Composite Sync on Microvitec M1438S

[caiusfabricius]

Hi all,
I recently bought a Mcrovitec M1438S monitor, it works fine with my Amiga 500 and Sharp X68000 (I built the cables myself using H and V Sync) but when I try to use its Composite sync input on pin10 (monitor has a DB23 female connector at the end of the cable) I obtain a black screen.I discovered it tryng to connect my arcade JAMMA supergun to this monitor (and I try also t connect the AMiga 500 using Compsite Sync and I get always a black screen).
Now, according to the pinout of the M1438S, it should accept composite Sync on pin10 but I'm wondering if this is true or my monitor has a problem on Composite Sync .The pinout here (it's the same of the Amiga RGB output):

http://ataricomputers.altervista.org...ga_M1438S.html

Does anyone know more about it?

[delshay]

Originally Posted by caiusfabricius

Hi all,
I recently bought a Mcrovitec M1438S monitor, it works fine with my Amiga 500 and Sharp X68000 (I built the cables myself using H and V Sync) but when I try to use its Composite sync input on pin10 (monitor has a DB23 female connector at the end of the cable) I obtain a black screen.I discovered it tryng to connect my arcade JAMMA supergun to this monitor (and I try also t connect the AMiga 500 using Compsite Sync and I get always a black screen).
Now, according to the pinout of the M1438S, it should accept composite Sync on pin10 but I'm wondering if this is true or my monitor has a problem on Composite Sync .The pinout here (it's the same of the Amiga RGB output):

http://ataricomputers.altervista.org...ga_M1438S.html

Does anyone know more about it?

no.

put a meter to the pin see if you get a reading,i think you will find its not connected internally.

[caiusfabricius]

Originally Posted by delshay

no.

put a meter to the pin see if you get a reading,i think you will find its not connected internally.

Ok, I have to open the monitor.So, do you think this monitor doesn't accept composite Sync or is prearranged to get it?

[pandy71]

what is the expected CSYNC level? video? (300mV) or TTL? (3.3V)

[caiusfabricius]

Originally Posted by pandy71

what is the expected CSYNC level? video? (300mV) or TTL? (3.3V)

I don't know.Anyway I opened the monitor and pin 10 of the DB23 connector is not connected on the motherboard so my last chance is to use a sync separator..waht a shame , I thought it could accept composite Sync (as Commodore 1084 and others..)

[Bloodwych]

It's a strange monitor that - they go to lengths adding support for native and higher frequency screenmodes, then neglect to add a horizontal stretch control (rid black borders in certain Amiga screenmodes) and this composite sync, saving a few pence.

This monitor needed both, but really it should have had a digital screen size memory system, as PC monitors of the time started to have, especially since it was around £299 brand new back in the day! That would mean games and Workbench could enjoy borderless fun automatically!

[zipper]

It was cost cutting - the 15" version did have memory and horizontal control IIRC.

[delshay]

you can adjust it to show a perfect picture when switching from AGA to GFX card.

internal adjustment inside the monitor (great if you have a dual video monitor input).

VERY HIGH RECOMMENDATION: do not open up a monitor unless you are a Qualified Engineer (EXPERT ONLY).

WARNING! very high voltage is present inside a monitor.

**ALL MODIFICATION AT YOUR OWN RISK**

[pandy71]

Originally Posted by caiusfabricius

I don't know.Anyway I opened the monitor and pin 10 of the DB23 connector is not connected on the motherboard so my last chance is to use a sync separator..waht a shame , I thought it could accept composite Sync (as Commodore 1084 and others..)

At first try to connect H and V lines to CSYNC source (connect CSYNC to both lines - maybe it works without separator)

[caiusfabricius]

Originally Posted by delshay

you can adjust it to show a perfect picture when switching from AGA to GFX card.

i

VERY HIGH RECOMMENDATION: do not open up a monitor unless you are a Qualified Engineer (EXPERT ONLY).

WARNING! very high voltage is present inside a monitor.

**ALL MODIFICATION AT YOUR OWN RISK**

Don't worry, I know how to discharge CRT and capacitors.

Originally Posted by pandy71

At first try to connect H and V lines to CSYNC source (connect CSYNC to both lines - maybe it works without separator)

I already tried this and doesn't work.Instead I tried a circuit with the EL4583 sync separator and it works.With the LM1881 it doesn't work because this IC doesn't provide true HSync.

[chiark]

That's good to know - I was just researching sync separators and had hit on the LM1881. EL4583 works? Great! Do you have a reference circuit for it?

[caiusfabricius]

Originally Posted by chiark

That's good to know - I was just researching sync separators and had hit on the LM1881. EL4583 works? Great! Do you have a reference circuit for it?

Yes, EL4583 works great, .It cost more than LM1818 but it provides REAL HSync.I built this simple circuit:


http://img838.imageshack.us/img838/8206/snap1nx.jpg

The only problem is that DIP version of this IC is going out of production (i found it on ebay), it will be product only in SOIC package.

P.S.
Components C2 and R3 in the circuit above are for a low-pass filter, it's up to you to put it or not.

[pandy71]

http://www.intersil.com/data/tb/tb430.pdf

But ISL59885 looks better and it is cheaper.

[ceaser]

ah bloody hell. i have a mv1538S myself and it's just crazy that it only has a 23 pin female yet is a multisync monitor. they're great monitors still, but yes they have almost no controls either. i had a mv1438S get broken in the mail and thankfully the US post was cool and paid me back and saved me and my friend from being angry. they're cool monitors but i love my 1960 despite it's tiny viewable area because of it's VGA connector