Blown Capacitor - PSU Repair

[prpr]

I obviously used the 'wrong' converter.
The site is hardly too verbose for the forum, compared to some of BH's epics.

 

[prpr]

Our Humax Fox T2 Freeview PVR stopped working; there was no circle of light around the power button and there were no signs of life anywhere else.

My subsequent actions are described on my website.

The relevant bit of circuit was already available in post #12.
Excellent work on the whole reverse engineering of the circuit and the diagrams though.
Would you object to it all being posted on here?

 

[Black Hole]

They are a bit too verbose to put on the forum

They can't be. You've obviously never read any of my posts. No, I'm not going to visit your web site : if you can't be bothered with us, I can't be bothered with you.

 

[prpr]

if you can't be bothered with us, I can't be bothered with you.

I think that's rather harsh. It's worth looking. I learnt more than one thing...
This is where the anti-spam forum stuff pushes useful content elsewhere, which is regrettable, but understandable.

 

[Black Hole]

Perhaps, perhaps not – this is where the community is. A web page is not peer-reviewed.

It's not the anti-spam which "pushed useful content elsewhere", it's the author who chose to. The anti-spam merely stopped him posting a link to it. The original claim (that a forum post could not contain it) isn't valid (probably).

 

[MikeGibbs]

Our Humax Fox T2 Freeview PVR stopped working; there was no circle of light around the power button and there were no signs of life anywhere else.

My subsequent actions are described on my website. They are a bit too verbose to put on the forum but I'm not allowed to post external links as I'm a new member so you could try scanning this QR code.

View attachment 7512

https:// mikesoft.co.uk/ Hummy/

 

[/df]

Anyhow, @MikeGibbs ...

...
Would you object to it all being posted on here?

 

[MikeGibbs]

The relevant bit of circuit was already available in post #12.
Excellent work on the whole reverse engineering of the circuit and the diagrams though.
Would you object to it all being posted on here?

Of course not, please feel free.

While I'm posting here I'd just like to say that it's a shame that some people need to be bad tempered. My hummy failed so I joined the forum and got lots of hints which lead to me fixing the power supply. I did the reverse engineering to see if the failure of the snubber circuit could lead to damage of the transformer driver. Having done that I thought that I could give something back for the help which I got from others.

 

[Black Hole]

Bad tempered? Only when there's a reason, and "blunt" rather than "tempered". People seem not to appreciate just how much time and effort has been put into this forum, completely voluntarily. Come along and say "I've done this [using knowledge acquired from us] but I couldn't be bothered to write it up [on the forum] and instead posted it in my own private domain" is surely a red rag to a bull. Despite what you say, it fails to acknowledge prior art, and fails to contribute. Not least, the forum is (partly, if not totally) funded by the traffic it generates and donations from grateful parties. Basically, you have acted for yourself and not for the community.

 

[Owen Smith]

Of course not, please feel free.

While I'm posting here I'd just like to say that it's a shame that some people need to be bad tempered. My hummy failed so I joined the forum and got lots of hints which lead to me fixing the power supply. I did the reverse engineering to see if the failure of the snubber circuit could lead to damage of the transformer driver. Having done that I thought that I could give something back for the help which I got from others.

I second the request for the information to be copied here so we definitely have it provided hummy.tv keeps running. We can't be sure how long personal web sites will last.

While I'm here, thanks for the work and posting it Mike.

 

[prpr]

Subbing from MikeGibbs' site:

Our HDR-Fox T2 PVR stopped working - there was no circle of light around the power button and there were no signs of life anywhere else. This is what I found when I checked the power supply:


Background information:
PW808 Power Supply, High voltage side

When I traced the circuit I couldn't see all of the components from all sides so I could not always determine their values by reading them off. Some of the resistors were clear, but those that were not I put my multi-meter across. So some of the resistors have standard looking values and others, those which I couldn't see, sometimes have odd looking values, but this is the best guess.
Similarly, some of the capacitors are shown with values if I could see them, but others only have their circuit designation.

PW808 Power Supply, Low voltage side

It was much easier to see the values of the components on the low voltage side of the power supply than it was the high voltage side.

From the circuit diagram it's clear that the snubber circuitry is protecting the STR-W6252D PWM switching regulator's power MOSFET. However, according to the datasheet, the Drain-Source breakdown voltage for the MOSFET is 650V minimum. So, fingers crossed, it might have survived.

The fix:
Clearly I needed a new C3, but I determined that C2 and the ultra fast diode HER108 were still viable. I ordered a new C3 from Bitsbox. The original was rated at 1kV but Bitsbox has a 3kV component so that's what I bought.
I replaced it and our HDR is working fine again.

Edit: Added SteveH's picture, as it shows the same fault much more clearly.

 

[SteveH]

I seem to have a similar problem. This is very useful Thankyou.