DEC VT220 Horizontal Roll & Power Problems
I’ve recently acquired a hand full of older DEC terminals. My favorite of these is a DEC VT220 from September 1984. It originally started up fine, but over the last 6 months it’s acted up in a couple of different ways. I thought I’d post about how I resolved these issues in case anyone else runs across them.
The first problem arose a few days after powering it on. The picture would roll sideways, so that static text looked like a bunch of lines moving horizontally. I consulted the service manual and in section 8-4 it mentions an adjustable horizontal hold circuit which sounded like what I was looking for.
Before we continue, I just wanna reiterate that CRT’s are dangerous, and have the potential to fatally shock you, so make sure you know what you’re doing before disassembly, and be careful!
Lorem ipsum odor amet, consectetuer adipiscing elit. Lacus efficitur purus ligula sit duis enim lobortis diam. Posuere ornare interdum fames lacinia et vivamus semper. Consectetur lacus interdum posuere risus aptent dictumst integer. Scelerisque per in maecenas eu urna. Penatibus lectus nunc nunc consectetur maecenas mollis. Iaculis nunc ligula sit accumsan nec placerat placerat. Leo primis justo felis turpis pulvinar egestas. Fusce pulvinar tellus taciti laoreet euismod fermentum class; montes donec.
Facilisi vivamus rhoncus; per ornare suscipit mus ex. Condimentum euismod nisl sem suspendisse commodo porta metus interdum purus. Odio eleifend feugiat mauris magna habitant nisl nam. Sed ultricies purus varius efficitur eleifend laoreet potenti. Ad ornare nisi montes torquent libero. Tristique vestibulum dis fames purus; pellentesque hac. Nam primis curae nascetur morbi enim cursus tempor. Torquent sollicitudin luctus accumsan egestas donec vitae.
Vitae risus tincidunt tempor fringilla porta gravida tortor inceptos cras. Eleifend himenaeos vivamus platea habitasse ac placerat dictumst. Ultricies dui sociosqu condimentum vulputate cubilia ipsum cubilia. Sed placerat dolor molestie eros in. Habitasse dis sodales parturient tincidunt malesuada placerat dis rutrum. Volutpat nec interdum netus vehicula ut ornare inceptos erat. Aliquam commodo laoreet lobortis a nunc rutrum luctus. Vulputate habitasse duis odio condimentum per mattis. Ridiculus sem himenaeos velit feugiat himenaeos.
Dolor blandit nunc ultricies tincidunt egestas duis. Malesuada gravida blandit faucibus porttitor dis. Penatibus est nulla porttitor aliquam integer. Ultricies nulla auctor molestie habitant integer! Consectetur torquent aliquam placerat urna ullamcorper nam. Rutrum ornare netus et taciti himenaeos etiam adipiscing natoque himenaeos. Placerat sagittis finibus himenaeos justo; cubilia imperdiet lacus at. Sagittis habitasse sed velit fames eleifend varius. Laoreet felis condimentum mus enim eros ligula nulla. Litora rhoncus sollicitudin fames bibendum fames eu elementum fermentum.
Nostra venenatis augue cursus conubia proin nisl. Vel sociosqu justo nisl feugiat adipiscing fermentum rutrum faucibus. Cursus vestibulum viverra eros tempor torquent semper consectetur pulvinar. Vel amet cursus elementum pharetra nibh pellentesque. Conubia lobortis finibus felis eu fusce dis erat. In interdum tempor eros potenti nibh sollicitudin ridiculus. Adipiscing duis platea aliquam hac rutrum suscipit.
Disassembly of the 220 was rather straight forward, with only a hand full of screws to remove from the body, and we were in like Flynn. The R203 potentiometer was in an easily accessible area, and after identifying it, I powered on the terminal and began to adjust it. Like magic with only an eighth of a turn the image stabilized and everything was readable again.
The second problem I had was it not powering on. I thought for sure that something on the power supply had given out, or maybe that it blew a fuse, but to my surprise the actual rocker switch on the back went bad. I wasn’t able to source an original part; however, I did find a compatible part at Mouser Electronics part #R5ABLKBLKFF0.
Installation was pretty straight forward. I tie wrapped the wires in pairs, and took photos of the original installation to make sure everything went into the same place. I used a pair of wire snips to cut the “wings” off the original switch, and once these were removed the piece came out without issue. The replacement part snapped in without too much effort. I then wired everything back up, and it powered on ready to see another day.