Dash printed circuit

[Steve McMahan]

I’m no expert, but I don’t think the dash printed circuit ribbon is suppose to look like this:



That circuit connects to this nut, looks like a ground (right above the part number to the right):



Here is the overall look from the back:



A few questions, is this a good replacement part from NPD:

https://www.npdlink.com/product/pri...2Bboard&top_parent=200001&year=1973&year=1973
I ask because I have zero experience working on dashes. I have the stock non tach dash, front view:



Do I replace the ribbon, voltage regulator, and ?? Also, are all of the light holes suppose to have lights in them? As you can see, quite a few are missing. Thanks, Steve.

 

[TheRktmn]

The circuit that burned is power to the clock. Make sure you repair/replace that before installing another printed circuit.
Does the clock have a separate fuse you can pull to cut power to it? I don't know.

I have no first hand experience with using the NPD PCB, I have installed a couple for customers and never heard anything back, so I am going to guess they are okay.

Replacing the IVR is up to you. I would not use one of the new solid state units - find a good used OEM one. To test it connect a ground wire to the mounting tab, apply 12V to the side marked IGN and use an analog volt meter or test light to check the ACC side for blinking/pulsing power.

The light holes with blue globes are to illuminate the clock. The ones without are for the warning (idiot) lights. If you have Oil, Temp and ALT gauges you wouldn't need those. One is for the BRAKES hydraulic system - you need that one.

 

[Steve McMahan]

My wiring diagram says f-4 powers the clock. I have idiot lights, so does that mean I don’t need lights in those holes (the ones missing)? I’m not sure I understand how to test the IVR. Can I remove it with damaging anything else to test it? Thanks, Steve.

 

[TheRktmn]

If you do not have regular gauges anywhere - OEM or aftermarket - you will need those lights.

The circuit board connects to the IVR with snaps like a 9V battery. There is 1 screw holding the IVR to the cluster, but you can test it w/o removing it.
You will need an analog (not digital) volt meter or test light and jumper wires to connect the IVR to a 12V battery.

The IVR is marked, but they are hard to read. Connect a ground wire from the 12V battery to the IVR mounting tab. With the tab pointing down and the snaps facing you, connect the 12V lead to the IGN side (MALE snap). Now connect your meter or light with one lead to the tab for ground and the other lead to the ACC (FEMALE) snap. The meter should bounce between 0 and 12V rather quickly. If using a test light the light will blink rapidly.
If you get pulsing the IVR is working.
If you get no pulse/voltage and your leads are connected correctly the IVR has failed.

 

[NG8264723]

I had mine rewired by hard wires by midlife. This is after a friend of mine restored an 73 and used the new printed circuit. It fell apart and burnt the front of the car up

 

[Steve McMahan]

Thank you for the test procedure. I’ll test it. I suspect it’s bad since none of the lights, fuel gauge, etc worked. It will be an adventure to rebuild it.

 

[TheRktmn]

The IVR only powers the fuel gauge. Lights are the light switch/rheostat and printed circuit.

I had forgotten that Midlife offers hard wiring for clusters. He can even customize it for a Rocketman tach instead of the clock

 

[Steve McMahan]

For now, I think I’ll just disconnect the clock. I’m at the “get it driving” phase, nice stuff to follow in the years to come. Thanks again for the valuable help, Steve.

 

[mrgmhale]

For now, I think I’ll just disconnect the clock. I’m at the “get it driving” phase, nice stuff to follow in the years to come. Thanks again for the valuable help, Steve.

Not a bad approach. If anyone calls you, "Chicken," remember it is better to live to fight another day sometimes. This may be one of those times. You have been provided some excellent suggestions by TheRktmn (not surprisingly). Attached are some files I came across a while ago that shows detail for the printed circuit ribbon, IVR, and related matters. On one of the pages (document page 33-55-03, page # 4 of the PDF file) the printed circuit ribbon is shown with some notes from the writer(s). I think it would be worth your while to at least look the files over to see if you can glean any useful details.

I am not sure if there is a difference between ribbons for idiot light vs analog gauge equipped vehicles, but I am betting they are different., Hopefully you will find something useful in the attached files. What I found interesting, if not just plain old amusing, is that I included some TheRktmn comments from way back when. He has been around for a while, heh heh... And helping folks like "the rest of us" cheerfully even long ago... Anyway, I found it fondly amusing.

 

[Steve McMahan]

Thanks Mrgmhale, those files were very helpful.

 

[mrgmhale]

Thanks Mrgmhale, those files were very helpful.

Excellent. I am glad I was able to provide some useful info. I do enjoy digging up info I have on hands, and sharing experience where I feel I can be helpful. In that way I stand amongst many worthy giants of info in this forum, all from whom i have learned ever more. I can only hope what I contribute is helpful to them also.

I love this forum.

 

[Steve McMahan]

Maybe we should call you The Librarian?

 

[mrgmhale]

Maybe we should call you The Librarian?

You must be referring to TheRktmn. He and MidLife seem to have far more expansive libraries than I do. And are so generous in sharing the knowledge, also. I marvel at ho well we all get along in this forum. It is a pleasure to be amongst such a great group of fellow enthusiasts. Seriously, for me it brings an extra layer of joy to an already fun hobby.

 

[Steve McMahan]

You said it well; while I won’t share my beer, I appreciate the conveyance of knowledge from those who could be working on their own car and instead stop, and help those of us who are car challenged. Those mentioned and Hemikiller, Kilgon, 71Fast, RIBS, and PoFoMoCo. I’m sure I missed others, so thanks also.

 

[Steve1973M1]

Hi,
If you do want a solid state device, here is the best solution. A linear "swicthmode" replacement that is accurate and the output is short circuit proof and will not burn up. It is available from digikey but you have to fit it inside of old VR. Its part number is VX7805-1000. Pin 1 is input, center pin 2 is ground and 3 is output. It is a 1amp linear ( switchmode , buck regulator) replacement to replace 7805 TO220 type regulators. Works from 8V to 36V in for the 5volt output model.
https://www.digikey.com/en/products/detail/cui-inc/VX7805-1000/7350292