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Old 19th November 2012, 12:00 PM   #21
DF96 is offline DF96  England
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Do we yet have a circuit diagram of exactly what the OP has done? Without this we are all fumbling in the dark.
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Old 19th November 2012, 12:11 PM   #22
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by DF96 View Post
Do we yet have a circuit diagram of exactly what the OP has done? Without this we are all fumbling in the dark.
Post #9

Unregulated supply with a 47uf reservoir cap and possible wiring problem of centre tap if it happenes to connect to the zero volt line.
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Old 20th November 2012, 02:48 PM   #23
JForged is offline JForged  United States
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Hi Audio peoples.

OK, I am still waiting on the correct cap but I did with two 480uf's in series to get close.

Also I have some more pictures for you guys.


Here is the PS in the case.
Click the image to open in full size.

Here is my breadboarded rectifer. Looks ugly but i'll dress it up when it goes in the case.

Click the image to open in full size.


And here are the readings on it. The ripple doesn't occur until I put a lamp or some other kind of load on it.

Click the image to open in full size.


So it looks like even with the larger cap I am still getting ripple. I have yet to modify the rectifier section with a regulator but will probably be doing that when I have some time this evening. I know that some ripple is probably unavoidable but any time I connect an audio circuit to this I can hear the heavy modulation.
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Old 20th November 2012, 03:01 PM   #24
DF96 is offline DF96  England
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Assuming this has to drive the valve heater as well as the 'HT', a 47uF is almost no smoothing at all. Two 480's (470's?) in series is 240uF, which will give you about 7V ripple. To get below 1V pk-pk ripple you need 1500uF. The regulator can then clean this up.

Find out how to do a ripple calculation. It involves calculating the charge removed fromthe cap for each mains half-cycle, then dividing by the capacitance.
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Old 20th November 2012, 04:37 PM   #25
JForged is offline JForged  United States
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Thanks DF96. I plugged in three 480 uf in parallel and the ripple was greatly reduced but now has movement to it.

Also, my scope will not see it under DC at this point only under AC. Anyone suggestions as to why this is.

I am relatively new to electronics and extremely new to scope operation.
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Old 20th November 2012, 05:32 PM   #26
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by JForged View Post
Thanks DF96. I plugged in three 480 uf in parallel and the ripple was greatly reduced but now has movement to it.

Also, my scope will not see it under DC at this point only under AC. Anyone suggestions as to why this is.

I am relatively new to electronics and extremely new to scope operation.
The only way you will kill all the ripple is either with a regulator (although we're not sure there is enough "headroom" to work with for that) or an active ripple filter.

The scope is essentially just a voltmeter, always remember that. So the reason you can't see the ripple on the DC is because the DC voltage drives the trace off the screen. When you AC couple the scope you are left with just the AC component riding on that DC voltage which makes it possible to see and measure easily.
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Old 21st November 2012, 04:27 PM   #27
JForged is offline JForged  United States
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Thanks Mooly.

Drifting off topic here a little bit, I have been digging around in the manuals for the 'scope trying to find a way to include some kind of reference grid or markers that sow the voltage at certain levels. Do you know if this is possible on any scopes?
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Old 21st November 2012, 04:38 PM   #28
Mooly is offline Mooly  United Kingdom
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Just looking at your pictures. So the scopes an "add on" for a PC ? I've never used one like that tbh so I don't know although it looks like you can read voltages off from the "settings" panel I use the traditional CRT display type with graticule etched on the screen.
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Old 21st November 2012, 04:40 PM   #29
JForged is offline JForged  United States
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Yea, I'd like to get one but money is tight. This was a usb scope for about $200. I'd like to get a nice techtronik scope some day.
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Old 21st November 2012, 04:44 PM   #30
Mooly is offline Mooly  United Kingdom
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I still think an analogue scope takes some beating and would take one any day over a digital. Bandwidth is everything, the one I use is a 100Mhz dual trace which is great for audio.


GERMANIUM Single ended Class A Headphone Amp.
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