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New to me GRIDcase 3 Plus

NeXT

NeXT

Veteran Member
Joined
Oct 21, 2008
Messages
9,188
Location
Kamloops, BC, Canada
I picked this up from consignment at VCF West on a gamble that it wasn't too bad. It needed a full strip and clean because the carrying bag it was in had been dumping sticky powdery foam everywhere but I think other than the battery eliminator/PSU and the lid it's all here. Opening it up found no co-processor or external video board (whatever) but it had a memory expansion and internal ROMs for GRiD-OS 3.1.5 and MS-DOS 3.2 and GRiDMaster. It also has one of the 26 pin JVC hard drives in an unknown condition (not the drop sensor wasn't tripped) and a gas plasma display that doesn't look broken or burned. The 3.6v battery also looks good, but I snipped it out anyways.
The main issue now is I can't get any life out of it. I'm feeding it 16v DC from my bench supply through the barrel jack on the back (center pin positive) but that tops out at 3A. I get a blink of the red LED on the screen, a hiss from the DC-DC supply and nothing else beyond the bench supply overshoots 3A, drops the voltage and then stabilizes with a 500ma draw. No drive spin-up, nadda.
Poking around I can see +5, +12 and +33 for the screen, so it's doing something but I cannot tell what else it wants. I unplugged the hard drive and that changed nothing. I unplugged the screen to see if it would at least give a POST beep blind but still, nothing.

IMG_4827.jpg


I know the battery eliminator/PSU brick needs a recap but what about the internal DC/DC module? It didn't look visibly leaky, but I'm not a GRiD expert weather or not these in particular are a problem.
 
The external GRiD power supply I have says 4A/16V. So maybe it needs just little more juice? But if you removed the HDD one would imagine the motor in it does not have to start anymore?
Maybe it shorts somewhere? I would look at caps everywhere.
Otherwise I would start looking at DC/DC module.
 
I have the exact same issue with a Gridcase-3-plus I bought as unworking (apart from the PSU hiss)
I can't figure it out as well. As I press the power switch off, there's a very light red blink on the led, but no other signs of life.
I've tried running it with the JVC HDD disconnected and different power supplies but nothing has worked.
Please update if you ever get it working.
 
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I know I have a power brick for the GRiDcase 1520 but it's either in a box near the front of my storage room or buried at the very back of the space and will take a while to get to it. That I know for a fact needs to be recapped as they are known to be problematic.
 
Continuing on with my issues I dismantled the machine once again to strip out and eliminate the drive, various ribbon cables and possibly anything touching the board in an attempt to see if that was causing a problem with the pwoer supply. Nope
While poking around however I observed the +5 collapsed to 1.35v but the current draw was still the same. At this point I was second guessing the internal DC-DC and removed it. The first thing I noticed was that the 2200mfd 10v capacitor at C4 was warm to the touch. Investigating further I found nothing around it was running hot but even five minutes later the capacitor was still notably warm, so it must be extremely leaky internally. To my confusion however when I pulled it out I found no signs of leakage underneath and it measured within tolerance for capacitance with an acceptable ESR. Putting it on a bench supply at 10v it sat there and couldn't see any sort of abnormal current draw so I'm a but baffled why on earth this capacitor got so hot.

Edited: Hold on a minute.
Directly underneath this capacitor when installed in the machine is an SCR with a long heatsink on it. This SCR seems to be controlled by a zener on the voltage rail and presumably shorts the rail to ground when the rail over-volts.
Well every capacitor in this is VENT/Jamicon which in later years I've never really trusted so I'm wondering if there are other capacitors in here that are lacking in capacitance and when the supply starts it overshoots the target voltage and that trips the zener.
 
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Smart me pulled both the battery and battery eliminator for my 1520 and stores it with my laptop peripherals, so while I'm working on getting caps for the DC-DC board I can also source the caps to rebuild the external power supply too! o:
 
Okay with the power supply recapped we have a good +16V source into the computer. With the DC-DC recapped we have a +5, +12, -15 and +33v DC for everything.
Still nothing. >:I

