Issues getting turbo LED display to work with a 386

[acadiel]

Hey there. I have a M396F 386 SX 33 board in a case and am having trouble getting the turbo LED and display to work correctly. None of the diagrams on Minus Zero degrees match mine.

Here’s the first problem:

As hooked up, the LED display shows a 16 when turbo is pressed and the Turbo light is on. But the PC operates at the slow speed as noted by the memory clicks. When I unpress the Turbo button, the LED display shows 06 and the turbo light is off, and the computer runs in fast mode. The three pin is connected to white/black on the two pin connector here in this instance.

I switch the three pin Turbo switch to the other two pins which are yellow/white. All it does is reverse the above. When pressed, the turbo light is off and it says 06 and it runs fast. When unpressed, it says 16, the Turbo light is on and it runs slow.

I think the board is showing the right stuff in the first instance, but the computer is the wrong speed.

Secondly, does anyone have a instruction set to show how you change the display with these jumpers?

Thanks!

 

[bladamson]

Oh the ones I've messed with, the jumpers just control the individual LED segments in both switch positions, so you can fart around with it to figure out what is what. What you want to do is get it to where the turbo switch and LED are working as they ought, even if the 7-segment displays show the wrong thing, and then rejumper them to match.

My supposition is that your 3-pin cable that attaches to the motherboard is supposed to be carrying +5v, ground, and the turbo LED line (to tell the board which 7-segment display configuration to display). The turbo LED itself probably plugs into your 7-segment board, and the turbo switch probably goes on the motherboard.

That is just supposition, though. I don't have any machines with this kind of dingus in them anymore to check, so look in your manual and/or probe your board to figure out for sure. Don't fry your motherboard. :O

 

[acadiel]

Here’s the manual for my board:

https://www.ultimateretro.net/motherboard/manual/m3-96f-sx-slc-615f3219e1b11303799237.pdf

The turbo switch has three positions on it’s female connector. The motherboard male connector only has two. So I can make either a NO or NC type connection. The button pressed in is working fine - the system is fast, but the LCD unit is showing the slower speed and lack of the turbo LED, which is connected via the LED board.

The Turbo LED connection from the motherboard is two pins. It hooks to the upper left (in the picture). I’ve tried it both ways. One way, the LED doesn’t change values when pressed/non pressed nor does the turbo LED turn on/off. The other way works as described in my original note. The speed on the LED and the status of the Turbo LED are reverse of the actual system speed.

The Turbo LED is tied to the state of the display since it’s hooked to it - so even if I reversed the LED values and got those correct, the Turbo LED would still be OFF when the system is fast, and ON when slow.

 

[acadiel]

Close up pictures. The turbo LED input from the motherboard plugs in the top left. The turbo LED itself plugs into the bottom center and the power is right next to it.

Not sure what those two jumpers at the bottom are.

 

[modem7]

Secondly, does anyone have a instruction set to show how you change the display with these jumpers?

None of the diagrams on Minus Zero degrees match mine.

My determination follows:

First (top) row of 7 positions
-------------------------------
"TUBO" printed to the left of this row.
This row controls the right 7-segment display for TURBO mode.
Jumper 1 = segment A, jumper 2 = segment B, jumper 3 = segment C, etc.
Current setting = jumper/segment A is on, jumper/segment B is off, jumpers/segments C through G are on.
Therefore, displayed is "6".

Second row of 7 positions
--------------------------------
This row controls the left 7-segment display for TURBO mode.
Jumper A = segment A, jumper B = segment B, jumper C = segment C, etc.
Current setting = jumper/segment A is off, jumper/segment B is on, jumper/segment C is on, jumpers/segments D through G are off.
Therefore, displayed is "1".

Third row of 7 positions
-------------------------------
This row controls the right 7-segment display for NON-TURBO mode.
Jumper 1 = segment A, jumper 2 = segment B, jumper 3 = segment C, etc..
Current setting = jumper/segment A is on, jumper/segment B is off, jumpers/segments C through G are on.
Therefore, displayed is "6".

