Proline DVD player + combined surround sound system

[tom66]

Got this thing cheap - it's a DVD player with built in 5.1.

Anyway, the symptoms are it does nothing when plugged in - it's completely dead.

If you listen carefully you can hear a clicking/ticking sound at 2-3 Hz. I scoped the rails and can see them rising, but they quickly fall, at the same rate. Power supply is trying to switch on but for some reason is failing.

I have replaced:
all bulging caps on the secondary side -> same problem
one non-bulging big cap on the secondary side -> same problem
the 22u/50V startup/Vcc cap (replaced with a general purpose 22u/35V) -> same problem

The power switch is Fairchild KA1L0380RB. Max Vcc is 30V so 35V cap should be fine.

All caps replaced with Panasonic FM or FR.

Big primary filter cap has about 332V across it which is good.

Power supply does exactly the same without load -> power supply probably at fault then.

Only dodgy thing at the moment is that Vcc seems to ripple about around 10-18V even with the cap replaced. Measured from either end of the cap, Vcc to GND. Vcc is provided through a high value resistor. Reads yellow purple yellow gold -> 470k 5%. Measuring it in circuit (with power off) drives my meter crazy, why? It doesn't look like it is connected in parallel with anything. I will try replacing it with a 470k resistor carbon film 5%, perhaps it is just broken, maybe it is burnt out from years of use, although it doesn't look like it. May explain ripple on Vcc. A bad cap failing open, assuming 300V across the resistor, would have it dissipating 0.191W, which is within limits. But a cap failing shorted would bump it up to 0.234W, still within limits, but running near.

At a loss at what to try next?

How do I test the opto?

[tom66]

Re: Proline DVD player + combined surround sound system

470k removed, measured 468.8k, seems good, replaced it anyway, still broke.

Anything else to test?

[tom66]

Re: Proline DVD player + combined surround sound system

Ah!!!

Noticed 5V rail was completely dead.

Tested diode - DEAD SHORT, both ways.

The 5V is used by the feedback so if it is dead then it will not start.

Hope this is the only problem but it's faulty either way and it wouldn't work without it.

[PlainBill]

Re: Proline DVD player + combined surround sound system

Ah!!!

Noticed 5V rail was completely dead.

Tested diode - DEAD SHORT, both ways.

The 5V is used by the feedback so if it is dead then it will not start.

Hope this is the only problem but it's faulty either way and it wouldn't work without it.

Good catch. Your analysis was faulty, however. A shorted diode on any transformer secondary will kill the operation of the power supply. In addition to the primary and secondaries, the standby (main on a single supply design) transformer has another winding (which I refer to as the tertiary winding) which provides run power for the SMPS controller. With a short (or even just excessive load) on the secondary, the tertiary winding does not generate sufficient voltage to provide power to the SMPS controller.

The ticking sound you observed is an excellent clue. Your noticing the dead power supply rail and following it to the cause was good troubleshooting.

PlainBill

[tom66]

Re: Proline DVD player + combined surround sound system

Good catch. Your analysis was faulty, however. A shorted diode on any transformer secondary will kill the operation of the power supply. In addition to the primary and secondaries, the standby (main on a single supply design) transformer has another winding (which I refer to as the tertiary winding) which provides run power for the SMPS controller. With a short (or even just excessive load) on the secondary, the tertiary winding does not generate sufficient voltage to provide power to the SMPS controller.

The ticking sound you observed is an excellent clue. Your noticing the dead power supply rail and following it to the cause was good troubleshooting.

PlainBill

I'm not sure a shorted diode would short out the secondary though? The diode's purpose is to block and rectify the AC from the transformer. If the diode is no longer blocking AC, I am worried that it could have toasted some other components on the main board. On the other hand, AC into a capacitor is virtually a dead short. So it might have been saved by the cap shorting it out.

I think the winding you talk about is the bias/Vcc winding for powering the SMPS controller? See schematic - the 22ohm (R8) and diode (V7) provide power to the switcher once the startup cap (C7) is charged through the 470k (R3). The only difference between standby and bias is that the bias doesn't need to be mains isolated as the controller is purely primary side.

There is no standby power supply - the power supply is either on or off. Oddly, there is a pin called STBY/ONOFF on the board. But it's not connected to anything?! The only on/off is through a *real* mains on/off switch at the front and the soft on-off through the remote.

[PlainBill]

Re: Proline DVD player + combined surround sound system

I'll point out a few things. in no particular order.

1. You provided neither a model number nor any pictures. In the future I will ignore any of your threads that fail to provide basic information.

2. Some smaller TVs have a single power supply; in general any TV over 24" will have a dual supply.

3. At startup the SMPS controller gets it's power from the rectified mains voltage. The tertiary winding provides run power. Calling it a bias voltage is incorrect.

4. A typical frequency for a SMPS controller is 70 Khz. At a guess, the 5V filter cap is in the order of 1000 uF. You can figure out the impedance there, for all practical purposes it is an AC coupled dead short.

5. What @#%@#% schematic?? That's something else you didn't provide!

PlainBill

[tom66]

Re: Proline DVD player + combined surround sound system

I'll point out a few things. in no particular order.

1. You provided neither a model number nor any pictures. In the future I will ignore any of your threads that fail to provide basic information.

Pics attached.

But no model number on the back anywhere...!

All I know is it is a Proline 5.1 + DVD combined unit.

2. Some smaller TVs have a single power supply; in general any TV over 24" will have a dual supply.

Most do. I've only seen the occasional small CRT without one. All LCDs thus far seem to have one.

