I have successfully blown Genuine vintage Philips 40W + 40W amplifier which was so popular in its time , literally ever diyer of the era made some clóne as it was featured in a old hifi book. Output Power transistor BD182 are gone in one channel , so i need a replacement .
Any recommendation ? Shall i replace both channel ?
Any recommendation ? Shall i replace both channel ?
BD182 can be replaced with 2N3055 or others in the TO-3 case. You may need to replace driver transistors and other parts.
BD 182, Tube BD182; Rohre BD 182 ID39269, Transistor
BD 182, Tube BD182; Rohre BD 182 ID39269, Transistor
I already tried 2n3055 from CDIL /BEL/Onsem but I got horrible oscillation . BEL was most tamed in my opinion .
I replaced driver transistor BD139/BD140 . My granny had them from 80s.
2n3773 is much worse . I have no other power transistor to try.
I replaced driver transistor BD139/BD140 . My granny had them from 80s.
2n3773 is much worse . I have no other power transistor to try.
C7, 27pF is the Miller cap on the VAS - try a higher value, 100pF is a commonly used value. The old BD182 has so little bandwidth that it was the dominant pole of the amp response I reckon. Modern transistors are a lot faster so the amp has much more HF gain to stabilize.
Correction Elements C4,5,6,7,9. Some may be changed or deleted. Look at similar schemes 70-80 on the forum.
No, unless you want a dedicated amplifier for subwoofer use. Otherwise, you'd better stay within the pF (1 pF = 10-3 nF) range.
On top of that, those Philips/Mullard »mustard« capacitors aren't bad at all, but there's also no need to overrate them.
Best regards!
Being wrong by a factor of a thousand will fail utterly.
µ = micro = 10^-6 = 0.000001
n = nano = 10^-9 = 0.000000001
p = pico = 10^-12 = 0.000000000001
Swapping an old diffused device for a modern epi is an opportunity to increase the bandwidth of the original design. Rather than slugging it with a larger Miller cap, I'd be looking at reducing the capacitances, particularly the 680pF feedback and 10nF VAS shunt.
Would need to do some sims to optimise.
(You could also convert to fully complementary with 2N3055/MJ2955 if you wanted, but not essential.
Is the oscillation on the lower half (negative going) part of the signal?
Would need to do some sims to optimise.
(You could also convert to fully complementary with 2N3055/MJ2955 if you wanted, but not essential.
Is the oscillation on the lower half (negative going) part of the signal?
Not the fact that this is the exact original of the 70s, if (Transistors Base Numbers BCxxxx to BDxxxx | Cricklewood Electronics ) did not invent the time machine.
Modern BJT with similar specifications.
Modern BJT with similar specifications.
I have used Cricklewood Electronics for many years and have never had any problems with their devices.
First simulation results suggest:
- remove C3, C6, C7, R12 and C5.
Add a 220 pF capacitor in series with a 100 ohm resistor and connect between the collector of Tr2 (BD139 VAS) and emitter of Tr1 (PNP input).
Caveats - this method was used successfully by Dr Bailey. It requires a low input impedance to keep the frequency response of Tr1 high. Depending on the pre-amp you may need to do one or more of the following:
(a) add a 1.5k resistor in series with the input (C2) and if that makes little difference add a 100pF from Tr1 base to ground.
(b) if your power supply leads are longer than 100mm between the PSU caps and the supply rails, add 100uF caps locally, connected from the PSU + rails on the amp PCB and common ground point.
Simulations did not reveal any oscillations in the output, after swapping between devices, but there were oscillations internally, in Tr1, (not a good sign) which were eliminated by the pahse lead compensation above.
- remove C3, C6, C7, R12 and C5.
Add a 220 pF capacitor in series with a 100 ohm resistor and connect between the collector of Tr2 (BD139 VAS) and emitter of Tr1 (PNP input).
Caveats - this method was used successfully by Dr Bailey. It requires a low input impedance to keep the frequency response of Tr1 high. Depending on the pre-amp you may need to do one or more of the following:
(a) add a 1.5k resistor in series with the input (C2) and if that makes little difference add a 100pF from Tr1 base to ground.
(b) if your power supply leads are longer than 100mm between the PSU caps and the supply rails, add 100uF caps locally, connected from the PSU + rails on the amp PCB and common ground point.
Simulations did not reveal any oscillations in the output, after swapping between devices, but there were oscillations internally, in Tr1, (not a good sign) which were eliminated by the pahse lead compensation above.
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