capacitor which tells me that the primary is good. Looked next at the FET driving the transformer 7062. The drain has 165 VDC. Pin 1 (Vcc) on IC 7061 has 0.0 VDC. Pin 1 on the optoisolator 7074 has 70 VDC. Pin 2 also has 70 VDC. Pin 1 on the IC 7056 has 1 VDC, but pin 8 has 0.0 VDC.

Any suggestions on what to check next?

[ahickman]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Bump?

[drpj23]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

How do those diodes check out?

[budm]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

OK, lets check the snubber Diode D6055 to see if it is shorted.
Then please take the resistance reading of the IC7061 (TEA1507P) all the pins with ref to the Ground pin of the IC.
Then also check or replace the start-up cap C2067 (68uf 25v).

[ahickman]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Snubber diode D6055 checked out well (19 ohms and infinite ohms).

IC7061 resistances wrt PIN 2 are as follows:

1. 1 ohm
3. 30 ohm
4. 35 ohm
5. 35 ohm
6. 25 ohm
7. infinite
8. 35 ohm


Startup cap checked out fine on ESR meter, but will replace as recommended.

[ahickman]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Budm, any suggestions?

[budm]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

SYMBOL PIN DESCRIPTION
VCC 1 supply voltage

GND 2 ground

CTRL 3 control input

DEM 4 input from auxiliary winding for demagnetization timing, OVP and OPP

Isense 5 programmable current sense input

DRIVER 6 gate driver output

HVS 7 high voltage safety spacer, not connected

DRAIN 8 drain of external MOS switch, input for start-up current and valley sensing

Your readings:
1. 1 ohm
3. 30 ohm
4. 35 ohm
5. 35 ohm
6. 25 ohm
7. infinite
8. 35 ohm
Your readigns do not look right. Are the reading shown with letter K, or M?
Otherwise they are badly shorted out.

[ahickman]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Your readings:
1. 0 ohm
3. 0 ohm
4. 343 K ohm
5. 10 K ohm
6. 308 K ohm
7. infinite
8. infinite

Not at all sure why the DVM was off. May have to change out the battery.

[budm]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Pin 1 is VCC pin, should not be reading 0 Ohm.
Pin3 also looks wrong.

[ahickman]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Remove the IC and Pins 1 & 2 are shorted.

[Th3_uN1Qu3]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

There you have your problem. Before replacing the controller IC, check the diode that supplies Vcc to it, it could be shot.

[ahickman]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Will do. Just checked Mouser and Digikey for a replacement and see that this particular chip is not stocked. Suggestions on a replacement?

[tom66]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

eBay or Mouser?
http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40

May be a common failure....
http://www.ebay.com/itm/1PCS-TEA1507...item27c93218c8

[ahickman]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Found one. Thanks.

[ahickman]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Replaced the IC and she came up! Thanks to all.

[budm]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Thanks for the repair feedback.

[tom66]

Re: Phillips / Magnavox-26MF605W/17 - bad PS

Great to hear -- obviously a common failure, sellers say it is for "Philips/Magnavox"...