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Hitachi AP53 Chassis, Convergence out, STK's statically check, Res / alignment question

Greetings,

Went out to look at a Hitachi Projection TV, Convergence was way out, thought I would pull the chassis and bring it back to the shop for Convergence module and resistor replacement. Well, I forgot to get the model # off the back, It is an AP53 Chassis. Someone repaired it before, looks like all the low value current limit resistors were replaced. Funny thing, Many are of different values, they have obviously been replaced. Here goes, RK15, 16 are 5.6 Ohm RK20, 21 are 4.7 Ohm RK25, 26 are 8.2 Ohm RK30, 21 are 6.8 Ohm RK35, 36 are 6.8 Ohm RK41, 42 are 4.7 Ohm none are open, I pulled all three STK4274's out and checked them with my homemade huntron, all check the same, thought I might find at least one with open output transistors looking back into the chip. All three of these were replaced as well, could tell by the excessive silicone transfer compound that was used. All of the diodes and caps check out OK (with esr meter). I'd like to install the proper value resistors for starters. Does anyone have the values of these, or, perhaps a spot where I can download the manual with the convergence/ alignment instructions? This set is from my Dr. who did my heart surgery back in November, would like to get it working for him.

Thanks in advance,

Markus

Reply to
Markus
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Model is ?????

Reply to
kip

Kip,

Must of left the paper with the model # on it inside of the set.. Think that it was a 46UX20B or 21K, really can't remember, chassis is definitely a AP53, It was manufactured August 1995. He is out of town for a couple of weeks, learning how to use some sort of new CT heart scanner.

Thanks for the reply,

Markus

Reply to
Markus

These are correct values from the Schematic..

kip

Reply to
kip

Kip,

Thanks for checking, looked a little out of place. I ordered the stks and will check the power supplies that feed them. I think I worked on this same chassis a few years back. Think it had some sort of power problem. Seen a few with the 'frosted up lens' problem. This one looks pretty clean especially for its age.

Take care,

Markus

Reply to
Markus

While the chassis is out just go over it with Mag Glass for dry joints especially in the Conv Section.

kip

Reply to
kip

Kip,

Checked today, parts should be in tomorrow. I'll let you know how it goes. I did some searching for a setup guide to get to the hidden convergence screen, think that I found it, will let you know. I went over the board with a magnifying glass, could find nothing out of the norm. All diodes checked OK with my fluke meter, most of the time if they are poor they will check high in the forward direction. Read some ware that these PCB's break, funny thing is when I was removing it the back got caught under the bolt in the center of the chassis (lower cabinet anchor) I could see how that could happen. This board doesn't look cracked. What bugs me is that the STK's checked OK (statically) I did solder a couple funny looking joints, however, non of those really looked open. I noticed there are LEDS for the various power supply's. When I install it and fire it up I'll have to check those. Just have a gut feeling that this sucker is going to be a tuffy, wish I had the whole unit back in my shop. Thanks again for checking those resistors. I dug around on the net, thought I could find a manual for it, just found the alignment instructions.

Take care and have a great day,

Markus

Reply to
Markus

Reply to
kip

Kip,

I called him yesterday after I got home, he was home, so, I took the chassis back, hooked it up and fired it up, worked fine. I replaced all three STK4274's and a couple funny look'n electrolytic caps. Plus re soldered all of the cold joints. While I was there I spent some time and cleaned up the optics, Looked great. Not very long ago I worked on his main Proj TV, it is an AKAI, PT4293HD, it was totally dead. Pulled that chassis, found the STK393-110's shorted and a hand full of 3.9 ohm flameproof current limit resistors open. Took it back and reassembled it. It worked fine, however, this set went out during a storm. Must of powered down with loss of Horz drive without killing the beam current. Has a line right up the middle on the red tube. Funny thing, I did some checking, looks like it is a Samsung, the circuit boards are G10 epoxy boards, mechanically a good design, however, makes me wonder if getting a tube, or, set of tubes for it would be worth it. I use to do all of our Campus Barco projectors, I always hated flipping on the switch the first time with the tube beam current enabled after doing a tube job. Do you think it would be worth the repair? Do you have a source for replacement jugs for these beasts? I know that sending the jugs out for rebuild is out of the question being the phosphor is toasted. Checking on the net it looks like this is a bummer model, ever seen one of these Akai PT4293HD 's?

Thanks again for the help,

Markus

. >If you want the manual let me know I will send it to you.

Reply to
Markus

Glad you are up and running... Oh ont he projectors I ahve zero info as those I DTWABP.

Reply to
kip

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