Looking for component list BOM for TDS544A oscilloscope - Page 1
Forum section: electronics / testgear

author: radioguy123
author_rank: Regular Contributor
timestamp: December 01, 2019, 05:58:33 pm
content: Looking for the BOM component list for the TDS544A Tektronix oscilloscope.Especially for the power supply.I found the TDS520B component level service manual. This DOES have the BOM.But that is the wrong version of power supply.I need the component list for the power supply that has Q9. possibly BU508A. Not absolutely certain of this.And there are thermistors RT4 and RT5 and I don't have a clue what these are.Also VR4 and VR5 I need part numbers for.Thanks if someone could help.

author: radioguy123
author_rank: Regular Contributor
timestamp: December 02, 2019, 02:37:28 pm
content: I know these are really old. But someone has to know what components are.thanks

author: Alfons
author_rank: Regular Contributor
timestamp: December 02, 2019, 03:57:17 pm
content: Maybe here:http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix.

author: AndyC_772
author_rank: Super Contributor
timestamp: December 02, 2019, 04:43:19 pm
content: I'm fairly sure no such documentation exists.That component service manual you have is an oddity. IIRC it was produced to meet a contractual requirement that Tek absolutelyhadto provide component level documentation for the 520B if they wanted to sell it to the US government.They never released it voluntarily, nor is there equivalent documentation for any other model in the TDS5/6/700 series range.

author: radioguy123
author_rank: Regular Contributor
timestamp: December 02, 2019, 05:04:34 pm
content: Hi Alfons and Andy.I know about the ko4bb site. I'm pretty sure I've downloaded all the stuff there.There just isn't any component types listed for my version of power supply.The power supplies I have are 620-0063-02 and 620-0063-04They both look fairly identical to me.They both have the Q9 transistor in the stand-by circuit. Also the RT4 and RT5 and the VR4 and VR5 show no part numbers.I am presuming the RT4,5 are some kind of current limiting thermistors ? and the VR4,5 look like a MOV or TVS device. It does mention 220v and 250v.Some of these parts are burnt beyond recognition so that doesn't help.I have found some threads where there is discussion about repairing this model of supply.A BU508 is mentioned for the transistor part number. But no one talks about the other parts.

author: nctnico
author_rank: Super Contributor
timestamp: December 02, 2019, 05:34:04 pm
content: I think there are some schematics floating around for various versions of these power supplies. However they are mostly the same (the components placement can be different) so by a little bit of tracing / reverse engineering you should be able to fix the PSU using the TDS520B service manual.

author: radioguy123
author_rank: Regular Contributor
timestamp: December 02, 2019, 06:05:24 pm
content: Hi nctnicoI know which version of power supply that I have.I have the schematic for that version.The problem is the part numbers for the parts I mention above are not on the schematic.I have the schematic and BOM for the other version of this supply.The parts I mention above are not on the other version that I have the BOM for.I know the transistor is a NPN. But I have no idea of the specs.I know there are thermistors and TVS devices but no clue of their characteristics.

author: nctnico
author_rank: Super Contributor
timestamp: December 02, 2019, 07:06:30 pm
content: Can you post a picture of the PSU and where these components are located? And post the schematic for the PSU you have (or a link to where the schematic can be found)?

author: andy3055
author_rank: Super Contributor
timestamp: December 02, 2019, 07:27:53 pm
content: Will this help?http://hakanh.com/dl/docs/hardtofind/TDS544A_A17-A19(PS).pdf

author: radioguy123
author_rank: Regular Contributor
timestamp: December 02, 2019, 08:55:09 pm
content: Andy yes that is the schematic. Except this one has some notes written on it. WOW !!!Even the TVS have a part number written there.The thermistors have something there too. But I can't seem to google them ?Thanks so much.

author: andy3055
author_rank: Super Contributor
timestamp: December 02, 2019, 09:07:16 pm
content: Glad it helps you.

author: siggi
author_rank: Regular Contributor
timestamp: December 29, 2019, 10:23:11 pm
content: When you replace the BU508A, make sure to check and replace C17. It sees a pretty high ripple current, and when it goes high-ESR, the transtor's on-time runs away. This tends to burn out the TVSes and then shortly the switching transistor is gonsky too.