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Making a few B&W LAI XY Vector PCBs


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Hmm... would make an interesting project. At least you have the mystery can sorted.

 

Regards,

 

Johns-Arcade.

 

The RHS winding of the Wyse LOPts can be used, and the LHS can manually be wound around externally

 

I could make 13 of them. That's how many I have. Or we could use WG6100 LOPTs

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I will still push to get this prototype board running as I have invested so much time into it.

 

But I am going to redo the design in a 2nd batch, as it will make assembly much easier. Maybe I will do 12 - 20 of them

 

This whole centre section is getting redone

http://www.amazingarcading.com.au/LAI_KZ_Redo-sm.jpg

 

I am moving from left to right

The board will be double layer, but all parts will still be soldered from the back only (Single layer)

There will be a small top layer around the holes, this locks the component in. Great for strength around the headers etc.

http://www.amazingarcading.com.au/LAI_KZ_Redo2-sm.jpg

 

The top layer is to be used to get rid of (most of) the links

It takes longer to design, but it means I have more room for the screen printing. It's worth it

 

The resistors near the Darlington Transistors have been moved over too, as they are really hard to fit where they were

 

John, I will replace the one you have when the newies come in. This may take a few months to get back

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I will still push to get this prototype board running as I have invested so much time into it.

 

But I am going to redo the design in a 2nd batch, as it will make assembly much easier. Maybe I will do 12 - 20 of them

 

This whole centre section is getting redone

http://www.amazingarcading.com.au/LAI_KZ_Redo-sm.jpg

 

I am moving from left to right

The board will be double layer, but all parts will still be soldered from the back only (Single layer)

There will be a small top layer around the holes, this locks the component in. Great for strength around the headers etc.

http://www.amazingarcading.com.au/LAI_KZ_Redo2-sm.jpg

 

The top layer is to be used to get rid of (most of) the links

It takes longer to design, but it means I have more room for the screen printing. It's worth it

 

The resistors near the Darlington Transistors have been moved over too, as they are really hard to fit where they were

 

John, I will replace the one you have when the newies come in. This may take a few months to get back

 

I'm happy to pay for a replacement Dez :)

 

Regards,

 

Johns-Arcade

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  • 3 weeks later...

Hey guys

 

I have a few questions. Other electronics guys may be able to help me here

 

Here is an LAI XY Schematic. The different thing about it is I have drawn in (in blue) parts which are normally missing on the board

 

They don't appear on the schematic or parts list.

 

Have a look

http://www.amazingarcading.com.au/LAI-KZ-XY-Schematic_2015_DB_Rev-01-Nils-corner-sm.jpg

 

The LHS area in blue is the Y axis only. The equiv also is unpopulated on the X axis too. But only Y is shown here

 

What you see on the boards is a link between my asterix and GND. So all of this circuitry is missing, & not used

 

So can anyone else confirm, is this an attempt at a spot killer circuit?

 

What's the pot for then? To set the level at which it turns off?

 

What type of transistor would it be? NPN / PNP? (I think NPN)

 

It looks to me that it is a failed attempt as they forgot to turn off both axis if one of the X OR Y input drops low.

 

The present circuit would only turn off the low axis but keep the other axis running (So a single bright line visible on the screen)

Edited by dezbaz
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Cost cutting?

 

Regards,

 

Johns-Arcade.

 

I will populate the spots. May look at a spot killer circuit.

 

LAIs tend to keep running with a single line up the middle. It would be nice if it switched the beam off and lit an LED

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Wow, I found a writeup on them components in the G05-801 manual

 

They are a correction circuit (Pincussion??)

Have a read. This is page 15 of the 801 manual. Bold text relates to this little circuit

 

Both X and Y channels are practically identical with only minor differences in some component values to accommodate the differences in input signal levels of ? 10V and ? 7.5V respectively, and to accommodate the 4:3 aspect ratio of the CRT. Because of this we will investigate only the X channel.

 

The amplifier is a direct coupled voltage to current converter. It is current through the yoke that will produce the magnetic field to deflect the electronic beam. The small signal response of the amplifier is DC to approximately 1 MHz with the large signal being limited mainly by yoke inductance and available supply voltage to a maximum slew rate of 2300 Hz at ? 25V supply. The voltage gain is slightly less than unity as measured across the sense resistor R620, R720. The input signal of ? 10V is applied to P703-1 by a generator that is capable of delivering this voltage into a 1K ohm load.

 

The signal is gain corrected to compensate for inherent CRT non-linearity in deflection by R731, R733, R734 and the components located within a bridge rectifier formed by D730, D731, D733 and D734. Q730 is the active gain correction element whose break point can be controlled by R736.

Germanium diodes D732 and D735 are used to soften the turn on point and produce a closer 1st order approximate to the desired pre-distortion necessary to correct for the CRT deflection characteristics. Due to the bridge configuration, the same control element is used for positive and negative break points resulting in a very symetrical correction factor which is highly desirable without having to precisely match the gain correction components as would otherwise be necessary.

