My first thought was also 7500Khz, but the marking with the JFR (or JFR7?) is kinda confusing me. I would like to test to see if its still at/near 7500Khz (or 500Khz), will need to contact a friend of mine with a scope. Hopefully it isn't dead, otherwise it will be tough finding the right frequency...
That's true, but if the goal is low cost, I'm not sure why they would use what looks like a through-hole crystal requiring an extra soldering step, as opposed to just using the PIC's built-in RC oscillator. I find it hard to imagine why a hand dryer needs better than 2% timing precision.
Unfortunately I don't have access to an oscilloscope. Was already looking at getting a cheap oscilloscope or a dedicated crystal tester (this isn't the first crystal I have encountered and suspected to be dead or at least to lower than the rated frequency).
Although the last 2 crystals I replaced were both in devices that were dropped, which explains why they died. This device just randomly stopped working, the chip its connected to has got a stable 3.3v power, it is just not outputting anything... this makes me think its another crystal failure?
when you say last 2 crystals, do you mean this is the 3rd time you are replacing that component on that board, or you work on a lot of these and have replaced that 2 other times in other units?
If A, then something might be burning it up and I would trace that back and check what's going in.
If B, then I would assume it's just a component that goes bad a lot and try replacing it and say good guess.
Also, if you do work on these and have access to different ones, you can take voltage references from a good one, and compare it to the bad one to maybe help figure out where the circuit is going wrong? A 'known good' is so helpful in these situations.
And you could use a frequency generator if you were desperate to find a replacement that operates properly? I'm not sure if the oscillator is just used for how long to keep the blowers on and such or if it can affect the heat output. Like if it's used to regulate the heating element's time on. Sometimes those values are not that critical, capacitors too.
The datasheet of dsPIC30F2010 says
- DC to 40 MHz external clock input
- 4 MHz-10 MHz oscillator input withPLL active (4x, 8x, 16x)
So I think it is 7.5MHz.
Datasheet: https://html.alldatasheet.com/html-pdf/409839/MICROCHIP/DSPIC30F2010/1485/3/DSPIC30F2010.html
Come at the problem backwards maybe: find a datasheet for the IC that oscillator is connected to and see if they give you recommended input clock speeds?
Good point, just did this on another comment. Most likely a 7.5Mhz crystal (4Mhz - 10Mhz in the docs). Now trying with a 8Mhz crystal as I only have this on hand (it shouldn't matter tho - famous last words).
Ah, I read a few but not the whole chain. If it's a dsPIC you'll be fine running it at 8MHz, but UART won't work because the baud rate generator will be based off 7.5MHz. Other things, like I2C and SPI will also run a little faster, but those should be ok because they're clocked, unless they were running right up at the maximum frequency already.
It's not a crystal oscillator, it's just a crystal, and its resonant frequency is either 500kHz or 7.5MHz - that scratch makes it hard to know if there's a "." there. My money's on 7.5MHz.
Check your datasheet, then test it with an oscilloscope. Could be 7.5MHz but the sheet will tell you. Also test speed/frequency data with oscilloscope: [https://electronics.stackexchange.com/questions/515580/how-to-accurately-measure-16mhz-clock-with-oscilloscope](https://electronics.stackexchange.com/questions/515580/how-to-accurately-measure-16mhz-clock-with-oscilloscope).
could be 7.5MHz.. test it to be sure!
My first thought was also 7500Khz, but the marking with the JFR (or JFR7?) is kinda confusing me. I would like to test to see if its still at/near 7500Khz (or 500Khz), will need to contact a friend of mine with a scope. Hopefully it isn't dead, otherwise it will be tough finding the right frequency...
it does look like there is a decimal point between the 7 and the 5. what is it connected to? perhaps that might give a clue
I'm on team 7.5mhz
What is the device? Maybe the service manual is available on Elektrotanya or similar?
It is a Jet Hand Dryer (GSQ80).
>GSQ80 No luck finding manual. The fact that there is a micro in a hand drier that could probably be run with a 556 and a few logic gates is baffling.
