Sony SDM-HS73 on for 2 seconds then off

[Welchs101]

I have a sony SDM-HS73 which turns on for about 2 seconds and then turns off.

I opened up the monitor and found a few "burnt" caps. See enclosed pics.

Any idea what caused this?
I measured the resistance of the burnt blue cap and it measured ~ 14kohm so i think this is a bad cap.

I measured the resistance of the burnt black cap and it measured open. WHile it may be ok it probably should be replaced i know.

I did test all 4 of the bulbs and ONE of the bulbs appears to be BAD. Could a bad bulb have caused this?

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

ok....just looked at the caps again and i thought it was odd to have 3 blue caps and one black.........turns out the black cap is actually blue but has been "cooked" and turned black.

I dont think just a bad bulb could cause this could it?

[retiredcaps]

Re: Sony SDM-HS73 on for 2 seconds then off

Never seen a board where the inverter transformer is on the back side!

I would check the all inverter transformers to make sure they are not shorted or open. They may have caused the blue caps to blow?

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

retiredcaps,

Can you suggest what to measure to make sure transformers are ok?

[Rtech]

Re: Sony SDM-HS73 on for 2 seconds then off

Why is it unusual ???????Its Sony !!

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

Couple of questions to help me learn a bit.

1) Those blue capacitors which got burned.........what are they for? From a circuit perspective........what function do they perform.

2) The marking on those caps are "27K, 3KV". Could i replace those with some "22J, 3KV"..........i dont have any 27K,3kV but i do have an old power supply board which has some 22J, 3KV.

[PlainBill]

Re: Sony SDM-HS73 on for 2 seconds then off

Couple of questions to help me learn a bit.

1) Those blue capacitors which got burned.........what are they for? From a circuit perspective........what function do they perform.

2) The marking on those caps are "27K, 3KV". Could i replace those with some "22J, 3KV"..........i dont have any 27K,3kV but i do have an old power supply board which has some 22J, 3KV.

1. They remove any DC offset in the output voltage.

2. Yes. Table 2 at http://wiki.xtronics.com/index.php/Capacitor_Codes shows the original were 10%; your proposed substitute are 5%.

PlainBill

[retiredcaps]

Re: Sony SDM-HS73 on for 2 seconds then off

retiredcaps,

Can you suggest what to measure to make sure transformers are ok?

Normally, we would test just the secondaries, but given the extent of the damage to the blue capacitors, let's test all the pins.

a) Number the pins on the transformers anyway you like
b) black probe on pin 1, red on pin 2 - record ohm
c) black probe on pin 1, red on pin 3 - record ohm
d) black probe on pin 1, red on pin 4 - record ohm
e) etc
f) black probe on pin 1, red on pin last - record ohm
g) black probe on pin 2, red on pin 3 - record ohm
h) black probe on pin 2, red on pin 4 - record ohm
i) etc
j) black probe on pin 2, red on pin last - record ohm
k) black probe on pin 3, red on pin 4 - record ohm
l) etc
m) finally, black probe on pin last-1, red on pin last - record ohm

All transformers should match. Some will read 0.3 ohms which is normal.

If you have a ring tester, it would be a lot easier!

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

Thanks for the info on what caps do .....i will have to look up some info on this.

Regarding % tolerance. I see the "K" and "J" for 10% and 5% respectively. But what about the 27 and the 22..........what do they mean.




Took a while to make the measurements on the transformers T1 adn T2.

I entered data into excel and i am enclosing here as a picture.

Is this how you wanted it measured.

[PlainBill]

Re: Sony SDM-HS73 on for 2 seconds then off

Thanks for the info on what caps do .....i will have to look up some info on this.

Regarding % tolerance. I see the "K" and "J" for 10% and 5% respectively. But what about the 27 and the 22..........what do they mean.




Took a while to make the measurements on the transformers T1 adn T2.

I entered data into excel and i am enclosing here as a picture.

Is this how you wanted it measured.

Oops, missed that one was 22, the other 27. No, that won't work. They are 27 pF, 3KV caps.

PlainBill

[retiredcaps]

Re: Sony SDM-HS73 on for 2 seconds then off

Is this how you wanted it measured.

Yes. Please post measurements for T2.

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

retired caps.........i am sorry.......i did include the T2 data i just labeled it wrong............i will correct the excel picture and repost it.


let me know if you dont understand the pic or if i have done something wrong and i will corrrect it.

[retiredcaps]

Re: Sony SDM-HS73 on for 2 seconds then off

All the inverter transformer measurements look okay.

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

Thanks. If you dont mind me asking what were you looking for in the data?

Also, the more i think about it the more i think it cant be the bulb.......or can it. Here is what i was thinking. I only found "one" bulb that was "bad". But yet two caps are bad. If only a single cap was bad and it matched the location of the bulb then i would think its the bulb but i dont.

What do you think?

Is there anything else i can check?

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

One more question i thought of.

From the pics i sent out earlier you can see that there is one cap on each end of the inverter section just prior to the bulb connection that is "burned"..........but there are two caps at each end.........why is only one cap at each end burned........why not both?

Does anyone have any ideas?

[alexanna]

Re: Sony SDM-HS73 on for 2 seconds then off

Is there anything else i can check?

How do the “JST” style Connectors on the ccfl bulbs look? Any burning or discoloration?

[retiredcaps]

Re: Sony SDM-HS73 on for 2 seconds then off

Thanks. If you dont mind me asking what were you looking for in the data?

1) Before I knew how to identify the secondary transformer pins, I used to measure every possible combination. After a while, you know that some pin combinations are 0.3 ohms and some are 1M+ ohms.

2) For the secondaries, they are within 3%.

3) Both transformers show the same results so that implies both are "good".

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

i dont see any discoloration on the bulb connectors using a bright light and magnifying (sp?) glass.

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

see enclosed pics.

Between the two transformers are two devices.

Device A: International rectifier F7389
Device B: O2 Micro OZ960

I ohmed out the F7389 based on the datasheet (see enclosed) and it looks ok.

Not sure how to verify OZ960......

Any thoughts?

[Welchs101]

Re: Sony SDM-HS73 on for 2 seconds then off

I think at this point i dont really have anything else that i know to try. So what i was thinking was replace the bulb.....which i just did...........replace the bad burnt caps, resolder the transformer leads (which has helped in projects in the past) and turn on the monitor and see what information i can get.

But before i can do this i was wondering.........in an earlier post i mentioned i had "22J" caps but not "27K" caps.

PlainBill,
you said that i probablly could not use the "22J" caps to replace the "27K" caps........but could i use the "22J" caps just to power on the monitor and troubleshoot it a little more? WOuld that be ok you think?