To remove the pcb undo all the plugs and heat sink, and potentiometer shafts. Not terrible. Do you think it would be necessary to repair it? From what I see, the caps look fine and transistors fairly recent. Those two blue wires are connected to the PCB common ground. It looks no worse than the Hafler amps from the same era. I don't see any power drivers, could it be lateral Mosfets? In my opinion, nice.
It looks WAY easy to repair, compared to anything modern.
No, those aren’t lateral mosfets, they are darlingtons. Early photo clearly shows MJ1101x. Cant make out the last digit, which would tell you the voltage grade. THAT is still the biggest unanswered question here. Wether or that it’s enough heat sink hinges on the Vcc.
As a darlington design from the 70’s it’s a 0.1-0.2% THD kind of thing. Probably not BAD sounding, but you’d probably notice a Honeybadger or wolverine to be better.
No, those aren’t lateral mosfets, they are darlingtons. Early photo clearly shows MJ1101x. Cant make out the last digit, which would tell you the voltage grade. THAT is still the biggest unanswered question here. Wether or that it’s enough heat sink hinges on the Vcc.
As a darlington design from the 70’s it’s a 0.1-0.2% THD kind of thing. Probably not BAD sounding, but you’d probably notice a Honeybadger or wolverine to be better.
I assume the board used is one, perhaps two layers but it seems to have massive tracks? Does the track width (copper/gold content) matter to sound quality? My newer amplifiers all have far less track 'volume' meaning they are much, much thinner but perhaps have more pcb layers.
@drummerman111 ,
Is there a removable panel on the bottom of the chassis to allow full access to the underside of the circuit board?
Is there a removable panel on the bottom of the chassis to allow full access to the underside of the circuit board?
The wide track is for low inductance. Just good practice, which helps some of the mystery problems that can arise if design details are ignored or overlooked. The power supply is “assumed” to be low impedance, up to very high frequencies. If it physically isn’t, you can develop instabilities, have higher noise or distortion than you would expect from a simplified model of it.
Today everything can be simulated to death. It isn’t always, but the computer power is there if you have the tools.
Today everything can be simulated to death. It isn’t always, but the computer power is there if you have the tools.
The newer amp most likely takes the 21'st century "dirty" power into account. SMPS's , digital noise - scope a local powerstrip
with all the phone chargers and PC's plugged in and running. All sorts of content besides the 50/60hz waveform.
With a double sided board , you can get the +/- rails to cancel and layout software will allow the calculation of amperage vs.
track width/thickness. The routing of the NFB trace , where the output inductors are (no dual wound cancelling inductor) ??
I doubt whether this amp was built for 20ppm or below. 200-300Khz gain bandwidth , you don't need fancy layout.
The new amp also might be double sided 2 oz. copper , with tracks on both sides (black circle) 4mm X 2 = 15A current.
The single sided power tracks are calculated to be 17A (7mm + 2 oz.)
I have software that can tell me the R-L-C of a particular arrangement of a specific track.
OS
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The amplifier/s pictured are not mine and I can't remember whether it had a removable panel underneath to gain access. I owned this almost 30 years ago.