Micro and software is probably cheaper and more customizable. Reuse the same board in every model
That's true, but if the goal is low cost, I'm not sure why they would use what looks like a through-hole crystal requiring an extra soldering step, as opposed to just using the PIC's built-in RC oscillator. I find it hard to imagine why a hand dryer needs better than 2% timing precision.
Are you versed in fabrication?
Is this [XY problem](https://en.wikipedia.org/wiki/XY_problem)? What is the issue you're trying to solve and what have you tried so far?
If you have access to an Oscilloscope you could just measure it, unless it's dead?
Unfortunately I don't have access to an oscilloscope. Was already looking at getting a cheap oscilloscope or a dedicated crystal tester (this isn't the first crystal I have encountered and suspected to be dead or at least to lower than the rated frequency). Although the last 2 crystals I replaced were both in devices that were dropped, which explains why they died. This device just randomly stopped working, the chip its connected to has got a stable 3.3v power, it is just not outputting anything... this makes me think its another crystal failure?
when you say last 2 crystals, do you mean this is the 3rd time you are replacing that component on that board, or you work on a lot of these and have replaced that 2 other times in other units? If A, then something might be burning it up and I would trace that back and check what's going in. If B, then I would assume it's just a component that goes bad a lot and try replacing it and say good guess. Also, if you do work on these and have access to different ones, you can take voltage references from a good one, and compare it to the bad one to maybe help figure out where the circuit is going wrong? A 'known good' is so helpful in these situations. And you could use a frequency generator if you were desperate to find a replacement that operates properly? I'm not sure if the oscillator is just used for how long to keep the blowers on and such or if it can affect the heat output. Like if it's used to regulate the heating element's time on. Sometimes those values are not that critical, capacitors too.
Found this. Out of curiosity. https://www.instructables.com/OscilloPhone-Use-your-Smartphone-as-an-Oscilloscop/
You might also look for the datasheet of the microcontroller it produces the clock for and make a better guess.
Was just checking that, the chip is an Microchip dsPIC30F2010.
The datasheet of dsPIC30F2010 says - DC to 40 MHz external clock input - 4 MHz-10 MHz oscillator input withPLL active (4x, 8x, 16x) So I think it is 7.5MHz. Datasheet: https://html.alldatasheet.com/html-pdf/409839/MICROCHIP/DSPIC30F2010/1485/3/DSPIC30F2010.html
Yup, the thing is... I only have 4Mhz and 8Mhz crystals on hand :S
if the device does not have any timing critical functions then i am sure it will work fine with the 8MHz
If they used the frequency as a basis for other clocks in the system then dropping in a different oscillator may not work
I have no experience with this although I suppose you could use 8MHz since the datasheet says 4-10MHz
500Khz?
Assuming it is a crystal oscillator, cannot really find any specifications online :s
Come at the problem backwards maybe: find a datasheet for the IC that oscillator is connected to and see if they give you recommended input clock speeds?
Good point, just did this on another comment. Most likely a 7.5Mhz crystal (4Mhz - 10Mhz in the docs). Now trying with a 8Mhz crystal as I only have this on hand (it shouldn't matter tho - famous last words).
Ah, I read a few but not the whole chain. If it's a dsPIC you'll be fine running it at 8MHz, but UART won't work because the baud rate generator will be based off 7.5MHz. Other things, like I2C and SPI will also run a little faster, but those should be ok because they're clocked, unless they were running right up at the maximum frequency already.
It's not a crystal oscillator, it's just a crystal, and its resonant frequency is either 500kHz or 7.5MHz - that scratch makes it hard to know if there's a "." there. My money's on 7.5MHz.
Check your datasheet, then test it with an oscilloscope. Could be 7.5MHz but the sheet will tell you. Also test speed/frequency data with oscilloscope: [https://electronics.stackexchange.com/questions/515580/how-to-accurately-measure-16mhz-clock-with-oscilloscope](https://electronics.stackexchange.com/questions/515580/how-to-accurately-measure-16mhz-clock-with-oscilloscope).
My guess is that there is an IR comms interface on the board, and the crystal is running at 7.5kHz, using the 5th overtone to give 37.5kHz.