Wells K7500(?) P793 no vertical

Culito

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I've been searching around and found a few random threads, but nothing specific.

Monitor evidently had never been worked on - all original caps, still siliconed to the CRT tube. It had a nice run!

I did a cap kit, reflowed a bunch of bad solder joints, new vert IC, new R402 (1.2 ohm, was badly burned as well as the area all around it). I am now getting +25V at the vert. test point.

What sucks is I'm helping out an arcade 30 miles away, so I'm bringing the chassis back and forth to my house. So, if there's anything on the chassis I can check with a meter before I run it back to the arcade, that would be great.

Thanks folks.
 
there are a bunch of counterfeit tda1771 IC's out there.

if you have good voltage verified on the LEG of the IC NOT just the test point, i am betting your new IC is bad.

was the old one no good?

if it was working, put it back in.

Peace
Buffett
 
I saved the original IC. I replaced it with a NTE7183 which I wasn't too excited about, but it cross-referenced according to MCM Electronics.

Just sitting on the bench, I am getting continuity between the test point and the IC pin.
 
I'm a proponent for shotgun repairs, but only if the parts relate to the issue at hand. if the monitor didn't work at all before, what compelled you to replace the vertical IC? this is a very common mistake people make, just like replacing HOTs for the sake of whatever... "oh, I thought the old one was worn out" yeah, transistors don't just wear out, they either work or they don't.

I would put the original back in and see what happens. I don't know if the 400 section relates to vertical deflection off hand (the burned up resistor you replaced) -- I don't work on monitors exclusively, I have to fix anything and EVERYTHING, so I'll probably never be able to memorize the sections or exact part numbers off monitors.

hopefully you put the old part in and it just works though.
 
I'm not a "throw parts at it" type either. When the monitor came to me, there was no vertical deflection. Just a thin line across the screen.

Pulled chassis, the resistor that supplies the voltage to the vertical section was burnt and separated. This to me implies a short further down the line, which I assumed was the vert. IC. Replaced both. Cap kit because it was necessary.

And here we are...
 
So!
I pulled the NTE IC and reinstalled the original TDA. When I powered it up, no screen, and the resistor I replaced for the +25V vert supply immediately became blazing hot.
This, to me, seems like the original TDA chip is shorted, which was what I had thought at first.

So does it sound like I need a new TDA1771 at this point? Where would I find an authentic one?

Has anybody confirmed that the NTE replacement does not work?

Thanks!
 
So!
I pulled the NTE IC and reinstalled the original TDA. When I powered it up, no screen, and the resistor I replaced for the +25V vert supply immediately became blazing hot.
This, to me, seems like the original TDA chip is shorted, which was what I had thought at first.

So does it sound like I need a new TDA1771 at this point? Where would I find an authentic one?

Has anybody confirmed that the NTE replacement does not work?

Thanks!


i have some in stock

https://www.arcadepartsandrepair.com/store/monitors/tda1771/
 
Welp, I'm back where I started.

Put the new TDA1771 (thanks security0001) and still no vertical deflection. Just a horizontal line. Still getting +25V to the IC.

I'm reading around 5 ohms across the vert. deflection coil on the CRT.

Any suggestions on what I should be checking next? I never have much luck with these things...
 
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