Omnibot 2000

I’ve been stripping / cleaning / repairing my old Omnibot 2000. Something I’ve been meaning to do for the last 7 odd years since I bought the fella.

I’m nearly at an end with stacks of pics on strip down and rebuild and lots of ideas on how to replace dodgy components.

Will make a new page under the “Geeky” section of the retrotechy website once Omnibot 2000 rebuild is complete and he’s fully functional again.

Until then, here’s a pic of Omnibot 2000 helping out around the lab….

Not All MP3 / CD to Cassette Adapters Are The Same

Cassette adapters that allow you to plug your mp3 player into your car cassette deck are a cheap and viable alternative to buying a new sound deck with a media port included however I couldn’t believe the difference in sound quality between some of these units!

I started off with a cheap unbranded universal adapter that I picked up from Asda (I say cheap….It was actually £7 and have since found the same ones on line for like £1.50).

I thought that these devices were pretty simple and therefore there wouldn’t be much difference between one manufacturer and the next. Was I totally wrong!

The cheap adapter suffered from several issues:

1. An annoying background hiss even at the lowest volumes
2. The Bass would completely disappear at higher volumes leaving tinny treble sound
3. the sound output was biased towards the left hand side of the stereo output meaning I had to offset the car stereo balance to compensate.

So I decided to do some research on whether I could get a better adapter.

I found this helpful review from back in 2005 which named the Sony CPA-9C adapter as the best of the bunch.

I then found a later review on the same website which named the Philips PH2050W as an even better adapter.

A quick google and I found that the price of these was around £12 except for one seller who was selling two brand new ones for £6??!! (Cheaper than the “Cheap” one I owned and a spare one included!).

I ordered and plugged in and WOW, what a difference! No background hum, No left right balance offset, big deep booming bass and immediately noticeable sound quality improvement.

The Philips PH2050W cassette adapter is by far the best adapter to use. This technology is getting old now and is no longer being developed but if you do have cause to require one, get on google and track a Philips unit down. Its well worth it!

Retrotechy Speccy Graphics Viewer / Editor

I’ve been tinkering with this ZX Spectrum graphics viewer/editor for a while now so I thought it was time to put it up for download. You can find it here.


The last thing that has been added is the TV screen view mode.
Basically you would normally rip graphics by arranging the bits in the file into rows of 8 bits / 16 / 24 / 32 etc. until you find the right width column to display the stored graphics as in the picture below:



You can see that the rows have been adjusted to 24 bits wide and the graphics become evident hidden within the file. When the programmer wants to use the graphics they are written into the display area of the memory in a certain way and they come up on your TV screen.


However the display part of the memory writes the graphics onto the screen in a unique way. If you consider a ZX spectrum with attached TV screen with the top row of pixels displayed being row 0, it will stream the bits linearly from the display area however it will draw on screen row 0, row 8,16,24,32,40,48 and 56. It will then jump back to row 1,9,17,25 etc etc. Once its done 8 rows of 8 pixels depth it then starts on the middle of the screen in the same fashion and then the lower part.


So thats just a monochrome screen of pixels on a background. It then reads the colour info from the attributes part of the speccies memory which follows straight after the display area.


Starting from the top left of the screen, each 8pixel by 8pixel block has a byte of attribute info associated with it that is only relevant for that 8×8 square. This byte of attributes contains Paper colour (background colour), Ink Colour (Pixel Colour), a bright bit and a flasher bit, both of which are either off (0) or on(1).


The speccy actually has a 15 colour pallette, not 8 as I thought. It has black, white, Yellow, Blue, Green, Red, Cyan and Magenta however it can also display all but one of these colours in two different levels of brightness, the exception of course being black. Total of 15 colours.


Each 8×8 square has a single foreground colour, a single background colour and both colours must be either from the bright pallette or the less bright pallette, not one from each.


The flasher bit… is a waste in my opinion. If its set to one then the ink and paper colours in that 8×8 square will swap themselves every half second or so. Personally I think having a bright bit for both the paper and the ink would have been a better use for it.
Using this method you can store a whole screen of coloured graphics in a small amount of memory, leaving more memory for better games. On the other hand you can see where the colour clash (Also named attribute clash for the now obvious reason) that the Speccy was infamous for came from.


Anyway you can now switch the display from bit mode to TV mode:



To be fair, the TV screen mode is probably only really useful to look at title screens Looking at the rest of the Speccy file is likely to show you colourful blocky garbage!

Berzerk PC

Whilst I was messing around with Berzerk 3D, I knocked up a Berzerk port of the original arcade shooter for PC in Blitz Basic.
The robot AI still needs a bit of tweaking as they seem to be avoiding each other / corners of walls.
I think the code needs one last going over, a good clean up and some minor tweaks. But for now it seems good, functional and bug free! (Famous last words…)
Can be downloaded from here.

