Showing posts with label DIY. Show all posts
Showing posts with label DIY. Show all posts

Tuesday, 16 October 2018

Vectrex - hack

Found a second Vectrex. :-)
I have two now, one to play and the second to use  for vector rescanning.
This has come all the way from France.


As a retro gaming collector, it hurts to modify this. So I'll try to make as few changes as possible.

Time to open her up.
Be very very careful of the tube. Even after not being powered for weeks they can still retain lethal voltages. So discharge it first.

I used this screwdriver (place under the protective rubber CRT cap) which I attached to ground via the alligator clip. Listen for the pop !
I can't stress enough the risk of discharging the tube. If you are not sure what to do , get a qualified technician. These voltages can kill.

Some pics .. this is the CPU section




In the pic below, the CPU section is on the base, and the XYZ driver board is positioned vertically. It is to the left of the tube.
The CPU is connected to the XYZ driver board in the un-modified vectrex
The CPU is what creates the images.


 In the pics below, the XYZ board lies behind the heatsink.

You need to separate these two boards. and wire the XYZ inputs to the back.
I'll use 3.5mm jacks.

Another view of the CPU board. The Red, Blue & Yellow connector is the XYZ connector.
Unplug this.

Rather than cut the female XYZ connector ive decided to use a header to make a new male connector 
 
It may look confusing, that I have 6 jacks .
3 connect to the CPU, and 3 connect to the XYZ driver board.

The pic below is the inside of the case. First, connect all the grounds. 
 


In modifying the vectrex, what I am doing is finding a way to replace the CPU's control voltages with control voltages from a modular synthesizer.
 
So most people just cut the 3 leads leading to the XYZ driver board and connect that to the modular synth.
This is fine , however, the CPU is now useless... and you can no longer play games, unless you reopen the vectrex and reconnect everything.
 

Below is the outside of the case.

All I have done is bring the 3 wires that connect to the CPU , to the back of the machine and attached 3.5mm jacks. (The ones on the left)
 
I have also brought the 3 wires that connect to the driver board , to the back of the machine. and attached 3.5mm jacks. (The ones on the right)
 
So if I wish to connect a modular synth, use the 3 jacks on the right (DONT connect to the left).
 
The (3 right) X,Y,Z inputs are CV inputs to the driver board.
I understand that 0V (on both X and Y) its the centre and that
±9V works on the on the horizontal X input and ±11V on the vertical Y input.
... to be tested.
 tHE green wire is ground.

The inside of the jacks


Connect like this to return the Vectrex to normal so you can play games again
I could instead add a switch, though this would involve more holes & drilling.
I've attempted to keep any destruction of this vectrex to a minimum.
So the only permanent modification was drilling the 6 holes for the 3.5mm jacks. All the original wiring is preserved!!! So you can re-connect the wiring for gaming action!

Now that you've modded it what standard eurorack audio modules should you use??
In my test I used:

The elby matrix mixer is a real winner. The bluelantern Thruzero VCO & the steiner microVCO also worked nicely.
Other possible modules:
+ Synovatron CV tools, DPO, MATHS, Wogglebug.
"Maths is usually the Z input, I'm mainly just playing with the speed of the pulse - as if it's a really fast envelope.
Then two or more outs from both oscillators in the DPO are going to X & Y,..."

+ e340 for X & Y. -- cloud generator
+ Thonk/Fonitronik Cascade 
+ If you have a ARP 2600 or a TTSH, the voltage processor is excellent for modifying the 3 input signals 
+ Pip Slope and an O/A/x2 from ALM / Busy Circuits
+ PDO and Akemie's Castle 
+ Clouds  
+ 4MS Shifting Inverting Signal Mingler  

A bit about vector rescanning

My understanding is that the vectrex isn't prefect for vector rescanning as it does not have the bandwidth ....but it kinda works in limited ways
It is better suited for lower frequency oscillographics.  

However, if you still want to do vector rescanning you need:
1.Video Input to extract luma from your video source
2. H & V ramps generator .

Thus if you are using Cadet modules you only need one Ramps, a Sync Gen and an Input. 
A LZX visual cortex (VC) has all of this.
Connect the horizontal ramp to the X, the vertical ramp to Y and the luma output (of the VC or the VideoInput) to the Z.
 

Links
+ Muffs- vector modification
+ Vectrex Hackaday
+ Hacking a vectrex - Lumpybanger
+ Zektor - using the vectrex monitor
+ Muffs - vector rescanning for dummies
+ Muffs - good oscilloscope for vector rescanning
+ Rutt-cadetra blog

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LZX - Cadet III - Video input

As the name says this Eurorack module allows you to get external video into the synth.
It amplifies the input signal.
It is best used for monochromatic input cameras or devices with Genlock capability.
I understand that you will however need the Cadet I to get a steady video signal even though
the Cadet III doesn't use the 14 pin sync header.

The Cadet III has brightness and contrast knobs. It converts the input video into a black and white "Luma" signal.
These aren't official build notes, just my records to help me trouble shoot.
It's a work in progress.
Do let me know if you spot any errors or omissions.



u9 - TL431BQLPR
I'm trying this instead.

"2N3904 and 2N3906 is OK. These are generic NPN/PNP parts." (CreatorLars).

