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Old 4th Apr 2024, 10:41 am   #1
Xyience
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Default Identifying a CRT and driver board

A recently purchased Italian built arcade game (1979 Zaccaria's 'The Invaders') came complete with an original-looking monochrome CRT and driver board.

One problem is that I have no idea of the model or manufacturer for either.

Any help with an identification would be thankfully received.

I have attached a number of pictures which should be useful. This includes a section of the original circuit diagram, written in Italian but giving no clues at to manufacturers.
I think the sticker fell off the CRT's neck. The white plastic coil covers are marked 'Firenze'

The monitor is showing limited signs of life: The power supply on the board is working (at least I have 12V and 30Vdc where expected) and the CRT heater looks to be working. However, there is no picture and no crackles from high voltage.
I have swapped out the electrolytics, reflowed many solder joints, replaced a BU606D (horizontal o/p transistor?) and checked many components on the board and neck board. The cabinet has definitely spent time in a damp place.

Perhaps if I can identify the monitor I can fix it. This is my first deep-dive into a monitor and it is proving a real challenge.
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Old 4th Apr 2024, 11:09 am   #2
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Default Re: Identifying a CRT and driver board

Well the first picture is the galloping Maggot so Plessey.

We did have a load of of in house stuff developed in the early 80's originally designed as a information remote terminals for police fire ambulance etc.

I think they had 6" or 8" monitors.

I don't know if they sold many.

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Old 4th Apr 2024, 12:01 pm   #3
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Default Re: Identifying a CRT and driver board

Perhaps it could have been made by Iskra or Nordmende, just guessing based on the connector types.

Is the label on the LOPT readable? It might give a clue.

Dave
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Old 4th Apr 2024, 12:49 pm   #4
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Default Re: Identifying a CRT and driver board

What's the signal standard? Some monitors won't power the line output until they get a valid sync signal.
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Old 4th Apr 2024, 1:50 pm   #5
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Default Re: Identifying a CRT and driver board

I don't think Plessey made CRTs. So maybe they made the full monitor with a bought-in CRT from Brimar or Mullard/Philips?

Plessey made TVs for all sorts of brands, radios, car radios, traffic lights! telephone infrastructure, RADAR, you name it. Some big stuff went out under their own name, but they acted as a contracted manufacturer for consumer goods brands. and own-brand products for retailers. There often isn't any Plessey markings on the contract stuff.

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Old 4th Apr 2024, 5:22 pm   #6
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Default Re: Identifying a CRT and driver board

I wonder if the Plessey label is a red herring?

I'd suggest a Hantarex which were used in some Zaccaria games. It's not an MT3000, but possibly an earlier model?

'm sure there's another Italian manufacturer from that period - the label Firenze (Florence in English) is a clue.

Not that it helps much, but there's still some info around.
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Old 4th Apr 2024, 7:26 pm   #7
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Default Re: Identifying a CRT and driver board

Mike T - I have never heard of the galloping maggot. I wonder if this label did come from elsewhere?

Dave - The label on the LOPT reads '11 249257091' with the 11 in a yellow circle with a green flash on the side.

Kevin - The game board is not working so that has not helped testing. The input to the monitor driver is two pins - signal and return. I have tried to use the analog output from a DVD player to see if the CRT has life. I will try again.
A label in the cabinet says that the monitor has been calibrated with a 15.625kHz quartz crystal if that helps to identify the signal type required.
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Old 4th Apr 2024, 7:33 pm   #8
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Default Re: Identifying a CRT and driver board

Quote:
Originally Posted by Xyience View Post
Mike T - I have never heard of the galloping maggot. I wonder if this label did come from elsewhere?
That's what many of us old Plessey boys called it.

Its actually quite clever it spells Plessey as if displayed on an oscilloscope.

https://en.wikipedia.org/wiki/Plessey

It's possible it came from elsewhere but Plessy made stuff for others and had their fingers in many different Pies.

Cheers

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Old 4th Apr 2024, 9:15 pm   #9
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Default Re: Identifying a CRT and driver board

Quote:
Originally Posted by Welsh Anorak View Post

I'm sure there's another Italian manufacturer from that period - the label Firenze (Florence in English) is a clue.

Not that it helps much, but there's still some info around.
Seleco springs to mind
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Old 4th Apr 2024, 9:22 pm   #10
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Default Re: Identifying a CRT and driver board

Black and white video games of this era, including 'The Invaders', generally produced a composite video signal output to be fed in to a monitor or modified TV set used as a monitor. The monitor should produce a blank raster even with no input signal.

I know there are many computer terminals and computers which directly drive the line output stage from the computer's video circuitry, and therefore don't produce EHT or a raster until the computer is running, but these monochrome arcade games don't work that way. At least I've never seen one that did.

I can't help with the origin of the monitor chassis, I'm afraid, except that to say it looks more Italian than Plessey.

