Re: [time-nuts] VCXO in a watch timing machine
HI John, Did you ever resolve this? I am curious if adjusting the VCXO to exactly 18,000,000 Hz correctly shows the gain/loss of a watch? I'm buying a MTG 1900 that has exactly the same VCXO and the same adjustment Cheers, Ingo ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
Ed,
Interesting point, I hadn't considered that the frequency should be off !
{32768
x 550 = 18,022,400.000} So, maybe it has drifted the other way ?
However, looking at the Witschi web site suggest that their instruments sense by
picking up audio or vibration via some kind of sensor as they talk about
checking
motors and buzzer noise from the watch. That being the case it is more likely
the 18 MHz should be right on frequency.
Well, unless we hear back from the guy and he answers questions put to him, we
really won't know whats up.
BillWB6BNQ
Ed Breya wrote:
How do you know that the frequency range is incorrect for the function?
Assuming this is for calibration of wristwatches, maybe the idea is to
set them to some nominal value at room temperature, then expect them to
drift to the right frequency at skin temperature or so. There would
have to then be some relationship between the approximately 18 MHz and
the ideal 32,768 Hz watch crystal frequency.
If the idea is to divide the 18 MHz down to an accurate version of 50/60
Hz or 1 Hz, then yes, it looks like something's wrong. But, does it need
to be a VCXO, or just settable to the right frequency? I believe that
18.00 MHz is a standard frequency for VCXOs and TCXOs, so readily
available from typical vendors, or you could build an oscillator as good
as needed. The package dimensions seem like a standard 14 pin (only 4
are used) DIP style - very common.
I think most of those modules use a limited tuning voltage range like
0-5 V if the supply is +5 V. If you haven't already, check to be sure
the full tuning voltage range is covered at the module. You can usually
get a little higher frequency by exceeding the tuning voltage -
especially if there's nothing to lose anyway if it's damaged - but
unfortunately it's hard to get lower frequency since the varicap diode
will reach zero or forward bias if you go very far the other way.
Also, if the supply voltage is off, it could have drastic effects on
operation. Changing the supply voltage a little can affect the frequency
and tuning range, so this is another option for slight adjustment - but
may give unpredictable results.
Ed
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
Hi Some very good questions - thanks for the responses. No schematic (or documentation of any description - Ebay purchase), but I've done some dismantling and had a poke around with a multimeter. This is what I find: The power supply provides +5.2V and +/-6V. Strangely, the silkscreen on the board power connector says +5V, +8V, -8V and -24V. The power supply has no components or wires for this latter voltage, so that's a bit of a mystery. The -24V rail disappears off into some components, so maybe it's an 'option' on another model? Anyway, let's not get sidetracked. The 1k pot is sandwiched between two 3k resistors (surface mounted on the back, so not immediately obvious). I get 0V - 2.2V - 3V - 5.2V, so only 0.8V adjustment range. The lower the voltage, the lower the frequency, and vice versa, so I could just short the resistor that's connected between ground and the pot? Modern mechanical watches are relatively impervious to changes in temperature - balance springs and balances are made from materials which are much better in that regard than their carbon steel forbears, which required split bi-metallic balances to compensate. I agree that 18MHz does seem an odd number. The counter can work with watches that beat at 5, 5.5, 6, 7, 8 and 10Hz so you'd think it would relate to those in some integer way. Regards John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
Hi I suspect the 18 MHz is simply the clock to a CPU chip. Cheap CPU + code is more cost effective than a bunch of random logic. If the gizmo works that, there's a microphone picking up the ticking and the CPU does DSP to figure out what's going on. Bob On Feb 5, 2013, at 6:18 AM, john j...@ic0n.org.uk wrote: Hi Some very good questions - thanks for the responses. No schematic (or documentation of any description - Ebay purchase), but I've done some dismantling and had a poke around with a multimeter. This is what I find: The power supply provides +5.2V and +/-6V. Strangely, the silkscreen on the board power connector says +5V, +8V, -8V and -24V. The power supply has no components or wires for this latter voltage, so that's a bit of a mystery. The -24V rail disappears off into some components, so maybe it's an 'option' on another model? Anyway, let's not get sidetracked. The 1k pot is sandwiched between two 3k resistors (surface mounted on the back, so not immediately obvious). I get 0V - 2.2V - 3V - 5.2V, so only 0.8V adjustment range. The lower the voltage, the lower the frequency, and vice versa, so I could just short the resistor that's connected between ground and the pot? Modern mechanical watches are relatively impervious to changes in temperature - balance springs and balances are made from materials which are much better in that regard than their carbon steel forbears, which required split bi-metallic balances to compensate. I agree that 18MHz does seem an odd number. The counter can work with watches that beat at 5, 5.5, 6, 7, 8 and 10Hz so you'd think it would relate to those in some integer way. Regards John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
