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Old 6th March 2009, 05:19 PM   #291
Nuuk is offline Nuuk  United Kingdom
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Ditto Barry. You should make a career out producing those diagrams!
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Old 13th March 2009, 12:42 AM   #292
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Default Neon switch help required...

I went to buy an IEC socket, fuse and switch combi unit for building my first gainclone, and they only had the version with a DPST switch with neon. The brand is Bulgin and I got it from RS in the UK.

The datasheet confuses the hell out of me. I'd be fine without the neon bit. Please help me out!!

There's 4 pins on the switch 1,2 on one side and 4 & 5 on the other.

They're all isolated at off. At on, 1 joins to 2, 4 joins to 5. 2 bridges to 5 within the rocker, passing through a resistor and a neon bulb.

How should I wire it up to the socket and the traffo? I'm wondering if the live passes through the resistor and neon by using pins 1 in and 4 out. It doesn't make sense to me that it would.

Here's a URL to the item: http://uk.rs-online.com/web/search/s...duct&R=2111001

Many thanks
Lucas
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Old 13th March 2009, 04:34 AM   #293
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LucasAdamson,

AC input cord is wired to pin 1 and 4. Output to transformer is pin 2 and 5. When you flip the switch on, that will make 2 and 5 live, so the neon bulb is lit. Since it is AC power, and since neon bulbs don't care about polarity, you could put hot and common AC leads on either way, hot to pin 1 or to pin 4, but if there is other circuitry involved like the fuse, whichever pin that connects to should be wired with the hot AC lead.
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Old 13th March 2009, 01:37 PM   #294
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Thanks for that. So basically, I wire it just as I would were there no neon bulb there at all. I had it up and running last night by dismantling the switch to check what the pins were and what did what.

I have a power supply up and running now so thanks for that. I put the hots to the resistor side of the light (1&4), so that it would run through the resistor before reaching the bulb. I had to dismantle the switch to work it all out though, as there was no diagram.

Impossible for a man of my education without this forum. Many thanks!

Lucas
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Old 13th March 2009, 09:52 PM   #295
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Default Transformer woes...

My transformer is a little shy on voltage (32v) but its amperage is plenty (about 900va), it has dual secondaries at 16v, Im wanting a lm4780 set up maybe 5 channels, I have 5 lm3866 chips also but i think the voltage requirments are close to the same. Do you all think it will work ok? Here are the transformer specs:

Winding # 1 Primary 120v 7.50a 680m 50m ohms
Winding # 2 Secondary 16v (Tab1 to Red) 27.5a 18.0m ohms max.
Winding # 3 Secondary 16v (Tab2 to Red) 27.5a 18.0m ohms max.


Thanks guys!
J
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Old 14th March 2009, 08:00 AM   #296
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Default Re: Transformer woes...

Quote:
Originally posted by jamesjmcgee
My transformer is a little shy on voltage (32v) but its amperage is plenty (about 900va), it has dual secondaries at 16v, Im wanting a lm4780 set up maybe 5 channels, I have 5 lm3866 chips also but i think the voltage requirments are close to the same. Do you all think it will work ok? Here are the transformer specs:

Winding # 1 Primary 120v 7.50a 680m 50m ohms
Winding # 2 Secondary 16v (Tab1 to Red) 27.5a 18.0m ohms max.
Winding # 3 Secondary 16v (Tab2 to Red) 27.5a 18.0m ohms max.


Thanks guys!
J

Many people choose to get the max output they can. That is reasonable, but you have to decide what YOU need. Source voltage, times gain, determines output voltage. Look at the datasheet to see how close your integrated amp swings to the rails, then you know if your calculated, attempted voltage, is within the limit of the voltage you are using.

To put it another way, you'll have a well regulated amp using that transformer, whether it "works" has to do with the volume level you feel it needs, and it depends on the speaker impedance too.

I don't like going deaf prematurely, and I like using parts when it suits a budget, when you already have an expensive part, so I say give it a try (I am too lazy to calculate out what the result is, but that is enough voltage to get reasonable volume for many uses, even if it's not a lot for the value of the transformer, so you will have to decide what the transformer is worth versus buying something else).
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Old 14th March 2009, 01:53 PM   #297
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James.
What is your expected load? You are probably going to need more voltage if 8 ohm but might be great for 4 ohm. Don't use anything that will cut the voltage such as a voltage regulator. Better to measure your transformer instead of worrying about specifications. Send it to me if it is too low because I need to drive low impedance load. I will even pay the shipping hehe.
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Old 14th March 2009, 08:31 PM   #298
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The load (speakers system) have not been decided upon yet, I have 4 small 3" 15watt 8ohm mid range speakers I was going to use to build the 2 front channels, (Parallel wiring) for 2, 4ohm 30 watt mini cabinets. but I figure see what I can do with the amp first, then get what i need for the speakers.
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Old 25th March 2009, 08:12 AM   #299
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Quote:
Originally posted by Tripmaster


Thanks for pointing out my mistake!

First Power Supply with -V Zener replaced

-V

'A' -28v
'B' -33.4v
'C' -34.5v
Output -25.8v

Voltage across JFet -5.4v
Voltage across 130R -1.1v
Current across 130R 8.5mA

+V

'A' +27.6v
'B' +28.6v
+34.5v (Total voltage taken from drain pin of J309)

Output +25.5v

Voltage across 130R +1.0v
Voltage across JFet +5.9v
Current across 130R 7.7mA


Second Power Supply

-V

'A' -27.8v
'B' -33.8v
'C' -34.8v
Output -25.6v

Voltage across JFet -6v
Voltage across 130R -1v
Current across 130R 7.7mA


+V

'A' +27.7v
'B' +29.0v
+34.3v (Total voltage taken from drain pin of J309)

Output +25.9v

Voltage across 130R +1.3v
Voltage across JFet +5.3v
Current across 130R 10mA

Hi Andrew

The readings for the (faulty) second power supply haven't changed at these points apart from the output reading.

http://www.diyaudio.com/forums/showt...83#post1783883

Richard
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Old 29th March 2009, 07:22 AM   #300
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Hi!, this PSU help is gr8
.........but I didn't get two things.....


...in the addendum section..
under --"How much capacitance do I use in the in the power supply?"
its mentioned-----".....and 1000 uF on each pin of the chip amp. "
please explain.


Again,.......is the '35A bridge' used in the chassis grounding same as the bridge used in the rectifier.

Thanks.
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