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Old 4th Apr 2024, 9:56 pm   #11
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Default Re: Identifying a CRT and driver board

Hello,
looking at the pcb I feel pretty familiar with the appearance. Please let us know the manufacturer of the components: ERO capacitors? PREH potentiometers? Can you show us the whole circuit diagram, please? Somehow all reminds me of MIVAR, Italy.

A little older than this one here:https://classicarcade77.wordpress.co...ervizio-mivar/

Joe
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Old 4th Apr 2024, 10:10 pm   #12
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Default Re: Identifying a CRT and driver board

Although they are different LOPTs, the one in pic 4 looks to have been made by the same company as the one fitted to the Thorn 1590/91 chassis. There are similarities with the e.h.t overwind mouldings. I think Plessey used to make scan coils for some Thorn mono portable TVs and quite possibly line output transformers as well.

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Old 4th Apr 2024, 10:43 pm   #13
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Default Re: Identifying a CRT and driver board

Are there any code numbers (article codes etc.) on the silkscreen or copper layer of the PCB?

Also, did Plessey have an Italian branch?
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Old 4th Apr 2024, 10:58 pm   #14
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Default Re: Identifying a CRT and driver board

No Italian branch to my knowledge Plessey Controls did have small offices in Hong Kong, Holland and Johannesburg as I worked out of those offices in the 1980s before the Siemens takeover.

Cheers

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Old 5th Apr 2024, 11:16 am   #15
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Default Re: Identifying a CRT and driver board

Thanks for the continued help

Joe - I have attached the whole circuit diagram as a zipped jpeg (2MB to avoid lost details)

The original electrolytics are marked 'ITT'
The dustproof pots are 'PIHER SPAIN'
The open pots are marked 'cTs' and 'AB'
The board itself is branded 'MAS' (see picture)


Maarten - The two boards on the metal chassis are marked HA/0 and HA/01 in the copper. The neck board is similarly marked 'TK4 4G'
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Old 5th Apr 2024, 4:00 pm   #16
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Default Re: Identifying a CRT and driver board

Looking at the diagram, I tend to agree it needs a composite feed. A 'scope would be a great help here. You might spend (and have spent) a lot of time on the monitor when the fault might be elsewhere.

Does the BU606 get warm? If cold it suggest no line drive which would chime with a lack of video. Maybe you have some other games to try, or is that asking too much?

I am certain it's Italian, and could be using a Plessey LOPT.

Many monitor manufacturers seemed to be Italian for some reason and the monitor market was generally ignored by the likes of Seleco, Zanussi, Indesit and the other TV big boys. Hantarex was the main player, though I have only seen their colour models.
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Old 5th Apr 2024, 9:39 pm   #17
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Default Re: Identifying a CRT and driver board

Dear Xyience,

thanks for the diagram, that should help further in diagnosis.

As you have mentioned, you noticed the crt heater to be working. That is important to know. Please verify (i.e. by measuring the a/c voltage)! The heater is energized from a part of the LOPT, and this would indicate the BU606 to be fine and in operation as well as it's feeding circuitry.

If so, I'd focus on the ht winding of the LOPT and the ht rectifier.

Joe
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Old 6th Apr 2024, 9:57 am   #18
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Default Re: Identifying a CRT and driver board

Thanks Joe - I'd not realised the OP had heaters lit which narrows things down.

Measuring the heater voltage other than with a true RMS meter is unlikely to help - as long as they appear about the right brightness the line output stage is probably functioning to a degree.

If there's no EHT there's not much left other than the overwind and diode in the LOPT as Joe says. Of course you'd need an EHT meter to check this. The EHT rectifier is in the overwind which might be open circuit. But first you need to check there really is no EHT and you're not chasing your tail.
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Old 6th Apr 2024, 3:38 pm   #19
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Default Re: Identifying a CRT and driver board

Referring to the LOPTx in pic 4 of the first post, it looks like the stick rectifier is in the attachment to the e.h.t overwind. I think the two plastic end caps can be withdrawn from the rectifier's housing for access to it.

Regards,
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Old 6th Apr 2024, 6:28 pm   #20
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Default Re: Identifying a CRT and driver board

Lots of excellent avenues to explore; thank you for the help:

Glyn - I have a games emulator that outputs VGA, and found a 'VGA to AV composite' widget on eBay that looks like it will create a signal compatible with the monitor. I will get one ordered.

As you can tell I have more broken electronics than skill or experience. I do
have a 'scope, but it was a £15 DIY digital kit that I am loathe to put near high voltage. I will put a better scope higher on the 'want it' list. [can I test the oscillators safely with my current scope?]

Joe & Glyn - The circuit diagram doesn't reflect the actual set up in this case. The heater voltage is not created by the LOPT as shown - it comes directly from a large transformer elsewhere in the cabinet. It reads 5.98Vac which I thought a little low but probably fine

However - There is 580Vdc at the neck board via diode 118, and the 140Vdc comes from a secondary on the LOPT - so lots of signs of life.

Symon/Glyn - The overwind measures 500ohms to Earth, and there is a selenium stick rectifier which is the subject of another thread. 'TV18-2KT diode, test/replace'
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