Picked up a couple of Maplin 50 watt vintage amplfier modules. - diyAudio
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Old 7th September 2012, 11:59 PM   #1
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Default Picked up a couple of Maplin 50 watt vintage amplfier modules.

I picked up a couple of Maplins vintage 50 watt amplifier modules off ebay for 99p ! OK paid 3-99 p+p but still a bargain.
I built one of these in 1980 and I had forgotten how good they sound.
It was oscillating slightly when I got it but I fixed that with a 150pf across Q4 collector-base.

The second module has a few transistors missing so that is a future project if I can find the old transistors, or I might have to find more modern equivalents.
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Last edited by nigelwright7557; 8th September 2012 at 12:18 AM.
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Old 28th September 2012, 10:42 PM   #2
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Finally got the second amp up and running. Someoen had put in a pnp instead of an npn transistor and upset the voltages.
The pcb was a bit wrecked but I amanged to repair it.
Found the obsolete transistors on ebay and at 123spares.co.uk
These really are great sounding amps.
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Old 29th September 2012, 04:14 PM   #3
MondyT is offline MondyT  United Kingdom
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Nice find Nigel!

I remember these well back from the early Maplin "Catalogue" days, before Maplin turned into consumer electronics joint it is today. I always wondered what the 50W kits sounded like as I never built one. Do you happen to have the original schematics as I wouldn't mind a copy?

Cheers
Ray
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Old 29th September 2012, 08:11 PM   #4
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Quote:
Originally Posted by MondyT View Post
Nice find Nigel!

. Do you happen to have the original schematics as I wouldn't mind a copy?

Cheers
Ray
50W HiFi Power Amplifier LW35Q Maplin Kit
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Old 29th September 2012, 10:21 PM   #5
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Quote:
Originally Posted by MondyT View Post
Nice find Nigel!

I remember these well back from the early Maplin "Catalogue" days, before Maplin turned into consumer electronics joint it is today.
Cheers
Ray
Maplin used to do some really good projects in the 1980's.
I built their disco with record decks, pre amps and mixer.
I found the 50 watt amplifier wasnt loud enough for a disco so I used Maplins 225WRMS amplifer and that was really loud.
I built Maplins sound to light unit and that worked well.

Maplin have changed a bit. Resistors are about 17p each and I buy them from RS the same for 1p in 100 off.
I went in to buy a HDMI lead one day and was gobsmacked at the price, I got one on ebay instead for 2.

They are expensive now but they are handy if I am short of a component or two. Less than a mile away.
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Old 29th September 2012, 10:38 PM   #6
JPM14 is offline JPM14  United Kingdom
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the 150w bipolar amp which was rated at 225w 4 ohm! the kit transistors were 2N3055 and MJ2955. ha it is a laugh, they were never going to do it with reliability given their SOAR voltage of 60v. Powerful amp it is though, I had mine on MJ15003 and 15004 Motorola trannies back in '94
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Old 29th September 2012, 10:44 PM   #7
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I used the 225WRMS amp for many years on a disco and it was given some serious stick and was on for many hours continuously at a time.
The power supply was a bit close for comfort but the amp ran fine.
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