Hello all I am new to the forum and to small electronics in general so sorry if this is in the wrong spot or if call things the wrong name. Anyways I’ve been trying to diagnose this tachometer from a project truck of mine and I will post detailed pictures of it below. Anyways, it obviously dosent work I’ve noticed what I believe is a 14pin high bridge getting extremely hot and I believe that is is fried, as well as what I believe is a resistor that is red in color with a single yellow band that also gets extremely hot. Problem is I can’t find any schematics for this tach, can’t find any matching bridges, and I’m not sure what the ohm rating on the resistor is with it being a single band. Also all of the sharpie on the back was not put there by me it was there before so theirs a possibility someone may have messed with it. I’m not for certain where to start. Please help.
Delta Prime
- Jul 29, 2020
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Google Dotson 720 factory service manual if you have not done so already the files is too large to upload it includes schematic for RPM gauge tachometer & it’s free to download. and believe me I know the price is high for an OEM product. Also, I think they replaced it. The H bridge with a 23 pin programmable could be wrong but that’s the scuttle butt.
That "resistor" you are talking about is likely a zener diode. I see ZD2 just to the right of it on the board. The sharpie markings appear to be the circuit traces to reference which solder points are connected to each other. But you are right. Someone has likely been in there before and did some kind of work on that thing. There are obvious solder differences on the component side of that board.
PANASONI AN603 CDIP-14 on ecTransistors.com
Find pricing for integrated circuits, Buy Directly from ectransistors.com:PANASONI AN603 CDIP-14 Enjoy ✓Fast Shipping Worldwide! ✓Limited Time Sale ✓Easy Return.
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Do you think the AN603 you sent in the link will work fine for this? Just want to make sure it’s compatible but I’m not sure how to. Also how does one go about telling the watt rating of the zener diode? Are they banded like resistors? Thanks!That "resistor" you are talking about is likely a zener diode. I see ZD2 just to the right of it on the board. The sharpie markings appear to be the circuit traces to reference which solder points are connected to each other. But you are right. Someone has likely been in there before and did some kind of work on that thing. There are obvious solder differences on the component side of that board.
PANASONI AN603 CDIP-14 on ecTransistors.com
Find pricing for integrated circuits, Buy Directly from ectransistors.com:PANASONI AN603 CDIP-14 Enjoy ✓Fast Shipping Worldwide! ✓Limited Time Sale ✓Easy Return.www.ectransistors.com
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Just out of curiosity was the Manual you looked at for the 1983 1/2 to 1985 ish model. I’m only asking because they underwent a gauge cluster change after 83 and the tach was changed too. They changed it again after 1985ish I believe as well.Google Dotson 720 factory service manual if you have not done so already the files is too large to upload it includes schematic for RPM gauge tachometer & it’s free to download. and believe me I know the price is high for an OEM product. Also, I think they replaced it. The H bridge with a 23 pin programmable could be wrong but that’s the scuttle butt.
Also do you have a link by chance to website you found that fsm on? I can’t seem to find it. Thanks!
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Delta Prime
- Jul 29, 2020
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I am assuming that (AN603) is the correct IC for that board, since it is on that board now, so the provided linked one should work in its place. The schematic Delta Prime suggested would probably help you find out if that is the case, and may even give you the diode specs.
If that was mine, I would start testing the components (diodes, caps, resistors, etc,) I was able to check and go from there. In any case, that purple Electrolytic Capacitor should be changed out, especially if it is original. You can do most of the testing with a fairly adequate multimeter, just make sure you pull one leg out of the circuit when you do them. It looks like your board is marked with the component identifiers next to each component. Look up the testing procedures for each, if you are not sure how to do it.
Just making sure, the tach needle moves freely when you try and move it? And how are you powering this up in order to check it so far? Is it being done out of the vehicle not using the vehicle wiring hardness?
