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Old 18th December 2002, 05:23 PM   #1
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Default schematic questions

i have some questions about this schematic....

can you please tell me what the components labeled #1, 2 and 3 are ?

I'm an electronics newbie.

Also, what is the component located just to the right of the power input plug? It looks like a Cap in a box.

Thanks for all your help

-maz
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Old 18th December 2002, 06:03 PM   #2
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Default question

This is an intriguing schematic!

#1 is the input RCA, that one's easy.

#3 is a neon stabiliser; think of it as the tube version of a zener diode, except that it's threshold voltage collapses if it ignites..

#2 is a set of 4 LDRs (light dependent resistors) in a light-tight enclosure with a lamp. (The CdS means Cadmium Sulphite Cell, a LDR type). The lamp current determines the light level and therefore the resistance of the LDRs. That in turm controls the volume level in the four amp stages. The schematic part with the neon is an oscillator, that flashes the light and generates a vibrato effect. Look to the right: there is a selection switch selecting either vibrato (the controlled chain) or chorus.

The component to the left of the plug is an auxiliary mains socket for an extra piece of gear.

Seems this is a guitar amp or effect unit or something?


Jan Didden
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Old 18th December 2002, 06:09 PM   #3
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wow! very impressive, janneman!

It IS in fact a guitar / instrument effect pedal. This one simulates the rotary speaker sound of a Leslie Speaker. It is a pretty ancient schematic, i think....

i've been trying to get my hands on a schematic to a Dunlop Roto-vibe pedal, which does the same thing but uses newer and i'm sure cheaper components. This is it's precursor and i estimate it's from the 50's-60's.

The Q's seem to be pretty rare, from what my google searches are turning up.
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Old 18th December 2002, 08:28 PM   #4
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1 is an audio type connector.

2 looks like polarized capacitors, not neon lamps- base to emitter voltage is usually <0.7V, so neon wouldn't do anything. I am at a loss to explain why they have circles around them when other electrolytic caps in the schematic do not. They appear to be marked 1u, as in 1 uF.

3 are cadmium sulphide photocells- resistors that vary based upon light from the lamp.

The component near the plug is what the drawing says, an AC power outlet.

MR
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Old 18th December 2002, 09:04 PM   #5
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As far as I can see parts #2 have the text "1u" (u meaning greek mu) so they should be capacitors. I cannot add any intelligent
contribution to the "circle mystery", though.
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Old 18th December 2002, 10:10 PM   #6
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Quote:
Originally posted by Christer
As far as I can see parts #2 have the text "1u" (u meaning greek mu) so they should be capacitors. I cannot add any intelligent
contribution to the "circle mystery", though.

Possibly a different type of capacitor, Disc Ceramic, Mica, or similar small value component?

Just a thought!

-Dan
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Old 18th December 2002, 10:23 PM   #7
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Hello,

Thats a univibe right? At one of the other forums I frequent, a man by the name of John Hollis remade a more modern, simpler version that many people are very satisfied with. The schematic is at http://www.hollis.co.uk/john/circuits.html . It is called the easyvibe.

-Chris
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Old 19th December 2002, 01:09 PM   #8
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Default Circle mystery

Some Japanese schematics show a circle drawn around components that are mounted on the reverse side of the PCB.
There are other clues to it being Japanese drawn; the capacitor nomenclature, and transistor types.
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Old 19th December 2002, 01:12 PM   #9
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"The japanese!?!? Those sandal-wearing goldfish-tenders?!? Impossible!" -Mr. Burns


*looks around the room for the Simpsons fans*
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Old 19th December 2002, 01:17 PM   #10
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Default schematic

Looking back I think the others are right, they are electrolytics and not neons. As is pointed out, neons would have too large firing voltage for this equipment. The circuitry around these caps looks like a relaxation oscillator, where caps are charged until the transistors switch and then discharge the cap, then it all starts all over again. Haven't had time to look to that in detail though.

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