'X' tagged component on PCB  - Page 1
Forum section: electronics / beginners

author: Birstall
author_rank: Contributor
timestamp: January 18, 2018, 06:52:06 pm
content: I have a Radio Shack 22-803 c 1995. which was working fine until I took the back off of it and found a bent part and when I straightened it, it fell off and was lost.The item was a very small cylinder and was soldered to the PCB with two wires. See attached photo. I have a new DMM on it's way but since I am trying to learn electronics, I thought that I should be able to make this simple repair If I knew what the heck it was.The LCD now flashes random numbers.Your advice would be much appreciated.TIA

author: Mukrakiish
author_rank: Contributor
timestamp: January 18, 2018, 06:58:32 pm
content: Judging by the little pad space and that it was soldered on in a different way than most components, I'd wager it was a crystal for oscillating. It is most likely used for the micro buried beneath the epoxy glob there. Someone with more knowledge will chime in with a more thorough answer though.It would be a simple fix I suspect as long as you get the equivalent crystal put back on.

author: sevenofnine33
author_rank: Contributor
timestamp: January 18, 2018, 07:10:19 pm
content: It was definitely a crystal oscillator. They are marked with the letter x when making a pcb.Did it look like this:https://www.elprocus.com/wp-content/uploads/2016/04/Crystal-Oscillator.jpgorhttp://www.component7.com/image/cache/catalog/product/passive_component/32.768%20KHZ%20Quartz%20Crystal%20-TC38-800x800.jpgUnfortunately, you can't change it with some other random oscillator. It must have the same frequency as the original oscillator.Best thing you could do is either find the schematic of the circuit or find the missing component so you can read what was it's frequency.

author: Birstall
author_rank: Contributor
timestamp: January 18, 2018, 07:12:20 pm
content: Thanks to both of you for replying. It didn't look like either one of those photos. I'd guess it was about 5mm long and maybe 1.5 mm in diameter.It did resemble a miniature capacitor with the two wires were coming out of the bottom of the component. It was made of unpainted metal

author: sevenofnine33
author_rank: Contributor
timestamp: January 18, 2018, 07:14:34 pm
content: Check out the other image I attached. Was it that?

author: Birstall
author_rank: Contributor
timestamp: January 18, 2018, 07:17:40 pm
content: Yes that's it. Thanks so much. I guess I need to find someone with the same MM or find a schematic.

author: AndyC_772
author_rank: Super Contributor
timestamp: January 18, 2018, 07:31:22 pm
content: Does the product have a real time clock? If so, it's almost certainly a 32.768 kHz watch crystal, and you can probably get away with replacing it with almost any watch crystal that has the same frequency.

author: Birstall
author_rank: Contributor
timestamp: January 18, 2018, 07:38:33 pm
content: If you mean real time clock as in telling the time, the answer is no. If there is some other 'clocking' activity, I have no idea.It's a very simple Auto Range DMM with auto power off which I suppose requires some kind of timing.

author: james_s
author_rank: Super Contributor
timestamp: January 19, 2018, 12:35:55 am
content: It was probably a common 32.768kHz crystal, those were used in tons of things simply because being mass produced for quartz clocks they were cheap and readily available.Likewise the 3.679MHz colorburst crystals show up in all sorts of stuff that has nothing at all to do with NTSC or even TV, again because they were made in huge quantities and are cheap.When one needs a stable clock source and the absolute frequency is not critical it makes sense to use something that's cheap.

author: wraper
author_rank: Unknown
timestamp: January 19, 2018, 12:46:28 am
content: I would try 4 MHz crystal,as it what I usually have seen in various tuners with PLL.

author: james_s
author_rank: Super Contributor
timestamp: January 19, 2018, 12:48:31 am
content: 4 MHz in a multimeter? I highly doubt it, there's no need for anywhere near that high a frequency, it would only increase power draw. I'd bet money on 32kHz.

author: wraper
author_rank: Unknown
timestamp: January 19, 2018, 12:51:52 am
content: Quote from: Birstall on January 18, 2018, 06:52:06 pmFYI such crystals are bent to be lying in parallel with PCB in 99% of cases. In this case legs were not even bent, they were just soldered onto pads, without going through any holes.

author: wraper
author_rank: Unknown
timestamp: January 19, 2018, 12:57:30 am
content: Quote from: james_s on January 19, 2018, 12:48:31 amFor some reason I thought it was radio,LOL. However IIRC some cheap multimetrs had 4MHz crystal or maybe some similar value. Certainly not 32kHz.

author: Birstall
author_rank: Contributor
timestamp: January 19, 2018, 02:27:36 am
content: Thanks for your input. I have decided to order some 32kHz crystal oscillators and will give them a try. If they don't work well it was fun trying.I want to thank you all for your help and education, I know a lot more than I did before I posted.

author: amyk
author_rank: Super Contributor
timestamp: January 19, 2018, 03:08:00 am
content: That footprint is almost certainly 32k crystal. Higher frequency crystals tend to have a different arrangement.

author: Signal32
author_rank: Frequent Contributor
timestamp: January 19, 2018, 03:58:01 am
content: Quote from: amyk on January 19, 2018, 03:08:00 amNot necesarelly:https://www.aliexpress.com/item/10PCS-LOT-12MHZ-12-000MHZ-4MHZ-6MHZ-8MHZ-11-0592MHZ-16MHZ-24MHZ-Passive-DIP-crystal-oscillator/32786751729.htmlIt seems they can go up to 110592MHZ O.o

author: wraper
author_rank: Unknown
timestamp: January 19, 2018, 08:33:38 am
content: Quote from: Birstall on January 19, 2018, 02:27:36 amI bet it won't work. If you get crystal in MHz range, it will at least somewhat work. Probably too slow/fast or with some other issues but still.

author: cowana
author_rank: Frequent Contributor
timestamp: January 19, 2018, 10:49:11 am
content: Quote from: Signal32 on January 19, 2018, 03:58:01 amThat's 11.0592MHz (commonly used for 8051s to get easily create standard serial baud rates)

author: SL4P
author_rank: Super Contributor
timestamp: January 19, 2018, 11:21:52 am
content: Can we just cover a couple of academic points...a) it’s highly unlikely to be a crystal *oscillator*... yes it’s probably a crystal without the supporting components placed around it on the pcb.b) as a newbie, don’t overheat the crystal when soldering, as it is feasible to permanently pull the crystal ‘off frequency’.ok, pedantry mode off, i can now enjoy the weekend.

author: Birstall
author_rank: Contributor
timestamp: January 19, 2018, 01:13:56 pm
content: Thanks I'll be careful, I do own a reasonably good soldering iron so I can moderate the heat.I'm a bit confused as to what this crystal does in the circuit of a multimeter.

author: amyk
author_rank: Super Contributor
timestamp: January 20, 2018, 01:50:52 am
content: Integration-based ADCs need a timing reference.

author: Birstall
author_rank: Contributor
timestamp: February 17, 2018, 04:55:11 pm
content: Just an update, I received the crystals and the DMM is now working perfectly. Thanks for everyones help.

author: james_s
author_rank: Super Contributor
timestamp: February 22, 2018, 10:00:55 pm
content: Glad you got it working.Like I said, these 32kHz crystals are common. All you need in a multimeter is a clock for the DAC and something to drive multiplexing of the display, there is usually no microcontroller in the older ones. Using a crystal in the MHz range just means you use more power and have to add more stages to the counter that divides it down to what's needed by the various parts of the circuit.