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Old 8th Jul 2020, 4:01 pm   #1
radioman
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Default RS Stereo Amplifier PCB

Hi folks,
I found this at the side of a box of assorted parts that I'd acquired some time ago.
I don't have any circuit to go with it, so I'm not sure what IC it was designed for.
I initially thought it might be for a couple of Plessey SL403A but that wasn't rated at 5W output.
Was there a later higher power version of this IC that RS used to sell ?

Andy
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Last edited by radioman; 8th Jul 2020 at 4:06 pm. Reason: added some text for clarity
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Old 8th Jul 2020, 4:47 pm   #2
Electronpusher0
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Default Re: RS Stereo Amplifier PCB

Odd, the box says 5W but the pcb is silk screened 3W.
Perhaps another case of rms vs peak vs music power.

Peter
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Old 8th Jul 2020, 4:58 pm   #3
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Default Re: RS Stereo Amplifier PCB

Quote:
Originally Posted by Electronpusher0 View Post
Odd, the box says 5W but the pcb is silk screened 3W.
Perhaps another case of rms vs peak vs music power.

Peter
Or the other old trick of adding each channels power output, so instead of 2 x2.5W its 5W?

A.
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Old 8th Jul 2020, 5:02 pm   #4
duncanlowe
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Default Re: RS Stereo Amplifier PCB

It seems you were right:
https://www.vintage-radio.net/forum/...d.php?p=922763
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Old 8th Jul 2020, 6:35 pm   #5
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Default Re: RS Stereo Amplifier PCB

I remember those and built one to provide an extra 2 channels when Quadrophonic discs first appeared. They worked well and I’ve probably got it somewhere in my piles of stuff. Don’t ask as it’s a large double garage that is almost impossible to get into.
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Old 8th Jul 2020, 10:26 pm   #6
radioman
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Default Re: RS Stereo Amplifier PCB

Thanks for all the replies - having read the thread in the link posted above, it would be useful to see the RS datasheet R/185 :
Does anyone have a copy or scan ?
I still think there must have been an update to the IC used and that's why there's a yellow sticker on the envelope, which mentions "... each 5W AUDIO AMP"

Andy
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Old 9th Jul 2020, 8:20 am   #7
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Default Re: RS Stereo Amplifier PCB

I think that is just the way it was worded and slightly misleading. It was about the time when manufacturers started to make more extravagant claims about power outputs. 2.5 watts per channel at low distortion equals a 5 watt (RMS) stereo amp. The maximum output, incl distortion, was probably 3.5 watts. I believe these I.C's were made by Plessey who initially rated them at 1.5 watts and sold by the infamous Clive Sinclair as 10 watt amplifiers. They also need an additional heatsink or they will fail quickly.
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Old 9th Jul 2020, 9:58 am   #8
Terry_VK5TM
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Default Re: RS Stereo Amplifier PCB

The Sinclair amp was the IC10, late 60's, but it also had a pair of output transistors driven by the IC.

A whopping 59/6 in 1968.
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Old 9th Jul 2020, 10:34 am   #9
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Default Re: RS Stereo Amplifier PCB

The Sinclar chip package itself was branded IC10. I still have one that works and another that's died.

Alan
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Old 9th Jul 2020, 12:49 pm   #10
G6Tanuki
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Default Re: RS Stereo Amplifier PCB

I vaguely remember something about those ICs originally being designed by Plessey for use as servo-drivers or Radar scanning or something where the output current slewed relatively linearly and slowly rather than being distinctly-peaky like an audio signal: in such applications they worked just fine. BUT the little wires linking the semiconductor 'slab' to the leadout-pins were rather thin, and when they were subjected to instantaneous high-power transients on a regular basis the effect of repeated thermal-cycling resulted in them embrittling and going open-circuit.

[I have a vision of a test-suite full of amplifiers all playing Ravel's Bolero into dummy-loads....]
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Old 9th Jul 2020, 10:23 pm   #11
radioman
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Default Re: RS Stereo Amplifier PCB

Thanks everyone - yes, I've read that they weren't very reliable..
Maybe RS were trying to compete with the adverts for Sinclair IC10's !
Anyhow, I don't have any of the IC's needed and even if I did, I don't think I'd bother using them now.

Cheers,
Andy
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