Help finding replacement (equivalent) transistor for a Proton D1200 Amplifier - Page 1
Forum section: electronics / repair

author: neverendingstudent
author_rank: Regular Contributor
timestamp: October 13, 2025, 03:24:09 am
content: Hello fellow EEVBlog nerds!I have a Proton D1200 amplifier on my bench - a rare customer repair (I don't advertise as a repair service, I buy/fix/sell typically, but a customer saw an army radio I had for sale, saw my bench, and asked) it's from decades ago and the parts in it aren't made anymore.I've already sourced replacement power transistors for the 2 main ones that blew, but then I found that another smaller transistor had shorted out.The part in question is a Sanken 2SA958 PNP transistor, a TO-220 size/package. Datasheet here:https://www.alldatasheet.com/datasheet-pdf/pdf/270377/SAVANTIC/2SA958.htmlWhile I was successful in using Digikey to search out a functional replacement for the larger power transistors that blew (Sanken C3519A 74 Y) with somewhat equivalent transistors, albeit of lesser Hfe gain in some Sanken 2SC3856 transistors - I've not been able to find a replacement / equivalent for the 2SA958.Help?Is there a useful tool I can plug the old part into that will spit out a new part? Different site to search through that will be likely to bear fruit? I'd feel crappy if I got this far in the repair and then had to tell the customer "sorry, that time and money was for nothing, here's your expensive brick".

author: wraper
author_rank: Unknown
timestamp: October 13, 2025, 03:45:26 am
content: If it's with no heatsink, on a small heatsink, or mounted with silpad (not mica/ceramic) insulator on a large heatsink, I'd use 2SA1668 (with no insulator, just thermal paste).

author: Haenk
author_rank: Super Contributor
timestamp: October 13, 2025, 04:36:46 am
content: My book states Sanken 2SA1668, TOSHIBA 2SA968, NEC 2SB546A, HITACHI 2SB861, MATSUSHITA 2SB940, ROHM 2SA1964

author: neverendingstudent
author_rank: Regular Contributor
timestamp: October 13, 2025, 05:14:11 am
content: wraper, Haenk, thank you both.The transistor is just freestanding PCB thru-hole soldered with no heatsink.Haenk: you said 'My book states' - is there a resource I can use to look this kind of thing up myself in the future?

author: Haenk
author_rank: Super Contributor
timestamp: October 13, 2025, 06:29:06 am
content: Quote from: neverendingstudent on October 13, 2025, 05:14:11 amI have some japanese data/comparison/replacement books. These sometimes pop up on ebay. Literally hundreds of pages of raw data

author: kripton2035
author_rank: Super Contributor
timestamp: October 13, 2025, 08:31:19 am
content: 2SA958 seems still available in francehttps://www.e44.com/composants/composants-actifs/transistors/transistors-bipolaires/pnp/si-200v-2a-30w-20mhz-to220-2SA958.html

author: wraper
author_rank: Unknown
timestamp: October 13, 2025, 10:31:41 am
content: Quote from: kripton2035 on October 13, 2025, 08:31:19 amI'd believe that to be genuine not more than sold on ebay, aliexpress = it's a salvaged used transistor at best.

author: kripton2035
author_rank: Super Contributor
timestamp: October 13, 2025, 02:35:11 pm
content: e44 is a reputable seller in france. I don't think it is refurb or clone.

author: wraper
author_rank: Unknown
timestamp: October 13, 2025, 03:13:49 pm
content: Quote from: kripton2035 on October 13, 2025, 02:35:11 pmThey do not even tell component manufacturer, they cannot be a serious component seller. Also for example Jaycar which has over 130 physical stores keeps selling counterfeit XR2206 (discontinued) for many years. When the component is obsolete, its availability from retail sellers is a big suspect. Most likely they get a significant part of their stock from China.