ECS Denise in an Old A2000?

[Tsargon]

So, my 1084S died a while ago and I've been working on monitor options for my A2000.  I'm currently using an CBM 1702 that I use for my C64 off the black and white RCA port.  I've tried several VGA solutions, none of them working including several variates of scandoublers.

Well, I began to slowly realize that my A2000 may not be as ECS as I originally thought.  I am the original owner of the machine and purchased it in August of 1990 (do you see where this is going?).  I didn't have the money to purchase a 3000 and Commodore had a nice deal through a student loan program: get an A2000 with double floppies and a A2088 XT bridgeboard with the OCS and WB 1.3 and when the ECS and WB 2.0 becomes readily available, they will upgrade you for free.

I took the machine to my local Commodore dealer (North Coast Programming in Willoughby, Ohio in suburban Cleveland... loved that store!) and they upgraded me.  Now, when I upgraded to OS 3.9 and as I began to do some investigation, it looks like my ROM was a 2.04 ROM and the Agnus is the ECS Fat Agnus but it looks like my Denise is the old OCS Denise!  After doing some research, I'm not surprise as it looks like the ECS Denise did not become readily available until after my upgrade.

So, the reason for this long, rambling story is to lead to this question:  Is it possible to swap my OCS Denise with an ECS Denise?  The motherboard for the A2000 is an A2000-CR Rev 6, IIRRC.

Thanks for your help!

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Tsargon

[Tsargon]

Olecranon wrote:

by Tsargon on 2006/8/22 17:11:24

I've tried several VGA solutions, none of them working including several variates of scandoublers.

Which scandoublers have you tried?  I have two A2000's that use a scandoubler/VGA monitor combination.

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I have tried a Commodore dongle (works just fine for my A1200), a custom built one I found out on Aminet (worked fine when hooked up to the CBM 1902 I have for my C128D) and a ToastScan Scan Doubler with Flicker Fixer (works just fine for my A1200).

Is it possible to swap my OCS Denise with an ECS Denise?

Yes it is.  One of my A2000's has the ECS Denise.  I think the ECS Denise has a couple of 31Khz video modes that will drive a VGA monitor (with the 23pin to 15pin VGA adapter).  I suppose this will work fine for using just workbench, but I dont think this will work if you play games?  I'm not sure here.

[/quote]

Excellent excellent excellent!  I rarely play games on it.  I use it mostly to hack around, develop software and relive some good old memories!  I have an old SVGA monitor I use for the A1200 and it works just fine going down into the 22.25 kHz range.

For the games, my goal is to fix the 1804s.  I know it has something to do with the power supply, but I'm not excatly sure what it is (all indications point to a bad capacitor, but I'm haven't found the culprit!).

Thank you!

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Tsargon

[Tsargon]

Markus_Bieler wrote:
Yes ECS-Denise (8373 R4) is pin for pin compatible

Look here

Yep, that's the guy I had my eye on!  I'm going to order it ASAP.

Thanks!

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Tsargon

[Tsargon]

After reading some of the comments, I decided to run some tests first.

First, the Commodore dongle is just a 23-pin to 15-pin converter with no other electronics.  It works just fine on the A1200.  The scan doubler, as I think I mentioned previously, is the ToastScan Scan Doubler with Flicker Fixer.

So, I put the scan doubler on the A1200.  It works, but the image is washed out and fuzzy (I really didn't take the time to adjust the doubler, however).  I then dropped the A1200 down to NTSC mode and the scan doubler continued to operate.

Next, I booted the A1200 into ECS mode and the scan doubler performed admirably.

Then, I booted the A1200 into OCS mode.  Again, the scan doubler worked fine.

So, I attached the scan doubler back onto the A2000 with the same results of an unusable image.  The image is a barely discernible WB image.  It is shifted almost a third of the way to the right (no amount of adjusting on the monitor will fix it) and it seems to be split onto the next line.  The image is also very shaky and there seems to be no color.  Switching to interlace just squashes the image but does not improve or degrade it any more.  It's really unusable as you can just make out the pointer, but you seem to have a 50-50 chance on clicking what you're pointing to!

So, I'm starting to think there is something just plain wrong with the A2000.  The mono-RGB works fine, but it looks like the 23-pin port is bad.  Can this be the sign of a bad Denise chip?

Thanks!
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Tsargon

[Tsargon]

CLS2086 wrote:
Seems like you have the dead video capacitor, and a dying PSU too

I can look into the capacitor (should be a moderate repair job), but what make you think the PSU is dying?

I do have a lot tucked into that box (GVP accelerator loaded with RAM, SCSI drive, dual floppies, A2088 bridgeboard, X-Surfer, an old SupraRAM card and something else that I don't recall what it does :inquisitive:), so that might be the issue...  The PSU is the original from '90.

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Tsargon

[Tsargon]

Well, I went ahead and order the ECS Denise and it came in yesterday.  I installed it this afternoon and here is what I now have...

I now have the DblNTSC modes available on the B&W RGB out and they work fine on the old CBM 1702 monitor, albeit very hard to read the text!

The ToastScan scan doubler is still putting out the same unusable image when in any of the available NTSC modes.  Here is the interesting part... when I move into any of the DblNTSC, the image is clear on the scan doubler, but it is very faint and there is no color.

When I remove the doubler and use the DB23toDB15 converter with any of the DblNTSC modes, the VGA monitor shows the picture clearly and with color.

What I'm guessing is the digital RGB output must be shot since, from what I remember, VGA is analog and it's signal is clear.  I looked at the A2000 schematics and looked around the DB23 video out on the motherboard and I saw what looks like several swollen bumps on the HY200 Vidiot "chip".  In fact, it looks like a large resistor pack.  Are the swollen bumps normal?  Or, is it some type of capacitor pack as I've seen bad capacitors that are swollen in the past.  Information on the Vidiot is sparse... it looks like it amplifies the output from the Denise for the RGB, but I can't determine whether it's the digital RGB, analog RGB or both!

Looking at the schematic some more, I doubt it's the Vidiot.  It takes the 4 bit R, G and B digital signals and the sync signal and passes them on to the DB23 port's analog R, G and B signals and the composite signal for the B&W RGB RCA port.  The digital signals do not seem to go through extra post processing like the analogs do.  But, there are three ICs directly off the Denise.  Those might be suspect!

As for the ECS Denise causing split memory as mentioned in a previous post, I don't see it.  I looked and the 1 MB of chip RAM, the 2 MB of expansion RAM  and 16 MB of fast RAM are as they always have been!

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Tsargon