Hi John, OK ! It is good that the other resistors were there. It is also good that a lower EFC voltage lowers the frequency. I am not sure what standard values are available to you in the UK. I picked a standard value in the US that would roughly center the pot's range equally around 2.1 volts. So, I would suggest paralleling a 5.1K 1% metal film resistor across the lower 3K resistor. Attaching from the bottom of the pot to that resistor string's ground point would probably be easier then trying to attach directly across the SMT 3K resistor. The 5.1K added resistor puts the bottom resistance value at 1888.9 Ohms. The whole string would nominally be 5888.89 Ohms and ups the current in the string from 0.743 ma to 0.883 ma. A small change and should not be a problem as to power dissipation in the upper 3K. The voltage at the bottom of the pot should be near 1.67 volts and the top of the pot should be near 2.55 volts. That should place the range so that the VCXo goes below 18 MHz. If not then select the next lower standard value. Try to obtain 1% metal film at 1/8 watt or second best carbon film at the same ratings. Do not use the OLD carbon composition type resistors. As Bob points out and I also agree, if your unit looks like the type I saw on the web site, then the 18 MHz oscillator most likely runs the computer system. That does not necessarily mean it is also the clock that is clocking the A/D that is digitizing the sound. So, varying the 18 MHz may not change your results. The important clock, for accuracy, is the one that clocks the A/D inside your unit. Time will tell. After you add that resistor and then readjust the 18 MHz based upon your counter, you will know if the watch is on time the next day. If not then it will require further study of the circuitry. Good luck, BillWB6BNQ john wrote: Hi Some very good questions - thanks for the responses. No schematic (or documentation of any description - Ebay purchase), but I've done some dismantling and had a poke around with a multimeter. This is what I find: The power supply provides +5.2V and +/-6V. Strangely, the silkscreen on the board power connector says +5V, +8V, -8V and -24V. The power supply has no components or wires for this latter voltage, so that's a bit of a mystery. The -24V rail disappears off into some components, so maybe it's an 'option' on another model? Anyway, let's not get sidetracked. The 1k pot is sandwiched between two 3k resistors (surface mounted on the back, so not immediately obvious). I get 0V - 2.2V - 3V - 5.2V, so only 0.8V adjustment range. The lower the voltage, the lower the frequency, and vice versa, so I could just short the resistor that's connected between ground and the pot? Modern mechanical watches are relatively impervious to changes in temperature - balance springs and balances are made from materials which are much better in that regard than their carbon steel forbears, which required split bi-metallic balances to compensate. I agree that 18MHz does seem an odd number. The counter can work with watches that beat at 5, 5.5, 6, 7, 8 and 10Hz so you'd think it would relate to those in some integer way. Regards John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
Hi Bill I've just checked - the oscillator does indeed go to the XTAL pins of the Philips microcontroller. The crystal I thought was for the mc turns out to be for the LCD display controller. I'll have a rummage for some resistors. Thanks John On Tue, 05 Feb 2013 05:20:48 -0800, WB6BNQ wrote: Hi John, OK ! It is good that the other resistors were there. It is also good that a lower EFC voltage lowers the frequency. I am not sure what standard values are available to you in the UK. I picked a standard value in the US that would roughly center the pot's range equally around 2.1 volts. So, I would suggest paralleling a 5.1K 1% metal film resistor across the lower 3K resistor. Attaching from the bottom of the pot to that resistor string's ground point would probably be easier then trying to attach directly across the SMT 3K resistor. The 5.1K added resistor puts the bottom resistance value at 1888.9 Ohms. The whole string would nominally be 5888.89 Ohms and ups the current in the string from 0.743 ma to 0.883 ma. A small change and should not be a problem as to power dissipation in the upper 3K. The voltage at the bottom of the pot should be near 1.67 volts and the top of the pot should be near 2.55 volts. That should place the range so that the VCXo goes below 18 MHz. If not then select the next lower standard value. Try to obtain 1% metal film at 1/8 watt or second best carbon film at the same ratings. Do not use the OLD carbon composition type resistors. As Bob points out and I also agree, if your unit looks like the type I saw on the web site, then the 18 MHz oscillator most likely runs the computer system. That does not necessarily mean it is also the clock that is clocking the A/D that is digitizing the sound. So, varying the 18 MHz may not change your results. The important clock, for accuracy, is the one that clocks the A/D inside your unit. Time will tell. After you add that resistor and then readjust the 18 MHz based upon your counter, you will know if the watch is on time the next day. If not then it will require further study of the circuitry. Good luck, BillWB6BNQ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
