Siglent SDG1025 Ribbon cable connector (TCXO Upgrade) ? - Page 1
Forum section: electronics / repair

author: JohnPi
author_rank: Regular Contributor
timestamp: August 04, 2018, 02:41:39 am
content: I want to replace the standard 25 MHz XTAL with a TCXO one in my Siglent ARB (there's marked location on the PCB). However I can't figure how to disconnect the 2 ribbon cables on the main board -- see photo.Do I just pull on the cable ? Does the small white flap along the edge fold down ? does it lift up ?Any guidance would be appreciated.

author: pigrew
author_rank: Frequent Contributor
timestamp: August 04, 2018, 02:47:27 am
content: For the smaller connector, the black part will move, either folding down or pulling up. It shouldn't take much force to pull up the ribbon.EDIT: For the other connector, they put silicone over it to prevent it from being unlatched. You'll have to removed the silicone, and it looks like it uses the same black mechanism to release the FFC

author: tautech
author_rank: Super Contributor
timestamp: August 04, 2018, 02:54:15 am
content: Remove the white silastic from the socket to allow you to lift the retaining tabs to release the ribbon cable.EditThe rear black tabs are the locking mechanism, lift each end to release the ribbon cable.Reinsertion is the reverse.Later units now have a silkscreen line to indicate correct insertion depth. Maybe add a line with a Sharpie to indicate when it's fully inserted.

author: JohnPi
author_rank: Regular Contributor
timestamp: August 04, 2018, 05:22:56 am
content: Thanks -- I pulled off the smaller cable, but the silastic was hard to remove from the larger one, so I left it. With just the smaller one removed there is enough leeway to get the board in a position to solder in the new TCXO ($11 on eBay). A slight problem as it wouldn't power up the 1st time -- the new TCXO's GND wasn't properly soldered.It all works now (original was 25 000 2xx Hz, this is 25 000 003.x (drifts ~ 0.2 Hz as it stabilizes).

author: sanman
author_rank: Contributor
timestamp: August 04, 2018, 04:26:05 pm
content: Cool. Would you share a link to the TCXO you ordered from eBay?

author: pigrew
author_rank: Frequent Contributor
timestamp: August 04, 2018, 04:55:33 pm
content: Not that I have this unit, but could you also mention what the original TCXO/OCXO was? Did it output sine or square? Voltage? voltage control or disable pin?

author: JohnPi
author_rank: Regular Contributor
timestamp: August 04, 2018, 08:21:44 pm
content: The original was a just a single 2-pin packaged XTAL -- this replaces this with a packaged XTAL TCXO (temperature compensated crystal oscillator). Looks like it is now $0.20 lower cost ! --https://www.ebay.com/itm/1PC-10m-TCXO-TCXO-10MHZ-precision-0-1PPM-10-000MHZ/131687374769?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D53209%26meid%3Dece4d236f37b4c54b452fb9c8351ad1a%26pid%3D100623%26rk%3D2%26rkt%3D5%26mehot%3Dag%26sd%3D131687372050%26itm%3D131687374769&_trksid=p2047675.c100623.m-1I think the pinout on all these is standard. There is a marked spot with solder pads & holes for this on the PCB -- you just remove the existing 2-pin 25 MHz, install this and add a wire from the output to the old XTAL location. my old one was 25 MHz + 200 Hz; new one is 25 M + 2 Hz. Also appears to be more stable after power up (total < 1 Hz drift overnight). The old XTAL wouldn't come off with just a heat gun (there might have been some glue also) -- I had to use a soldering iron and loosen up each wire individually.I think it's a square wave (didn't check). It drives the old location via a 12 ohm (R213) on the board.

author: tautech
author_rank: Super Contributor
timestamp: August 04, 2018, 08:45:43 pm
content: Just a little note about the sealant on the ribbon cable socket locking tabs.I've never seen it (that I can remember) in Siglent equipment and these days they add a piece of fabric tape to hold the ribbon cable in from accidental disconnection.The risk of slipping and damaging traces with a scalpel or other sharp blade when cutting the sealant away is high so the tape they use now is a better solution.

author: pigrew
author_rank: Frequent Contributor
timestamp: August 04, 2018, 08:51:07 pm
content: Ah, I see what you did. I didn't realize it had been a XTAL.You may want to also remove the two load capacitors (C190 + C18?) and resistors ( R60+R61) that were required for the XTAL. They're now loading your TCXO, which isn't a good thing. My guess it that they are around 30 pF which is likely nearing the "absolute maximum" of your TCXO.It almost looks like the flywire is not needed. R213 may connect the TCXO output to the processor.

author: JohnPi
author_rank: Regular Contributor
timestamp: August 04, 2018, 09:46:29 pm
content: This isn't my idea -- it's around the web. I don't have a schematic, so I'm not sure what's connected to what. I did check and the 12R is not connected to the XTAL, so the flywire seems needed.Those R,C appear to be connected to the original XTAL, but the caps look like ceramics (I didn't try to measure). R60 (marked 01A -- what's that notation ?) is 100R, R61 (marked 01E) is ~ 700k (inverter bias ?). I'm not really worried about overstressing the TCXO.Does anyone have a schematic of this area ?

author: tautech
author_rank: Super Contributor
timestamp: August 04, 2018, 10:05:25 pm
content: Quote from: JohnPi on August 04, 2018, 09:46:29 pmNot a schematic but some searches around the forum for SDG1025 TCXO find numerous mentions and many stem from posts by Katie Wass. Unfortunately her vid seems no longer available.https://www.eevblog.com/forum/testgear/siglent-sdg1025-arbitraryfunction-generator-under-some-tests/msg852290/#msg852290This one confirms the jumper wire is needed.

author: JohnPi
author_rank: Regular Contributor
timestamp: August 04, 2018, 10:08:37 pm
content: @Tautech -- Since you're a distributor -- do you know if Siglent ever released an ethernet (LAN) or GPIB version of this ? Most of the ICs appear populated on the board -- is it possible that I could get LAN functionality by adding an ethernet jack (where ?).

author: tautech
author_rank: Super Contributor
timestamp: August 04, 2018, 10:30:49 pm
content: Quote from: JohnPi on August 04, 2018, 10:08:37 pmNah, LAN was only added into the later X model AWG's.GPIB can be achieved with Siglent's USB dongle although it only comes with a USB A plugso can only be used in the front USB socket.Forgot to add link:https://www.siglentamerica.com/accessory/usb-gpib-adapter/

author: JohnPi
author_rank: Regular Contributor
timestamp: August 05, 2018, 06:50:27 pm
content: FYI -- I noticed Ch1 behaving strangely after my TCXO upgrade -- output amplitude wouldn't change for settings between 2.0 and 3.0 Vpp, then would jump to the 3 V value, then again no change until I set to 4 V. I rebooted -- no difference. I then ran the self-cal which appears to have fixed it. Not sure if/how this could be related to the TCXO upgrade.