Re: HFE and Testing
I had one of these today with one shorted 5705. I always replace the 5707's in pairs due to lot to lot variation in transistors which can cause failure upon replacement. Both transistors in the royer need to be close gain wise. fu9024 and fuse were fine but will be testing it before it goes back together.
While I'm waiting on deliveries, I re-soldered all traffo, caps, trannies, diodes, links inductors etc on the inverter and also replaced 2 1000uF 10V caps(ESR >> than spec). All others had excellent Capacitance and ESR... so brazenly I have...
Mikeley
ESR Man
Last Activity: 02-23-2014, 03:31 AM
Joined: 10-08-2010
Location: Ireland
-
Re: Ring Tester Question
Ron K
I've swapped the clips for an old set of multimeter probes. I kept the wires about the same length, but shorter would be fine also. Seemed to make no difference in my case.
I have been using it away for a few months now with 100% success.
MLLeave a comment:
-
Re: CGA computer monitor
Monitor all ran fine when returned to owner. The H-sync was 31.4-31.5KHz. Monitors such as these do not conform to CGA/EGA standards, in this case, recapping and the occasional faulty power supply seem to be the only issues. The TTL levels, and pin outs match these standards but timing is everything!...Leave a comment:
-
Re: Samsung 930B re-capped, no backlight
What readings did you get for each regulator? Last questions for tonight, did you have boards back in the metal chassis frame with all screws back in when you had the logic board connected and powered with problem present?
Was the LCD and front panel also connected to the logic board at the time? Try with everything connected once more, if that was the case, remove the LCD panel connector, check 5V and 13V.
Reconnect and remove front panel, remeasure voltage in order to eliminate each of these.Leave a comment:
-
Re: Samsung 930B re-capped, no backlight
It is likely to be the 5V rail powering the logic PCB having an excessive load.
But the PSU may also still have a problem with it's feedback circut and the backlight Inverter could have trouble!
First, isolate and eliminate shorts from logic PCB causing the overload condition in the powersupply:
If you have another logic PCB, substitute it. Otherwise, check the 5V and ground wiring back through the connector to the logic board.
Check for shorts by measuring resistance across each of the voltage...Leave a comment:
-
Re: Samsung 930B re-capped, no backlight
What voltages can you measure on the CN2 connector now??
Have you got stable 5V and 13V?Leave a comment:
-
Re: Sony SDM-HS73 Turns on for a few seconds then black screen
Its a 2SD1691 NPN Power transistor.
Google it... Emitter, Collector, Base as your look at the shot.Leave a comment:
-
Re: Hanns-G HG281D 28" TFT - Multiple Problems
Inkragpnor, same time zone as Ireland! Bet it gets dark earlier than 4:30pm!
Your PCB may be discoloured, but it looks ok.... looks like a diode, perhaps a schottky and this might run warm during normal operation. Often these are mounted well above the board to help dissipation. I would not fret about it for the moment.
We need to check if the standby voltage is available at the connector.
I assume you are checking with all boards fitted, screwed into the chassis, all connected up?
...Leave a comment:
-
Re: Hanns-G HG281D 28" TFT - Multiple Problems
Post your pictures. Can you clarify, do you have any indication of power on the monitor when mains is switched on/plugged in and or on button is pressed? Is there any sign of life?
Do you have a meter to check voltage and resistance available? If the monitor is completely dead, you will need something to do some basic checks. Have you used a meter before?
Goes without saying, as a novice, you need to take care around potentially lethal voltages, mains etc.Leave a comment:
-
Re: Dell E172fpb
Lesson in dry joints!
The Diode measurements illustrates the problem of interpreting with other components in circuit.
Best diagnostic method is lowest ohms on a digital meter when in circuit. Out of circuit, diode check is useful, identfication of the base, forward drop etc. Polarity can impact, good to always check both ways.
Finally, you might want to consider replacing capacitors as these can be the cause of running hot! I tend to replace caps when they fail specification and always check all of them with an ESR...Leave a comment:
-
Re: Dell E172fpb
2SC is NPN
As you look at the front of the transistor, (writing side)
Pin 1 Base
Pin 2 Collector
Pin 3 Emitter.
Unsure how familiar you are with measurements. Make sure you include the decimal point when reading the meter. On diode check, the meter is displaying Volts. Be sure of probe and pin positions.
