Nearly finished but have one more question, on the original version the mosfets are not electrically insulated from the heatsinks. Can I assume there is no need to insulate on a cased version?
Sorry, should have made it clearer, I am putting my aca mini in an aca case so without isolation Q3 and Q4 are both on the same sink and so will also be connected to DC -ve. Ground, Earth and -ve always confuses me!! ??
If they are on the same heatsink they should be isolated. The screw attaching the Fets to the sink will need a sleeve to also detach the screw from connecting with the Fet tab.
So here's a weird one. My original ACA mini has been giving me stellar service for 3 years now. It uses all BOM parts including the switch. I discovered today that the amp is ON (and LED lit up) when the switch is in the "off" position and vice versa! The amp is working fine though. So it has always been like that or something has changed. The BOM switch is "on-on" so orientation on the board shouldn't matter so I can only think that one of the on board components is starting to fail, but really I'm clueless??
Not really they can't.
The data sheet for these is about the most incomprehensible thing I've seen 🙂 and it reads almost as if its configurable.
https://configured-product-images.s3.amazonaws.com/Datasheets/100.pdf
I'm sure that I would have noticed this when I built the amp if it were like this from the start but what could have changed?
Probably nothing has changed 🙂
What do you mean by 'on-on'? Does it have three positions with a centre OFF or do you mean something else?
The switch is listed as a single pole double throw which means the middle pin connects to one end pin or the other end pin depending on position.
Switch the amp OFF and measure continuity with your meter from the centre pin to the end pin/s. With the switch looking like this, the centre pin should read to the end pin marked. Move the switch the other way and the centre pin connects to the other pin.
These two points need linking to turn the amp ON:
The above image can be interpreted as ON/OFF marked on the board being correct as to the pins that need linking to give on and off but the switch toggle has to move in the opposite direction to achieve that.
So I say nothing has changed, its always been like that. Also while being pedantic about this, the PCB layout does not match the circuit diagram in such matters as LED and resistor R0. The LED goes to ground in the circuit diagram and to the positive rail on the PCB layout.
So all amps with this switch on the board, when "on" will have the toggle pointing to the off side of on/off text on the board, am I the only pedant to have lost sleep over this ?? 🙁
That depends on the orientation of the board doesn't it?
Can one not just rotate the switch through 90°. Job done?
Can one not just rotate the switch through 90°. Job done?
I built my own chassis' and for the most part, built the amps upside down, ie installing the boards from the bottom.
When I had finished, I realised I had installed the switches upside down.
I'd neglected to remind myself that when installing them, the amps were upside down lol.
I just rotated them as above.
When I had finished, I realised I had installed the switches upside down.
I'd neglected to remind myself that when installing them, the amps were upside down lol.
I just rotated them as above.
Err... yes and maybe 😀
Would the switch not be better taken off the board and mounted properly on the case somewhere?
The silkscreen labeling for this switch has been a source of confusion since the store kits first became available, back around August 2022. See back around posts #998-1001 or so. What I said in post #1001 still seems relevant: