oscillator not running on micro - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: September 16, 2025, 06:38:43 pm
content: Hi,I have a piece of audio gear, schematics not available, that stopped producing a digital output clock and now isn't operating. The gear is very involved as it does format conversions. I checked the 12Mhz crystal on the micro, it is boxed, not a metal can, and it isn't running. It has the proper voltage on both pins and I verified it against another of the same units. Before I put a crystal in it, I'm wondering if anything else could cause the crystal to not oscillate?I've not seen this before, usually crystals run just about forever without impact. It doesn't have loading caps on it. The crystal is a small blue box, about 2x8x8mm high. I can get another unit for about $60 shipped. These days the shipping of small parts would probably cost me $15 total at Mouser, maybe I can order one from eBay for cheap, but considering I can get another box for not that much more, and be assured it works (this could have some other funky problem), I'm debating ordering the crystal. OK, I'm cheap.ThanksJerry

author: golden_labels
author_rank: Super Contributor
timestamp: September 16, 2025, 07:50:00 pm
content: Does it have 2 or 4 pins? If 4, it’s a complete crystal oscillator. Thosecontain a complete circuitgenerating a clock signal. Unlike crystals (crystal resonators), which are just a piece of crystal with 2 pins.If that’s correct, $60 sounds like way too much. Unless this is some highly specialized, high accuracy, ultra low drift element. Typical ones go for about a dollar.

author: wraper
author_rank: Unknown
timestamp: September 16, 2025, 08:02:43 pm
content: IC being dead is more likely that crystal itself. Bear in mind that probing the crystal can disrupt oscillation too.QuoteI think he meant $60 for another device.

author: cncjerry
author_rank: Unknown
timestamp: September 16, 2025, 08:24:16 pm
content: the device has two-pins, marked what looks like "ON I" or "ON 1" and 12000C, could be a "QN", hard to see. For grins, I soldered on a 10Mhz crystal and the micro came alive. So the oscillator has failed and I guess I'll just try to order something like it. Since the 10Mhz crystal seems to be oscillating OK, and the device can use an external clock, it will probably run with the 10Mhz crystal on it, but I'll find another. A 12Mhz crystal (metal can) looks like it would work, but usually they have loading caps on them, so I don't know if maybe I'm just lucky.Thanks for the input.Jerryp.s. The device that failed is a tascam if-ae8. They can be had for $40 plus shipping now, probably about $1K orignal price 30yrs ago.

author: golden_labels
author_rank: Super Contributor
timestamp: September 16, 2025, 09:51:07 pm
content: With 2 pins it must be some kind of a resonator. The package and markings resemble ones used by many ceramic resonators. The logo is that of Matsushita and their portfolio includes ceramic resonators, so everything seems to agree. Since they’re of low accuracy, you should be able to replace them with anything that works.However, check microcontroller’s docs to see if they can be drive a crystal resonator directly, if there are any external capacitors required, and — if yes — what values are preferred.

author: cncjerry
author_rank: Unknown
timestamp: September 17, 2025, 12:28:23 am
content: if it is a ceramic resonator, they would have three pins, no? I guess there could be three pins under it, can't see without removing the PCB. I'm going to try to get under it.Thanks

author: wraper
author_rank: Unknown
timestamp: September 17, 2025, 12:50:20 am
content: Quote from: cncjerry on September 17, 2025, 12:28:23 amUsually they have 3 pins. But 2 pin ceramic resonators exist too.

author: golden_labels
author_rank: Super Contributor
timestamp: September 17, 2025, 03:59:20 am
content: See Yuechung International Corp’s (YIC)ZTB series ceramic resonator (THT version, at the bottom)as a specific example of a 2-pin kind. They also use a similar style of a package, though their markings don’t follow the common value-in-kHz convention.

author: cncjerry
author_rank: Unknown
timestamp: September 17, 2025, 06:42:24 am
content: It's a lot of work to get the PCB out. I thought about milling a hole under the resonator...It could be a three-pin with a center ground and integrated loading caps. I read some data sheets today and I see where some ceramic resonators have integrated caps. If only resonator component opened and the caps are still OK, then maybe that is why my crystal starts and oscillates OK.Given that it is working with the 10Mhz, I think I am just going to purchase a 12Mhz crystal and solder it in like I did with the 10Mhz. I haven't tried recording with the it yet, but I can use an external word clock to keep it all synced, assuming the NEC micro processor creates the clock because I don't see any other crystals or resonators.If I found the actual device for sale, I looked all over for Matsushita resonators, but it could be 30yrs out of production as this was made in the 90's. I am amazed at how some of this old gear still works. I have Betamax tape decks used for an old digital recording setup that still work perfectly and they were made in the 80's.Thanks for looking.Jerry

author: coromonadalix
author_rank: Super Contributor
timestamp: September 17, 2025, 02:10:10 pm
content: if like the picture its a 2 wirepossible cause crystal osc by itself became bad, the added capacitors on its leg are not enough to make it oscillate too high or low values, physical damages, open circuiteven saw at one time putting scope probes would make it oscillate,we see the picture 12Mhz white squared one, normally you need to remove it if you try other oscillator, but you can or could have capacitance effects, or even the micro who's bad in some waysand changing it for the metal one could be problematic for the capacitors, try to get the mcu datasheets, it will tell you the basic values, at some point you could have one of the pins who act as frequency input to clock the cpu ... if say as written you have a 4 legged crystal can / block ... in some cases with an external generator you can stimulate the mcu / cpunormally the mcu has 2 pins dedicated for the 2 pins crystalsince it works with 10 Mhz finding a 12Mhz should not be too hard, if you have some scrap boards or old stuff with mcu you could be lucky ? ordered many std values 4 8 10 12 24 Mhz crystals on ebay and aliexpress so far no problems, just the waiting time ....normally with a 10Mhz instead of 12Mhz any time related stuff / functions / timers would or could be affected, external controls with time base ? unless the mechanism too need a correct clock source (witch i never saw) ? else should work okay