Toaster 4000 repairs?

Kevin Brice

VT[2] Aficionado
Not sure how many people still hang out here, but does anybody know of someone who might still repair Amiga Toaster cards? I've got two that are having some issues:

Card 1​

  • No signal on Preview Out. I tried the analog board from Card 2, but it didn't make a difference. The solder joints for the BNC connector look fine to my eye.
  • A bunch of effects (maybe just AGA ones?) are blown out and have a lot of pink in them. When they show up on my RGB monitor, they look fine. The red background generator looks a bit too pinkish to me, but I'm less sure about that one. I've run AutoHue a few times with nothing except a camera connected with no change. Pictures attached.

Card 2​

  • Main board has a blown capacitor I haven't replaced yet, so I don't know its state otherwise
  • Some of the BNC connectors have broken solder joints that I still need to fix.
  • Memory board causes picture jitter and serious color shift for any kind of output when tested in Card 1. Again, AutoHue makes no difference.
If it's just a configuration error on my part with Card 1, do let me know. Otherwise I'd love to get these looked at by someone who has a better idea of what they're doing. :) Thanks!
 

Kevin Brice

VT[2] Aficionado
For anyone who stumbles upon this later, I've got both cards fixed.
  • Card 1 had nothing wrong. I was using the Flyer BNC board without the ribbon cable connected to the Flyer, which disables the Preview output.
  • Card 2 also had a nonfunctional 12v trace, perhaps from the capacitor exploding. I added a bodge wire after replacing the capacitor, and it works fine now. Not sure what was up with the RAM board before, but no trouble with that anymore either.
  • The pink graphics are because of a voltage problem with the Amiga's DAC causing the RGB signal voltages to be too high. I haven't completely diagnosed it yet, but it also affects the DB23 connector. I didn't realize the DB23 connector was also bad because somehow the A520 composite adapter I was using compensates for the overly high signal voltages to show a perfect picture.
Apparently forgot to attach a picture earlier, so I'll attach it here.
 

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Kevin Brice

VT[2] Aficionado
To draw this to a close, I've got the Amiga fixed as well (for now, at least).

Anybody who's perused the Toaster FAQs might notice the similarity to this note about AGA genlocked graphics, where the -5v voltage regulator at U198 has failed. Unfortunately, that wasn't the issue - the output voltage was just fine. For lack of a better idea, I replaced it anyway to no effect.

The Toaster 4000 card uses the analog lines for genlocked graphics, not the digital lines like I'd assumed. I'd thought the pink was from one or more of the analog RGB channels into the Toaster being too hot, but it turned out to be the result of all of the signals being too hot. And when the signal is too strong, those excessively strong colors show as pink through the Toaster. That stumped me for a while since that would've impacted the DB23 video output, and the DB23 output looked fine using my A520 adapter. (I usually use an Indivision AGA for my monitor, which bypasses the analog signal.) The A520 turned out to be a misdirection - the voltage was way too high on the RGB analog channels, but the A520 was just rolling with it somehow. Other devices attached via SCART or VGA looked completely blown out. So don't use an A520 if you're trying to figure out if your DB23 port is functioning correctly, as it's way too forgiving.

The problem ended up being the voltage reference line on the Amiga's Digital to Analog Converter (U460), the chip that converts Lisa's 24-bit digital signal into an analog signal. That voltage was way too high, and the 5v line into the DAC (+AVID) was pulled down to around 3.5v. Replacing ceramic capacitors C460A-F mostly fixed the issue, but the issue came back if the board flexed in just the right way. Reflowing the two connected pins on the reference voltage chip at D507 seems to have fixed it the rest of the way. It may not have been necessary to replace the capacitors, but on the chance resoldering the old ones might have temporarily let them limp along with internal cracks just long enough for me to reassemble the machine and then fail again, I replaced them all while I had the machine apart.

+AVID is still lower than I'd expect (usually around 4.4-4.5v when the 5v line is up around 4.8-4.9v), but the reference voltage is correct, and both the DB23 port and genlocked graphics now function correctly.
 
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Kevin Brice

VT[2] Aficionado
Just kidding, one more note! There's another trigger for slightly blown-out graphics, but much more subtly in a way that will make you question your sanity: not having anything connected to the RGB DB23 port. Unlike on OCS/ECS machines, Toaster will start without anything connected there. But apparently it still won't work quite right. Plugging in a monitor or a DB23 terminator seems to fix the issue.
 

Kevin Brice

VT[2] Aficionado
Upon thinking about this further, this makes sense: the Toaster card expects the monitor to be providing 75 ohm termination on the RGB lines.
 
Yeah, I can confirm that Toasters actually required an Amiga RGB monitor (ie:1080 or 1084) to be attached to the DB23 display port. Newtek documented this someplace in the Toaster docs. I remember some company selling a DB23 terminator so you could run a Toaster and also use Picasso II VGA display card. In my case, I just kept an old worn out 1080 Monitor plugged in to terminate the DB23 port. I gave up on that after a while because running a hybrid Picasso/Toaster setup was really not worth the hassle. I needed to get work done and it was simpler (for me) to just switch back to using a standard Amiga setup.
 

Kevin Brice

VT[2] Aficionado
If you go to the sight and read the threads about it on EAB then you will be all caught up.
Okay, cool - I think I'm already caught up, then, but I may have missed something on EAB. :) Already got a copy of Millennium from Amiga on the Lake I still need to install. Thanks so much again for hosting the open source project and 4.3 install media!
 

DiscreetFX

Make Your Films Effective
I'm happy to do it, I always believe the source code to the Amiga Video Toaster should not be lost. I'll host it till the end of time.
 
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