Russian op amp- К553ЧД2 (I think) - Page 1
Forum section: electronics / general

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 12, 2024, 07:53:08 am
content: So yeah... anyone got any info on these? So far I haven't managed to turn up any info. I believe the marking says К553ЧД2, pic attached. I'm repairing a drum machine for a customer and Ithinkthe issue is one of these little buggers. I can't find a datasheet let alone a replacement so far though

author: squadchannel
author_rank: Frequent Contributor
timestamp: September 12, 2024, 07:57:04 am
content: https://www.elektroda.pl/rtvforum/topic739537.html#3800971LM301?nah. wrong pin count.https://www.ebay.com/itm/281710967751LM201?datasheet:https://eandc.ru/pdf/mikroskhema/153ud2.pdf

author: shapirus
author_rank: Super Contributor
timestamp: September 12, 2024, 08:08:39 am
content: Quote from: David Aurora on September 12, 2024, 07:53:08 amThat's because it's actually К553УД2 (aka K553UD2), you got one of the letters wrong.There's some info. This pdf has proper text, so it can be translated, assuming that you can't read russian:https://www.kontest.ru/datasheet/unkn0wn/k553ud2.pdfLooks like an average op amp: ±15 V supply voltage, 1 MHz GBP, 7.5 mV offset voltage, 0.5 V/μS slew rate, ±10 V output swing, but the pinout is interesting, you can see it here:https://ic-info.ru/upload/iblock/39b/153%D0%A3%D0%942_6_553%D0%A3%D0%942_6_740%D0%A3%D0%945.pdf(it's a scan, so you'll have to use something like google lens to translate it).It has some balance/compensation pins, supposedly to tune the frequency response, whatever that might mean. I've never seen anything like this in the western op amps so far, but I'm quite sure that there must have been one that this soviet one was copied from.I'm attaching the docs here in case the links go offline.update: so yeah, appears to be a 14-pin version of LM301, and that one seems to be very hard to find.

author: Mahagam
author_rank: Regular Contributor
timestamp: September 12, 2024, 08:15:43 am
content: It can be replaced with LM201/LM101. But you need recheck the package of this chip.

author: shapirus
author_rank: Super Contributor
timestamp: September 12, 2024, 08:17:37 am
content: If you fail to find the 14-pin version, then, since it's a single op amp package, I guess you can simply create a custom 14 pin DIP to an 8 pin SO-8 adapter with a corresponding pin to pin routing and solder an SMD version of an 8-pin LM{3,2,1}01 onto it.

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 12, 2024, 12:13:45 pm
content: Bloody legends, thanks! Will dig into this info next time I sit down with it

author: wraper
author_rank: Unknown
timestamp: September 12, 2024, 12:16:26 pm
content: Made at ALFA factory, Riga, Latvian SSR.

author: floobydust
author_rank: Super Contributor
timestamp: September 12, 2024, 06:15:07 pm
content: It is basically a uA709 clone, going back to 1965. Early single op-amp in DIP-14 package that quickly became DIP-8.709 had a weakness for blowing up if the output was overloaded or shorted, no current-limiting.No adapter PCB needed.What you do is use a DIP-8 part and put it in down two rows of pins on the PCB so the pin connections line up.Use a 709 or 741 etc. DIP-8. New part pin 1 is at pin 3 on the PCB footprint.The compensation network you'll have to look at and remove to useuA741it's internally compensated and so those PCB parts would get noted down and removed, but the design bandwidth is important to keep.

author: Zero999
author_rank: Super Contributor
timestamp: September 15, 2024, 04:15:05 pm
content: Quote from: floobydust on September 12, 2024, 06:15:07 pmWhy is that a problem? The same is true of the NE555, most microcontrollers and logic gate ICs. How many op-amp circuits do you see which rely on this feature? Op-amps seem to be fairly unique in having short circuit protection.

author: floobydust
author_rank: Super Contributor
timestamp: September 15, 2024, 05:13:07 pm
content: I remember reading 709 customers having failures, either an oops moment or power-on transient or maybe if it oscillated, the output transistors would fail.So the reliability complaints seems to have driven adding active current-limiting. That's long ago. It could have even been EE's accustomed to working with tubes.The 709 can drive an audio transformer with more grunt to overcome magnetization currents, so in vintage gear (compressors, reverbs) it can make a difference, the extra peak output current.