Hitachi 57F710E Power Issue

[navagator]

Re: Hitachi 57F710E Power Issue

Or going by your diagram, when I touch my + meter lead to #4 and my - lead to # 3 my meter reads .482v and when I reverse the process my meter reads .OL, then I place the + meter lead on #2 and my - lead on #1 I get a reading of 0v and when I reverse that process I also get a reading of 0v.

[R_J]

Re: Hitachi 57F710E Power Issue

You are only checking 2 diodes the one between 4 & 3 is likely good, the one between 2 & 1 is shorted, there are 2 more diodes between 4 & 3 and 3 & 1, but it doesn't matter if one is shorted the bridge needs to be replaced. One shorted diode will blow the primary fuse.

[navagator]

Re: Hitachi 57F710E Power Issue

Ok, I'll have to get one ordered. It's a S1WB S60B4N. I couldn't find this exact one online, is there another one that's interchangeable?

[R_J]

Re: Hitachi 57F710E Power Issue

Any 1 amp, 600v, 800v or 1kv bridge rectifier that will fit will work, there are likely hundreds that would work.
diodes inc. DF06m or DF08m or DF10M are 1 amp versions

Try searching for S1WB S80

Where do you plan on ordering from? digikey?

[navagator]

Re: Hitachi 57F710E Power Issue

I'm looking for one that will fit correctly. I removed the rectifier from the board and measured the distances between the legs and found them to be approximately 7.5mm x 8.5mm.
The Diodes Inc. rectifiers you suggested have measurements of 7.6mm - 8.9mm x 5mm - 5.2mm. so I'm not sure they'll fit. What few S1WB rectifiers I found don't have any measurements for leg spacing.

[navagator]

Re: Hitachi 57F710E Power Issue

Can the legs be bent/adjusted enough to fit?

[R_J]

Re: Hitachi 57F710E Power Issue

I didn't look that close at the dimensions, so the DF0x series is smaller, The DBL105G, DBL106G or DBL107G would be closer.
Just search for 1 amp 600v or 800v bridge rectifier in a dip4 case, I see S1WBS60 and S1WBS80 listed on amazon and ebay if that's where you are ordering from.

[navagator]

Thank you for your help. I odered the rectifiers from Digkey. They were supposed to be here tomorrow but it appears the delivery date has been changed to Monday.

[navagator]

The rectifiers came and I installed one, replaced the glass fuse and plugged the board in. The fuse didn't blow and everything seems to be back the way it was. I checked C940 and got a reading of 12.7v AC. I checked the 2 Pico fuses you mentioned E940, E941 while in circuit for continuity and there was continuity. I couldn't find anymore fuses that resembled those, if you see anymore fuses please point them out to me and I'll check them.

[navagator]

I took a few new readings and thought I would post them. There is approximately 108 to 115 volts DC coming off of the new rectifier, it's fluctuating real bad. If I remove the glass fuse inline right after the DC positive leg of the rectifier, I get a reading of 113.3 to 113.4 volts DC with very little fluctuation. There is approximately 120 volts AC going into the rectifier. Still no DC voltages on the secondary side of the board.

I assume there is something wrong after the rectifier. There is a larger capacitor after the fuse and I believe some kind of switching chip or IC offline switch flyback after that (I901) chip # A6159. And a few other caps, resistors, a diode, and a small transformer. Perhaps one of these components have failed?

[navagator]

I ordered some components from Digikey and my order came today, the first thing I did was install the regulator IC (I901). Unfortunately that didn't fix the problem. So the next thing I did was replace the filter capacitor (C908), after that I noticed that the DC voltage coming out of the bridge rectifier was now reading a stable 167 volts. But nothing else changed, still no DC voltage on the secondary side. I then changed out C912, C911, C909, C905, and I904. There was still no change. R908, R909, R910, R906, D106, and D907 test ok.




What could be left, perhaps the small transformer? There is a stable 167 volts DC going to pins 3 and 5 of the transformer.




Thanks in advance.

[navagator]

I did make some progress today. First I removed the voltage regulator just off of the switching transformer on the secondary side and tested it, there was a a steady 5 volts DC coming off of the output leg, so I reinstalled it. Then I removed capacitor (C940) and replaced it with another capacitor I had of the same capacitance but a slightly higher voltage spec. and applied power to the board, I then had a voltage reading of approx. 7.75 volts DC coming off of C940 and a steady 5 volts DC coming off of the voltage regulator, however I didn't hear any of the relays click in.




I reinstalled the board in the TV in hopes the issue was resolved but unfortunately it wasn't. Still nothing.