Apple Multiscan 15AV - can't get it to work with a IIsi/IIci

[croissantking]

Spinning off from @bigmessowires thread about DIP switch adapters, I am trying to get my 15AV to work with my Macintosh IIci. According to the service manual that's freely available online, this monitor should work with any II-series Macintosh without an adapter. @Phipli, I believe you also confirmed this.

This means that this monitor should be compatible with the composite sync singal put out by the II-series' onboard video.

When hooked up to the IIci, the monitor remains dark. I have tried using an 8-pin adapter set up for a 13" RGB display, and am confident that a signal of 640x480@67Hz is being output - as confirmed by hot plugging an Apple Hi-Res RGB Display.

I have also tried the 15AV on a IIsi built in video, and a Toby card that's fitted in the IIci. Again, it remains dark.

It does work fine on my more modern Macs supporting multisync, so not sure what's going on with it. Could it be that there is circuitry specially to handle the composite sync signal, and it has a fault?

 

[Phipli]

When hooked up to the IIci, the monitor remains dark. I have tried using an 8-pin adapter set up for a 13" RGB display, and am confident that a signal of 640x480@67Hz is being output - as confirmed by hot plugging an Apple Hi-Res RGB Display.

I don't understand why you're using an adapter with switches? This is an Apple monitor. You don't need an adapter. Get it working without first, it's just extra complexity.

 

[croissantking]

I don't understand why you're using an adapter with switches? This is an Apple monitor. You don't need an adapter. Get it working without first, it's just extra complexity.

I understand, I just meant that I have tried both with and without an adapter.

 

[Phipli]

The first thing I'd check is continuity through the cable. Those cables used to get mangled and you'd often find they had bad connections.

 

[dougg3]

I saw @croissantking's original info in the other thread where the service manual claims support with Macintosh II family machines. At least, I think that's the service manual. I see that blurb in this doc.

I found the actual user manual for the 15AV, and looking deeper into it, I'm starting to think whoever wrote that section of the service manual might have been a little...optimistic. Are we sure that the 15AV is known to work with the IIci/IIsi?

The user manual doesn't list CSYNC (pin 3) as being hooked to anything in the pinout:


Also, both the user manual and the service manual say the input signals are red, green, blue, and separate sync.

If this pinout is 100% accurate, that monitor definitely wouldn't work with the IIci and IIsi because they don't output separate VSYNC and HSYNC in their 640x480 mode. Although @bigmessowires 's proposed sync separator would probably make it work if you used it to separate out the CSYNC into HSYNC/VSYNC and converted its VGA output back to DB-15.

It's also possible that there is something wrong with your monitor and this pinout in the manual is flat out wrong. I've learned not to trust everything in Apple's documentation. But I thought I would point out that pinout diagram...

 

[bigmessowires]

Yes, use the Mac video cable if you have it. It should simplify things. Good suggestion to verify continuity of each pin through the cable.

640x480@67Hz

It's more than just the resolution and refresh rate - it's also a question of which sync signals are used. For most Mac models and video cards, when running at this resolution and refresh rate they'll output independent signals for HSYNC and VSYNC, on different pins. But for the IIci and IIsi and Toby, they output CSYNC on a third pin, as well as sync-on-green. If your monitor doesn't support at least one of CSYNC or sync-on-green, or your cable has a broken CSYNC connection, then you won't get any picture.

I just saw Doug's info that the 15AV may not actually support CSYNC, in which case it's not going to be able to work.

 

[croissantking]

Yes, I am thinking that the 15AV doesn’t support composite sync. I can only find reference to separate sync in both the user manual and the service manual.

 

[Phipli]

Yes, I am thinking that the 15AV doesn’t support composite sync. I can only find reference to separate sync in both the user manual and the service manual.

The IIci also outputs sinc on green at the same time didn't we divine? Sync on all colours to be fair. Or am I getting muddled.

 

[volvo242gt]

This really old thread on the 'fritter might be of use...

Mac To Vga Sync On Green | Applefritter

www.applefritter.com

Apparently the 15AV is one of those monitors that cannot handle composite sync. Uses HSYNC.

 

[dougg3]

The IIci also outputs sinc on green at the same time didn't we divine? Sync on all colours to be fair.

Yup, that's exactly what we figured out. Unfortunately it seems doubtful that this monitor supports sync on green either.

 

[NJRoadfan]

Weird that an Apple monitor wouldn't support all sync types. One thing you could try is jumping Pin 3 to Pin 14 on the DB-15 (like Mac-to-VGA adapter do). Its possible the monitor supports composite sync on the horizontal sync input. An ugly but easy way to do this is to use a Mac-to-VGA adapter with the correct sense setting with C-sync routed to the VGA h-sync pin, and then use a VGA to DB-15 adapter to convert back.

 

[dougg3]

I just came to the realization that I actually own one of these exact monitors. I can confirm it works with my LC 475 but not my IIci.

 

[croissantking]

Weird that an Apple monitor wouldn't support all sync types. One thing you could try is jumping Pin 3 to Pin 14 on the DB-15 (like Mac-to-VGA adapter do). Its possible the monitor supports composite sync on the horizontal sync input. An ugly but easy way to do this is to use a Mac-to-VGA adapter with the correct sense setting with C-sync routed to the VGA h-sync pin, and then use a VGA to DB-15 adapter to convert back.

I know, it’s not very Mac-like at all.

What are my options in terms of adapters, or which Nubus video cards would split horizontal and vertical sync?

 

[NJRoadfan]

The Apple 8-24GC is called out in the 15AV manual specifically and should work. Basically any NuBus card that isn't the original unaccelerated Apple card.

 

[croissantking]

Would a regular 4•8 or 8•24 card work? I think the accelerated GC will be expensive to obtain.

 

[NJRoadfan]

I don't see why they wouldn't, although I don't know the specifics of Apple's earliest cards. 3rd party cards should work as well.

 

[croissantking]

I don't see why they wouldn't, although I don't know the specifics of Apple's earliest cards. 3rd party cards should work as well.

Cool - I think a video card/dual screen setup will be my first IIci upgrade.

Good to know it’s not my monitor that’s being weird, although kinda disappointing it’s limited in this way.

 

[bigmessowires]

From my tests so far, literally anything will work except a IIci, IIsi, original Toby card, or monochrome video card. The "Macintosh High Resolution Video Card" will work and is available for about $40 on eBay. If I ever finish my sync splitter adapter project, that will be another option.

 

[croissantking]

From my tests so far, literally anything will work except a IIci, IIsi, original Toby card, or monochrome video card.

Would the LC/LCII also have the limitation?

 

[bigmessowires]

No, those computers have more modern video.