With Red Probe on Base (Pin 1) you should measure .6 Volts approx to pin 2, and again pin 1 to pin 3(.560 Volts is ok). The meter forward biases the junctions of the transistor. Any other combination should...Leave a comment:
-
Re: Dell E172fpb
I would recommend inspecting and resoldering all joints on the inverter side of this PCB. They generally are a mess based on my experience. Resistors, capacitors, inductors and large schottky diodes between the traffos and around the transistors are particularly prone to dry joints.
Recheck the fuse. After completing the resldering, try it again.
You may also have electrolytic caps dried out and I would also recommend checking with an ESR meter if available, or just replace these as you have it opened up.Leave a comment:
-
Re: Hanns-G HG281D 28" TFT - Multiple Problems
Now that is good news and result! I would not rule out the capacitors on power supply yet.
In the absence of an ESR meter, the most reliable way to solve your problem is to replace the electrolytic caps on the PSU board. These caps are stressed most by high ripple currents, and harmonics in filtering the rectified output from the power supply. Typically these caps are the issue. Post the make, values and any other numbers on the PSU Caps. Measure height and diameter and order accordingly.
See post #3...Leave a comment:
-
Re: "WC" brand capacitor
Anyone ever figure out where these caps come from? Who made them?
I also have ones with 'Timax' brand all are SM series 85C types... wild guess that they are from the same place. I have a bucket of these from some industrial monitors.
All have manufacture dates in and around 1993! Not too bad I suppose considering, whatever about the 'WC' branding!
Want to check out the ESR/Impedance and ripple specs for replacements in the future.Leave a comment:
-
Re: Hanns-G HG281D 28" TFT - Multiple Problems
Will have fingers crossed tha the rectifier is the problem here.
Check for short capacitors/MOV's circled and perhaps ensure the varistor is ok, ie high resistance at room temperature and if you heat gently with a hairdrier, resistance should fall rapidly. This component protects the circuit from high inrush currents when the circuit is energised from the mains.
Also check your filter Cap. Any signs of leakage? They rarely fail, but sometimes do. Measure resistance and capacitance, aside from that...Last edited by Mikeley; 01-02-2011, 09:21 AM.Leave a comment:
-
Re: Sceptre x22wg-Gamer 22" LCD
For more technical insight into ESR, impedance, lifetime and so on see [URL="http://www.rubycon.co.jp/en/products/alumi/technote.html"]http://www.rubycon.co.jp/en/products/alumi/technote.html[/URL]
In particular look at the third section 'Performance of Aluminum Electrolytic Capacitor'. There is a pdf that can be read.
I also downloaded the attached doc from that site to help select capacitors depending on application.
MLRe: Sceptre x22wg-Gamer 22" LCD
For more...Leave a comment:
-
Re: Hanns-G HG281D 28" TFT - Multiple Problems
Appreciate the problem removing the Heatsink. You would need a stronger iron to do it.
Looking at the MOSFET readings, I would say leave them where they are for the moment. All readings are at least a couple of hundred ohms.
I would expect something like a 001 ohm reading on the 200ohm lowest scale if there was a dead short. You could still have open circuit or other failure modes. Some might suggest removing and doing various tests at this point.
For the looks like 'Resistor component'...Leave a comment:
-
Re: Hanns-G HG281D 28" TFT - Multiple Problems
Ok,
From the data sheets you will see that both types of MOSFET have a diode connect in reverse across Drain - Source.
If you are getting low resistance in a particular direction, can you clarify what pins you are checking, what colour leads are connected and what values you measure? What range are you using on your DMM etc?
In fact all 3 MOSFETS should give pretty similiar results on your meter. The problem is what 'What's is similar or typical?' So report what you measure, there...Leave a comment:
-
Re: xplio computer monitor
Hi,
Nice video tutorial on Capacitor basics... [url]http://www.youtube.com/watch?v=YCSNWi3UHf4&feature=fvw[/url]Re: xplio computer monitor<br /> <b...ture=fvw[/url]Leave a comment:
-
Re: Hanns-G HG281D 28" TFT - Multiple Problems
Phihong Technology Company in Taiwan manufacture this power supply and it's found in several other Monitors/TV's also. The link below shows a very similar PCB to your board.
[URL="http://www.phihong.com.tw/tw/ViewProduct.php?p_id=165"]http://www.phihong.com.tw/tw/ViewProduct.php?p_id=165[/URL]
If you do get it running, expect a 5V standby voltage, and once the monitor powers on 5Volt, 12Volt and 24Volt outputs.Re: Hanns-G HG281D 28" TFT - Multiple Problems
Phihong TechnologyLeave a comment:
No activity results to display
Leave a comment: