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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 26th Apr 2012, 11:30 am   #1
sparkymike
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Default RSC Guitar Amplifier.

I am trying to rejuvenate an old RSC guitar amplifier that has been lying dormant in the loft for several years. Am I correct in that RSC were Radio Spares of Croydon? I seem to remember seing these amplifiers for sale in the 50's or 60's. Budget model much cheaper than anyone else at the time.
However, I am in dire need of a circuit, mainly to make sure it has the correct valves in the correct bases. I have switched it on for a brief period and there is the lack of reidual hum from the speaker and thus no output. All the valves have anode current, but apart from the rectifier which is correct, the others valves may not be in correct bases. (A good case for marking the chassis with valve numbers.) I will upload photos later.
I bought this unworking with some other radios so it has never worked yet in my posession I hasten to add.
Mike.
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Last edited by sparkymike; 26th Apr 2012 at 11:43 am.
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Old 26th Apr 2012, 12:03 pm   #2
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Default Re: RSC GuitarAmplifier

Radio Supply Co. based in Leeds. there were several models , for hi fi, guitar & bass (eg Bass Regent in theory=30w ) Early models used 807s in the output, later EL34.
They were ok for the money and fairly reliable as I recall. I have a feeling they were actually made by Linear ( as in Linear Conchord) somewhere in Yorkshire. Is yours a single ended EL84 about 3w? The circuits were pretty standard , nothing funny going on.
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Old 26th Apr 2012, 12:06 pm   #3
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Default Re: RSC GuitarAmplifier

RSC were Radio Supply Co. in Leeds
Have a look here at the A11 which is similar to yours

http://www.chambonino.com/work/linear/lin10.html

Looks like a kit job, but yours appears to have been built without the first preamp stage

Others will know more - Was RSC effectively the same company as "Linear" ?

Andy
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Old 26th Apr 2012, 12:42 pm   #4
sparkymike
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Default Re: RSC GuitarAmplifier

I have had two Linear Concords in my time and they look very much like this amp re. wiring.
I would be interested if anyone has an advert of the time when this was new.
Mike.
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Old 26th Apr 2012, 1:07 pm   #5
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Default Re: RSC Guitar Amplifier.

Mike. Looking at a PW advert from November 1966 it would appear that this is an R.S.C A11 12-14 Watt amplifier. Price then £8:15:0 in kit form or £11.15.0 ready built.

SellerS were R.S.C Hi-Fi Centres Ltd. They had branches all over the place, but the mail order centre was in Leeds.

Line up was 2 X ECC83s, 2 X EL84s and an EZ81.

Any chance of a picture of the front panel.
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Old 26th Apr 2012, 2:12 pm   #6
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Default Re: RSC Guitar Amplifier.

Also from the site Andy posted

http://www.chambonino.com/work/linear/info1.html

The photo in post 1 only has 4 valves, so probably a single ended output, but the photo also appears to show two EL84 size valves ??
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Old 26th Apr 2012, 2:25 pm   #7
sparkymike
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Default Re: RSC Guitar Amplifier.

Well had a chance to try and puzzle out the valves. I am mystified by the ECC83, or whatever it should be. The heaters are pins 5 and 9, but I thought that ECC83 pins were 4 & 5 Anyone got any clues about this? That valve position is top left in the photo. I can do a close up if required. The heater lights up when powered up.
I have also uploaded the cabinet details. I would like to know the make of the speaker.
Mike.
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Old 26th Apr 2012, 2:30 pm   #8
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Default Re: RSC Guitar Amplifier.

Pin 9 is a heater centre tap.
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Old 26th Apr 2012, 2:43 pm   #9
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Default Re: RSC Guitar Amplifier.

RSC had a regular, rather crowded, two page ad in PW, and I think PE, through the late 60s to at least October 1971, the date of the PW from which I've taken the ad.

As Graham says, this looks like the A11 hi-fi 12-14 watt amplifier. The picture is a little different, but they could have altered the layout and transformers a bit (the ones in the picture look shrouded), or it might be an artist's impression.

I suspect RSC were a sales and marketing company, not design and manufacture.

There was another company called Radio Component Specialists, who were based in Croydon. They sold the odd amplifier but mainly sold parts, record decks, transformers etc.

Pete.
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Old 26th Apr 2012, 2:52 pm   #10
sparkymike
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Default Re: RSC Guitar Amplifier.

What is the idea behind the heater center tap? Is that to make it fail safe if one tap goes down?
Mike.
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Old 26th Apr 2012, 2:53 pm   #11
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Default Re: RSC Guitar Amplifier.

