Corvette C3 Tachometer Repair Debugging, usualy it is replacing the board, but is it now?. FY6900 go.tonyalbus.com/FY6900_Ali FY6900 go.tonyalbus.com/FY6900_BG #corvette #C3 #tachometer
Hi, top demonstration of diagnostics, it is beautiful to see that it is necessary to go through the whole device and not rely on the first judgment. The coils are basically a voltage divider and when they are interrupted, a good board may not show the correct values when measuring. I have such a comparison for the broken continuity of the circuit "If it does not go from the forest, it will find a way from the river" in some cases it leads to a fatal failure of the surrounding circuits. Beautiful work, nice day 🙂Tom
I have been watching all your frequency counter videos -- very enjoyable -- I just purchased a Philips PM6669 off of eBay (I'm still waiting for it to arrive). Anyway, this is an interesting topic too. Subbed! I look forward to more videos. Keep up the great work.
@@TonyAlbus And thank you for the sub! Cool -- it would be nice to see you C64 back in action. Yes, I was in need of a quality counter and was doing some research when I found your channel. I have ordered a 10MHz reference from AliExpress, as well. So I should be in good shape now.
I am not sure about this, but there is also possibility, that the meter is combination of linear motor and some resistive feedback, so then you should see something like coil, that pushes respective pulls that needle depending on polarity and another terminal that changes its resistance to the common pin according to needle position. This configuration is very common in industry and I think it is not impossible to use the same configuration in this case. One of that pins was sticked at something little above 5V, which is near the center of the PSU voltage, so it opens the possibility to pushes or pulls (going + or GND) the needle. Then the feedback signal is used to compare to the measured signal using some opamp (which in my opinion that IC is) that controls the coil of the linear motor. If this is the case, the common issue with theese indicators is the feedback loosing its connection due the oxidation of resistive track. Then the needle moves almost eraticaly sticking at some points etc. So I think the best solution is just opening the meter and I think it would be absolutely clear what's happening when you open that meter's case. I also think that this is problem with the meter, not with the board itself. But if that meter is bad, there is no possibility to make it worse when you open it. So I think it's safe to do it.
I am currently looking at this style of corvette tach (1981) for a friend as well. The "coil" checks good. It measures about double (420 ohms) from the left post to the center post and about 220 ohms from the center to the right hand post. So it checks ok. I measured the 14 pin resistor network as well. The only measurement that does not "jive" with the measurements you show at 7:19 in the video is the 537K resistor in the middle. I measure 238.64K on the one I have here. Just wondering if that is a typo ? All the other resistors in the network are within 100 ohms of your measurements. I guess the 14 pin (this one is marked National Semiconductor 935 with a 7777 below it). I'm wondering if it is a custom IC, as the closet part number to it seems to be a LM3900 Quad Op-amp. Great video by the way.
Hi, i do not remember that well, as it has been a while. but from what i know, this frequency to voltage IC usualy blow. i think i have in the link replacementboeard. as your coil seems good, that could be a soloution for you.
Very interesting. My C3's tach increases to about 3,000 rpm then oscilllates wildly between 3,000 and 4,000 rpm as the revs are increased. From what you say here, I guess the freq to voltage converter has gone crazy.
Hello James, in my test, one of the coils is broken, but a more common problem is indeed the f2v converter, the IC is not easy available, but you can find replacement boards, just be sure you pick the correct build year when you order. (as with all car parts)
@@TonyAlbus Yep, thanks. I've managed to buy a second hand tach which works fine when I put the sig gen on it. I'll have to swap boards because my original tach has a much better dial face than the used one I bought.
Thanks for video.. I have identical tachometer..would you guess as to why the tach after starting slowly after several minutes drops rpm to the point idle is like 100 rpm? And reads about 5-700 low andthe zero point drops evenafter resetting? It also jumps sometimes when turning off and on blower fan or rear defroster heavier loads. Is that the push pull you talk about and can you repair it? Looking forward to part 2!
Hi TF, most common is the frequency/voltage converter on the board is broken, those are not available and a replacement board is the solution.When the coil is broken(push/pull) it will need a meter replacement... as my friend did, so no part 2, sorry. On the Blower and heater... that could be separated.. those take both a lot of power.. and the voltage could drop, specialy with and old battery or old wirering... or simply becouse the altenater is working hard and realy is pulling the rpms down.. so i would first check battery and wireing if it is stilla problem you prob will have to look for a replacement board. good luck, i hope this helps.
Ik zie namelijk dat er verschillende printplaatjes te koop zijn voor dit 78-82 model, maar waar het verschil in zit weet ik niet, ik denk het type motor.@@TonyAlbus
@@luciendebeer5574 Hi Lucien, dat kan je het beste aan de verkoper van de printplaatjes vragen, ik kan je er helaas niet mee helpen. dit is iets dat ik voor mijn maatje heb getest, maar eigelijk is het niet mijn ding, ik weet de verschillen niet tussen de type autos, ik heb puur gekeken naar de techniek van de meter zelf.
Наука
Hi, top demonstration of diagnostics, it is beautiful to see that it is necessary to go through the whole device and not rely on the first judgment. The coils are basically a voltage divider and when they are interrupted, a good board may not show the correct values when measuring. I have such a comparison for the broken continuity of the circuit "If it does not go from the forest, it will find a way from the river" in some cases it leads to a fatal failure of the surrounding circuits.
