garAM10BC build thread

[Whoops]

Is there a lot of difference in the BC560 to 560C or B transistor?
In Brazil I only found BC550, BC550b, BC560, BC557 and BC557B.
Can I use BC550 and 560 (B) to replace BC550C / 560C?

B and C are the Gain/HFE ranges:

• "A" indicates low gain (110 to 220, typically 180) at 2 mA collector current,
• "B" indicates medium gain (200 to 450)
• "C" indicates high gain (420 to 800)

https://en.wikipedia.org/wiki/BC548

 

[metalockpick]

I suppose this is a Gary question...Might've posted this elsewhere, not someone who does web boards here.

On the garAM10- Turning the voltage up slowly on a Variac, I get the death hum and turned it off immediately so as not to smoke any components. All of the other DOA kits I built work perfectly (Very impressed with your garOA10).

Built a kit, all caps, diodes, resistors, transistors are correct and in the correct positions. Looking at the blank PCB traces on the website, I have no shorts where their shouldn't be, even the really fine pitch ones. Diode check shows no shorts in diodes or transistors, nor any fixed resistances across transistors that aren't due to resistors in circuit. All resistors measure correctly in circuit. No shorted capacitors. I did make the common mistake with the two diodes (pads, silkscreen and orientation don't follow standard practice (GARY!!!!), but I fixed that...Still death hum.

What transistors would be turning on to cause this?

I have the V2 boards, but they don't seem different than V1 (Are they?).
The low value 1/2 Watt resistors seem to be wired across transistors...Is that right?

Thank you, Metalockpick

 

[metalockpick]

I suppose this is a Gary question...Might've posted this elsewhere, not someone who does web boards here.

On the garAM10- Turning the voltage up slowly on a Variac, I get the death hum and turned it off immediately so as not to smoke any components. All of the other DOA kits I built work perfectly (Very impressed with your garOA10).

Built a kit, all caps, diodes, resistors, transistors are correct and in the correct positions. Looking at the blank PCB traces on the website, I have no shorts where their shouldn't be, even the really fine pitch ones. Diode check shows no shorts in diodes or transistors, nor any fixed resistances across transistors that aren't due to resistors in circuit. All resistors measure correctly in circuit. No shorted capacitors. I did make the common mistake with the two diodes (pads, silkscreen and orientation don't follow standard practice (GARY!!!!), but I fixed that...Still death hum.

What transistors would be turning on to cause this?

I have the V2 boards, but they don't seem different than V1 (Are they?).
The low value 1/2 Watt resistors seem to be wired across transistors...Is that right?

Thank you, Metalockpick

Fixed it. Outputs blew from the 914s in an improper orientation. This circuit also doesn't like lower than +&-15V! Great performance once it's up to proper voltage, though...