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Have this 72 open seater XKE - original owner & restored to like new. Original OPUS amplifier finally crapped out.
BUT GOOD NEWS - years ago I bought a load of stuff from a guy leaving JagWorld, and in the box was an OPUS amp & pickup. Bench tested to see if it produces a spark and it seems to work.
It one of these remote install units; have it mounted just below the reservoir tank.
THE PROBLEM: The amp only has 2 leads to the ballast - power & coil + (plus a ground for coil -). Nothing in the top slot of the ballast connector, so no connection to drive the tachometer. Thought maybe the coil signal is used, so I took apart one of the old amplifiers ... but the tach wire goes into a transistor; it's not just a ground.
How the heck do you drive the tachometer with these things?
Are you sure its a transistor? Later CEI systems had a 10K resistor between ( - ) Amp terminal and the Tach. Some confusion in early 70's XKEs wiring diagrams on which terminal ( + or -) on ignition coil goes the wire to the Tach. Try a 10K ohm resistor between ( - ) terminal on Ignition coil and the Tach. If not, try 110 ohm resistor on (+) terminal of ignition coil and Tach.
Rgds
David
Last edited by David84XJ6; Jul 26, 2019 at 02:55 PM.
THANKS FOR THE RESPONSE, DAVID! I was starting to lose hope!
The original (1972) OPUS amplifier had a separate wire to the top terminal in the ballast, like your top diagram. I popped it open, peeled off the potting compound and found where that wire attaches inside the amp - it's to 1 leg of an old scr transistor (small one about dime size). And the top resistor (#5) is, indeed, 100 ohms.
What I'm now using is one of those "remote mount amps - still the same, I suppose, except with long leads so the amp need not sit in the hot engine valley. Well, maybe it's not identical, since the 3-prong connector to the magnetic pickup is "reversed" (2 felmal instead of 2 male, or maybe the opposite - I forget right now). Anyway, I had to use the pickup that came with the remote amp, or maybe kluge up a way to ..... anyway, maybe it's not identical. But it appears to be.
Don't know what a 35DE8 disty is - looks like the amp is integrated into the distributor perhaps. If so, that's NOT what I have, since the remote amp looks exactly like the original OPUS amp.
Anyway, think maybe your advice is a good try. I'll splice from coil "-" into the top ballast terminal, so there is that 100 ohm resister in line. might work ...
Right now I'm pulling the fuel pump out to see why it's not pumping. I've had this car since new, but about 10 years ago went thru one of those stupid 3-year, cost-of-a-house rebuilds. As soon as the rebuild was done it went into storage. Ran at the time, but now the pump is clicking away but not doing it's job. So there is that also ....
Still has the original soft top, seats & interior, exhaust except for the resonator which finally rusted out, etc. But I cheated because the care came with that God-awful BW auto transmission, which I still have, but in the car is a 5-speed. Can't tell by looking underneath (or from the 3rd pedal & shifter) - everything came out in the original positions so the tranny swap came out as well as can be expected, I think.
Opus wiring to tachometer
