What does it mean?

[JohnnyBoy]

Help!

Looking at the attached picture,
on the bottom diagram there is
an A with a symbol below it.

What does that symbol mean?
Should it be wired to GREEN or
WHITE on the AC power cord?

Thanks.

An externally hosted image should be here but it was not working when we last tested it.

 

[Leolabs]

Easy question.Definitely not the green(earth).You may wire to black(live) or white(neutral).

 

[JohnnyBoy]

Hi Leolabs,

Thanks for the response. As it turns out the symbol below the A is supposed to be an LED.

Here's the situation... I bought a dual mono LM 3875 Gainclone from someone who bought it off of whoever built it. The SPST power switch has an LED, which lights up as soon as the unit is plugged in and stays on regardless if the amp is turned on or off. Upon investigation I discovered the power switch is wired in reverse, hence the LED always being lit up.

This problem made it difficult to power up the amp and in attempting to turn it on, it passed a lot of voltage in the way of a loud pop that destroyed an expensive fullrange driver. A simple oversight with dire consequences. Hopefully nothing else is wired up wrong...


Moral of the story... buyer beware.

j

 

[neutron7]

I dont think it is an LED, more likely a small neon. they would work with the voltage mentioned on the switch instructions.

 

[peranders]

This problem made it difficult to power up the amp and in attempting to turn it on, it passed a lot of voltage in the way of a loud pop that destroyed an expensive fullrange driver

... so a golden rule is to never connect any expensive before you are really sure that it's safe. Am I boring or what?

BTW: It was hardly the mains switch which caused the failure.

 

[heater]

What it means is that whoever built that amp had no clue what they were doing.
You are going to have to check every other connection as well, the soldering integrity, the mechanical build and the schematic. Well, you know, everything.

 

[gmphadte]

The switch correction will not prevent the pop and subsequent damage to the driver.
The problem is somewhere else. U have to install the delay(Dethump) circuit between the amp and the speaker.

Gajanan Phadte

 

[peranders]

A correctly designed Gainclone hasn't got any pops, at least not harmful ones.

 

[JohnnyBoy]

In addition to the switch wired backwards, the two volume pots (one for each channel – dual mono)
are also wired backwards meaning they rotate counter clockwise in order for the volume to increase.
Whoever built this amp clearly has a case of dyslexia. On the bright side, both channels do operate
when the amp finally fires up. I say finally fires up because it takes several clicks of the switch to do so.

The original purchaser tells me that the guy who built this amp has sold at least 10 Gainclones on ebay.
Scary stuff. If I find out who he is, I’ll be sure to make a public service announcement.

In the mean time I am hoping to find someone here in the British Columbia interior, preferably in the
Okanagan Valley, who knows what they are doing and can service this unit. Any takers or recommendations?

An externally hosted image should be here but it was not working when we last tested it.

 

[JohnnyBoy]

Here’s an update…

In addition to the loud pop, it takes several clicks of the switch to get the amp started. Now having reversed the switch both problems have been solved. All it takes is one push of the button and the amp fires up. Best of all no loud start up pop.

I’m still out a $200 driver, but at least the amp seems to be functioning properly. Who’d of thought that an SPST switch incorrectly installed could be so disastrous?

 

[AndrewT]

Hi,
is it normal US practice to leave the neutral unswitched?

What if the plug or socket were reverse wired or just as bad a bipolar plug inserted the wrong way round?