The board appears to have some decay/corrosion (bubbling) of the traces. That may be part of the reason for the heat buildup, if the current is being resisted due to the corrosion .
This is not a simple task troubleshooting these, so unless you have proper test equipment and pretty good soldering skills, it might be better to have someone else do it.
Ok thanks for the info I’m gonna mess around with it an see if I can’t figure it out.
73's de Edd
- Aug 21, 2015
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Kind Sires . . . . .
Statements . . . . . snippets
. . . . . what I believe is a 14pin high bridge . . . . . .
. . . . . . .can’t find any matching bridges, . . . . . . .
Methinks that youse guys are looking up and taking / making reference to a later date IC that actually ? accidentally ? numbered their IC as an AN603 product number also.
The one that you are seeing in that unit is the original OEM product that got its date code stamping of the 42nd week of 1984.
That AN603 unit is being of a Matsushita / Panasonic product line manufacture . . . . .viz . . . . its pointed apex triangle company logo just to the right of the crossing silver band.
Seems like Datsun had initially sourced the complete tachometer from KANTO SEIKI (1) in Japan or they (1) possibly then second sourced from ?
getting extremely hot and I believe that is is fried (AN603)( See*****)
as well as what I believe is a resistor that is red in color with a single yellow band that also gets extremely hot.
If that is located just behind the 2W marking on that green 2 watt metal film resistor, what my learned eyes are seeing is a glass encased, dual tinned, leaded. dual copper headers "device" with a central yellow band that fits the appearance of being a power diode.
If there is not shunting circuitry, put your digital VOM in its diode test mode and see if it doesn't test out as open circuit in one direction of applied probes position and then after transposing the probes position, it is then reading a developed Vf of 500-700 mv.
That tests as a diode does.
(*****) a continuance . . . . .
Now take your metering and switch into its lowest ohms function and test from where 12VDC power connects into that unit and visually trace those foils that might end up as being directly connected to a pin of that AN603. OR . . .OR . . . .OR . . . . that 12VDC passes thru a low ohms resistor like the GREEN metal film 2W 82 ohm unit or 1W 43 ohm . . . .OR our just tested yellow banded unit.
Also find a ground . . . .like the negative lead of that blue electrolytic capacitor and test to see what pins of that AN603 connect to ground.
Also test to both leads of that yellow bander, if being a 2 W Zener diode one lead typically grounds..
Now . . . . .some board layered deteris is covering some symbolization.
I clearly read R6 as being 15K ohms and R7 as 1K ohms but is the small frontal unit being given a R prefix ?
My best guesstimated read of its banding is blue-grey-grey which does not "resist" but it could be an 1N688 Hughes diode product. Do a diode and resistor test on that device also, as well, as if it has one lead being grounded. ( But my higher suspicion is that yellow banded unit being a 1 watt zener diode at >12VDC.
Evaluating the final photo . . . are the small gauge yellow and black wires at top, going to the meter movement.
At right bottom corner are being 3 pin connectors . . . . 12VDC-----Ground----Tach input signal ?
Also, is tach pic up magnetic to a cogged gear or being electrostatic pick up from the HV ignition coils wire ?
I had old Panasonic 1990 data books but found no data sheets on the AN603 nor was it ever picked up and being second sourced by Sylvania ECG Replacement Semicoductors nor RCA's SK series of same.
What I REALLY want to think, is that this AN603 is being a Digital to Analog converter function. The rotation pulses (digital) are being converted to a relatively comparitive analog (meter driving) DC voltage.
There is an LM2907 developed by National Semiconductor ----absorbed by (along with Bob Pease . . .RIP )- - - - - - Tejas Instrumentations that can be used for building up a VERY simple tach circuit.
Here is its Application Note . . . .
Its use with magnetic sensing is on page 9 figure 12 and its use with spark coil, electrostatixc, pickup on page10 figure 14.
BTW . . . . that input capacitor is just a 1 in wide clip on brass sleeve that electrostatically picks up firing spark plug impulses.