So perhaps I'm looking at something wrong and expecting that in 1986 GRiD was being a lot more aggressive with Power Management than I'm expecting. I can poke around the logic board and I see +5 at important places like the BIOS ROM, the CPU and the ROM mezz. At the hard drive connector I have both +5 and +12 which should make the drive spin up unless it's waiting for a signal to do so, so that if you are running DOS in ROM, technically you don't need the hard drive immediately after POST. You turn the machine on, it POSTS, loads ROM DOS and at that point if you need into the hard drive you can spin it up.
Likewise if GRiD is running a plasma display on Ni-Cd cells, they must have control over turning the entire screen on/off.
So my hypothesis is that we ARE getting power to the system, but it's falling over at this point before it can initialize the display controller and visually start POST and because the hard drive and the display are the only visual indicators of life, that's why it's acting stone dead when in reality the lights are on but nobody is home.
I'm tempted at this point to pull out the fancy-schmancy ZAX 8086 In-Circuit Emulator at this point and see what it's doing. Regardless I think it's safe now to button the machine back up because nothing that I can tell that's important hides under the DC-DC, hard disk or the battery/power bay.
 
Got it.

I was thinking of variables I may of missed and remembered I snipped the dead 3.6v CMOS battery out of it. It was dead before I got to it and the computer was sold as dead, so what if I gave it another battery....

CGS_12698.JPG

CGS_12699.JPG


Signed-on with a Phoenix BIOS, spun up the hard drive and booted into what I can only tell was someone's old PASCAL and C course activities they had been writing and compiling on the machine. The screen has a thin group of missing horizontal lines but pressing the edge of the screen a number of the lines come back, so it might still be repairable.
Okay, well at this point the system now runs and I'm committed but now I have to find the basic disk peripherals to actually use it, not to mention I'm still missing the back lid AND the latch that holds a battery pack in.
That's a me problem, so here at the very least is the cap list for the DC-DC board and the battery eliminator.

IMG_4852.jpg

IMG_4855.jpg
 
Oop! I forgot to mention I was probing the wire harness for the DC-DC module so if you also want to poke it with a multimeter and see what it's doing you can.
Keep in mind I'm probing this while everything is plugged in and the power switch is on. The grounding leads MUST all be tied to the chassis as I've noticed the mounting screws are not transferring ground to various components.

Red B+ 16v DC (Battery/AC Adapter voltage)
Black Chassis Ground

Brown +5v
Purple -15v
White +12v
Orange +33v (this is only if you have a plasma display)
Gray Chassis Ground
Yellow ~5v

The yellow wire is the only one clearly marked on the DC/DC board as "VREF" and it feeds back into the control side, so this is a return feedback voltage from the computer.
These feedback loops that reference from an external source are always dodgy because if you open the loop they often ramp the voltage up until something destroys itself, but here the SCR clamps a rail to ground so if it rises too far up it shuts the PSU down.

Since the DB25 on the side is just the internal floppy interface + DC power, if anyone knows the pinout it would be very much appreciated. :)
Likewise if anyone has spare parts to share or tips on removing the screen bezel to access the ribbons I'd like to hear about it.
 
Congratulations and thank you for all the details!
Seems like I need to recap the DC-DC board for my 3plus and it might work again.

As for disassembling the screen, IIRC on the metal spindles/rods sticking out of the screen enclosure, there are little plastic caps embedded in them that need to be removed and then you can unscrew it with a flathead screwdriver?
Its been like 6 years so I don't remember that well what was all involved and I only did it with a 1530 gas plasma screen enclosure. I also can't recall if there was a screw behind the cap that needed to be removed before hand.

rod1.png
 
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On 1520 these screws have plastic cap but inside they have X cross and can be removed with regular Philips screwdriver.
I have one gutted case for 15XX which I will probably utilize for a cyberdeck project, and I will try to design and print few missing plastic parts inside (keyboard holders/display latches, the round plastic piece that goes on the hinge and so on.
But I just started learning Fusion 360 yesterday ;-)
I am wondering about pinouts and connectors for DC/DC boards for GRiDcases, has anyone mapped them?
 
Well, I couldn't stop myself from clicking buy it now. And soon enough I will have GRiDcase 3plus on my hands.
 
Well, great news, HDD in my new GRiDcase 3P is definitely dead. And it does affect booting from APPROM. It came with GRiD DOS 3.20. I replaced it with GRiD DOS 3.3. It also boots from external floppy.
It booted only from APPROM when I had external floppy connected, I guess dead HDD was confusing it. After removing the HDD now it happily boots from APPROM alone.
So I need to look for alternative to JVC JD-S3812M0R0. I wonder if DREM.info emulator will do it?
Also, folks with working HDDs. What is the geometry of this 10MB JVC drive?
I bought some 26-34 pin FDD adapters from China, hopefully they will allow me to connect internal Gotek.
Now the remaining issue is something failing with my plasma screen. It looks like a disease that spreads between pixels. It also moves when scrolling screen up. So is it the screen or bad VRAM or character ROM?
 
