Hitachi 35UX85B TV - Dead with periodic "Chirping" sound

Not much to go on there. But look at a shorted horizontal output transisitor. The chirping is the P.S. trying to start then the over current sense kicks it off. Needless to say once the current drops it try's to do it again ad nausium.

Then there are a few things the can cause the transistor to short. Like bad connections on the drive xformer, bad hold down cap, and bad flyback transformer.

But then you could have a bad supply too.

"tman" bravely wrote to "All" (17 Oct 05 22:57:10) --- on the heady topic of "Hitachi 35UX85B TV - Dead with periodic "Chirping" = sound"

tm> From: "tman" tm> Xref: core-easynews sci.electronics.repair:345572

tm> A neighbor moving out left me this non-functional Hitachi 35UX85B, now tm> to get it to work!!! Upon Power-up the relay clicks, but there is no tm> audio, video (raster), or visible LED's on the front. This is tm> accompanied by an intermittent chirping sound (~1 - 2 sec. interval). tm> The "Chirp" is coming from the Power Block in the vicinity of T-902 tm> and is audible in a quiet room (sounds like there's an agitated mouse tm> in there....but there isn't). All fuses (2) check out fine. Upon tm> Power-down the "Chirping" will persist another 8 - 10 secs. after the tm> relay shuts off power. Boards look good as well, no obvious fried tm> components/connections, shorts or dry joints.

tm> I downloaded the service manual and it has all the schematics and tm> specs. but does not give much help in the troubleshooting flowcharts. tm> Before I cause too much havoc with my Fluke and soldering iron, does tm> anyone have a good idea of what are the likely suspects?

tm> Mucho thanks for any help.

Sure, from what you describe it seems like the switching power supply is trying to start up into a dead short, fails, turns off, and then keeps trying: chirp, chirp, chirp.

You will need to check the h-out Q, as a short there will definitly load down the smps. If it isn't the hot, then locate the v-out etc.

First consider that a dead short is something pretty obvious to locate. Once the short is found, then you have to determine what its causes were and repair the defective circuitry. Sometimes a dead short is just a symptom of deeper problems. Keep in mind a new replacement hot will blow in about 3.5 milli-seconds unless the defect is found.

Finding a dead short should be child's play with your Fluke, but it's the other steps that might be trickier, depending on your ability. An esr meter might be helpful to locate faulty electrolytic capacitors. Good luck and be careful around high voltage electronics.

A*s*i*m*o*v

... You mean 15" sparks are SUPPOSED to come out of this thing?!?

[snip...snip...]

Dumb suggestion (since you've probably already done this) but try unplugging it for a few minutes and not just hitting the power switch. I've an ancient JVC set that occasionally has symptoms very much like you describe and a "cold boot" always does the trick.

--
Rich Webb   Norfolk, VA

tman: You have to perform some troubleshooting at your end and post the testing and meter reading results then maybe you can get some more specific suggestions. As with any dead set, usually the very first things to investigate are the power supply and horizontal deflection circuitry. Since you have the manual and schematics.... and your Fluke... you are way ahead of anyone here on the newsgroup.... open'er up and get going. If you still do not know how to proceed then you should visit the website for this newsgroup at

there, with some searching, you will find a wealth of troubleshooting tips, repair information, component testing methods and IMPORTANT safety information that will help you to stay away from dangerous and lethal electrical shock hazards inside your television.... note that even when the television is unplugged from the AC power that these hazards can still be present.... be very careful. You have confirmed what seems to be a regular topic with newbie postings for repair help.... components and parts that "look" good can be very bad and must be tested... and a schematic and manual are of very little use and do not provide troubleshooting help to the novice repair person... a skilled and experienced tech who can fix the majority of equipment without a schematic will find the them very helpful in tough dog repairs. electricitym . . .

I had the same problem twice. The first time it happened was Nov 2004. It cost me $344 for in home service to get it fixed. It just happened again in Sep 2005. It was the same problem. There are 2 high voltage capacitors in the power supply section, C714 & C715 that can short, they may be blue in color, mine were. They are located on the main board on the right side of the TV when looking at it from the back. Most likely you will find at least one of them shorted. You will probably need to remove them from the board to get an accurate measurement.

I have a technical background as a radio repair tech, no experience with TV, but I was comfortable making an attempt at fixing this myself before dishing out a lot of money to the repair shop. There is very high voltage (thousands) produced inside the TV from the flyback transformer so be careful to make sure the CRT is disharged before tinkering around. Since this is a high voltage problem, most likely everything is discharged. The way I discharged the CRT was with an insulated screwdriver with a jumper lead to ground. It was already discharged as there was no popping noise when I tried it.

The original part # is 0244889. There is a substitute they are using now Part # 0244729. The substitute part is larger in size, maybe to handle the heat better. These can be found at several sites on line. I purchased mine at

They are $1.83 ea. If you find one of the caps shorted I would recommend replacing both of them. They are the same part 2000v 2200pf ceramic caps.

Since I fixed this problem, I have another problem. I have a buzzing sound in the audio when you have any kind of screen overlay like the guide or Tivo menus. I do not here it while watching TV. Don't know if it's related to the other problem or not. If anyone has any suggestions. I'm not sure I want to open the set up again though.

Good luck, hope this helps.

The buzzing is due to the routing of the wiring and Hitachi has put out a bulletin on it.

Open the tv up and move the wiring around to see if the buzzing changes.