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

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Old 1st Aug 2021, 9:57 am   #21
Malcolm T
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Default Re: 1970s disco light displays

We,ll more inspiration for me to build one and get the 60s and 70s vinyl out for a party or two LOL.
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Old 1st Aug 2021, 4:39 pm   #22
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Default Re: 1970s disco light displays

The chips should all still be available from the usual suppliers, most controllers used standard 74 series TTL or 4000 series CMOS logic. There were the odd ones with custom chips, probably pre-programmed early eeprom or eprom. Triacs are better choice for the mains switching as they are often designed to switch at near to the zero point of the mains sine wave thus cutting down on mains interference. Also using tab isolated triacs make for easier heatsinking, as no thermal insulators are needed.

The lighting displays could be any spot light in a suitable mounting, either in tall boxes or on horizontal 25mm dia round tube, sometimes sqare tube would be used. Then there were the light boxes which could contain spot/flood lights, as well as coloured gls light bulbs, even coloured pygmy types. It all depended on cabinet size and the effect required. Cabinets would often be sub divided internally with each area being a different colour, then an opaque plastic cover was fitted, so that when it lit up, it showed coloured patterns on the plastic cover. There were a lot of these built by the disc jocky's who wanted something different.

Both E27 and B22D types were used, although a lot of commercial gear was E27. Most personal builds used the B22D as they were easier to get hold off. Both cord grip and batten lampholders were used and cabinets were usually matt black exterior painted plywood. The original designs probably would not comply with todays electrical safety regulations on fire risk etc.

Something else to watch for when using original kit; there is more than one way to wire up the 8 pin Bulgin connectors and if the earth was wired correctly/incorrectly for the controller. Like wise not all controllers were properly isolated on the sound inputs, which could cause trouble for the amplifier output stage driving it.

You just had to check all the connections carefully and if not you often got fuses blowing.

Dave
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Old 1st Aug 2021, 7:33 pm   #23
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Default Re: 1970s disco light displays

Crikey this topic has stirred some memories .
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Old 1st Aug 2021, 8:05 pm   #24
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Default Re: 1970s disco light displays

That's what's so good about this forum eh?

Aub
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Old 1st Aug 2021, 9:16 pm   #25
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Default Re: 1970s disco light displays

Might be worth looking at Bigclive's channel/website as he used to do lighting controllers for fairground rides based on using an (E)EPROM that just got stepped through it's programmed data that then operated triacs to create light patterns.
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Old 1st Aug 2021, 9:20 pm   #26
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Default Re: 1970s disco light displays

Has anyone mentioned R95 bulbs yet? It seems these were common in spot boxes of time's past, I have two in the shed but are probably never going to get used again, another keepsake I suppose.
Can anyone remember the old SAI light controllers? They had a Jack socket input for the sound but I could never figure out what input it needed, it worked well on standard chase though, the output was weird at the time, this forum has taught me that it's an octal socket!
Gotta love old skool stuff!
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Old 2nd Aug 2021, 10:40 am   #27
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Default Re: 1970s disco light displays

Hi if my memory is correct you could get fluorescent lamps to work on sound to light using the correct ballast with an inductive controler kind regards Bob
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Old 2nd Aug 2021, 11:05 am   #28
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Default Re: 1970s disco light displays

Yes I once did this with small filtered fluorescents, using modulated DC from valve output stages for the three colour channels. This was a mechanical television project (depicted).

Steve
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Old 2nd Aug 2021, 12:55 pm   #29
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Default Re: 1970s disco light displays

The attached circuit (found using Google) is the sort of thing I remember from that era.

It connects to the speakers using a step-up transformer that also provides isolation (a small mains transformer, maybe 24v, backwards would do the job and have appropriate isolation). The filtering is basic but adequate to give some difference between the channels. It doesn't have any suppression and would probably need some adding if interference got back into the audio circuits.

The units sold for home use normally had a built in microphone so no direct connection to the audio equipment was needed. This is a typical example. Others would have had automatic level control rather than the pots.

https://www.electroschematics.com/so...rolled-lights/

In both cases the pots must have plastic shafts for safety.
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Old 2nd Aug 2021, 2:38 pm   #30
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Default Re: 1970s disco light displays

Like Des (post 19) I also built the Spectreuphon. I built a big cabinet with a 2-foot square screen of translucent Perspex. My display used coloured filters and a slow-rev motor driving a randomly shaped conical mirror made of tinfoil that diverted light from the treble channel very pleasingly. It provided a bright enough display for subdued-light conditions, and caused quite a stir at Art School where I was at the time. Happy days!
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Old 2nd Aug 2021, 3:57 pm   #31
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Default Re: 1970s disco light displays

There was a circuit design in a 1970s Practical Electronics magazine which I built - it used 741 op-amps as active filters to separate the audio into 3 channels [bass, mid, treble] which then fed Triacs to activate the bulbs.

