Sony PVM 2730QM - Power Supply

[R_J]

Re: Sony PVM 2730QM - Power Supply

Well then I wonder how swapping ic602 resulted in the 140 volts coming up on the bad power supply?
Does the 140 volts drop when connected to the monitor and turned on? or does it stay at 140 volts?

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

Does the 140 volts drop when connected to the monitor and turned on? or does it stay at 140 volts?

When I try to turn on the monitor with the faulty PSU the voltage of the 140V line remains stable but the voltages of the 8V and 15V lines drop down to 3V and 2.6V respectively. Also the values of +18V -18V lines drop down to 17.5V and 16.9V respectively. On the other hand, using the working PSU no voltage drops down. But why is that?

[R_J]

Re: Sony PVM 2730QM - Power Supply

Is R652 ok, also check R654, there may still be bad caps like C658 or C664,C663
ic651 gets it vcc from the 12 volt line so when that drops the ic no longer works so likely shuts down.
without a load the vcc on ic651 (8) should be 12 volts, is it ok?
You say R677 was faulty (I assume open) it could be that D656 is bad (leaky) You did replace r677 witha 0.56 Ω resistor correct?

[R_J]

Re: Sony PVM 2730QM - Power Supply

Since you have the two power supplies, check and compare the resistance of the components from one to the other. sometimes that can lead you in the right direction.

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

Is R652 ok, also check R654, there may still be bad caps like C658 or C664,C663

I've tested R652 R654 they are ok. I've swapped C658 D656 C663 C664 with those of the working PSU so they are ok.

You say R677 was faulty (I assume open) it could be that D656 is bad (leaky) You did replace r677 witha 0.56 Ω resistor correct?

Yes, but it wasn't open, just a lower value.

without a load the vcc on ic651 (8) should be 12 volts, is it ok?

No, on IC651(8) without a load I have 6V on the bad PSU 12V on the working PSU...

[R_J]

Re: Sony PVM 2730QM - Power Supply

Then that is likely your problem, If you have around 15 volts on D654, check R667, but more likely D664, D663 is bad or the ic itself is bad. Or it could be Q653, if it checks leaky, just remove it for testing, the power supply will function without it.

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

I've replaced (swapped from the working PSU) D654 and Q653 so they're ok. But around D654 A-K junction I've around 6V...

[CapLeaker]

Re: Sony PVM 2730QM - Power Supply

Yes, but it wasn't open, just a lower value.

To 99.99% resistors go higher or open in value than spec.

[R_J]

Re: Sony PVM 2730QM - Power Supply

I've replaced (swapped from the working PSU) D654 and Q653 so they're ok. But around D654 A-K junction I've around 6V...

The A - K of D654 are not joined, so I don't understand "arround D654 A-K junction". So what voltage is on the K of D654? Are you saying you get 6v on both sides of the D654 ?
What is the voltage on D654 cathode:
What is the voltage on D656 cathode:
Check the connections on T605 transformer pin #22, also measure the resistance from pin #22 of T605 to ground.


As for the original resistor R677 it is likely ok, like Capleaker said, resistor fail high or open.

The only resistors I ever saw that went down in value were some of the old allen-bradley type carbon resistors.

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

Voltages to ground: On D654 I've A 6.5V K 0V. On D656 I've A 12.2V K 0V.

T605 transformer pin #22 connection ok with D654. Resistance from pin #22 of T605 to ground: 0.1 ohm

[R_J]

Re: Sony PVM 2730QM - Power Supply

What do you mean 6.5V K 0V ???
If the voltage on D656 is 12 volts. that is good and normal
If the voltage on D654 is only 6.5 volts, and the diode hase been changed, either C654 is bad, or something is killing the voltage.
check the resistace on ic651 pin 8 to ground and compare it to the working p.s.
The fault must be in that circuit, either ic651, D664 zener is bad, D663 zener is bad

You could try lifting PS654 and see if the voltage on C654 comes up to 15 volts, that would eliminate anything on the other side of PS654, Just to try in standby mode.

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

Taking D663 D664 and IC651 from the non working PSU and soldering them on the working PSU, the result is that the working PSU is able to turn the tube on but just for a few seconds. After then it turns off automatically. So these 3 parts were clearly defective and should be replaced. Going to buy them in the next few days.

Unfortunately the viceversa didn't help. Taking these 3 working parts from the working PSU and soldering them on the non working PSU, the result is that the non working PSU is still unable to turn the tube on. The voltage on D654 is still 6.5V. I've also tried to lift PS654 but the voltage of C654 is close to 0...

[R_J]

Re: Sony PVM 2730QM - Power Supply

If you lift PS654 and get 0 volts on C654, that winding on the transformer can not be outputing anything. and the reason you were getting the 6.5v was from the 140 volt line via D660,R654 back thorugh R652.
I guess try lifting R667 and see if you get anything on C654, if its still 0 volts, I might start to suspect the transformer winding has a problem
Its almost looking like the trace is open between the transformer and diode? Sometimes it is just a slight crack in the trace right at the transformer connection.
You measured the winding and it was'nt open, so there's not much left
Maybe remove all the solder on pin#22 and inspect the connection and check the trace to the diode.
See if your meter can measure any a/c on pin #23 and #22, some meters can measure, it some can't
The a/c voltage should be close to the same on 22 as 23

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

Hi everyone.

I've replaced D663 D664 and IC651 with brand new but I got 1V on the 8V line. Then I've put back the previous D663 D664 and IC651 but now I still have 1V on the 8V line.

15V line is stable to 15.7 and the 140V line is still unstable around 140V. Voltages to ground: On D654 I've A 6.5V K 0V. On D656 I've A 1V K 0V. Voltages around C659 is 0.63V and around C655 is 0.7V. Something has been burnt?

[R_J]

Re: Sony PVM 2730QM - Power Supply

See if your meter can measure the A/C voltage on pin 22 of the transformer, then measure the a/c voltage on pin 23 and post them.

The power supply is working. if it was not you would NOT have 140v or 15v

Do you have a 12 volt light bulb around? remove R677 connect the lamp between pin 24 and 23 on the transformer and see if it lights.

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

On the working PSU on pin 22 I've around 2 mV and on pin 23 I've around 1mV. However on the faulty PSU my meter is even unable to measure any voltage. So the fault should be on the high voltage side? Btw it's ok that the D601 outputs +-131V on the working PSU but +108V-104V on the faulty PSU? I don't think that it's faulty since it has been swapped...

[R_J]

Re: Sony PVM 2730QM - Power Supply

Before I asked you to remove PS654 and check the voltage on C654. You reported you had Zero volts on C654
That means the transformer winding is bad or pin 24 is not ground or broken
This is the only reason for zero volts on D654 (PS654 removed)and zero volts on D656

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

I've checked again, and removed PS654 again. Now I've 2.5V on C654. On the 8V I've 0.6V. It's very unlikely that the transformer winding is bad, since it has been taken from the working unit.

[R_J]

Re: Sony PVM 2730QM - Power Supply

You have 140 volts, thats good, Do you have the +18 and -18 volts?
The power supply is switching the primary (pins 1 & 2) and giving the 140 volts,(pins 18 & 15). It is also giving the the feedback/run voltage (pins 9 & 11) or it would not work at all.

[sunomo1]

Re: Sony PVM 2730QM - Power Supply

Yes, +18V is +32V -18V is -27V. The problem is the 8V line...