Beautiful work, nice day 🙂Tom
Thank Tom
Hoi Tony,heb volgende week een nieuwe tachometer voor de Corvette....Thanks for helping...
Graag gedaan... hij staat er mooi op!
I have been watching all your frequency counter videos -- very enjoyable -- I just purchased a Philips PM6669 off of eBay (I'm still waiting for it to arrive). Anyway, this is an interesting topic too. Subbed! I look forward to more videos. Keep up the great work.
Thank you!...subbed your channel too, cool, i have my C64 somewere in a box, time to take it out...! Oh, Yes PM6669 super cool!
@@TonyAlbus And thank you for the sub! Cool -- it would be nice to see you C64 back in action. Yes, I was in need of a quality counter and was doing some research when I found your channel. I have ordered a 10MHz reference from AliExpress, as well. So I should be in good shape now.
@@MindFlareRetro Yes well done on the reference! that will give you some pease of mind... you counter will be spot on!.
great video. I have always wondered how these tachometers work . thanks
Thanks and welcome, good you enjoyed!
I am not sure about this, but there is also possibility, that the meter is combination of linear motor and some resistive feedback, so then you should see something like coil, that pushes respective pulls that needle depending on polarity and another terminal that changes its resistance to the common pin according to needle position. This configuration is very common in industry and I think it is not impossible to use the same configuration in this case. One of that pins was sticked at something little above 5V, which is near the center of the PSU voltage, so it opens the possibility to pushes or pulls (going + or GND) the needle. Then the feedback signal is used to compare to the measured signal using some opamp (which in my opinion that IC is) that controls the coil of the linear motor. If this is the case, the common issue with theese indicators is the feedback loosing its connection due the oxidation of resistive track. Then the needle moves almost eraticaly sticking at some points etc. So I think the best solution is just opening the meter and I think it would be absolutely clear what's happening when you open that meter's case. I also think that this is problem with the meter, not with the board itself. But if that meter is bad, there is no possibility to make it worse when you open it. So I think it's safe to do it.
Thanks, my friend already fixed it, i think i found a new secondhand
I am currently looking at this style of corvette tach (1981) for a friend as well. The "coil" checks good. It measures about double (420 ohms) from the left post to the center post and about 220 ohms from the center to the right hand post. So it checks ok. I measured the 14 pin resistor network as well. The only measurement that does not "jive" with the measurements you show at 7:19 in the video is the 537K resistor in the middle. I measure 238.64K on the one I have here. Just wondering if that is a typo ? All the other resistors in the network are within 100 ohms of your measurements. I guess the 14 pin (this one is marked National Semiconductor 935 with a 7777 below it). I'm wondering if it is a custom IC, as the closet part number to it seems to be a LM3900 Quad Op-amp. Great video by the way.
Hi, i do not remember that well, as it has been a while. but from what i know, this frequency to voltage IC usualy blow. i think i have in the link replacementboeard. as your coil seems good, that could be a soloution for you.
Very interesting. My C3's tach increases to about 3,000 rpm then oscilllates wildly between 3,000 and 4,000 rpm as the revs are increased. From what you say here, I guess the freq to voltage converter has gone crazy.
Hello James, in my test, one of the coils is broken, but a more common problem is indeed the f2v converter, the IC is not easy available, but you can find replacement boards, just be sure you pick the correct build year when you order. (as with all car parts)
@@TonyAlbus Yep, thanks. I've managed to buy a second hand tach which works fine when I put the sig gen on it. I'll have to swap boards because my original tach has a much better dial face than the used one I bought.
@@James_Bowie Perfect!
Thanks for video..
I have identical tachometer..would you guess as to why the tach after starting slowly after several minutes drops rpm to the point idle is like 100 rpm? And reads about 5-700 low andthe zero point drops evenafter resetting? It also jumps sometimes when turning off and on blower fan or rear defroster heavier loads.
Is that the push pull you talk about and can you repair it?
Looking forward to part 2!
Hi TF, most common is the frequency/voltage converter on the board is broken, those are not available and a replacement board is the solution.When the coil is broken(push/pull) it will need a meter replacement... as my friend did, so no part 2, sorry. On the Blower and heater... that could be separated.. those take both a lot of power.. and the voltage could drop, specialy with and old battery or old wirering... or simply becouse the altenater is working hard and realy is pulling the rpms down.. so i would first check battery and wireing if it is stilla problem you prob will have to look for a replacement board. good luck, i hope this helps.
Van welk jaar is de toerenteller? Van een corvette 78-82?
Hi, oh datw eet ik niet meer, hij was van een vriend van mij, de foto van excact die auto komt voorbij in de eerse paar seconde van de video
Ik zie namelijk dat er verschillende printplaatjes te koop zijn voor dit 78-82 model, maar waar het verschil in zit weet ik niet, ik denk het type motor.@@TonyAlbus
@@luciendebeer5574 Hi Lucien, dat kan je het beste aan de verkoper van de printplaatjes vragen, ik kan je er helaas niet mee helpen. dit is iets dat ik voor mijn maatje heb getest, maar eigelijk is het niet mijn ding, ik weet de verschillen niet tussen de type autos, ik heb puur gekeken naar de techniek van de meter zelf.