What feedback, have you got to tell me now. . . . . . . . .
73's de Edd . . . . .
Snoring . . . . . is just basically bragging that you are asleep.
.
Statements . . . . . snippets
. . . . . what I believe is a 14pin high bridge . . . . . .
. . . . . . .can’t find any matching bridges, . . . . . . .
Methinks that youse guys are looking up and taking / making reference to a later date IC that actually ? accidentally ? numbered their IC as an AN603 product number also.
The one that you are seeing in that unit is the original OEM product that got its date code stamping of the 42nd week of 1984.
That AN603 unit is being of a Matsushita / Panasonic product line manufacture . . . . .viz . . . . its pointed apex triangle company logo just to the right of the crossing silver band.
Seems like Datsun had initially sourced the complete tachometer from KANTO SEIKI (1) in Japan or they (1) possibly then second sourced from ?
getting extremely hot and I believe that is is fried (AN603)( See*****)
as well as what I believe is a resistor that is red in color with a single yellow band that also gets extremely hot.
If that is located just behind the 2W marking on that green 2 watt metal film resistor, what my learned eyes are seeing is a glass encased, dual tinned, leaded. dual copper headers "device" with a central yellow band that fits the appearance of being a power diode.
If there is not shunting circuitry, put your digital VOM in its diode test mode and see if it doesn't test out as open circuit in one direction of applied probes position and then after transposing the probes position, it is then reading a developed Vf of 500-700 mv.
That tests as a diode does.
(*****) a continuance . . . . .
Now take your metering and switch into its lowest ohms function and test from where 12VDC power connects into that unit and visually trace those foils that might end up as being directly connected to a pin of that AN603. OR . . .OR . . . .OR . . . . that 12VDC passes thru a low ohms resistor like the GREEN metal film 2W 82 ohm unit or 1W 43 ohm . . . .OR our just tested yellow banded unit.
Also find a ground . . . .like the negative lead of that blue electrolytic capacitor and test to see what pins of that AN603 connect to ground.
Also test to both leads of that yellow bander, if being a 2 W Zener diode one lead typically grounds..
Now . . . . .some board layered deteris is covering some symbolization.
I clearly read R6 as being 15K ohms and R7 as 1K ohms but is the small frontal unit being given a R prefix ?
My best guesstimated read of its banding is blue-grey-grey which does not "resist" but it could be an 1N688 Hughes diode product. Do a diode and resistor test on that device also, as well, as if it has one lead being grounded. ( But my higher suspicion is that yellow banded unit being a 1 watt zener diode at >12VDC.
Evaluating the final photo . . . are the small gauge yellow and black wires at top, going to the meter movement.
At right bottom corner are being 3 pin connectors . . . . 12VDC-----Ground----Tach input signal ?
Also, is tach pic up magnetic to a cogged gear or being electrostatic pick up from the HV ignition coils wire ?
I had old Panasonic 1990 data books but found no data sheets on the AN603 nor was it ever picked up and being second sourced by Sylvania ECG Replacement Semicoductors nor RCA's SK series of same.
What I REALLY want to think, is that this AN603 is being a Digital to Analog converter function. The rotation pulses (digital) are being converted to a relatively comparitive analog (meter driving) DC voltage.
There is an LM2907 developed by National Semiconductor ----absorbed by (along with Bob Pease . . .RIP )- - - - - - Tejas Instrumentations that can be used for building up a VERY simple tach circuit.
Here is its Application Note . . . .
Its use with magnetic sensing is on page 9 figure 12 and its use with spark coil, electrostatixc, pickup on page10 figure 14.
BTW . . . . that input capacitor is just a 1 in wide clip on brass sleeve that electrostatically picks up firing spark plug impulses.
What feedback, have you got to tell me now. . . . . . . . .
73's de Edd . . . . .
Snoring . . . . . is just basically bragging that you are asleep.
.
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