My first hardware home brew project.

[hex65000]

Greetings gang.

 

I am proud to say that I'm nearing completion of my first 5200 home brew project. It's not a huge deal, but it might be practical for the general public.

 

What is it?

I have managed to get my hands on a pair of 4-port 5200 systems, but of course, one needs that special switchbox. So that's my project -- the 5200 switchbox redesign.

 

Why this?

I needed an extra switchbox, and with current gen technology, I figured I could shrink the board down a bit and hopefully sell a few of these off once I get past the proto board. The current PWB dimensions are under 8 x 6 cm. It also acts as a nice first step for me in the design from idea to hardware process.

In other words, I was learning as I went with this. It also could serve the community in a practical way without getting too exotic.

 

Any limitations?

Two. I chose to omit the 300Ohm RF output. It added to the cost and board space. Really, who still HAS a 300ohm input TV in service?

The other is that I'm probably going to use an RCA phono jack for the video out v/s the male coax 'F' connector that typically goes on the box. I just HATE crimp parts and phono plugs are easy to work with.

 

How much will it be?

I have no idea. The killer is going to be the circuit board. I am going to be able to get a proto milled out at work so I can make sure I did an okay job with my layout, but that's it. I can't produce mass quantity PWBs at work. My prelim check on 2 layer circuit cards is that it'll be expensive unless I build like 100 - 1000 cards. If I can sell 100 boxes _I_ will be amazed.

For what it's worth, the parts list alone is around $20. Inductors and connectors are not cheap. (That's MY cost, and excludes the time it'll take to slap these beasts together and an external chassis.

 

That's expensive! can't you make it any cheaper?

I'd love to. One way is to buy a LOT of parts and get the price break from the electronics suppliers. The other way is to use crappier parts. The second route is not very appealing to me. The inital batch of passive parts will have the following properties:

1% Resitors (0.5W) For the two 0.33ohm resistors I subbed in a pair of 0.3 ohm 1% resistors rated at 5W.

5-10% capacitors (25V - 50V)

10-15% inductors

Bear in mind that I selected these so that they would easily handle current/voltage/tolerance ranges without blinking.

 

Notes:

- This was harder than I thought, but the home stretch is in sight.

- The Aromat relay that was used is now discontinued. Aromat has an equivalent available, but I found one done by a group called Omron that looks rather nice.

- Finding a .56uF cap in SMC forms wasn't easy (or cheap) a .47uF + .1uF cap solved that. -- and turned out cheaper than the .56uF thru-hole cap I did find.

- There are two things that will stop this show:Getting coils and finding a place for inexpensive PWBs.

- Specing mechanical bits for electronics can be challenging.

- The schematic on the Atari Age site for the 5200 box has an error. On the LM393 the output pin on the comparitor should be pin 1 not 7. (Pin 7 is the output of the second comparator which has both inputs tied to ground.) Visit TI's web site to verify this.

 

Hex.

[ I'll stop you... with handy cannon. Very handy! ]

[Bryan]

Sounds cool. Did you know that Best Electronics still sells the original switchbox new in the box for $12?

 

-Bry

[hex65000]

No I did not.

 

At least I spotted the Error on the Archives schematic.

 

Ah well, I can still do the proto and move on.

 

Hex.

[ Pie cannon??? ]

[hex65000]

You meant $19 right?

 

From their site:

 

CA018266 Atari 5200 CX522 4 Port custom TV switch box $19.00

 

I still doubt I can beat the price, but its not a blowout.

 

The first wave of pieces are on their way. Rah!

In the process of waiting for parts, I got my first 2 port 5200 fixed and running. The power jack was mangled and some idiot tried to strap a sub-par supply to what was left of the power jack. That mistake has been corrected and a proper jack is in place. There was some fudge factor because my repacement parts didn't match the PCB. However it's up and running like a champ now and I celebrated with some Keystone Capers goodness.

 

Hex.

[ Getting old gear up and running one part at a time... ]

[Bryan]

Sorry. The price must have changed since my catalog was printed.

 

-Bry