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a suitable transistor substitution for Delite amp
a suitable transistor substitution for Delite amp
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Old 31st May 2018, 01:15 AM   #11
Pascal Nguyen is offline Pascal Nguyen  Australia
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Quote:
Originally Posted by gmurray618 View Post

I do have a heat sink question.
My CPU heatsink copper plates had a poor surface finition, means poor heat transfers.
I treated them with my elbow grease (wet sand paper).
Extra measure has to be taken for active cooling system, an NC thermostat (a dollar or so) in series with the PSU in case of malfunctioning or forgot to turn fan on.
Cheers
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Old 31st May 2018, 04:41 PM   #12
Nelson Pass is offline Nelson Pass  United States
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a suitable transistor substitution for Delite amp
Use some goop with them.
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Old 2nd June 2018, 10:08 AM   #13
Pascal Nguyen is offline Pascal Nguyen  Australia
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Use some goop with them.
It would be fine for your environment, I suppose.
Mine, I do wet sanding daily, as Karaté Kid had to, with a purpose to have a Popeye arm.

Cheers and thanks for your kindness
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Old 2nd June 2018, 05:12 PM   #14
gmurray618 is offline gmurray618  United States
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Very cool. I like the idea of repurposing the old computers. This week I’ll check out the voltage coming out of the PC power supplies (not the 19.5V laptop bricks - the internal power supply). It wouldn’t be the worst thing to have to rectify and smooth + and - 20 to 30 volts like I did with the F5. It would jacknthe price up to have to get the transformers and caps but good lessons.

As for goop I’m going to try and save their little hands and use thermal insulation pads, similar to the ones in the ACA kit. CD-02-05-190 Wakefield-Vette | Mouser

Thanks for the help and encouragement. Right now I’m thinking having my class creat accounts here and post progress on a class thread. If I get jammed up I know there is a wealth of knowledge here.
George
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Old 3rd June 2018, 10:16 AM   #15
WalterW is offline WalterW  Netherlands
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a suitable transistor substitution for Delite amp
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Originally Posted by MossFed View Post
It would be fine for your environment, I suppose.
Mine, I do wet sanding daily, as Karaté Kid had to, with a purpose to have a Popeye arm.

Cheers and thanks for your kindness
It doesn't look very well sanded?
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Old 3rd June 2018, 01:53 PM   #16
tsmith1315 is offline tsmith1315  United States
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Quote:
Originally Posted by gmurray618 View Post
Very cool. I like the idea of repurposing the old computers. This week I’ll check out the voltage coming out of the PC power supplies (not the 19.5V laptop bricks - the internal power supply). It wouldn’t be the worst thing to have to rectify and smooth + and - 20 to 30 volts like I did with the F5.
An internal ATX-type computer power supply won't do it. 12V max, and the corresponding -12V is only good for an amp or so. The +12V output is pretty stout. You could run a handful car audio-type chip amps with it for a few watts of output each.
They do make for a quick and greasy benchtop supply with (IIRC) +12V, -12V, +5V,-5V, +3.3V available.
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Old 3rd June 2018, 03:15 PM   #17
gmurray618 is offline gmurray618  United States
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Thanks Tim (by the way, love your avatar). I’ll think of something else to do with them and plan on swing a proper transformer I suppose. So far administration is behind me on this project. Fingers crossed.
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Old 5th June 2018, 09:32 PM   #18
gmurray618 is offline gmurray618  United States
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So I was looking at transformers (100 VA 20V) to get +/-28 V, so I’ve got 56V to power the amp. So I run close to 1A through the light bulb that acts as a 40-50ohm resistor to bring the voltage about 12V to feed the collector. (Do I have it right so far?)

So my question is why not ditch the light bulb and use a 12V supply? (Yeah, I know the light looks cool �� but it’s a more expensive transformer)
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Old 5th June 2018, 10:20 PM   #19
aspringv is online now aspringv  Australia
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a suitable transistor substitution for Delite amp
The light is acting as a constant current source (ish) to the transistor. The transistor is creating the voltage output across that resistor...
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Old 5th June 2018, 10:31 PM   #20
woody is offline woody
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In this amplifier the voltage across that transistor is only 12v if no signal is being amplified. But when you are amplifying a signal the voltage across the transistor is changing perhaps from 2v to 30v . That light bulb just acting as a big resistor allows
for this voltage swing across the transistor. Without this swing there would be no ac
output that is NO music .
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