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Rotel RX-150A thrift store find

Z

Z_o-s-o

New Member
I was browsing the local thrift store the other day, and came across this Rotel rx-150a for 10.00, so I decided to pull the trigger. Aside from a few lamps, it seems like its in almost perfect shape. Anybody own on of these or have any opinions????













 
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I cleaned it up and replaced all the lamps and such and it runs pretty nice. One interesting thing I noticed is that upon measuring the DC mV current at the speaker terminals after letting it heat up for 10 minutes, I'm getting a reading of 170 mV on both sides. Im thinking thats too high unless its cap coupled right? I turned down the trimpots for the DC offset adjustment (they were almost all the way dialed out to the left) and the mV readings stayed the same, but it introduced some distortion to the audio so I put them back the way I found them. Any ideas?
 
Looking at the specs, the frequency response doesn't go too low so I'd say it's cap coupled. You may have been adjusting the center voltage, which is half the rail voltage measured at the input of the output cap. I think.
 
Thanks for clearing that up. So with it being cap coupled, the 170mV im seeing across both sides isnt a bad thing? Im glad I remembered the position on those DC balance trim pots. I put them back where they were and it sounds fine now.
 
Caps hold charges until they are discharged. When the unit is powered on, both sides of the capacitor try to stay the same until the output side is pulled down (usually a turn on thump), With headphones or speakers it should go to near zero. If you have 170mv with speakers, probably a leaky cap. There also is small DC from the feedback to the input transistors (TR502 and 602) and transistor or capacitor leakage may make DC offset higher.
 
You were right. Once I tested it loaded, It got down to about 2-3mV at the terminals. Seems like thats an acceptable value.
 
Congrats on the find! I picked mine up for about $15 a few months ago. I am pleasantly surprised with it though. Did you get the FM antennae with it?
 
43242code1 said:
Congrats on the find! I picked mine up for about $15 a few months ago. I am pleasantly surprised with it though. Did you get the FM antennae with it?
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Yea its been pretty good for me. Nice solid tuner, and everything works so I cant complain. I just replaced some lamps and gave it a good cleaning, and also added a cheap dipole antenna that Radio Shack had. Definetly not the most powerful thing around, but hey, thats what my SX-1000TW is for :music:

just dave said:
I'm diggin the green light,nice find.
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Yea the green tuner face is pretty sweet, and you cant see the dial with it off. Kinda stealthy.
 
43242code1 said:
Jealous about that sx-1000tw! I got lucky a few months back with a SX-880. Are you using headphones or speakers?
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I split between speakers and headphones usually. The Rotel gets all my listening time, as the FM tuner doesnt work on the SX-1000tw. So its on the side burner right now, its been in the family since the early 70s though.

How do you like your RX-150???
 
Hey, I know this is a really old thread though how are you finding the RX150A?

I'm running one of these in the man cave and find it's a really lovely sounding amp. Using some vintage Rola full range speakers + Toshiba RX150C bookshelves stacked which sounds wonderful. Not using the inbuilt phono stage but rather a Little Bear Pro T10 with an old Toshiba SR150C turntable and Shure SC35C with a V15 HE cart.

Considering updating to a Sand to 551 though not really sure if the change its worth it. The current setup its incredibly smooth and warm. Nothing to hurt my ears

Regards

Matt
 
mjw21a said:
Hey, I know this is a really old thread though how are you finding the RX150A?

I'm running one of these in the man cave and find it's a really lovely sounding amp. Using some vintage Rola full range speakers + Toshiba RX150C bookshelves stacked which sounds wonderful. Not using the inbuilt phono stage but rather a Little Bear Pro T10 with an old Toshiba SR150C turntable and Shure SC35C with a V15 HE cart.

Considering updating to a Sand to 551 though not really sure if the change its worth it. The current setup its incredibly smooth and warm. Nothing to hurt my ears

Regards

Matt
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Wow yea talk about late reply. It serves its duty in the man cave. Still sounds and runs great!
 
Mine has moved on to a mates place. Sounds fantastic in his place with the little Toshiba speakers, a low end Hitachi belt drive turntable with an Empire 2000 cart on it. Far better than it ever did at my place actually. It's in a better space :)
 
mjw21a said:
Mine has moved on to a mates place. Sounds fantastic in his place with the little Toshiba speakers, a low end Hitachi belt drive turntable with an Empire 2000 cart on it. Far better than it ever did at my place actually. It's in a better space :)
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I take it the space he has it in is a bit smaller? The amp tends to like a small to medium sized space because of the wattage. Push it too hard and the sound quality declines.
 
Another RX-150A fan here. Had mine serviced and it's on rotation on the 'vintage amp' spot in the reading room. Great FM tuner but yes, power is not its forte. Might have to get some high sensitivity speakers for it.
 
I recently picked one up for cheap, generally in good condition but could use a cleanup and looks like the left channel is dead. Can't speak to the audio quality yet but I'm a fan of the small form factor and the beautiful green display
 
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