Anyone have an idea what this may be? - Page 1
Forum section: electronics / beginners

author: TT_Vert
author_rank: Regular Contributor
timestamp: July 27, 2019, 02:04:36 am
content: Came from a retired zenith engineer.ThanksDave

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 27, 2019, 02:21:45 am
content: Stereo audio amp?Tim

author: Stray Electron
author_rank: Super Contributor
timestamp: July 27, 2019, 02:33:10 am
content: It looks like a dual output DC power supply with regulators made out of discrete parts. Very typical 1960s construction from before ICs became common. Take a look at the date codes on the parts.

author: oPossum
author_rank: Super Contributor
timestamp: July 27, 2019, 02:39:54 am
content: Two RCA jacks in the first picture, output inductors, and four conductor output lead suggest it is a stereo audio amplifier.

author: Brumby
author_rank: Unknown
timestamp: July 27, 2019, 03:55:47 am
content: There are a couple of hints that I see which point to the stereo audio amplifier thinking.Haven't seen black encapsulated transistors like those for a loooong time. (Although, if I looked, I could probably find a couple buried around here somewhere.)

author: ArthurDent
author_rank: Super Contributor
timestamp: July 27, 2019, 04:03:37 am
content: I'll also go with a stereo amplifier. It has a transformer with two 6.3 volt windings @1.5 amp that may not be used and one 60 volt center tapped winding at 2300 ma which probably gives about a +/- 30 to 40 VDC split supply. This chassis is just the power amp section with no controls and was probably part of an entertainment center where the radio/record player section had the preamp and the controls. I'm guessing that there are 2 or 4 larger transistors we can't see on the larger heatsinks on the other side of the chassis and they are the output transistors.It is missing one transistor and socket on the left side and all the electrolytics are probably totally dead. Probably not worth much other than the transformer which sells on eBay for some good money.

author: Circlotron
author_rank: Super Contributor
timestamp: July 27, 2019, 04:22:40 am
content: Yep, I’d say stereo audio power amp. The 0.33 ohm 5 watt emitter resistors and the zobel network inductors on the output is the clue. Likely the two big electros are for split plus and minus dc power rails as is usually the case for amplifiers.

author: TimFox
author_rank: Super Contributor
timestamp: July 27, 2019, 02:19:34 pm
content: The black plastic TO-5 size transistors are typical of Fairchild production, ca. 1970.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 27, 2019, 04:58:22 pm
content: TO-106 specifically, I think?Speaking of, the boards look identical except on the far left, one transistor is bent nearly out of its socket, and another socket is broken off completely. They're probably close enough to general purpose that they can be replaced by 2N3904s (or 6 as the case may be).Tim

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 27, 2019, 05:06:27 pm
content: Have a care powering that up, OP - the date code visible on one electrolytic capacitor is 13th week of 1967...Otherwise, either a power supply or an amplifier. I'd bet power supply, since they often end up being built for function, with little care about form (I know I'm guilty of such).

author: Benta
author_rank: Super Contributor
timestamp: July 27, 2019, 05:40:04 pm
content: Stereo power amp. The wirewound emitter resistors for a complementary output stage gives it away, as well as the output inductor networks. You can also see the complementary (heatsinked) driver transistors.

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 27, 2019, 05:42:19 pm
content: Quote from: Benta on July 27, 2019, 05:40:04 pmOops, I only clicked on the first picture; looking at the last one I agree this is likely an audio amplifier. No doubt a totem-pole output stage with truly atrocious distortion, too.

author: bd139
author_rank: Super Contributor
timestamp: July 27, 2019, 08:00:21 pm
content: I'd go with audio amp myself as well. My father built one almost identical other than enclosure and mounting. It sounded like ass.