400 Series 1 Build

[George S.]

Cool, another improvement.

 

[Hexis22]

Initial power test completed and output relay clicks as expected.

Power supply is healthy at +/- 86VDC

 

[Hexis22]

Control board mounted, wired up, and +/-15V supply voltages confirmed.

All output drivers installed and each TO-3 case confirmed isolated from chassis ground.

Initial Bias set to 350mV after 5 min power up.

Output offset on both channels measured 0.1mV.

 

[Pulpmillguy]

Nice clean build. Great work and always something to model your own after.

Whose output relay board is that? Is it Joe's or Don's?

Also, what is that circuit board that is on top of the power supply filter caps?



Never seen anything like that before. Does it come with them or is it an adder?

 

[Hexis22]

Nice clean build. Great work and always something to model your own after.

Whose output relay board is that? Is it Joe's or Don's?

Also, what is that circuit board that is on top of the power supply filter caps?

View attachment 78701

Never seen anything like that before. Does it come with them or is it an adder?

The speaker output DC protection PCB is from Don, with my components and assembly.

The power supply cap assemblies are from White Oak. The PCB converts the caps solder terminals to screw terminals.

 

[Hexis22]

RG-316 Coax installed between the RCA inputs and control board.

Initial sound check completed using an iPhone streaming into an AudioQuest Dragonfly Cobalt USB DAC.

Sounds fantastic, it's a keeper...

 

[Hexis22]

LED meter lights installed and wired up.

Meter level sensitivity leads connected to switch.

Assembly sticker added to upper cap.

Final assembly and testing next.

 

[MarkWComer]

Very clean looking job- beautiful work!

 

[Hexis22]

Very clean looking job- beautiful work!

Thank you!

I try to build every project as if it were my own equipment. The internal construction means more to me than outward appearance, not to say I don't like a sexy outer appearance...

Every solder joint, wire placement, and component is finished with purpose.

 

[Hexis22]

Fully assembled, tested, and ready for playing music and burn in.

After building several 700's, this 400 is a dream to work on with respect to weight and complexity.

 

[Gepetto]

Fully assembled, tested, and ready for playing music and burn in.

After building several 700's, this 400 is a dream to work on with respect to weight and complexity.

That is the way they were supposed to be originally built Eric. Very nice.

 

[wattsabundant]

I noticed on the relay board that R6 and C3 are not populated. This snubber protects the chip from the inductive kick of the relay coil. The values are .1uf and 100 ohm. The alternative is a clamp diode (1N4004) across the coil on the back side of the board with the cathode on pin 8. The snubber or diode is necessary for proper operation.

These days I use the diode and install an LED and current limiting resistor in place of the snubber. The LED lights when the relay pulls in. The clad will eventually get changed when I run out of the existing stock.

 

[Hexis22]

I noticed on the relay board that R6 and C3 are not populated. This snubber protects the chip from the inductive kick of the relay coil. The values are .1uf and 100 ohm. The alternative is a clamp diode (1N4004) across the coil on the back side of the board with the cathode on pin 8. The snubber or diode is necessary for proper operation.

These days I use the diode and install an LED and current limiting resistor in place of the snubber. The LED lights when the relay pulls in. The clad will eventually get changed when I run out of the existing stock.

Don, thanks for the comment.

I placed a 1N4004 diode on the underside of the board across the coil.

I just omitted the LED and current limiting resistor you place on R6 and C3.

 

[Hexis22]

That is the way they were supposed to be originally built Eric. Very nice.

Thanks Joe.

Your designs and kits are first rate and make assembly enjoyable.

 

[gene french]

LED meter lights installed and wired up.

Meter level sensitivity leads connected to switch.

Assembly sticker added to upper cap.

Final assembly and testing next.

wish i had some of your talent and patience...

 

[laatsch55]

wish i had some of your talent and patience...

You do, you just fail to manifest it....

 

[Hexis22]

wish i had some of your talent and patience...

 

[gene french]

You do, you just fail to manifest it....

i appreciate your confidence in me...i really do...
that work is impeccable ..

 

[gene french]

View attachment 78729

i got that tee short too!!!
lololol

 

[Hexis22]

This hobby will test the limits of anyone’s patience.