Help me work out this Turbo Speed Indicator, please.

[Lutiana]

I am working on moving my 486 machine into a more period correct case, one I found in a storage quite a while back. It has one of those speed indicators on it, but I cannot for the life of me work out how to hook it up and make it work.

Here are some images of the front and back of the board: https://photos.app.goo.gl/MKyEQ6q1P6DR35zNA

I have managed to work out that the 4 pin header at the top is the power in, Pin 3 is ground and Pin 4 is positive are for power in. If I throw 3V on those pins, then bridge pins 1 and 3, I get a nice bright 2 digits that are controlled by the top level of jumpers, all 14 sets control all 14 of the segments. If I bridge pin 1 with the right most pin if the upper restor bank, then I get the turbo number, though greatly reduced in brightness, and from there I confirmed that the lower 14 pins control the turbo number.

When I got the case the turbo LED lead from the board went into this display, and the turbe LED came from it. I did not capture an image of this unfortunately, but at least it tells me that this is the type that sits between the motherboard and the turbo LED, though I've no idea where those pins would plug in, there just doesn't seem to be enough pins on the thing.

The part number, AT-17, does not turn up anything when I try to google it.

Thanks in advance for the help!

 

[kgober]

I suspect that pin 2 is ground and pin 3 selects which of the two values to display, or vice-versa. you can supply power via either pin 1 or pin 4, your choice -- the trace side pretty clearly shows them bridged together. My expectation would be that the motherboard power LED connects to pins 3 and 4 (4 positive), and the motherboard turbo LED connects to pins 1 and 2 (1 positive). If it didn't work, I would reverse polarity on both connectors (i.e. pins 1 and 4 are both ground, and pins 2 and 3 are power LED + and turbo LED +).

Are you sure about a separate turbo LED? I don't see why you would need one when the numeric display provides that information already. You wouldn't need a separate power LED either, for that matter -- if the display is blank power is off. If leads are supposed to go from this board to more LEDs downstream then yes there aren't enough pins, unless it had a special wiring harness where some of the pins had 2 wires attached.

 

[Lutiana]

Are you sure about a separate turbo LED? I don't see why you would need one when the numeric display provides that information already. You wouldn't need a separate power LED either, for that matter -- if the display is blank power is off. If leads are supposed to go from this board to more LEDs downstream then yes there aren't enough pins, unless it had a special wiring harness where some of the pins had 2 wires attached.

The turbo LED has short leads that only reach this board, and the power LED is part of the keylock connector and is long enough to reach the motherboard. So I am positive that the thing is designed to have both the turbo LED light up and the display change as well as have a discrete power LED.

if I supply power to 3 and 4, then bridge 1 and 2, the bright number that comes up is lower than the dimmer number I get from bridging pin 1 to the resistor pad I mentioned. So I am assuming the the bright one is turbo off (controlled by top bank of jumpers) , and the dim one is turbo on (lower bank). I also assumed that the reason it got dimmer was because it would add to the power coming from the LED header for turbo, thus making it as bright as when the motherboard had that LED off.

I should also point out that there was one wire connected to one of the pins in the jumper back on the bottom oroginally, though I do not recall which pin nor what it was. I really should have taken some pictures of the damned thing.

 

[SomeGuy]

I've got a similar one in one of my machines. Looking at it, the four pins are connected as follows:

1: (left) Yellow wire, goes to turbo LED
2: black wire, goes to motherboard (although not plugged in to my motherboard since my current motherboard has no turbo header)
3: black wire, goes to power via a molex adapter.
4: (right) red wire, goes to power via the same molex adapter.

Then a black wire that comes from the turbo LED connects to the lower pin on jumper 1 of the upper row of jumpers. You have a jumper installed there, but from the look of it, any of the lower pins on the upper row should work. (Or, possibly the upper pin on the lower row).

Of course, sanity check all that in case yours has some minor difference.

 

[Robbbert]

The bunch of jumpers can be rearranged to change what shows on the display. For example my turbo indicator originally said 25 and 33, but I changed it so it says HI and LO.
Unfortunately I can't remember any more about it, how it was connected to the motherboard and so on.