Hi, I also own a GRiDcase3 and a GRiDcase 3 Plus, but none have the internal HDD. Typically a JVC 10 or 20MB with a 26pins connector.
My understanding is the JVC HDD is connected to the GRiDcase via a dedicated controller. I bought a coupe of JVC HDD, but I miss the controller: Would anyone please send me photo of the controller, info, anything that could be used to identify one for me? Connectors, pinout, any note/sign printed on the controller board...
My intention is adding the HDDs to my GRiDcase, so I bought a controller board used on a old Toshiba which was using the same JVC, hoping I can adapt it, but I please I need some support from you owners!

In return, here are some precious information:
Given the motherboard connector for the HDD is running XTA interface protocol (https://dosdays.co.uk/topics/xt_ide_vs_ide.php , have a look to last line on page ;-) ), a pre-IDE version of the protocol (running at 8-bits) there is no way in replacing the JVC HDD with a XT-IDE.
 
It is not XT 8bit IDE. It is 26 pin JVC MFM. I vot it working with DREM.info MFM emulator after about a week of debugging, rework and 6 firmware updates. Oleksandr now has settings and HDD image with DOS for the next person who buys it ;). I will be making a post about this adventure later.
 
0xDEADBEEF said:
Well, great news, HDD in my new GRiDcase 3P is definitely dead. And it does affect booting from APPROM. It came with GRiD DOS 3.20. I replaced it with GRiD DOS 3.3. It also boots from external floppy.
It booted only from APPROM when I had external floppy connected, I guess dead HDD was confusing it. After removing the HDD now it happily boots from APPROM alone.
So I need to look for alternative to JVC JD-S3812M0R0. I wonder if DREM.info emulator will do it?
Also, folks with working HDDs. What is the geometry of this 10MB JVC drive?
I bought some 26-34 pin FDD adapters from China, hopefully they will allow me to connect internal Gotek.
Now the remaining issue is something failing with my plasma screen. It looks like a disease that spreads between pixels. It also moves when scrolling screen up. So is it the screen or bad VRAM or character ROM?
Click to expand...
One of my two had the same plasma issue and then the entire display died. One of the IC became burning hot.
Did the Gotek worked for you?
 
OK, here is my brain dump of gridcase 3p related stuff

MFM controller + DREM3 PCB happy together.
gc3p_drem.jpg

bottom of MFM controller

gc3p_mfm1.jpg
Component side. It uses common WDC chip
gc3p_mfm2.jpg

The controller is connected to motherboard with an IDC cable, 34 pin as I counted. I believe it carries partially decoded ISA power.

I have mapped 26 pin floppy connector (next to power supply). In 3P it is directly routed to external DB25 floppy connector using flex cable, basically 1-1 pin mapping. In base gridcase 3 I believe it is directly connected to internal floppy and routed to external floppy too. PDF attached.

I have also attached STL file for 3d printing enclosure to hold together MFM controller + DREM + external floppy connector. (hdd plate no fdd v10.zip). I tried to sandwich it all together with bare gotek board but there is not enough vertical space ;(

Also, HDD image with DREM config (gridcase3p.zip)

And low lever format (llf13.zip) I used to format DREM.

The MFM controller is unique to GRiD. Maybe if you map the connector you could connect some ISA device, there but if it is already partially decoded you may be out of luck. but maybe if it is just IO/data + power and some other ISA signals maybe you can solder someting like XT IDE board there with compact flash?

Also, random JVC drives will probably not work, I think you need specifically JD-S3812M0R0, it has special protective plastic underneath to insulate from controller PCB and possibly other stuff for GRiD.

I think your best course of action is to burn 4 128KB EPROMs or 27C010 equivalent flash chips with GRiD DOS 3.3 and anything you want permanently available and add a GOTEK in place of FDD. unless you find broken gridcase and salvage the hdd controller.

Also, how is your plasma? I have two 3Ps and both have effed up displays with missing lines and some weird pattern spreading on screen when scrolling and so on ;(
 

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