The original Instrument Cluster Voltage Regulator has been called by many names including, Constant Voltage Regulator or simply, CVR. Ford's last year for six-volt systems was in 1955, and the Dashboard had no CVR. In 1956, Ford went to 12-volts. This was the only year the instruments were 12-volts and again, no CVR. In '57, Ford quickly went back to using six volts for all the gauges, corporate wide, and they remain as such today.
The OEM CVR works much the same as a turn signal flasher with three leads: One goes to Ignition power, one lead to ground, and the other to the gauges. So the original pulled 12-volts through a resistance wire that was wrapped around a bi-metal strip, to ground. As the bi-metal strip got hot, the normally closed contact would open, then cool and close, over and over as long as the key was turned on.
The assembly comes with an adjustment screw (that is painted), but none of the manuals explain how to adjust the timing. A 6-volt average of 12-volts would be an on and off time of 50%, or 50% duty cycle. I put my Fluke meter on one and checked for Hz. It was all over the map, from 0.4-seconds to 1.4" and very irratic. I realize this was a cheap way to get 6-volts back in the day. Now we have much better methods.
For the scope of this site I will retrofit a 6-volt Solid State regulator into the original metal case, showing each step. Then I will test it.
Time to talk about the Electronics...
This is the location and part numbers for Squarebird CVRs.
These are two broken units, removed from different Squarebirds.
The first job is to open the case.
I'm working on opening the third side.
That's it. Let's see the inside...
The bi-metal strip on the right side is wrapped with very small resistance wire which causes it to heat. This one is burned open. Notice the end of the tiny wire goes under an edge clip for the ground connection.
Notice the 'adjustment' jack screw and the grounding clip. This is a recipe for disaster.
One last look before I tear into it.
The original connectors are tight in the rivets. Notice I left a stub of metal after tearing the arms off. I will tin these and solder my 12-v 'Input' and 6-v 'Output' wires to them.
I removed the adjustment screw. This is a perfect hole to put a green LED to show the 6-v side works.
All holes I drill will be 1/8".
The solder I use (AQUABOND by KESTER) contains NO lead and is Silver Bearing. Yeah, it's the good stuff.
I am creating a flat, smooth 'bed' at the bottom of this stamping (for the regulator). They projection spot welded the bottom strap to the case, leaving dimples in the surface.
This is a Fixed Output, LM7806 Voltage Regulator in a TO-220 case. The center leg (2) is also electrically connected to the metal backing with the mounting hole. So conveniently, the case will be our NEG.
All I need is two capacitors (C1 = 0.47uF) and a very small LED with a dropping resistor (150-ohms). I am using the correct 0.1uF for C0, but a larger cap for C1 because car electrical systems are notorious for voltage spikes and drops.
To prevent metal fatigue, it's important to hold the leads with pliers, away from the case, while bending the leads. If disaster strikes and the leg comes off, a 'tab' will remain for an acceptable solder connection.
Place the TO-220 in the housing and mark the 1/8" hole.
These are the setup parts: A 1/8" pop rivet, a 1/8" hole brass washer, and heatsink compound. Now I am ready to wire.
Time to talk about the Electronics...
Solder three short leads onto the regulator. It's hard to see but I marked the power leads, red (12-v) and black(6-v).
Use plenty of heatsink grease and pop rivet the parts together. Set it aside for later.
I used epoxy to mount the LED. After it cured I added a dropping resistor (150-ohms@1/8-watt), heat shrink-ed the 6-volt leg and soldered it to the output post. Notice the NEG leg is sticking up.
I added the 0.1Uf capacitor to the same output tab. Now I have two NEG legs sticking up.
The (0.47uF@50v) Input cap neatly nestles in the middle. See how all three NEG legs stick up together?
Time to solder all the NEG leads together, then solder the power leads to their tabs. The next one I assemble will have shorter wires, but notice that half of the 'can' is empty. That is the portion where the bulky parts fit into.
I used a wide chisel to hem the edges.
Here it is... 12.56-volts from a car battery (IN), and a solid 6.00-volts (OUT).
The indicating LED looks like it belongs there.
I want to extend a special "THANKS" to Yellowrose (Ray Clark) and NYsquarebird58 (Marcelo Laviano) for sending me
their old CVR units. Without them, I was stuck with the electronics in a breadboard,
but no real way to test it. Now, we can save our Squarebird.org members at least US$25
over retail price.
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