The entire circuit sat at mains-voltage - the 741 bit was powered by a capacitive dropper. 'Safety' was obtained by feeding the audio signal through a 1:1 600-Ohm line-transformer.

My version worked reasonably well but would occasionally suffer a sort of latch-up where all 3 bulbs came on at full brightness and wouldn't go out even when the audio input was disconnected, and needed the mains removed to reset it. I suspect something somewhere was oscillating but I wasn;t going to go poking around with a 'scope bearing in mind the live-chassis.
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Old 3rd Aug 2021, 8:27 pm   #32
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Default Re: 1970s disco light displays

The bulbs were usually PAR38s. Usually with dichroic coverings to give the colours. I still have a box full somewhere from when had a mobile disco.
Ah! Those were the days.
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Old 3rd Aug 2021, 8:41 pm   #33
Malcolm T
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Default Re: 1970s disco light displays

Some of those old designs wer,nt too hot on H&S were they LOL
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Old 3rd Aug 2021, 9:22 pm   #34
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Default Re: 1970s disco light displays

I built one of the Helleman light computers when I did disco's back in the day. I added a clock and counter to make it step through all the programs in order as well as audio used to create the step pulses, all suitably isolated of course. It worked well with 2x 7 lamp light boxes and looked impressive. Trouble is I used some 9 pin plugs and sockets borrowed from work. My mate helped me set up one night and thought the locking ring was all part of the plug and rotated the whole assembly shorting all the wires together. The eprom wasn't happy and blew up. Myself and a friend spent ages using a micro professor and LED's to recreate the pattern sequences to burn to another chip. Lucky I was doing a C&G electronics course at the Norwich Skill centre at that time as they had all the gear I needed to do this task. It worked quite well. It's last job before I sold it on was wiring it to 7 sets of Christmas fairy light sets dotted around the room and on the tree. Looked very pretty but spent most of it's time set to all on.

The build PDF still exists here https://www.futurashop.it/Allegato_P...8220-K5201.pdf
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Old 4th Aug 2021, 7:09 pm   #35
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Default Re: 1970s disco light displays

Here is a schematic for the TTL disco lighting controller we used to service back in the day.

Mico lighting in Pudsey West Yorkshire still sell Par 36 - 56 lighting (they are a big theatrical supplier).
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Old 5th Aug 2021, 7:40 am   #36
Malcolm T
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Default Re: 1970s disco light displays

That looks pretty easy circuit , 4 channels yes ?.
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Old 5th Aug 2021, 7:17 pm   #37
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Default Re: 1970s disco light displays

Yes Malcolm, 4 channels; capacitive dropper. Health and safety, BS415?
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Old 6th Aug 2021, 10:45 am   #38
Malcolm T
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Default Re: 1970s disco light displays

OK, Is that a subtle joke at the end LOL.
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Old 6th Aug 2021, 11:53 am   #39
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Default Re: 1970s disco light displays

Quote:
Originally Posted by Paul Stenning View Post
The attached circuit (found using Google) is the sort of thing I remember from that era.

It connects to the speakers using a step-up transformer that also provides isolation (a small mains transformer, maybe 24v, backwards would do the job and have appropriate isolation). The filtering is basic but adequate to give some difference between the channels. It doesn't have any suppression and would probably need some adding if interference got back into the audio circuits.

The units sold for home use normally had a built in microphone so no direct connection to the audio equipment was needed. This is a typical example. Others would have had automatic level control rather than the pots.

https://www.electroschematics.com/so...rolled-lights/

In both cases the pots must have plastic shafts for safety.
That schematic is more or less the same for the ones that I built for the mobile disco, 150 Watt Cryselco bulbs from memory and plenty of crumpled up aluminium foil.

Lawrence.
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Old 6th Aug 2021, 12:11 pm   #40
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Default Re: 1970s disco light displays

Malcolm T only just seen this thread. I have the pdf of the article referred to in post 2, kindly provided by Symon. Pm me with your email address if you want it and I will send it. I think it is too big to post on here.
Rob
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