Arcade Collecting > Restorations & repair
I still go BERZERK !
Level42:
I'm not sure if static RAM would work on Berzerk but it seems to work like this so I'll leave it like that...
Since the little guy had fever today I was forced to stay home from work so I did some work on the Berzerk Joystick.
I still had problems to hit the diagonals and I really wanted it to improve.
First a little explanation about the construction of the joystick:
The red arrow points to the PCB. This carries the opto's (2 are draw, incicated by the yellow arrows). These point DOWN in a right angle. You can see that when the joystick is centered, the light will travel side-ways of the reflective disc (indicated with the green arrow). If the stick is moved, the disc will come over the opto and will reflect the infra-red light back onto the opto.
If you look at the design of the construction it's easy to understand why the diagonals are a problem:
The opto's are only on the primary directions (i.e: up, down, left, right):
The opto's are U2,3,4,5. The red arrows show where they should have added the other 4 for the diagonals....
The joystick works so, that the shiny disc that is connected to the joysticks tilts over to a certain direction when you move it. If you move it (f.i.) up, it will come close enough for the opto to "close" (start seeing the reflection of it's own infrared beam).
However if you move it diagonally, it will have to cover two opto's. Since the disc is circular shaped and even everywhere, the distance will be less then when you hit a primary direction.
This causes a very narrow angle to give f.i. both the up and left signals.
To be honest, Stern screwed up. They should have put opto's on every possible direction IMHO. But it was (as almost always) probably a cost thing. Anyway, that would be the best possible solution.
Since these opto's are long out of production, and I don't want to seriously hack the PCB (it would also require some extra TTL logic) I thought about a simple solution: how about bringing the PCB close to the disc.
This was very easy to do by adding some extra rings on the supports.
I first tested it with two added rings on each support. It worked great on the diagonals, but now I started having problems going in the primary directions. Apparently, if the disc gets TOO close, it's not working either.
The little graph in the datasheet proved this "theory":
You can see that the further away the reflective surface is, the less current it will conduct, which is logical. But also when the distance is very close, it will stop conducting (in fact, it drops much faster there).
So, I needed to find the right "balance". Thus I removed one of the 2 extra rings on each support and tested again. This time it worked perfectly !
I hit diagonals as easy as the primary directions !!! It's really like a different controller now ! :D
I also even further loosened the spring-tension. I don't really know why they included it in the first place. The stick does self-center by itself, but it does springs a little back and forth if you let it go. I played it a while without the spring attached and I was almost perfectly happy with it. It totally got rid of the required force to push the joystick. IMHO a joystick is not a means of muscle-exercise but this one sure felt like one (esp. before I loosened the spring). THe only problem I had without the spring connected was moving over VERY short distances (I mean one pixel here). This is often what you want to do with Berzerk. Stand around the corner of a wall and shoot EXACTLY 1 pixel over the edge of the wall. It was almost impossible to do without the spring.
So, I re-attached it and loosened it even further than before. I will need to seek for the ultimate compromise....
There's another thing I don't like about this stick:
The end-hit....(or how do you call it ?) When you hit the end of the travel it hits a very hard rubber like stuff. I don't know if this has become harder over the years or if it was intended this way, but I don't like it. Is there any stuff to weaken the rubber around ? Or should I try to get some new and cut a new block (if possible) ?
Anyway, I'm already MUCH happier than I was before. Almost all my games after I moved the PCB up a bit I got through to 10000 points with 3 extra men. I lost them quickly every time though so I still didn't brake my 12xxx record but I'm sure I will soon....
Did I mention this game ROCKS ?
To be honest I was a bit hesitant about the re-playability of Berzerk but man does it draw you back and back and back ! I love it !
Level42:
There may be a second way to adjust / correct this issue.
See the schematic:
The signal of the photo-transistor in the opto is compared to a reference voltage created by R2 and R3 (Schematic only shows 1 opto, but of course they're all the same). R2 and R3 could be replaced with a 10K pot. This way it's possible to vary the voltage that the opto's signal is compared to by the LM339. In theory this should allow to change the "range" of the opto. However, this will also require careful testing and finding the right balance.
As the extra rings on the supports are much simpler and seem to work great I settle for that, but in theory this should work.I think ;)
ChadTower:
I hadn't been keeping up with the other restorations...
Dude, fantastic job, on both the thread and the cab. I mean that. :applaud:
I like what you've done with the joystick to fine tune it but the pots are probably overkill. Seems like more potential to move away from where you are than further towards perfection. With that sort of adjustment potential I suspect you'd never be happy - you'd be tweaking it forever. ;D
I have three ZPUs sitting here and haven't added a new battery to any of them. I just might use this mod. Thanks for the great writeup.
Man I wish my dildo stick had shown up. Never did. I ended up changing direction a little bit on my Berzerk and will write it all up very soon... :)
Level42:
You did catch that Cmoore is doing a new run of CP's right Chad ? And also he is now looking into reproducing the dildo-stick !
Thanks for your nice words, glad to see someone likes it ;)
ChadTower:
Oh, no, I didn't know about the stick. That I would really like to have. I already have a repro CP so I don't need one for this cab. I'd buy a spare but I have only ever seen this one Berzerk other than the one at Funspot!
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version