 

The gain corrected signal is applied to the input transistor of a differential amplifier comprised of Q701, Q702 and constant current source Q703. The current supplied by Q703 will ideally split equally between Q701 and Q702 resulting in identical no signal collector voltage.

In practise it should be matched within 5% of the supply level.

Very heavy negative feedback is applied to the base of Q702 from across R720, a non inductive current sensing resistor, the voltage across which supplies an accurate representation of yoke current and forces the amplifier to correct any distortion present as well as holding a 0 DC condition at the emitter commons of output transistors Q707 and 0708 under 0 input signal condition.

The signal present at the collector of 0701 is current amplified by emitter follower 0704 and this in turn is used to drive Q705 which then drives the output transistors 0708 and Q707 forcing current through the X winding of the yoke and producing beam deflection.

 

The output transistors are current driven with the actual driver transistor being 0705 and its constant current source being Q706, 0708 and R717 are a network to suppress possible high frequency oscillation if the driving signal exceeds the maximum writing speed capabilities of the monitor. D707 is used to hold the bases of 0707 and Q708 separate by 0.6 of a volt. This results in output transistors that are biased Class B. Under no signal conditions no current is flowing through R719 and R718. Any small amount of crossover distortion that may result from Class B operation is removed by means of the very heavy negative feedback present. C706 is used to maintain a low impedance path across D707. Both Q703 and 0706 are constant current sources and except for the amount of sourced current and protection in case of failure, are identical.

For simplicity, we will only look at Q706 operation. R714 allows a current to flow through D704 and D703 from the negative rail to ground. D704 and D703 drop approximately 1.4 volts in the forward biased state. This voltage remains relatively constant. A small current will flow into the base of Q706. The base emitter junction voltage is typically 0.6V. This would leave .8V across R713, a 39 ohm resistor.

This corresponds to an emitter current of 20 ma. This effectively represents the constant current available from 0706. R709 is a suppressing resistor to prevent spontaneous oscillation of 0706. In case of a failure of 0704 or D703, the 360 ohm resistor across them forms a voltage divider with R717 and limits the current available to the constant current transistor Q706 and prevents its sudden destruction along with a handful of other components. C703 is an HF bypass. A 3K6 ohm safety resistor in the collector of Q703, the other constant current source prevents destruction of a large number of components should this current source fail. R721 is a resistor critically selected to damp the yoke and minimize any tendancy for ringing. ZD700 and ZD701 are transient suppressor diodes and their sole function is to clamp any voltage spike that may be induced in the yoke due to an arc in the CRT.

 

They serve no active part in beam deflection. In case of a failure of an output device or an extreme excursion of the electron beam, F700 will open and prevent damage to the yoke or sense resistor as well as remove all loading from Q707 and Q708, thus protecting those from potential failure also. ZD700 and ZD701 are transient suppressor diodes and their sole function is to clamp any voltage spike that may be induced in the yoke due to an arc in the CRT. They serve no active part in beam deflection.

In case of a failure of an output device or an extreme excursion of the electron beam, F700 will open and prevent damage to the yoke or sense resistor as well as remove all loading from 0707 and Q708, thus protecting those from potential failure also. R719 and R718 supply a small voltage drop to help control any tendency for thermal runaway in 0708 and 0707 under heavy loading and high ambient temperature condition.

 

- - - Updated - - -

 

Hey John, have you got a G05-801, or worked on them.

 

Was there a correction circuit you had to adjust?

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Wow, I found a writeup on them components in the G05-801 manual

 

They are a correction circuit (Pincussion??)

Have a read. This is page 15 of the 801 manual. Bold text relates to this little circuit

 

Both X and Y channels are practically identical with only minor differences in some component values to accommodate the differences in input signal levels of ? 10V and ? 7.5V respectively, and to accommodate the 4:3 aspect ratio of the CRT. Because of this we will investigate only the X channel.

 

The amplifier is a direct coupled voltage to current converter. It is current through the yoke that will produce the magnetic field to deflect the electronic beam. The small signal response of the amplifier is DC to approximately 1 MHz with the large signal being limited mainly by yoke inductance and available supply voltage to a maximum slew rate of 2300 Hz at ? 25V supply. The voltage gain is slightly less than unity as measured across the sense resistor R620, R720. The input signal of ? 10V is applied to P703-1 by a generator that is capable of delivering this voltage into a 1K ohm load.

 

The signal is gain corrected to compensate for inherent CRT non-linearity in deflection by R731, R733, R734 and the components located within a bridge rectifier formed by D730, D731, D733 and D734. Q730 is the active gain correction element whose break point can be controlled by R736.

Germanium diodes D732 and D735 are used to soften the turn on point and produce a closer 1st order approximate to the desired pre-distortion necessary to correct for the CRT deflection characteristics. Due to the bridge configuration, the same control element is used for positive and negative break points resulting in a very symetrical correction factor which is highly desirable without having to precisely match the gain correction components as would otherwise be necessary.

