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Orion 250sx with BJT on power supply
Orion 250sx with BJT on power supply
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Old 22nd September 2020, 04:58 PM   #1
picco76 is offline picco76  Italy
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Default Orion 250sx with BJT on power supply

hi,
i have bought this one, old orion 250sx.
this amplifier work, but have a strange noise from toroidal trasformer.
this amplifier is repaired (not from me), i have found on power supply BD911 device. is correct? Is power supply TL494 based.
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Old 22nd September 2020, 07:07 PM   #2
Perry Babin is offline Perry Babin  United States
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Is the noise audible in the audio?

Will it be audible when installed in the vehicle?

Typically, if there are no gate/base resistors, the transistors are BJTs. Having gate/base resistors doesn't guarantee that they will be FETs but they generally are. The BD911 in your amp is likely correct.
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Last edited by Perry Babin; 22nd September 2020 at 07:10 PM.
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Old 22nd September 2020, 07:15 PM   #3
picco76 is offline picco76  Italy
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Hi Perry,
This noise don't is udible on the speakers and don't is audible on the vehicle, is a little noise without cover
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Old 22nd September 2020, 07:17 PM   #4
Perry Babin is offline Perry Babin  United States
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I wouldn't worry about it. Sometimes simply moving the windings slightly can stop it.

Confirm that the output from the IC is at 20kHz or higher.
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Old 22nd September 2020, 07:35 PM   #5
picco76 is offline picco76  Italy
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Ok, i will check and let you know.
Thanks
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Old 22nd September 2020, 10:58 PM   #6
picco76 is offline picco76  Italy
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Quote:
Originally Posted by Perry Babin View Post
I wouldn't worry about it. Sometimes simply moving the windings slightly can stop it.

Confirm that the output from the IC is at 20kHz or higher.
One another thing, the resistor on the picture attached, on the green circle, 100ohm is correct?
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Old 22nd September 2020, 11:10 PM   #7
Perry Babin is offline Perry Babin  United States
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Wasn't it a 10 ohm in the original photo you posted?

I just looked through some photos and in a different version of the 250SX, it used D44VH7s in the supply. I'd say that's rare in these old amps. The 2N6488 was very common. The 6488 isn't as 'fast' as the D44 but worked well. This isn't to cause confusion. Just a note.
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Old 22nd September 2020, 11:19 PM   #8
picco76 is offline picco76  Italy
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Quote:
Originally Posted by Perry Babin View Post
Wasn't it a 10 ohm in the original photo you posted?
This resistor is present only in the last picture, i have measured 100ohm, but was changed (not from me)
Quote:
Originally Posted by Perry Babin View Post
I just looked through some photos and in a different version of the 250SX, it used D44VH7s in the supply. I'd say that's rare in these old amps. The 2N6488 was very common. The 6488 isn't as 'fast' as the D44 but worked well. This isn't to cause confusion. Just a note.
Yes is true, i have 240gx and 280gx first series with 6488 device on the power supply and works fine
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Old 22nd September 2020, 11:20 PM   #9
Perry Babin is offline Perry Babin  United States
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There is an identical driver circuit on the other side. Has someone replaced the corresponding resistor in that circuit as well?
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Old 22nd September 2020, 11:24 PM   #10
picco76 is offline picco76  Italy
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Quote:
Originally Posted by Perry Babin View Post
There is an identical driver circuit on the other side. Has someone replaced the corresponding resistor in that circuit as well?
Are both changed
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