Installed the LM1881N/NOPB. Its a video sync separator. It extracts timing information from
from standard negative going sync NTSC, PAL and SECAM video signals

The composite video signal enters on pin 2.
You would get a vertical sync and a horizontal sync signal out of pins 3 & 1 but these don't appear to be connected in the schematics. (I think these sync signals could be used to make ramps if you wish to do some vector rescanning)


installed the CD-4053. CMOS

 Re the 2x8 pin power header.
I've built just 2 x 5 pin headers since the schematics indicate pins 15,13,& 11 (for Gate, CV & +5v) arent connected. (Though I may will change this in the future if I find they are)



ICs used in this build:
CD4053BE - its a 3 channel multiplexer
LM6172IN/NOPB - op amplifier
LM1881N/NOPB - video sync separator.
TL431BQLPR - voltage shunt regulator
TL072IP - op amp
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Links:
LZX official
Muffs - Cadet series DIY/assembled

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Click here to access the Video Index page

LZX Cadet II - RGB Encoder

Some build pics of the Cadet RGB encoder.
The RGB encoder - handles the output coding.
It takes 3 color inputs from Cadet system and converts them into a composite output.

It's based around this module from the visionary system.
It's how the video exits the system. ... so I'd usually put it at the end of the chain.
It does need the sync cable.

These aren't official build notes, just my records to help me trouble shoot.
It's a work in progress.
Do let me know if you spot any errors or omissions.

 The PCBs come with one surface mount IC pre-assembled (AD724.)




C17 & C28 - they are labeled on the BOM as DPN. >....?????
Might leave these unpopulated for now.

C20 & C21 are 10uF Tantie caps

 Mouser : 581-TAP106K025SCS

They are polarized. The long lead is positive.


I'm missing the
595-TL431BQLPR ............there is a 26 week wait from mouser at time of writing.
It's a shunt regulator . Marked on the PCB as U11.

I'm trying the 595-TL431BQLP  instead.
I think the pin out is identical.

"TL431 variants, check the datasheet to make sure the pinout is the same as the one specified. Some of the variations have different pinouts. If pinout matches it should be okay. LM4040 is another substitute. These are all 2.5V precision voltage reference parts." (CreatorLars)

also (IN RELATION TO LATER MODULES)
"2N3904 and 2N3906 is OK. These are generic NPN/PNP parts." (CreatorLars).


ICs used in this build:
SN74HC14N
AD724JRZ
CD4053BE
TL431BQLPR
LM6172IN/NOPB
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Links:
LZX - official 
LZX - help - component substitutions

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Click here to access the Video Index page

LZX Cadet I - Sync Generator

Some pics from the build of a LZX cadet module for video synthesis.
I must thank the entire team from LZX for making this DIY system possible.
Building these modules from scratch is a great way to learn.
I am an independent builder and have nothing to do with LZX industries. 

The original system 21 collection has the ideal amount of modules to get started :
1x sync
1x video input
1x ramps
1x encoder
1x scaler
4x processor
4x fader
4x hard key
4x VCO

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I've read that there are more modules in development.
Cadet XI Noise Generator
Cadet XII Wavefolder/Freq Doubler
Cadet XIII 3-Input Mixer
Cadet XIV Gamma Shaper  

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For the moment, I'm just building one of each as I already have a  LZX system and just wish to complement it.

This is the first ... a Sync Generator. It's one of the basic / essential modules.


This module produces the master synchronization signals for your videosynth (in both PAL and NTSC so that the signal stays steady on screen. The camera and monitor must be synchronized.

Syncronization can be divided into horizontal & vertical sync.
"Horizontal sync maintains the horizontal lines in step; without horizontal sync the picture will break up into diagonal lines. Horizontal sync tells the camera and monitor when each horizontal line begins and ends. 
Vertical sync also keeps the picture stable; without this, the image will roll. 
Vertical sync tells the camera and monitor when each field begins and ends. Both together are essential to a stable rectangular shape. Sync then can be conceived of as an electronic grid which provides horizontal and vertical orientation to the image." ETC

I understand you can also use this to sync external "audio" oscillators.

The LM1881 is the IC that provides the Hsync & Vsync (from pins 1 & 3 I think).
These signals are processed by a ATMEGA microprocessor





These aren't official build notes, just my records to help me trouble shoot.
Do let me know if you spot any errors or omissions.

I will possibly need to remove these IC sockets. I recently read that socketing ICs aren't good in video module applications.

LZX VI Fader assembly notes:

"We recommend you avoid socketing the ICs. Capacitance in the sockets can affect higher bandwidth
circuitry more than it would in audio applications."

IC sockets add capacitance to the connections to the pins in the circuit.
It could potentially limit bandwidth or add ringing/oscillation to the circuit.

 iNSTALLING jacks, etc.
Ive gotten rid of those IC sockets.

 Making do with a SPDT (on-on) switch I had on hand.
 R13 calls for a zero-ohm resistor. I've ordered some, but in the meantime will test with some wire.

Re the power header:
This first sync generator module must be built using a 2 x 8 header.
+5 V isnt connected, however pins 15 & 13 which usually carry CV & gate signals in audio modules are used to transmit VSYNC & HSYNC in a LZX modular. 


ICs used in this build:

LM6172IN/NOPB
LM1881N/NOPB - video sync generator
SN74HC14N
CD74HC4538E
CD74HC4046AE














Links
+ Cadet modding - LZX  community Help


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Video Index page