It's so the valve can be operated from 12V (filaments in series) or 6V (filaments in parallel). Not sure what happens if you only use one filament.

Do you have a link between pins 4 and 5?
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Old 26th Apr 2012, 3:13 pm   #12
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Default Re: RSC Guitar Amplifier.

It was possibly sold as a guitar practice amplifier, and not in a chassis only version, hence the unshrouded transformers. What are the controls labelled?

PS the speaker is probably a Fane
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Last edited by AC/HL; 26th Apr 2012 at 3:23 pm. Reason: PS
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Old 26th Apr 2012, 3:23 pm   #13
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Default Re: RSC Guitar Amplifier.

I'm not sure about the exact business arrangements, but certainly some of the RSC stuff was built in Leeds as one or two of the local hams worked there. G3TDZ springs to mind, as he used to publish various amateur projects in SW Mag. There was a guy called Trevor who managed the RSC shop in the Grande Arcade (or Victoria arcade?) in Leeds before moving on to Globe Scientific owned by a guy called Gerry, who were popular purveyors of SW radios, car battery chargers (built by schoolboy me!) and unmarked transistors .
I think RSC wound all their own transformers, both for use on the amps and for sale in the shops.
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Old 26th Apr 2012, 4:36 pm   #14
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Default Re: RSC Guitar Amplifier.

I have an idea that the company, which traded under the name RSC, changed what they claimed the letters stood for from Radio Supply Co to Realistic Sound Centres, at some point in the 1970's.

I have a few transformers which I bought from them - I'm sure they had their own winding shop.

As noted above, Radio Component Specialists is another outfit.

As to the valve line-up, the valveholders with pins 4 & 5 linked must be ECC83's (the heater power supplied betwen pin 9 and pins 4 & 5. The valveholder with several (4?) connections to the mains transformer - possibly with low-value resistors in series with a couple of wires - must be the EZ81. The remaining two valveholders, by elimination, must be the EL84's.
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Old 26th Apr 2012, 4:58 pm   #15
sparkymike
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Default Re: RSC Guitar Amplifier.

I now think I have worked out the valve line up. It is very slightly like the Mullard 7watt stereophonic amplifier, but one channel.
This amp used ECC83 and two ECL 82's and EZ 81. My unmarked valve would seem to be ,or should be an ECL 82 I think. I had thought it was single ended output which was leading me up the blind alley, but I am now certain that it is push pull, as most of the resistors on both bases are duplicated. The ECL 82 looks like it is used in both modes ie. triode and pentode, thus saving components on a low price amplifier.
A circuit would still be very handy.
Mike.
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Old 26th Apr 2012, 5:20 pm   #16
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Default Re: RSC Guitar Amplifier.

Quote:
Originally Posted by AC/HL View Post
Also from the site Andy posted

http://www.chambonino.com/work/linear/info1.html

The photo in post 1 only has 4 valves, so probably a single ended output, but the photo also appears to show two EL84 size valves ??

On that page there's something about the history of RSC and further down there's an ad including the A11. Its just about possible to read the valve line up, which is ECC83 x2, EL84 x2 and EZ81, as Graham said.

In the ad there's also the RSC Senior 15 watt lead and rhythm guitar amplifier which looks a bit like Mike's.

I would have thought they would stick to EL84s and push them a bit harder, rather than use ECL86s.

Pete.
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Old 26th Apr 2012, 6:48 pm   #17
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Default Re: RSC Guitar Amplifier.

Hi,

Thatís my RSC A11 on John Chambers amp site. As youíll see it was a bit of a basket case when I first got it.

There was a thread (link below) on this site about this and Linear amplifiers.

http://www.vintage-radio.net/forum/s...id=2&styleid=2

Regards
Terry.
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Old 26th Apr 2012, 6:56 pm   #18
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Default Re: RSC Guitar Amplifier.

I do believe RSC used to sell a lot of Fane speaker drive units. Best first guess for what's in that cabinet. I used to look in occasionally at their shop in Thornton's Arcade, Leeds.

David
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Old 26th Apr 2012, 7:25 pm   #19
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Default Re: RSC Guitar Amplifier.

Hi,

I agree itís a Fane or an Audiotrine speaker, which are one and the same thing, as Audiotrine were re-badged Fane speakers and sold via the RSC shops.

Terry.
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Old 27th Apr 2012, 6:29 am   #20
sparkymike
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Default Re: RSC Guitar Amplifier.

Well it now looks like I will have to draw out the circuit as a small resistor in the output circuit has drawn a high current and gone pop.!! One side goes to earth and the other goes to each output valve via two 1 meg resistors to pins 1 (triode grid.)
I have marked the resistor on the thumbnail.
Mike.
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