 

The gain corrected signal is applied to the input transistor of a differential amplifier comprised of Q701, Q702 and constant current source Q703. The current supplied by Q703 will ideally split equally between Q701 and Q702 resulting in identical no signal collector voltage.

In practise it should be matched within 5% of the supply level.

Very heavy negative feedback is applied to the base of Q702 from across R720, a non inductive current sensing resistor, the voltage across which supplies an accurate representation of yoke current and forces the amplifier to correct any distortion present as well as holding a 0 DC condition at the emitter commons of output transistors Q707 and 0708 under 0 input signal condition.

The signal present at the collector of 0701 is current amplified by emitter follower 0704 and this in turn is used to drive Q705 which then drives the output transistors 0708 and Q707 forcing current through the X winding of the yoke and producing beam deflection.

 

The output transistors are current driven with the actual driver transistor being 0705 and its constant current source being Q706, 0708 and R717 are a network to suppress possible high frequency oscillation if the driving signal exceeds the maximum writing speed capabilities of the monitor. D707 is used to hold the bases of 0707 and Q708 separate by 0.6 of a volt. This results in output transistors that are biased Class B. Under no signal conditions no current is flowing through R719 and R718. Any small amount of crossover distortion that may result from Class B operation is removed by means of the very heavy negative feedback present. C706 is used to maintain a low impedance path across D707. Both Q703 and 0706 are constant current sources and except for the amount of sourced current and protection in case of failure, are identical.

For simplicity, we will only look at Q706 operation. R714 allows a current to flow through D704 and D703 from the negative rail to ground. D704 and D703 drop approximately 1.4 volts in the forward biased state. This voltage remains relatively constant. A small current will flow into the base of Q706. The base emitter junction voltage is typically 0.6V. This would leave .8V across R713, a 39 ohm resistor.

This corresponds to an emitter current of 20 ma. This effectively represents the constant current available from 0706. R709 is a suppressing resistor to prevent spontaneous oscillation of 0706. In case of a failure of 0704 or D703, the 360 ohm resistor across them forms a voltage divider with R717 and limits the current available to the constant current transistor Q706 and prevents its sudden destruction along with a handful of other components. C703 is an HF bypass. A 3K6 ohm safety resistor in the collector of Q703, the other constant current source prevents destruction of a large number of components should this current source fail. R721 is a resistor critically selected to damp the yoke and minimize any tendancy for ringing. ZD700 and ZD701 are transient suppressor diodes and their sole function is to clamp any voltage spike that may be induced in the yoke due to an arc in the CRT.

 

They serve no active part in beam deflection. In case of a failure of an output device or an extreme excursion of the electron beam, F700 will open and prevent damage to the yoke or sense resistor as well as remove all loading from Q707 and Q708, thus protecting those from potential failure also. ZD700 and ZD701 are transient suppressor diodes and their sole function is to clamp any voltage spike that may be induced in the yoke due to an arc in the CRT. They serve no active part in beam deflection.

In case of a failure of an output device or an extreme excursion of the electron beam, F700 will open and prevent damage to the yoke or sense resistor as well as remove all loading from 0707 and Q708, thus protecting those from potential failure also. R719 and R718 supply a small voltage drop to help control any tendency for thermal runaway in 0708 and 0707 under heavy loading and high ambient temperature condition.

 

- - - Updated - - -

 

Hey John, have you got a G05-801, or worked on them.

 

Was there a correction circuit you had to adjust?

 

Yes, I've worked on G05-801's (not very common here), have one in an Asteroids and a complete spare. It has been a while, but I can't remember an adjustment circuit fitted to the deflection board.

 

Regards,

 

Johns-Arcade.

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  • 2 months later...
I bought 2 like this from KFE in Sydney

http://www.kfe.com.au/images/P8100009.JPG

 

This one is a 14", but I have mainly 20" ones

Should be nice to finally have a working repro

 

I'm not even sure where all mine are. I went digging through monitor bits and pieces, but didn't seem to find any of my LAI vectors or other material. They must be buried in a box somewhere (I hope).

 

Post up the completed chassis once you're done Dez.

 

Regards,

 

Johns-Arcade.

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  • 7 years later...

Time to resurrect this project.

I have a working LAI Asteroids 14" Cocktail.

I've been going over old notes & lists

Found an error on the schematic near the H/Hold can L801, if anyone is interested (R811 used to be shown going to ground)

Values for the H/Hold inductor have been added too. But I can't find anything just yet to replace them

The 20" schematic is modified

The 14" schematic has had a once over too, for the first time

I have 10 blank boards, with enough parts to make 6 or 7 complete boards.

Plus I found a way to allow for replacement of the STK-00xx ICs easily

STK.jpg

STK-sm.jpg

Edited by dezbaz
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