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Cody's Goon


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2 hours ago, Captain Obvious said:

My thoughts? If the two tachs were in series and the one in the dash worked fine, then I think there is an internal problem with the 510 tach. I mean, there's a slight possibility it has something to do with the ballast resistor, but I suspect the gauge itself.

I also think there is nothing to be gleaned from the seeming "proportionality" of the tach readings. I think that's a red herring.

Steve, If you want to send me that tach, I'll open it up and do some reverse engineering on the guts? If nothing else, it'll be a great story about a tach that traveled all over the country. "510 Tach Tour!"    LOL

I'll try wiring it like it suggests on Dime Quarterly, and if it doesn't behave better, I can send it to you.

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4 hours ago, SteveJ said:

I'll try wiring it like it suggests on Dime Quarterly, and if it doesn't behave better, I can send it to you.

Not surprisingly, there was no change. But I did take the time to mark the polarity on the tachometer wires to make it easier to identify which wire goes where in the future. I couldn't find my red electrical tape (that had been sitting in the same place in the garage for about 10 years until I reorganized last year), but I did find some red heat shrink that fit over the spade connector.

20220814_181902_001.jpg

At least I had fun testing. I'm interested in Bruce's analysis. I could do a visual on the discrete components, but I think Bruce has better skills in that realm.

Edited by SteveJ
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Well this may all be for naught... I got a head start based on the pics from that Dime Quarterly thread I started looking for info on the IC chip - AN603.

Based on the logo, it looks like a Matsushita (now part of Panasonic) part, but I couldn't dig up any info about it at all. So if I can't find anything about what's going on inside that chip, I might not be able to do much with it. I mean, I can certainly do a macro level reverse engineering and infer what's going on inside that chip, but that may be about it.

And if it looks like there's something wrong inside the chip, I certainly won't be able to get a replacement except from another old donor part.

I wonder if they used that same chip in the current sense Z tachs... Those are at least easier to find at this point.

Anyway, regardless, I'll do what I can.

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1 minute ago, Captain Obvious said:

Well this may all be for naught... I got a head start based on the pics from that Dime Quarterly thread I started looking for info on the IC chip - AN603.

Based on the logo, it looks like a Matsushita (now part of Panasonic) part, but I couldn't dig up any info about it at all. So if I can't find anything about what's going on inside that chip, I might not be able to do much with it. I mean, I can certainly do a macro level reverse engineering and infer what's going on inside that chip, but that may be about it.

And if it looks like there's something wrong inside the chip, I certainly won't be able to get a replacement except from another old donor part.

I wonder if they used that same chip in the current sense Z tachs... Those are at least easier to find at this point.

Anyway, regardless, I'll do what I can.

Apparently DQ also has an article on grafting in the tach from an S110 200SX. There are several NOS tachs on ebay now. It's not cheap, but it would probably be a fix Cody could enjoy for a long time.

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9 minutes ago, Captain Obvious said:

Well this may all be for naught... I got a head start based on the pics from that Dime Quarterly thread I started looking for info on the IC chip - AN603.

Based on the logo, it looks like a Matsushita (now part of Panasonic) part, but I couldn't dig up any info about it at all. So if I can't find anything about what's going on inside that chip, I might not be able to do much with it. I mean, I can certainly do a macro level reverse engineering and infer what's going on inside that chip, but that may be about it.

And if it looks like there's something wrong inside the chip, I certainly won't be able to get a replacement except from another old donor part.

I wonder if they used that same chip in the current sense Z tachs... Those are at least easier to find at this point.

Anyway, regardless, I'll do what I can.

This AN603, @Captain Obvioushttps://shop.ectransistors.com/PANASONI-AN603-CDIP-14-.html

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11 minutes ago, SteveJ said:

Apparently DQ also has an article on grafting in the tach from an S110 200SX.

Yeah, that's the article in which I found the pics I was talking about. This is a 200SX on the left and 510 on the right.
TachRepair Photo1.png

Oh, and youtube says the current sensing Z tachs don't have any IC's at all. Nothing integrated. Just discrete transistors.

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22 minutes ago, Captain Obvious said:

Who knows... Maybe? Those sites always seem to have stock of any IC you are ever looking for. But do they really? I don't think I'd ever trust them enough to even try

After a little research, I would concur with your assessment. 

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