Motorola U8344 U8338. Who knows these guys?  - Page 1
Forum section: electronics / repair

author: galbip
author_rank: Newbie
timestamp: April 13, 2020, 11:22:58 am
content: Hi guys, I'm trying to repair a old linear power supply I build at school 30 years ago....I couldn't find any reference to the two TO-3 power devices.One is markedU8344the otherU8338 Aboth components have Motorola logo.Can someone help me?Thank you

author: tunk
author_rank: Super Contributor
timestamp: April 13, 2020, 11:29:10 am
content: Maybe they are date codes?

author: galbip
author_rank: Newbie
timestamp: April 13, 2020, 11:36:15 am
content: I have attached a picure.They both report K75MEX, perhaps is the foundry reference

author: picburner
author_rank: Frequent Contributor
timestamp: April 13, 2020, 12:11:53 pm
content: In fact the correct name is "K75MEX", the other numbers are datecodes as tunk rightly told you.There is no datasheet on the net, only some sites (like Aliexpress) that sell it.Based on the characteristics of the power supply, try to find a replacement if they are broken.

author: amyk
author_rank: Super Contributor
timestamp: April 13, 2020, 01:24:58 pm
content: https://www.eevblog.com/forum/chat/help-finding-specs-for-transistor-u8425/Suspiciously similar...

author: gorge441
author_rank: Contributor
timestamp: April 13, 2020, 03:47:30 pm
content: I guess you already got whats you want to know.Anyway, It is a data code and the RCA databook will help you to find.

author: galbip
author_rank: Newbie
timestamp: April 13, 2020, 03:50:21 pm
content: Thank you for your support.Actually, no way to find datasheet.Following the traces on PCB, the two devices are connected in parallel with 0,33Ohm balancing resistors on the emitters.One is dead...So any power NPN transistor should do the job.Thank you

author: SilverSolder
author_rank: Super Contributor
timestamp: April 13, 2020, 07:45:26 pm
content: Quote from: amyk on April 13, 2020, 01:24:58 pm...complete coincidence. Gotta love synchronicity...

author: galbip
author_rank: Newbie
timestamp: April 14, 2020, 12:08:48 pm
content: Okay.... I give up.....It seems impossible to find information on these K-series devices....However, I found this link with many very old databooks:http://www.rsp-italy.it/Electronics/Databooks/hope can be useful to someone.

author: Circlotron
author_rank: Super Contributor
timestamp: April 14, 2020, 01:03:27 pm
content: Quote from: galbip on April 13, 2020, 03:50:21 pmMake sure it is for linear use, not switching.Linear one will have better SOAR.https://en.wikipedia.org/wiki/Safe_operating_area

author: coromonadalix
author_rank: Super Contributor
timestamp: April 14, 2020, 02:57:45 pm
content: like 2n3055, 2n3771 ...the k75 i dont think its a darlington ??

author: M0HZH
author_rank: Regular Contributor
timestamp: April 14, 2020, 03:10:21 pm
content: If it's a linear PSU you built in school, almost certainly it would use 2N3055 or similar; it was the "de facto" transistor for such applications back then. Plus, it's probably a generic design that would work with any high-power NPN.

author: SilverSolder
author_rank: Super Contributor
timestamp: April 14, 2020, 04:08:52 pm
content: Quote from: Circlotron on April 14, 2020, 01:03:27 pmIs this true of bipolar as well as MOSFET?

author: coromonadalix
author_rank: Super Contributor
timestamp: April 14, 2020, 07:27:42 pm
content: you can make psus with mosfets too yes