Berzerk 3D Remake…

Have done some work on a Berzerk 3D remake. I felt that while other remakes were good, they kind of lost the original frantic gameplay somewhat. My goal was to remake without affecting the gameplay.
Unfortunately it’s become a Frankenstein’s Monster mish mash of various ideas that when mixed together just don’t look good or work brilliantly.
It’s not been a completely wasted effort as have learnt a lot about 3D coding and found a lot of new stuff out about Blitz3D and I’ve enjoyed doing the work on it but as a completed game I think that it would suck!
Whilst the maze was fine I had trouble integrating a protagonist that matched to the background.
The idea then changed to having a 3D background but kind of using this as a background and then adding actual game graphics similar to the original over the top.
When this didn’t match up will I tried adding sprites that were more animated than the originals.
However overall 3D berzerk just doesn’t work for me, no matter how it’s tackled it takes too much gameplay away from the source material. The only way to make a decent Berzerk remake is to stick to the source material and sharpen it up some, that means 2D or 2D in 3D.
I will keep what work has been done up for download and anyone interested in the source code give me a shout and I’ll happily share.
There is a runnable version available for download here.

Shit Tinted Glasses?? BBC Micro – Beebem Playing Fire Track


Ok, I’ve heard of “Rose Tinted Glasses” a lot in the retro gaming world. Getting a chance to play an old game from your past on an emulator only to find that it was a pile of crap!! It leaves you wondering why yourself and everyone else went totally banzai over it!!

Well time for the old switcheroo….reverse rose tint! I had a quick play of “Fire Track” on BeebEm the other day and was amazed to find that it was a smooth acomplished lil shoot-em-up. From what I remember of playing it “In The Day” on my Beeb B it was gregariously couloured, jerky and generally left you with a headache and some travel sickness!!

Playing it on emulation was a pleasure, and I kept going back for another go! Most shmups on the Beeb were hideous affairs (Some exceptions!) but this lil fella kept me hooked…In fact i want another go right now!!

Kudos to BBC Micro B Fire Track. A kuul Shmup still worthy of todays attention!!!!!

Sega Game Gear Repair II – Second Game Gear Stripped Down

The second of my Game Gears that I’ve stripped down is the single ASIC version. This has a higher wet capacitor count on the motherboard by one.

Having checked the capacitor values out against the list on the link on the previous Game Gear Repair post I again found some differences which may just be down to what capacitors were thrown in there at the time.
C4, C14, C42 and C11 are all 10uF / 16V on my one rather than 10uF / 6.3V. Whilst this is probably donw th 16V ones being cheaper than 6.3V ones at the time it may be best to err on the side of caution and replace with 16V ones, this could have been a mod due to 6.3V ones leaking excessively.


This one does show some minor signs of wet capacitor leakage. Whilst it hasn’t actually spilt over the motherboard and caused corrosion, there is some sweatiness around a few of the caps.

I now have one final Game Gear to open and check before I have to decide on the actual caps I’m using as replacements. I currently thinking dry alluminium electrolytic ones to negate having to replace them all again in 15 years time!

Sega Game Gear Repair – Game Gear prepped for surgery!!!!

After reading some wise words about Sega Game Gear Repair Here I now have one of my three game gears stripped and ready for surgery.
From the link above you can see that Sega Game Gears have two different motherboard versions, one with a single ASIC chip and one with two ICs. The wet and potentially leaky capacitor count is also different depending on the version you have. It seems that the first one I’ve picked to perform the capacitor transplant on has the 2 ASIC chip motherboard (top half of picture) which also has one less capacitor to change, however before I start ordering capacitors by the bucketfull I need to check the other two to see which revisions they are.
I will make a couple of corrections to the capacitor list for the two ASIC version motherboard, the capacitors are situated very tightly together but C38 should actually read C37 and C14 should read C6. Looking at the motherboard itself I can see how the author of the link above would get these things easily confused!
I should point out at this stage that I found no actual evidence of leakage from any of the capacitors but the Game Gear itself had started to display some evidence of capacitor drift. Switching it on from cold would just get you a blank screen for a few seconds followed by it switching itself back off again. The second switch on would just get you a blank screen, off and on a third time and it leapt into life.
The bottom half of picture shows the inside of the back of the game gear with power board lower right and audio board lower left.
This Game Gear has had previous surgery on the audio board as when I first got it the audio from the external speaker wasn’t working. This also turned out to be a capacitor issue. Two of the caps on the audio board start to try out after a while causing loss of sound so if you’re carrying out the repair on the motherboard, it’s probably a good idea to change the audio board caps as well for some non wet types.
I’ll mention the 4.5mm Gamebit head screw here. The Sega Game Gear itself is held together by 6 standard phillips head style screws and a “Gamebit” head screw. This 4.5mm gamebit head screw is basically a screw with an odd shaped head that a standard screwdriver won’t undo and is used as an anti-tamper screw to stop you opening your Sega Gamegear. Nintendo and other manufacturers also use the gamebit so if you take consoles apart regularly it may be worth investing in one. Just google 4.5mm gamebit and you should be able to get one no problem.
If you want to save yourself a fiver and have a decent set of thin nose plyers then it is possible to get the gamebit screw off by holding the screw head in the pliers very tightly and then gently turning the screw head round. BE ADVISED!! If you don’t do this very very carefully then you can damage both the Game Gear case and the Screw head so it’s off of your own back which method you chose and I accept no responsibility for damage etc done by people too tight to pay a fiver for the 4.5mm gamebit socket!!