This video shows how to reassemble an HP 95LX pocket computer from 1991. The video provides detailed instructions for returning your 95LX from parts to a working unit.
Atari 400 repair and composite video mod
I recorded a set of videos recently documenting some troubleshooting of an ATARI 400 system, and the conversion from RF to composite video. There was so little info out there about this mod that I thought even my crummy video would help.
The embedded video above is the 4th and final part that shows the composite conversion. Here are links to the other parts and some docs and forum posts I found along the way…
Part 1: https://youtu.be/mojxsA4EAFQ
Part 2: https://youtu.be/9mvjiq9HEIk
Part 3: https://youtu.be/qBcRygpFbtI
Atari 400/800 Service Manual:
http://www.jsobola.atari8.info/dereat…
S-Video to Composite info:
https://www.epanorama.net/circuits/sv…
Atari 400 video mod info:
https://atariage.com/forums/topic/178…
https://atariage.com/forums/topic/209…
The TurtleCam returns…
I picked up a cheap Raspberry Pi 2 model B a while back and decided to use it to resurrect the TurtleCam. I added on the old version Raspberry Pi 5MP camera and got a BME280 ic2 temperature / pressure / humidity sensor from AdaFruit, mixed in a little Python and WeeWx magic and boom… Instant webcam / weather station. 🙂
I’ll eventually update this post with build details but in the meantime you can check out the live feed from the TurtleCam by clicking on the image below:
Adapting a Yashica GSN 45mm f/1.7 lens for the Sony E Mount
Ages ago I bought a broken Yashica GSN as a parts camera to repair the rangefinder mechanism on my keeper GSN. (You can read about that surgery here)
When I cannibalized the parts camera, I took the lens off (probably the only part of that camera which was in decent shape) hoping to one day adapt it for use on a Leica M body or something similar. Well, the lens wound up, like a lot of my projects, kicking around in a drawer for years and just gathering dust. Then the NEX series of cameras came along and with them adapters for every conceivable lens imaginable. Slooowly, eventually, the dim flashbulb in my head went off, I remembered the long forgotten GSN lens and I got to wondering if and how I could pair it with my NEX 5n.
My main issue always came down to how to focus this little beastie. When I had removed the lens from the GSN, along with disabling the shutter and fixing it in the open position, I removed all the of the focusing mechanism and filed down the lens mount flush with the helicoid. (The holes seen were for wires and a metal rod that triggered the shutter inside the lens.) In hindsight I should have obviously left at least a part of the focusing hardware in place so at this point whatever was going to focus this lens was going to have to be an external thing. |  |
This is where one of my favorite adapters for the NEX series of cameras comes in; Sony E-mount adapters that have a helicoid built in which are meant to allow for close(er) focus with M-mount lenses. These adapters have gotten dramatically cheaper as more Chinese made versions have become available. If you search eBay for “nex helicoid” you will find plenty in the $35-$40 range which is likely the same as the one I have. There is even one that goes for about $18 that can be found by searching for “tinray helicoid”. |  |
At the moment, and as you can see from the photos, this is in the prototype stages, and I am simply using blu-tack to fix the lens to the adapter. I was actually lucky to have removed as much of the focusing mechanism as I did because in this setup with this particular helicoid adapter infinity focus is very close to spot on. It currently focuses just a little bit past infinity, but I plan to shim that when I do the final mounting. The only tricky bit has been to tripod mount the camera and check the focus in the corners to ensure that the lens is fairly aligned with the sensor. Of course, this being blu-tack, it is as easy to push and prod the lens in to a rough alignment as it is to knock it right back out. :-/ Eventually, I want to get a Hawks v3 helicoid adapter (much better quality!) for use on my a7R. I will then use some JB Weld on this adapter to permanently fix the GSN lens to the helicoid. I’ll update this page when that happens. |  |
In the meantime, here is a sample shot with the prototype mounted GSN 45mm f/1.7 lens shot at f/5.6 on a Sony NEX 5n (To view the full size 2464×1638 pixel JPG right-click on the image and open it in a new tab.)
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Nexstar SE Wedge
The final part of my Nexstar project was getting it on a wedge which would make auto-guided long exposure shots possible. Unfortunately, the Nexstar wedge has long since been discontinued and even if it hadn’t — $160 for a weenie little wedge for this scope was a bit much for me. So I decided to buy a cheap used wedge from an older Celestron system and make whatever modifications were needed to get it to work with the Nexstar.
What I didn’t expect was how little modification was needed to get an old 1980’s era Celestron C8 wedge to work with the Nexstar SE. All the holes, both on the tripod and drive base lined up perfectly and the only modification I really had to make to the wedge was to hammer out the center guide peg.
Mounting the NexstarIn the first photo on the right, the wedge with the center peg removed has been mounted on the Nexstar SE tripod. The center peg on the tripod fits well as it is much smaller than the space left by the removed wedge peg. The tripod bolts hold everything in alignment and there is little to no lateral movement of the wedge in relation to the tripod. The bolts are 5/16″ x 24 x 1.5″ cap screw bolts from the local hardware store. The azimuth adjusters work perfectly with this setup as long as you don’t tighten down the cap screw bolts too much. One rather major item of caution is the length of the bolts that attach the Nexstar drive base to the wedge. Inside the drive base is a gear (right under the fork arm) that rides very close to the opening for the mounting bolts and is completely unprotected. (Seen in the 2nd photo.) If a bolt is too long and protrudes very far inside the telescope, this gear will bind against the mounting bolt probably causing damage to the drive base. These bolts are 3/8 x 16 — I got lucky and had an extra set from my old Losmandy GM-8 that were the right size but much too long. I cut and sanded them with a Dremel and then added some thick washers just to be extra careful. The final image on the right shows underside of the wedge with the Nexstar mounted. Another modification I made was to remove two of the rubber feet from the Nexstar base to allow for more latitude range before the Nexstar base impacts with the side of the wedge as the drive base is slightly wider than the wedge. With the rubber feet removed I can get the latitude all the way to the 14 degree mark before the base connects with the wedge — with the rubber feet on, this was more like 30 degrees. The rubber feet peel off without too much difficulty and if I ever what them back on, they’re easy to reattach with some rubber cement glue. (I left one of the rubber feet on to designate the ‘top’ of the mount.) |  |
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Adding a Latitude AdjusterMy very first telescope back in 1999 was a Meade LX50 on which one of the first modifications I made to it was upgrading the rather flimsy wedge latitude adjuster that came with that scope. Since then I’ve had the old adjuster kicking around from box to box mainly because I’m a pack-rat but now I’m glad I never threw it away! The length of the bar turned out to be too long for the Celestron wedge by only about 3mm. I cut and sanded the bar down to size with Dremel cutting and grinding disks (at one point I had to wear work gloves because of how hot the bar was getting!) until it was a snug fit and then ‘painted’ any visible scuffs with a black Sharpie. The end result almost looks like it was meant to be there. 😉 Once down to size, I fixed the bar in place to the lowest point on the latitude guide groove on the wedge with a couple of bolts and washers to hold it in place. The long latitude adjustment screw fits well to the underside of the wedge and since this setup is not going to take a bunch of weight (certainly much less than the LX50 it was originally designed for!) it works very nicely. This modification also added a great deal of stability to this wedge. I was lucky to have saved the LX50 latitude adjuster and I think that even if I didn’t have it, I would have eventually wound up trying to make something similar out of wood. One thing I’d eventually like to add is a pair of knobbed bolts in place of the current cap-screw bolts I have for the latitude adjustment on each side of the wedge so I can loose the allen wrench I currently have to use to loosen them. |  |
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