No video out on 030 upgraded Mac Plus

[wottle]

I recently picked up a Mac Plus that had been updated with a Total Systems 68030 accelerator board. On powering it up, I get a nice clear startup chime, but no video. The floppy is toast, but I can see activity on my FloppyEmu when I have it plugged in.

I've independently tested the CRT (it has very bad burn in, but worked fine when I put it in a Plus-upgraded 512k machine I have), and the analog board (I used this machines analog board to run the previously mentioned 512k with Plus upgrade). I do get a glow in the glass behind the CRT when using the logic board with the acclerator, just no picture on the screen.

So on the surface, the analog board and CRT seem fine, but I get no video output at all. Any thoughts on things I can try? Anyone have experience with these accelerator boards.

One thing that was interesting is that when it arrived, there were 4 IC hooks connected to the analog board, 2 going to a fan mounted over the analog board, and 2 going to a box mounted behind the floppy, then a connector from that box to a connector on the accelerator board. the small box looks like it may be some sort of a power supply. I'll inspect in more details. However, I'm not entirely sure these connectors are actually connected to the correct legs on the analog board. The fan was connected to the CR23/24, and the connector to the box were connected to C25/26. Maybe these should be connected somewhere else and that is causing issues. All other connections to the analog board are standard.

Does anyone know if there are resources to the install guide for the Total Systems 68030 accelerator for the Mac Plus? I'm hoping I can use it to confirm everything is hooked up properly. I found a video showing the accelerator as well as a forum post about the same card: https://68kmla.org/bb/index.php?thr...us-with-total-systems-accelerator-board.3706/ that appears to show the IC hooks connected to the same place as mine.

Thanks for any advice you can provide!

 

[wottle]

Update: I must have gotten mixed up when I was switching CRTs, analog, and logic boards. It does appear my issue is with the analog board that cam with the plus. I was able to confirm with a good logic board that the symptom remained (startup chime with no image on the CRT). I removed the accelerator board and the logic board is in good shape - the Nichicon caps don't appear to have leaked, but I'll consider replacing them since they're hidden under the accelerator board. So, after confirming the analog board as the issue, I grabbed a working one from my upgraded 512k and put it in, first with the accelerator removed - it booted up and an image appeared. I then threw the accelerator back on, reconnected the IC hooks to the new analog board, and crossed my fingers. Fortunately, it booted up fine to the question mark disk. I made a 7.0.1 image with the Gemstart extension added (the accerlator driver) and it booted up. I got the accelerator extension loaded (its icon gets wheels and then it races across the bottom of the screen). When I went into the Gemstart control panel, it shows the 20MHz 68030 as loaded, recognizes that the SCSI port is connected (I used the SCSI port on the accelerator to plug in my BlueSCSI because it's faster and provides term power), and has the option for an FPU. I might see if I can get one, although I don't use any apps that would take advantage of it.

So, I now have a working Plus with an 030 accelerator, 4MB RAM, and faster SCSI, but no analog board for my 512k (upgraded to a 1MB Plus).


I did a closer inspection of the logic board, and all the caps seem to be in good shape. According to this page, I'm going to take a look at these components:

5. Monitor Black Out with/without Startup​

Symptoms
As to the symptoms when turning on the power, there are four types including
(1) Black monitor with startup bong;
(2) Black monitor with startup bong and with spining sound of fan and hard disk drive;
(3) Black monitor without startup bong but with click noise; and
(4) Black monitor without startup bong and without click noise.

Diagnosis
The most probable cause of this trouble is damage of the CR2/CR3 rectifiers or the Q2 transistor.
Troubles of the T2 flyback transformer sometimes results in this problem.
The broken CR5 rectifier also causes these symptoms, though rarely.
CR2 and Q2 are placed on the outer surface of the metal cage, which shields the flyback transformer on the analog board. The cage metal around CR2 and Q2 is locally discolored/charred, or these parts are exploded by high temperature.
If the CR3 rectifier is damaged by heat, explosion of CR3 usually occurs. CR3 is placed on the inner surface of the shielding metal cage.
When CR3 is damaged but not exploded, the Q2 transistor may be damaged simultaneously. In this case, Q2 is sometimes burnt and sometimes is not.
When Q2 is burnt out but CR3 seems to be OK, the CR5 rectifier is probably damaged.
Even if all CR2, CR3, CR5 and Q2 appear to be OK, the inner circuits of these parts are sometimes destroyed by heat.