Have you actually tried to 'beat' a watch. Most of these devices use a audio pickup and sense the mechanical impulse from the drive system. They then indicate whether the watch is fast or slow I have one which uses the sound card to do the dsp and the secret sauce is the pickup and amplifier. Yes I work on clocks when I have time I would not assume the VCXO is out of spec unless you have a known good unit to compare against. Encouraging pirate manufacturers by buying their product is another topic for another time. If you had purchased a used unit you would have been able to get support for it. Sent from my iPhone On Feb 5, 2013, at 11:38 AM, john j...@ic0n.org.uk wrote: Hi Bill I've just checked - the oscillator does indeed go to the XTAL pins of the Philips microcontroller. The crystal I thought was for the mc turns out to be for the LCD display controller. I'll have a rummage for some resistors. Thanks John On Tue, 05 Feb 2013 05:20:48 -0800, WB6BNQ wrote: Hi John, OK ! It is good that the other resistors were there. It is also good that a lower EFC voltage lowers the frequency. I am not sure what standard values are available to you in the UK. I picked a standard value in the US that would roughly center the pot's range equally around 2.1 volts. So, I would suggest paralleling a 5.1K 1% metal film resistor across the lower 3K resistor. Attaching from the bottom of the pot to that resistor string's ground point would probably be easier then trying to attach directly across the SMT 3K resistor. The 5.1K added resistor puts the bottom resistance value at 1888.9 Ohms. The whole string would nominally be 5888.89 Ohms and ups the current in the string from 0.743 ma to 0.883 ma. A small change and should not be a problem as to power dissipation in the upper 3K. The voltage at the bottom of the pot should be near 1.67 volts and the top of the pot should be near 2.55 volts. That should place the range so that the VCXo goes below 18 MHz. If not then select the next lower standard value. Try to obtain 1% metal film at 1/8 watt or second best carbon film at the same ratings. Do not use the OLD carbon composition type resistors. As Bob points out and I also agree, if your unit looks like the type I saw on the web site, then the 18 MHz oscillator most likely runs the computer system. That does not necessarily mean it is also the clock that is clocking the A/D that is digitizing the sound. So, varying the 18 MHz may not change your results. The important clock, for accuracy, is the one that clocks the A/D inside your unit. Time will tell. After you add that resistor and then readjust the 18 MHz based upon your counter, you will know if the watch is on time the next day. If not then it will require further study of the circuitry. Good luck, BillWB6BNQ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] VCXO in a watch timing machine
Hi I'm hoping to get some information on the VCXO that sits in my watch timing machine. The timer is a Chinese clone of a Witschi timer - the heart of the thing is an 18MHz VCXO marked 'SCTF 03'. There's a BNC socket that outputs the crystal frequency and a 1k pot to adjust the frequency. The snag is that I can only adjust the frequency between 18,002,359Hz and 18.000,958Hz. I have a Hewlett Packard and a Thurlby Thandar frequency counter which give me readings that broadly agree - I'm quoting the HP because I trust it more! The hardware frequency in my scope doesn't have the resolution at 18MHz, but agrees that it's fast.These figures translate to a maximum of 11.32s/day fast and a minimum of 4.63s/day fast. This is borne out in practice by the behaviour of watches - if I adjust them to 0s/day, then they are fast, but if I aim for -5s/day then they are about dot-on. So if my workings-out are correct, I can 'pull' the VCXO by 78ppm, which seems reasonable, but offset away from the nominal 18MHz. Is this a common failure of VCXOx? Can anything be done about it? The device is about 18.35mm long by 10.8mm wide (and 7.7mm high) - is this a standard size, and if so who would sell an 18MHz VCXO (UK)? Any advice gratefully received. Regards John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
