Amiga A1080 Monitor Schematic

I asked around for this schematic about 6 months ago but had no luck at the time. Thought I'd give it a try again. I have come up blank searching the Net, except for a guy in Britain that claims to have a hardcopy for sale. The A1080 was the first monitor released with the Amiga 1000 in

1985. I'd really like to get this repaired because you just can't find monitors today that will sync on a 15 khz RGB signal. The composite video input also makes it useful another application for I which use it. Yes, I do have experience working with high voltage circuits, in case someone was going to warn me about it.
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                      Rick Jones

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Rick Jones
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I doubt a schematic will do you much good, what's the problem with the monitor? These have been around long enough someone will probably have an idea of what to look for.

Reply to
James Sweet

Google some of the part-numbers (particularly the FBTX transformer), and see if you get any hits that way.

Reply to
Colin

Actually I replied mentioning a guy who had one for sale in the USA.

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listed as a 1080A.

A common problem was dry joints all through around the area concerning the FBT and horizontal stage. Go over the whole board resoldering everything.

Otherwise check out the Monitor Repair FAQ.

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Dave

Reply to
Dave

Hi Rick, try this web site

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they have all sorts of service manuals. Found the Commodore 1080P manual. See YA lopos

Reply to
News

15 kHz RGB/video monitors are still being manufactured by companies catering for medical, industrial, or broadcast needs.

See, for example,

Moreover, if you live in Europe (or can get an European PAL tv set from some specialist store, or order one abroad), they usually have RGB, CVBS and Y/C inputs via the Scart socket, can decode NTSC colors, and will sync to both 525/60 and 625/50 signals.

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Jukka Aho

No vertical deflection, thin line across the center of the display. I've replaced the electrolytic capacitors throughout the unit and the vertical deflection driver transistors. There's no signal coming out of the TA7644 IC to the base of the vertical driver transistors, but the signals on other pins of the IC have active signals running. It may be the TA7644 is bad or some inputs to it. I need a schematic to troubleshoot it further.

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                      Rick Jones

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Rick Jones

an

Or just replace the IC and see what happens. Signal going into it but no signal coming out is a reasonable indication that it's bad.

Reply to
James Sweet

From a tech's website... it might be something you haven't thought of:

**** Vertical circuit: this monitor uses descrete components (no ICs). The output transistors are Q304 2SC2073 and Q305 2SA940. Note that this monitor has a service switch in the center of the bottom board towards the left side. That switch should be in the NORMAL position. If in SERVICE, the vertical sweep will collapse to a single horizontal line (used for CRT setup adjustments). ****

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is an excellent source.

Reply to
Ryan P.

try contacting this guy.. you may also find what you need at his web page.

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twbrown

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twbrown

On Tue, 07 Jun 2005 18:51:08 -0500, Rick Jones put finger to keyboard and composed:

FWIW, this datasheet has the pinouts for the TA7644:

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- Franc Zabkar

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Reply to
Franc Zabkar

Already have that. That's how I was able to scope some of the signals. Unfortunately it shows nothing other than the pinouts - no internal workings diagram, no sample circuits showing interfacing to other components, etc.

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                      Rick Jones
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Rick Jones

Spoke with Ray 6 months ago. He originally had the schematic for another CBM monitor labeled as similar to the A1080. When I tried to troubleshoot mine with that schematic I found out different. I told Ray and that's when he changed the information on his site.

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                      Rick Jones
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Rick Jones

On a long shot... have you tried contacting Toshiba itself?

Reply to
Ryan P.

Rick, Just in case my last message didn't get through... I have a 1080, so if you run out of ideas, I'll crack mine open and work with you to troubleshoot yours.

Ray

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Ray

I did 6 months ago when I first tried troubleshooting this. I asked for information on the TA7644 chip but the person I talked to at the time couldn't help me. I actually thought today of giving it a try again, but it's been 20 years since this monitor was manufactured so getting data on an obsolete chip like that seems very unlikely.

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                      Rick Jones
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Rick Jones

That might be one way to go about it. While I have 30+ years experience in electronics none of it is with video circuits. I know there's no base drive out of the TA7644 chip to the base of the vertical deflection transistor pair. I have no idea what input conditions, if any, are necessary on that IC for an output to be present at that pin. Someone earlier posted a link for an NTE replacement IC which has the IC pins labeled.

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                      Rick Jones
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Rick Jones

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Note that this monitor has a service switch in the center of the bottom board towards the left side. That switch should be in the NORMAL position. If in SERVICE, the vertical sweep will collapse to a single horizontal line (used for CRT setup adjustments.

Reply to
Colin

Well, the switch couldn't throw itself. The display slowly collapsed to a thin line across the center over a period of 2-3 months. Changing the caps and vertical deflection transistors didn't correct that. I suppose that switch *might* be dirty. I can spray some contact cleaner in/on it to make sure.

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                      Rick Jones
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Rick Jones

That

sweep

adjustments.

You`ll probably kick yourself if it turns out to be the problem.

Reply to
Colin

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