Even if all these semiconductors are OK, destruction of the R22 resistor also can cause Symptom(2) as described above (Black monitor with startup bong and with spining sound...).

Should I even bother with recapping if it could be the flyback? I do get a glow in the back of the CRT tube, does that indicate anything about the health of the flyback?

 

[wottle]

Additional update, and a lesson. I hadn't actually gotten around to inspecting the underside of the analog board, but probably should have started there. Sure enough, there were a few cracked solder joints. That may also explain why I thought the analog board had tested good in my 512k. Possibly it the joint was making a good enough connection on that go around. So, planning on replacing the caps on the analog board and using it in my 512k, along with the CRT with massive burn-in. And the already recapped analog board, along with the better CRT will go in the 030 20Mhz Plus.

So, my lesson, and perhaps a cautionary tale to others, is to try the simplest fixes first before going down a rabbit hole of more complex issues / fixes.

 

[wottle]

Also, here’s a few pictures of the Total Systems Gemini II 20Mhz accelerator board on the Plus logic board, for anyone curious. Later, I’ll also take a few photos of the correct pins for the IC hooks that attach to the analog board.

 

[Patrick]

nice find. and yeah. i'm more often then i care to admit pulling apart a computer only to find out i left the computer unplug. (or something equivalent easy)

 

[Patrick]

Thats kinda interesting you have a 030 upgrace for a macplus.

I have a mac plus with a brainstorm upgrade. which is just a fast 68000. i found it to be unstable. (i think maybe i have other problems with the logic board that may or may not be related to the upgrade)

How is yours performing? have you tried keeping it on doing some work to see if it crashes ?

 

[wottle]

Thats kinda interesting you have a 030 upgrace for a macplus.

I have a mac plus with a brainstorm upgrade. which is just a fast 68000. i found it to be unstable. (i think maybe i have other problems with the logic board that may or may not be related to the upgrade)

How is yours performing? have you tried keeping it on doing some work to see if it crashes ?

Not yet. I've got it pulled apart for a thorough cleaning and retro-bright. Still need to do a full restoration of the floppy. Once I have it all nice and pretty, I'll try to run an extended test.

I also have a Mac SE with a MicroMac (or similar) 25MHz 68030 upgrade board. That one I've had some stability issues with, but not sure if that's the accelerator, something on the main board, or software. Haven't needed to do much on it, as I tend to use my SE/30 for any B&W retro computing.

I'll let you know how it goes.

 

[wottle]

Also, anyone know what the empty U12 socket would be used for? It almost looks like a second CPU socket.

 

[GiGaBiTe]

Also, anyone know what the empty U12 socket would be used for? It almost looks like a second CPU socket.

I would guess for a 68020. There were quite a few Mac upgrades that had options for either a 68020 or 68030 to fit different price points. It's cheaper for them to make a board to support both CPUs and just fill out whatever CPU they want for what model.

I have a LC/LCII/CC upgrade board with a 68030@25 MHz on it, but it also has pads for a 68020 and a different GAL for the slightly different equations required.

 

[wottle]

Ah, that makes sense. Build one PCB that could be used for both 020 and 030 accelerators. Having PCBs manufactured was probably a lot more costly to create the tooling, so for lower volume, making a board that served both purposes would probably save money.

 

[tweedy]

@wottle sorry to dredge up a dead thread, but I recently acquired a similar Gemini 030 that didn't come with the "Gemkit" power supply, fan, and battery port scsi cable. However, I do have one of those cables from another adapter, and it looks like it should fit the header on the Gemini. Could you let me know about, or take a photo of, the orientation of the cable when it's plugged into the Gemini board?

And am I correct that the power supply just sends 5v to the four pin connecter at P3?