Yes standard size this is a ABRACON - AOCJY1 from Newark , don't know if they stock 18 Mhz but you should be able to order one. First check power supply voltage and pin out. - Original Message - From: john j...@ic0n.org.uk To: time-nuts@febo.com Sent: Monday, February 04, 2013 5:10 PM Subject: [time-nuts] VCXO in a watch timing machine Hi I'm hoping to get some information on the VCXO that sits in my watch timing machine. The timer is a Chinese clone of a Witschi timer - the heart of the thing is an 18MHz VCXO marked 'SCTF 03'. There's a BNC socket that outputs the crystal frequency and a 1k pot to adjust the frequency. The snag is that I can only adjust the frequency between 18,002,359Hz and 18.000,958Hz. I have a Hewlett Packard and a Thurlby Thandar frequency counter which give me readings that broadly agree - I'm quoting the HP because I trust it more! The hardware frequency in my scope doesn't have the resolution at 18MHz, but agrees that it's fast.These figures translate to a maximum of 11.32s/day fast and a minimum of 4.63s/day fast. This is borne out in practice by the behaviour of watches - if I adjust them to 0s/day, then they are fast, but if I aim for -5s/day then they are about dot-on. So if my workings-out are correct, I can 'pull' the VCXO by 78ppm, which seems reasonable, but offset away from the nominal 18MHz. Is this a common failure of VCXOx? Can anything be done about it? The device is about 18.35mm long by 10.8mm wide (and 7.7mm high) - is this a standard size, and if so who would sell an 18MHz VCXO (UK)? Any advice gratefully received. Regards John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. attachment: ocxo.JPG___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
John; Are the voltages correct in the circuit? Perhaps something has drifted such that the control voltage range is incorrect? -- Joe Leikhim Leikhim and Associates Communications Consultants Oviedo, Florida jleik...@leikhim.com 407-982-0446 WWW.LEIKHIM.COM ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
Hi John, First question is do you have a schematic ? Second question: Is the 1K pot directly across the VCC to ground ? Or is it in the middle of a resistor string ? Normally, the EFC pin has a nominal center point that is around 1/2 of the VCC going to the VCXO module. Also, the EFC pin's input resistance is fairly high, in the order of around 50K. So it would seem unlikely that the 1K pot is all there is between VCC and ground. That would imply 5 ma of current flowing through the 1K pot, which seems a little high for the needed function. A typical current level would be more like 1 ma. So, before you go crazy changing out the VCXO check to see if the 1K pot is in a resistive string. If that is the case, then you could adjust one of the fixed resistors to put the pot range so that it covers above and below the 18 MHz mark. As previously mentioned, it would pay to measure some of the circuit parameters to make sure things seem proper. BillWB6BNQ john wrote: Hi I'm hoping to get some information on the VCXO that sits in my watch timing machine. The timer is a Chinese clone of a Witschi timer - the heart of the thing is an 18MHz VCXO marked 'SCTF 03'. There's a BNC socket that outputs the crystal frequency and a 1k pot to adjust the frequency. The snag is that I can only adjust the frequency between 18,002,359Hz and 18.000,958Hz. I have a Hewlett Packard and a Thurlby Thandar frequency counter which give me readings that broadly agree - I'm quoting the HP because I trust it more! The hardware frequency in my scope doesn't have the resolution at 18MHz, but agrees that it's fast.These figures translate to a maximum of 11.32s/day fast and a minimum of 4.63s/day fast. This is borne out in practice by the behaviour of watches - if I adjust them to 0s/day, then they are fast, but if I aim for -5s/day then they are about dot-on. So if my workings-out are correct, I can 'pull' the VCXO by 78ppm, which seems reasonable, but offset away from the nominal 18MHz. Is this a common failure of VCXOx? Can anything be done about it? The device is about 18.35mm long by 10.8mm wide (and 7.7mm high) - is this a standard size, and if so who would sell an 18MHz VCXO (UK)? Any advice gratefully received. Regards John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] VCXO in a watch timing machine
How do you know that the frequency range is incorrect for the function? Assuming this is for calibration of wristwatches, maybe the idea is to set them to some nominal value at room temperature, then expect them to drift to the right frequency at skin temperature or so. There would have to then be some relationship between the approximately 18 MHz and the ideal 32,768 Hz watch crystal frequency. If the idea is to divide the 18 MHz down to an accurate version of 50/60 Hz or 1 Hz, then yes, it looks like something's wrong. But, does it need to be a VCXO, or just settable to the right frequency? I believe that 18.00 MHz is a standard frequency for VCXOs and TCXOs, so readily available from typical vendors, or you could build an oscillator as good as needed. The package dimensions seem like a standard 14 pin (only 4 are used) DIP style - very common. I think most of those modules use a limited tuning voltage range like 0-5 V if the supply is +5 V. If you haven't already, check to be sure the full tuning voltage range is covered at the module. You can usually get a little higher frequency by exceeding the tuning voltage - especially if there's nothing to lose anyway if it's damaged - but unfortunately it's hard to get lower frequency since the varicap diode will reach zero or forward bias if you go very far the other way. Also, if the supply voltage is off, it could have drastic effects on operation. Changing the supply voltage a little can affect the frequency and tuning range, so this is another option for slight adjustment - but may give unpredictable results. Ed ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
