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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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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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.
 
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)
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
 
I've found photos of a 2125SX that uses the same type of drive circuit. The resistors appear to have burned at one time but the replacements are 33.2 ohms.

On one end they go to the bases but the other end doesn't look like it goes to ground. In the first photo, ground is very near one terminal but it doesn't connect to it.
 

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