Polaroid TV - PSU HA220T2A1 repair

[tn245]

Quick question. Got this TV PSU with the primary mosfet Q5 shorted. Going to change the mosfet and smps ic. The gate resistors and diode have exploded so unable to read their values. What values should be used here for R74 R35 and D6? The mosfet is 6n60 and smps ic l6565.

[budm]

Re: Polaroid TV - PSU HA220T2A1 repair

You can use what the application circuit uses.

[tn245]

Re: Polaroid TV - PSU HA220T2A1 repair

Thanks. The configuration here seems slightly different from the application circuit. In that on the board R74 is in series with R35 and D6 which are in parallel with each other. Does that make any difference?

Application gate drive:

[Andrew F. Ali]

Re: Polaroid TV - PSU HA220T2A1 repair

No it shouldn't...Try it...you have nothing to loose.

[tn245]

Re: Polaroid TV - PSU HA220T2A1 repair

There seems to be a bit more going on with this PSU. I fired it up with a 100W bulb in series. It lights bright then goes out, but I've got no +5V standby. Main cap is at 330V. Which part of the circuit is responsible for +5V? I find it hard to figure out without a schematic. Nothing else seems to be shorted.

[tn245]

Re: Polaroid TV - PSU HA220T2A1 repair

Pin 8 Vcc of IC5 is fluctuating between 10 and 12V so it is not starting up. Have replaced start up cap and zd1 but still fluctuating. Start up resistors, 3 in series at 255K each measure ok. What else could be causing the fluctuating Vcc?

[dick_barton]

Re: Polaroid TV - PSU HA220T2A1 repair

There's a repair kit which may be able to guide you.
http://www.ohmsupplies.co.uk/epages/...roducts/KIT198

[tn245]

Re: Polaroid TV - PSU HA220T2A1 repair

Thanks. Looks like I've replaced or tested everything listed in that kit so far. They don't list the smd resistors and diode I had burned interestingly. Maybe I should replace the start-up resistors anyway even though they are testing ok on the meter.