Just what it says... repair briefs from people other than Sam. If you have a repair brief, feel free to [contribute] (or send me [e-mail]).
Also, check out Sam's official Repair Briefs.
(From Ren Tescher (firstname.lastname@example.org)
Reverse the disassembly procedure and test.
Adjustments: I found no adjustments were needed.
Elapsed time: The first one took most of the afternoon, the second one took about an hour.
Disclaimer: Lethal voltages exist inside monitors even after they have been unplugged, if you do not know where these voltages are or how to nullify them, do not attempt repairs yourself, but give this article to a qualified video service technician.
Much thanks to Jason Sodergren (email@example.com) for pointing me in the right direction.
Service Manuals (~$55US) are available from:
Hitachi America, Tel: (510)661-0777
We also have an HM-4119-S-AA-O (Sun part# 365-1000-01) with a similar problem. I just completed the repair on the above model and its procedure is the same. (It is the same faulty capacitor C307). This model was 4 years older than the other 2, but it is nearly identical inside. Also, thanks to Hitachi for building a good monitor and making schematics available.
Let me know of your Hitachi/Sony Sun monitor repairs and I'll keep a no-cost file available for all.
(From the Editor)
The TV was in good shape, as demonstrated by the fact that I could watch a nice, single pixel vertical picture with the yoke disconnected. The original HOT was not to be found so I had ordered the non-insulated version (after months of delay). I first suspected the yoke. I measured about 70 ohms for the vertical section but only 3.5 ohms for the vertical. However, I checked all the other TVs I have (waiting to be fixed) and was convinced that this value was acceptable (it varied from 1.8 ohms for a large 19" to 20 ohms for a monochrome monitor). So, that wasn't it. I then traced the circuit... as per Sam's guides, I next suspected the start-up circuit for the HOT... alas (sigh) that checked out. I DID find a slightly out-of-value cap in the PS, 250V 47uF had become ~15uF but replacing it did not improve anything (I was going on the assumption that the PS was going into over-current with the HOT in-circuit but worked fine without it).
Well, that was the end of the line. I then remembered the sparks when bringing the set on a Variac - GET ONE NOW! - and realized "Duh, maybe the insulator sparks at that low voltage but downright leaks at full voltage". This is one of those things that can't really be tested... so I dug up a strip of silicone rubber insulator and put it in place of the mica. Switched on the Variac: 30V... no sparks, gentle whine from the PS, 60V... HV UP (heart rate up), 120V... perfect picture!
The #%&*@ problem was the mica insulator!
Comments: I was SO close to giving up... what kept me going was knowledge that everything BUT the HOT circuit was fine. I realized what was wrong after a few days of desperation... the mica insulator I used, a rather thin one, is great for low-voltage applications but it just isn't up to the task as a HOT insulator. Lesson learned. BTW, I looked over the original HOT (one of those plastic-encased versions that didn't need an external insulator) and, golly gee, a spark-etched burn (hole) could be seen on the back surface. If they had used an insulated HOT AND some insulator, this set would have still been working.
Lesson: Don't use [thin] MICA in HV apps or suffer weird and non-related symptoms and problems. I used an over-sized strip of silicon rubber insulator... got it from some stripped device.
Well, as luck would have it, someone gave me a Panasonic 'Color Point' TV, model# CT-3053.The symptoms were that it would work fine for about 15 minutes, then shut off. It would then have to cool off for awhile before it would re-start. Also, I noted that the remote was in particularly bad shape.
I opened 'er up, checked for any charge remaining on the caps (there was none), and gave it a look-see. First thing I noticed was the board had visual 'I've gotten hot' signs around a few resistors and a zener diode. One resistor's connections appeared particularly bad. I re-soldered all of these suspect connections, as well as the large connectors leading to the deflection, degaussing coil, etc. I put the back on (so the cat didn't get too curious ;-) and plugged it in. Nothing! I removed the back and inspected my work again to make sure I didn't forget to plug a connector back in. A thorough check revealed nothing amiss. I slapped the back on again, plugged it in, and was rewarded with nothing. Alright, I said as I unplugged it.
I opened the back and begain to trace the circuit on the input side. Two fuses checked out A-OK, as did the relay coil, the 4 diodes in the bridge, etc. Not having an isolation transformer handy, I didn't attempt to measure B+. However, since I didn't hear the relay come on, I could be certain it wasn't receiving B+. I then tested the resistance between the prongs of the plug and their corresponding places on the board, as well as all connections to/ from the main components in question. I put my meter across the prongs of the power plug to see if there was any resistance. There was 64 ohms! Aha! I said. I then attempted to find out exactly WHERE this resistance was coming from. Especially since it was so low. I carefully examined the input circuitry once more, and the only place hot was going on the board was to the relay and wait a sec... a jumper wire! The jumper wire then went to one of the board connectors that I thought previously was the degauss coil. Turns out it was really for a power transformer! I had spied the transformer earlier, but thought it was for the speaker, since this was an older TV. I then traced where the secondary went, and measured it. .1 ohms, it looks OK. I then spied yet another fuse. It checked out. So, I proceeded to trace this second power supply.
Leesee... one side goes to ground... other goes thru a diode... onto a cap and ground... to a transistor... hey! two of the leads on the transistor have little rings around them! I then move the leads with my fingers, and they move back and forth in the hole. Whip out the iron and fix these bad connections, do another scan for bad joints, and slap the back on. I say something like 5 bucks says it'll work and plug it in. I hit the power button and the set comes to life!
Everything seems to be working great, so I slap the screws back into the back. However, I notice curious patches of colour on the screen. It seems to be in serious need of a degauss. Turning it on and off a few times doesn't fix the problem, so it's off with the back! Checking the degauss coil reveals that it's OK. The thermistor, however, isn't in as good of shape. I pull it out, as it's reading open. I find an identical unit in another junker and slap it in. A few good ons/offs and the set's as good as new!
Now that I got the set working, the remote's next. It seems to be OK, however a few of the buttons are punched through. (it uses an overlay) The buttons consist domes with little plastic spacers on top, covered by the overlay. Thank Glub that none of the spacers were missing! I paint the spacers black (they were white) and stick clear tape over them. Looks lots better than it did. So now I have a free TV to replace my older non-cable-ready one! :-)
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