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#1 |
Badcaps Veteran
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![]() I picked up an old school Timex T121 desk clock from a garage sale. It runs fast, it picks up about a minute or 2 minutes a week.
I wanted to see if there was some sort of crystal or something I could replace that would correct that. I opened it up, however I don't see any type of crystal on the board, although truth be told I am not sure what I am looking for. The only thing that looks like a crystal is a small silver cylindrical component, but that is on the LCD board, not the main board, so I don't think that has anything to do with keeping the time. I know some old digital clocks ran off counting the signal of your mains voltage vs using a crystal, how can I tell if this is that sort of clock and if so can it be adjusted? And from my understanding those types of clocks there only are off a few seconds a month. Pics of both sides of the main board and the back side of the LCD board (still in the housing) Last edited by Per Hansson; 07-01-2022 at 11:22 AM.. Reason: Offsite images uploaded |
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#2 |
Great Sage 齊天大聖
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![]() does the metal cylinder say 32.768 on it?
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#3 |
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![]() I can't see much pics are thumbnails?
I find the crystal tuning is done wrong and they run fast, these 3V clocks. The loading caps are important and how fast they run changes with battery voltage too, I think it's worse with older batteries. Probably a tuning fork crystal 32.768kHz can be pulled and swapped out. |
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#4 |
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![]() I uploaded the pictures here, now they are big instead of a 100 pixel thumbnail!
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"The one who says it cannot be done should never interrupt the one who is doing it." |
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#5 |
Badcaps Veteran
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![]() Ahh much better pics
![]() The other side of the board with the crystal, would have to see a pic for what tuning caps if any are there. |
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#6 | ||
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![]() Quote:
Quote:
One thing I realized, the internet tells me some of these older clocks work off the phase of the mains voltage, I had this plugged into a battery powered UPS, maybe that was throwing that off? I unplugged it and plugged it into a wall outlet and it seems fine so far although its only been a day |
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#7 |
Badcaps Veteran
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![]() Unless you are going to the battery pack continuously which could explain the situation to why maybe running fast
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9 PC LCD Monitor 6 LCD Flat Screen TV 30 Desk Top Switching Power Supply 10 Battery Charger Switching Power Supply for Power Tool 6 18v Lithium Battery Power Boards for Tool Battery Packs 1 XBox 360 Switching Power Supply and M Board 25 Servo Drives 220/460 3 Phase 6 De-soldering Station Switching Power Supply 1 Power Supply 1 Dell Mother Board 15 Computer Power Supply 1 HP Printer Supply & Control Board * lighting finished it * These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10% 1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later ) 2 Hem Saw Computer Stack Board All of these had ![]() All of the mosfet that are taken out by bad caps ![]() |
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#8 |
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![]() The UPS must have been it, ever since it's been plugged into the wall it is keeping accurate time (so far at least)
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#9 |
Badcaps Veteran
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![]() Not all UPS have a pure sign wave most of them probably have modify sign wave inverter this might be the issue
I have a clock that is also plugged into a UPS power supply and it also runs a minute faster but does not seem to run faster than this over time however if this clock does not see power from the outlet it runs slow and the longer it off line the slower it runs and this is with a fresh 9 volt battery Last edited by sam_sam_sam; 07-04-2022 at 05:35 PM.. |
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#10 |
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![]() Only makes sense if the UPS detects a problem and turns the inverter on. Other than that it kicks in the AVR a first. My guess is the power supply.
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#11 |
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![]() Still keeping accurate time when plugged into the wall, so must have been the UPS impacting the sine wave.
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#12 |
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![]() Well that’s the thing… a normal ups is in bypass mode during normal operation. All there is for protection are a bunch of MOV’s.
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#13 | |
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![]() Quote:
I live in area that especially in the summertime in past years it would go to battery back at least a dozen times a day and sometimes more often than this but this has improved in the last couple of years and it not as much of a problem as it use to be I would buy cheaper ups battery backup that did not have line conditioning and I had several devices go bad from this of ups so if have expensive equipment I look for ups that have line conditioning and I have had better experiences Last edited by sam_sam_sam; 07-08-2022 at 04:10 PM.. |
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