3. At startup the SMPS controller gets it's power from the rectified mains voltage. The tertiary winding provides run power. Calling it a bias voltage is incorrect.

That's the 470k's job to provide the bootstrap power.

I've heard it called bias in a TOPswitch PSU control IC, they are usually used for standby power and mains switchmode wall warts.

I call it the Vcc winding because it directly drives Vcc of the 4-pin switcher IC.

4. A typical frequency for a SMPS controller is 70 Khz. At a guess, the 5V filter cap is in the order of 1000 uF. You can figure out the impedance there, for all practical purposes it is an AC coupled dead short.

Xc = 1/(2pi*f*C) IIRC, comes to 2x10^-9 so seems about right for dead short... ignoring ESR of a few milliohms.

5. What @#%@#% schematic?? That's something else you didn't provide!

PlainBill

My error! Getting confused and forgot to post it. Here it is:

Page 10 has the power supply.

I got a schematic by googling the PSU model.

While the schematic is similar it is not identical. Still, it was useful in debugging the PSU.

[tom66]

Re: Proline DVD player + combined surround sound system

Replaced the diode, it works! Great. Simple fixes I like.

[tom66]

Re: Proline DVD player + combined surround sound system

Okay, it powers up. But it makes a buzzing sound on the speakers (sounds like 50/100 Hz) and won't read discs. I am thinking a ground loop. But I have attached all grounds. What other places are there to check?

[joste]

Re: Proline DVD player + combined surround sound system

Hi Tom66,

I would change that big primary filter cap anyway. Sometimes it can cause weird things. If you have a buzzing sound around 50Hz, this would be my lucky guess.

[Th3_uN1Qu3]

Re: Proline DVD player + combined surround sound system

I second that suggestion.

[lti]

Re: Proline DVD player + combined surround sound system

What about the IC with a burnt sticker on top of it? That could be the reason why it won't read a disc.

[tom66]

Re: Proline DVD player + combined surround sound system

Hi Tom66,

I would change that big primary filter cap anyway. Sometimes it can cause weird things. If you have a buzzing sound around 50Hz, this would be my lucky guess.

Okay, I'll add it to my next component order and see if that makes a difference.

The amplifier has an odd configuration: it is powered from a separate transformer. The transformer is very large, although probably underpowered. I can't help but think a good SMPS could have powered the 60W amplifier side, and have reduced the cost... This whole player is odd, though - it's like it's made from loads of different OEM parts and through some miracle it manages to work, when it's not broken, of course.

[tom66]

Re: Proline DVD player + combined surround sound system

What about the IC with a burnt sticker on top of it? That could be the reason why it won't read a disc.

I think that is the decoder and CPU. I peeled the sticker off, just looks like it is worn from heat, chip is fine. As I have an interface on the VFD I don't think it is fried. It is trying to read the disc: the laser head moves back and forwards over the disc, and the disc spins, but it eventually just says "NO DISC" on the front VFD. Opening/closing drive works fine. Oddly, most noise seems to come when it opens and closes. It can determine the difference between having a disc and no disc - without a disc it gives up in 1-2 seconds; with one, it takes about 1 minute.

[joste]

Re: Proline DVD player + combined surround sound system

I think that is the decoder and CPU. I peeled the sticker off, just looks like it is worn from heat, chip is fine. As I have an interface on the VFD I don't think it is fried. It is trying to read the disc: the laser head moves back and forwards over the disc, and the disc spins, but it eventually just says "NO DISC" on the front VFD. Opening/closing drive works fine. Oddly, most noise seems to come when it opens and closes. It can determine the difference between having a disc and no disc - without a disc it gives up in 1-2 seconds; with one, it takes about 1 minute.

So Tom66, this looks like your laser has gone half-blind (somewhat out of focus): when the disc is inserted, the unit tries to read out the data (type of the disc, sessions etc.) but the beam is not focused enough to clearly read it, so it gives up after a minute. When the disc is absent, the unit spins twice or trice and reads "no disc". This is quite normal.

My question: did you try plain audio CD instead of DVD? Sometimes lasers can not read one, but still manage to read other type of discs.

Looking forward to your answer.

[tom66]

Re: Proline DVD player + combined surround sound system

So Tom66, this looks like your laser has gone half-blind (somewhat out of focus): when the disc is inserted, the unit tries to read out the data (type of the disc, sessions etc.) but the beam is not focused enough to clearly read it, so it gives up after a minute. When the disc is absent, the unit spins twice or trice and reads "no disc". This is quite normal.

My question: did you try plain audio CD instead of DVD? Sometimes lasers can not read one, but still manage to read other type of discs.

Looking forward to your answer.

Good news - it does play audio CDs, and with no buzzing. This is weird! So do you think I just need to clean the laser?

[joste]

Re: Proline DVD player + combined surround sound system

Well, that can be your first try.

If cleaning doesn't help, I'd suggest to go for much trickier operation: adjusting laser focus (if possible).

But, first things first - lens cleaning (but be careful with pressure applied and no liquid!).

[tom66]

Re: Proline DVD player + combined surround sound system

That was easy. I rubbed the laser with a bit of tissue paper and it now reads DVDs and CDs. Easy fix ! I guess it must have had a bit of dirt on the lens.

[joste]

Re: Proline DVD player + combined surround sound system

So Tom66, would you call it "problem solved"?

[tom66]

Re: Proline DVD player + combined surround sound system

So Tom66, would you call it "problem solved"?

Yep .

When a disk is first loaded into it, the audio has a slight buzzing sound... some kind of weird glitch. But once loaded and playing, the audio is crystal clear. I'm not sure if I even need to replace that 47u/400V capacitor on the input now.