jmac95
New Member
Good morning and hello!
I’m new to AK and relatively new to the world of vintage audio. I got started in home theater equipment about a year or so ago and delved into vintage in the past half a year thanks to some Bose 301 IIIs given to me by a professor. I’ve done some simple repairs before, like refoaming speakers, cleaning the controls on my Sony STR-7065 with contact cleaner, replacing caps in a Thorens TD125 MKII and Apple Macintosh Classic logic board, but do not yet understand the inner workings of receivers and amplifiers. I’m wanting to learn more!
After noticing it while exploring my new job a few months ago, I finally asked if I could take home the vintage amplifier I had seen tucked away in an attic. It’s a Harman Kardon "Stratophonic Series" SA2000 Stereo Integrated Amplifier. From the research I’ve done and friends in the Skylabs discord it seems this is a transformer-coupled integrated amplifier with germanium resistors from about 1962-64, potentially out of a stereo console. It’s been sitting in a climate controlled environment for years as the dust was thick and the note taped to the top is as old as the document itself: "DO NOT turn this on! There are no speakers connected. If turned on, damage will result." I first thought this meant the amplifier would be broken, but upon testing with a dim bulb tester and a junk speaker it seems to work properly. I measured the DC offset of the speaker terminals with nothing connected and volume down at 0.6V on one channel and 0.2V on the other channel, but with it being transformer coupled I don’t yet have a reference for what’s good and what needs repairs. Beyond that I’m not sure what to test.
It’s a relatively undocumented model so I was grateful to find it had the owner’s manual and schematic with the unit. I uploaded them to @QUiKSR20 ’s database (TVAD - Document Archive) for reference and to help anybody else who comes across this amp. From looking around on AK it seems to be the same era and perhaps similar design to the Stratophonic series SR300-400-900 etc receivers but as an integrated amplifier.
Since it’s recently pulled out of retirement, I want to learn more about it and make sure there aren’t any pressing modifications or repairs I should perform. It seems to run nicely so far. The volume knob is scratchy, so I want to clean it with some contact cleaner (WD-40 Specialist Contact Cleaner quick-drying) but want to make sure it won’t damage anything. The on/off switch is part of the volume pot. Is a recap necessary/worth it or is it good to run as-is? Is it safe to test with only one speaker or is it necessary to have two speakers connected at all times? I also use a Douk VU3 and VU3 Pro for audio switching, which have loads built in for tube amps - I’m guessing but want to make sure they’d be safe to use with this.
Also, for sitting for so many years the inside of the unit is clean and dust free but the front plate has markings, tape residue, and some patina/corrosion on the metallic part of the knobs that’s not coming off with isopropyl alcohol. Is there anything with which I should clean or avoid cleaning the faceplate and knobs?
Thank you all, I’m looking forward to cranking some tunes on it! Maybe some period-correct Beatles, and definitely some newer music too.
I’m new to AK and relatively new to the world of vintage audio. I got started in home theater equipment about a year or so ago and delved into vintage in the past half a year thanks to some Bose 301 IIIs given to me by a professor. I’ve done some simple repairs before, like refoaming speakers, cleaning the controls on my Sony STR-7065 with contact cleaner, replacing caps in a Thorens TD125 MKII and Apple Macintosh Classic logic board, but do not yet understand the inner workings of receivers and amplifiers. I’m wanting to learn more!
After noticing it while exploring my new job a few months ago, I finally asked if I could take home the vintage amplifier I had seen tucked away in an attic. It’s a Harman Kardon "Stratophonic Series" SA2000 Stereo Integrated Amplifier. From the research I’ve done and friends in the Skylabs discord it seems this is a transformer-coupled integrated amplifier with germanium resistors from about 1962-64, potentially out of a stereo console. It’s been sitting in a climate controlled environment for years as the dust was thick and the note taped to the top is as old as the document itself: "DO NOT turn this on! There are no speakers connected. If turned on, damage will result." I first thought this meant the amplifier would be broken, but upon testing with a dim bulb tester and a junk speaker it seems to work properly. I measured the DC offset of the speaker terminals with nothing connected and volume down at 0.6V on one channel and 0.2V on the other channel, but with it being transformer coupled I don’t yet have a reference for what’s good and what needs repairs. Beyond that I’m not sure what to test.
It’s a relatively undocumented model so I was grateful to find it had the owner’s manual and schematic with the unit. I uploaded them to @QUiKSR20 ’s database (TVAD - Document Archive) for reference and to help anybody else who comes across this amp. From looking around on AK it seems to be the same era and perhaps similar design to the Stratophonic series SR300-400-900 etc receivers but as an integrated amplifier.
Since it’s recently pulled out of retirement, I want to learn more about it and make sure there aren’t any pressing modifications or repairs I should perform. It seems to run nicely so far. The volume knob is scratchy, so I want to clean it with some contact cleaner (WD-40 Specialist Contact Cleaner quick-drying) but want to make sure it won’t damage anything. The on/off switch is part of the volume pot. Is a recap necessary/worth it or is it good to run as-is? Is it safe to test with only one speaker or is it necessary to have two speakers connected at all times? I also use a Douk VU3 and VU3 Pro for audio switching, which have loads built in for tube amps - I’m guessing but want to make sure they’d be safe to use with this.
Also, for sitting for so many years the inside of the unit is clean and dust free but the front plate has markings, tape residue, and some patina/corrosion on the metallic part of the knobs that’s not coming off with isopropyl alcohol. Is there anything with which I should clean or avoid cleaning the faceplate and knobs?
Thank you all, I’m looking forward to cranking some tunes on it! Maybe some period-correct Beatles, and definitely some newer music too.