Uploaded August 2024 | Updated September 2026, 2 weeks ago
My Harman/Kardon 150+ is getting its semi-yearly workout tonight. Quadrophonic 4x30WPC or 2x70WPC in bridged stereo mode.
From around 1971. Apparently this model had overheating issues and was replaced by the 900+.
This thing just wants to work! 100% original except for the dial and VU meter lamps. This is twin transformer powered with 4 identical amplifier driver boards. Performed a re-bias six months ago and all boards were significantly lower out of spec.
It’s loaded with polystyrene capacitors, which apparently typically don’t go bad. But it certainly has its share of electrolytics and I can only imagine most are out of spec. Overall the power is a little starved when the bass kicks in, and the dial lights exhibit significant dimming, so I hold off a little on turning it too loud.
Tone circuit is a little uneven between left and right channels when increasing and decreasing, so I run the controls flat and front end the audio with some EQ.
Has speaker fuses, and I use one amperage less, just for insurance.
I had a 75+ in college, and I ended up blowing it out by putting higher amperage fuses in. This is before I cared for electronics.
What strange is this particular receiver does not seem to put out any DC upon power up. But the 75+ I used to have and others have mentioned that you can get significant DC for the first 5 to 10 seconds.
My Harman/Kardon 150+ is getting its semi-yearly workout tonight. Quadrophonic 4x30WPC or 2x70WPC in bridged stereo mode.
From around 1971. Apparently this model had overheating issues and was replaced by the 900+.
This thing just wants to work! 100% original except for the dial and VU meter lamps. This is twin transformer powered with 4 identical amplifier driver boards. Performed a re-bias six months ago and all boards were significantly lower out of spec.
It’s loaded with polystyrene capacitors, which apparently typically don’t go bad. But it certainly has its share of electrolytics and I can only imagine most are out of spec. Overall the power is a little starved when the bass kicks in, and the dial lights exhibit significant dimming, so I hold off a little on turning it too loud.
Tone circuit is a little uneven between left and right channels when increasing and decreasing, so I run the controls flat and front end the audio with some EQ.
Has speaker fuses, and I use one amperage less, just for insurance.
I had a 75+ in college, and I ended up blowing it out by putting higher amperage fuses in. This is before I cared for electronics.
What strange is this particular receiver does not seem to put out any DC upon power up. But the 75+ I used to have and others have mentioned that you can get significant DC for the first 5 to 10 seconds.
