Electrical geniuses

[BA80]

On the XS tach, what part on the circuit board is it that makes the tach jumpy or erratic? Is it the integrated circuit?

[WMarshy]

On the XS tach, what part on the circuit board is it that makes the tach jumpy or erratic? Is it the integrated circuit?

I thought it was just dirty connections that cause it... or bad alternator. Sorry, cant help much. Dont let the smoke out of the wires is all I know about electronics.

[motoman]

On the XS tach, what part on the circuit board is it that makes the tach jumpy or erratic? Is it the integrated circuit?

Haven't had the issue myself, but have seen where cruddy connections down at alt. have caused tach to go wonky. Same for the main plug-in behind fuse panel, but you already knew that.

[DGXSER]

You want to be sure all the electrical connectors mentioned are clean first. Since you have multiple bikes, you could try running the problem tach on one with a known good tach and also put the good tach on the bike with a bad one. That will confirm if the issue is in the tach itself or on the bike.

If you confirm it is in the tach itself, then your down to some of the electronic components. I would first look at the capacitors on the board. You can see goo oozing out of them when they blow typically. Not to hard to replace.

[BA80]

Don all that Don. I have several apart right now trying to get at least one working right.

I've checked all the guage motors, for lack of the correct word, and they all work fine. Swapping circuit boards around I get different symptoms. Some work good at idle but go crazy with RPMs, some don't seem to work at all but jump now and then when revving. The one I have on Okie right now works fine until it gets to about 43K then it just kinda hangs there.

I'm certain it's a component on the circuit board that goes bad and I'm fairly certain it's the IC but I've heard that capacitors will go bad with age also. I'm not electronically inclined enough to test them though.

[trbig]

Okie right now works fine until it gets to about 43K then it just kinda hangs there.

Dang.. got a rotary engine in that thing?

[BA80]

Dang.. got a rotary engine in that thing?

OOPS........4.3K. Amazing how much difference a little dot makes.

[TopCatGr58]

Hey Greg,

The capacitors don't always balloon when they go bad, sometimes they just DRY UP...the fluid leaks out, but this also causes them to stop working properly. I had an internal power converter on a couple of Pro-level Editting VCRs. Aside from a voltage regulator chip that I replaced....I replaced ALL of the 20+ y/o capacitors on the IC board....whether they were ballooned or not. After that, they fired right up and have worked just great again!

You can get capacitors on eBay fairly cheaply, vs. Radio Shack, and more likely within the range you'll need along with the dual wire mount end. The values are on the ends...and you'll need to take photos or draw a diagram or mark on the IC which end is + vs. -, they are polarity specific!

T.C.

[BA80]

Have you ever had a tach apart and seen the circuit board TC? They are pretty simple and if we can figure out which component(s) need to be replaced to correct the malfunction it would be great.

I have at least a half dozen that don't work right and good ones are getting harder and harder to acquire for a decent price.

[TopCatGr58]

Why yes, Greg, I have...see the tach broken needle indicator repair tech tip! I'm not an electronics guru, but I would think that the ICs and other truly solid state components are probably not broken. I would look for evidence of electrical burns/heat damage to solder joints, that's how I found the damaged volt/regs in my power supply. Aside from that, the "fluiditic capacitors" are the most likely culprits.

Perhaps you could talk CZ into offering some real electronics analysis of a few of your tach PC boards????

T.C.

[BA80]

I have seen no evidence of circuit board damage or loose connections on any of them. I've gone over them with a magnifying glass and all looks good.

[skids]

Dang.. got a rotary engine in that thing?

Funny that you said that. I know a guy that has a rotory engine in a Kawasaki (stock).

[ViperRon]

One of the big issues with repairing the tach's is opening and sealing them without tearing them up. The round ones are a bit easier to do but still it takes some skill. If we could have one person pipe up and declare him/her-self as a guru at assembly it would be worth figuring out the electronics. It is a task for someone to figure this out just to repair his/her own for one repair. Plus the parts. Would be nice to find a member that could order electronics in bulk and create some type of turn around repair like we once had on the TCI. Doing any solder repairs on these older componet boards it would be nice to have a real solder station like a pace machine so the runs etc do not get lifted off the boards. If we had a volunteer maybe we could ask people to send all that junk we have that does not work, and we can't find time to fix. Then the person would have a pile to start with.

[crazy steve]

The problem with repairing these tachs is the input that Yamaha chose; rather than the pretty much 'standard' method of counting ignition pulses, they went with measuring AC frequency out of the alternator. There's plenty of repair shops for car/bike gauges, but very few for AC Hertz/CPS meters. Find out how this type of meter works, and you'll have a shot at fixing it.

[jayel]

my tach was jumping +-500rpm right at 4000, ran another ground wire from the reg/rec back to battery frame ground (clean and re-tighten) frame grounds too, problem solved tach no longer jumps