Powers up with +32V AND -32V but no output.
Cannot find a schematic anywhere.
Help please
Tony
tonydix
Member
Last Activity: 05-02-2022, 01:54 AM
Joined: 12-05-2013
Location: Bocas del Toro
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Cambridge Audio Amplifier P25
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Re: Digihome Vestel 500UNDC TV loses picture after a few seconds
I have tested the leds with my home built LED tester. They light up and if you power on the rest of the set we get a normal picture ( a little dim with my led tester) and sound.
In normal operation the leds come on for just a second So it appears that the drive circuit is shutting down. Thanks for your response. -
Digihome Vestel 500UNDC TV loses picture after a few seconds
Vestel 500UNDC using a vestel 17PS20 power board. Backlights come on and picture shows for a few seconds and then goes dark. Sound is fine. Is this a problem with the led strips or the backlight driver ? Many thanks -
Re: Lg 42pq3000 dead
No I do not have a replacement. My only thought now would be to break P1100 connection connect 5vstby to control board and then try to measure current being taken by each supply eg 5v, 12v, 17v to see where shutdown occurs. What do you think ?
TonyLeave a comment:
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Re: Lg 42pq3000 dead
So I tried to see what was happening with AUTO_GND.
Power on relays click and 5vstby is 5.1v
Touch voltmeter probe to AUTO_GND. 5.03v still have 5vstby at 5.1v
Now ground AUTO_GND relays click and 5vstby is lost.
Is this expected behavior ?
ThanksLeave a comment:
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Re: Lg 42pq3000 dead
Connected like you suggest get nothing at switch on. Remove all above wait 10 mins and reconnect 5vstby returns and relays click. Short Auto-gnd to gnd relays click and we lose 5vstby. What is connected to Auto-gnd ?
Thanks for your patience.Leave a comment:
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Re: Lg 42pq3000 dead
Good idea I didnt have 10ohms but 13 ohm draws 250 mA with a slight reduction in volts possibly the small dupont cables I was using.
I will try the other tests you suggest.
so is it :-
AUTO_GND to GND
And 5vstby - 1k - relay on
And 5vstby - 1K - VA
And 5vstby - 1k -VS
Many thanksLeave a comment:
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Re: Lg 42pq3000 dead
Any idea about ic100 on the control board is it 5v or 3.3v and which pin would have the standby supply ?Leave a comment:
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Re: Lg 42pq3000 dead
A bare unconnected control board definitely pulls 5v stby to zero when connected to the power board. The unconnected control board shows these resistances to ground :-
17v infinite
12v 1.2k
5v multi 1.4k
5vstby 1.4k
5v mnt infinite
ac detect infinite
relay on 7meg
vavs on 16meg
5v on infinite
5v st infinite
key on infinite
The other voltages supplied by the unconnected power board look ok to me except that 5v on,acdetect and relay on are all 0v
I don't see anything...Last edited by tonydix; 10-26-2021, 02:43 AM.Leave a comment:
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Re: Lg 42pq3000 dead
So have checked the components mentioned in the test kit. All seem OK.
Power board is on the bench connected to no other boards.
Connect power and we hear the relays click. Measuring pins at pg3 we get :-
m5v 5.1v
va 62v
vs 194v
So does this mean power board is ok and fault lies elsewhere ?
I appreciate your help.
TonyLeave a comment:
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Re: Lg 42pq3000 dead
You are correct. Removed STR W6252 and no short on its pins. Removed resistor and now no short across the diode. So all seems ok. I will now check other components mentioned in the kit, but I am still puzzled by the 5v standby being present until the control board is connected when it disappears. That leads me to think the fault is on the control board or in some startup circuitry. Thanks for your advice. TonyLeave a comment:
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Re: Lg 42pq3000 dead
My power board is EAY59544701. I have checked the diode D701 and it is fine.
There appeared to be a short across D304 which I have removed (see photo) the diode is fine but the short remains. Could it be the IC STR W6252 which has legs across this diode ? Thanks
Tony...Leave a comment:
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Re: Lg 42pq3000 dead
Please can you be more specific. Is the diode on the power board or on the control board ?
I have an interesting situation where 5vstby is up when the control board is unpluged but is lost 1 sec after reconnecting. Presumably a safe shutdown proceedure. Many thanks.
TonyLeave a comment:
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Puzzle over symptoms Motorola Smart Phone
I am trying to repair a motorola moto g play cell phone. It suddenly went dead. I have disassembled the phone and removed the battery and motherboard. The battery appears fine it takes and holds a charge and lights a 6 volt bulb. When I measure resistance from battery + terminal to ground I get approx 1 meg ohm and reducing suggesting capacitors are being charged. If I then connect the battery( 3.8 volts) nothing appears to happen but if I then disconnect the battery the resistance from battery + terminal to ground shows a short. After about 10 mins doing nothing the short disappears !. Is this...Last edited by tonydix; 01-16-2020, 09:34 AM. -
Re: samsung TV ps-42q97hd clicking
After further tests I now think the pulsing may relate to the isolation transformer I was running it through. Plugged it into the mains directly and immediately fried the two diodes DS888 and DS889. Suppose the 240 volt bulb I used had insufficient resistance and allowed too much current to pass when the supply was solid. Must now try to source the 2 diodes UGH !Leave a comment:
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Re: 10 amp 300v diodes
did you ever source these two diodes ?Leave a comment:
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Re: samsung TV ps-42q97hd clicking
Thanks R_J you were quite correct. Setup the board as described with a bulb load as in Andrew Ali' post #64941. Bulb lights but pulses regularly with 1 pulse per second. Vs voltage fluctuates between about 170 volts and 200 volts. Never quite reaches the required 207. Any ideas ? I made a video but don't seem to be able to link it. Thanks. TonyLeave a comment:
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Re: samsung TV ps-42q97hd clicking
Flocko thanks for the advice. 500 ohm between pson and ground produces relay click. 500ohm resistor between VS-on and Standby does not bring Vs and Va voltages up.
I have reflowed and checked all dodgy electrolytics. Any ideas please. Many thanks . TonyLeave a comment:
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Re: HP Pavillion G6
Sadly no joy those schematics do not reflect the board I have. But thanks everyone for trying.
TonyLeave a comment:
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Re: HP Pavillion G6
The silkscreen numbers are :-
6050A2412801.
MB-A02
2011-04-29
HSTNN-I94C
The schematics suggested above do not seem to apply. Searching for 6050A2412801 on this site suggest the mboard may be Invatec Rocky AMD rather than Quantum. Neither has the power connector labled as CN12 as on the board. I am puzzled !!
Thanks for all the help
TonyLeave a comment:
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