Fourth (bottom) row of 7 positions
--------------------------------------
This row controls the left 7-segment display for NON-TURBO mode.
Jumper A = segment A, jumper B = segment B, jumper C = segment C, etc.
Current setting = jumpers/segments A through F are on, jumper/segment G is off.
Therefore, displayed is "0".

 

[Chuck(G)]

These displays are nothing more than eye candy connected to a pushbutton. You don't even need to connect the switch cable the motherboard. I've still got one or two systems where I've set the display to say "Hi" and "Lo"

 

[acadiel]

Thanks, everyone.

I’ve gotten it to say “HI” and ”SL”. (Slow). The LED segments were the easiest thing to figure out.

When I have the turbo button pressed in, the speed is fast, and I see “Hi” on the display. The Turbo LED does NOT light.

When I have is pressed out, the speed is slow and I see “SL’ on the display. The Turbo LED does light.

It seems as though this is inverted for some reason (the LED). Notice in the picture the yellow/black connector - that’s the Turbo LED, which is about 4“ long - goes right next to the display. The black/red cord to the right of that is the power. The TURB jumper on the top left goes to the Turbo LED jumper on the motherboard.

Notice that there are two sets of jumpers at the bottom right - the left set is populated. This controls the two displays (HI/SL). If you take both out, the display won’t work. Take one out and either HI or SL disappears when the button is pressed. Etc.

I have no idea what the other two terminal/jumpers on the bottom right are.

 

[Chuck(G)]

Change the LED jumpers so that the sense is reversed (says SL where it said HI and vice-versa). Then use the other pair of pins on the 3-pin connector. The turbo LED will then work in the correct sense.

 

[acadiel]

I tried that - all swapping the three pin connectors does is change it to where the button has to be pressed OUT to be turbo and in to be regular speed, which is also backward.

 

[Chuck(G)]

It's not rocket science--the answer is there, you have only to look for it.

 

[acadiel]

I don’t think I’m communicating correctly. I’m talking about the turbo LED, which is hooked up to the PCB for the speed LEDs.

The only connector to the motherboard is that three pin connector. With the first two pins hooked up to the motherboard, the board shows the turbo LED ON with the switch OUT, and the system is on SLOW speed. With the second two pins hooked to the motherboard, the board shows the turbo LED ON switch the switch IN, and the system is on slow speed. Neither instance leads to the actual turbo LED itself next to the LEDs lighting up when the system is on fast speed. If I can get the turbo LED to light up when the system is on fast speed, I can adjust the jumpers for the speed LED display accordingly.

 

[Chuck(G)]

That's easy--how is the LED being driven? Is it from a totem-pole driver? If so, then the return, if currently, at Vcc, should be to ground. What does your motherboard's manual say about the turbo LED?

 

[acadiel]

If you look at post #4 above, you will see the actual Turbo LED+Speed LED assembly. The actual Turbo LED cable from the motherboard is plugged into where it says "TURBO" on the top left of the assembly. The motherboard (link in post #3) simply states that it supplies a + and a - on the Turbo LED pins. The assembly board also gets its power from a +5V connector (red/black - picture #3 post #4) and the Turbo LED itself plugs into it (black/yellow - picture #3 post #4).

As to your question about totem pole drives and such - I have no idea. All I have to work on is the motherboard manual (#3), the pictures of the board (#4), and the experiments I've done.

 

[Chuck(G)]

If, instead of an LED, you hang a DMM voltmeter across the turbo LED motherboard pins, what happens with the turbo button press? I'm trying to figure out if it's really the motherboard that has this confused or if it's your display.

I don't know that we could do much with the motherboard bug, if that's what it is. It could also be that the 2-pin LED connector is intended for a 2-color LED and voltage is reversed when the turbo switch is pressed.

 

[twolazy]

Ive had a few 386 and early 486 motherboards use a 2 pin header, but would use a dual color led. Try reversing the polarity of the led.