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Amp Camp Amp Kit V1.6
Amp Camp Amp Kit V1.6
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Old 12th November 2019, 08:36 PM   #601
myleftear is offline myleftear  Switzerland
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Default dual mono in a mini dissipante 300?

Hi friends!

I realized there's a Mini Dissipante 230 x 300, would 2 ACA's fit into one of these?
A PCB with the transistors makes pretty much 150 mm, so it seems it would.
But would they overheat, having 2 of them being so close to each other? (And then, it would be funny to have them turned 90į, getting a cube 230 * 200 * 200 IF this form factor would exist. sigh! )
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Old 12th November 2019, 09:44 PM   #602
Steve Luck is offline Steve Luck  New Zealand
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I'd say they'd get too hot but there'd be no problem stacking two 230 x 200 with no base plate on one and no lid on the other to create a linked internal space. Bit of box section ally from DIY store to fill the gap and drill a few holes job done. Buy two ACA specified cases and all the mounting holes in the heat sink will be pre drilled ready to go.
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Old 12th November 2019, 10:25 PM   #603
myleftear is offline myleftear  Switzerland
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Quote:
Originally Posted by Steve Luck View Post
no problem stacking two 230 x 200 ...

Thanks, Steve!
IĎm already investigating this direction as a viable alternative... with custom-made frontpanel and stuff
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Old 12th November 2019, 10:36 PM   #604
Steve Luck is offline Steve Luck  New Zealand
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I’m building power supplies in mini dissipate cases to stack on top of ACA 10mm stand-off where the self tappers go leaves a couple of mm gap between faceplates. ��
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Old 14th November 2019, 07:38 PM   #605
myleftear is offline myleftear  Switzerland
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Quote:
Originally Posted by myleftear View Post
What happens if I lower the bias to, say 10V? Nothing except that the amp starts to clip earlyer? And gets a bit less warm?
Quote:
Originally Posted by Mooly View Post
The heat dissipation should stay the same if you alter the midpoint voltage (bias is misleading because so many immediately think of quiescent current adjustment here).

With the midpoint set accurately each transistor dissipates the same power. If you alter the midpoint to say 6 volts then one transistor will dissipate much more power than the other due to the different voltage now dropped across each device. The current flow is unaltered.

The one with least voltage across it will be cooler. The total power dissipation of the two devices added together remains the same.
Just in case somebody else will have the same question:
I just found a nice graphic "explanation" of it at the german wikipedia ( Arbeitspunkt – Wikipedia ):

Click the image to open in full size.

Thank you, Mooly, for your explanation, which I only now begin to really understand!
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Old 15th November 2019, 07:47 AM   #606
Mooly is offline Mooly  United Kingdom
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Pleased to hear it's making some sense
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Old 16th November 2019, 10:55 PM   #607
bobertbk is offline bobertbk
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As I continue my intermittent troubleshooting it seems one of the most obvious issues I have is that on one board Q1 S is registering 24v when it should be zero. On close inspection nothing seems to be obvious on the board itself. Could this instead be an issue with how I have attached the ground wire?
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Last edited by bobertbk; 16th November 2019 at 10:59 PM.
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Old 17th November 2019, 07:25 AM   #608
Alan4411 is offline Alan4411  Wales
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You need to make a really good solder job where the 2 black wires and the 'twisted' wire meet the input connector. From the picture it does not look soldered at all.
The other solder joints do not look special either. They look 'blobby'. You should hold the iron against the joint a little longer, then the solder will flow into and around the joints when you get it right.
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Old 17th November 2019, 07:43 AM   #609
Mooly is offline Mooly  United Kingdom
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The source of Q1 should be connected directly to ground and so I suggest you check carefully where you are measuring your voltage from... in other words where the black meter lead is connected to.

An ideal point would be the outer part (ground) of the RCA input sockets or the positive speaker terminal assuming you have wired these as per the instructions.
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Old 27th November 2019, 07:04 AM   #610
ThermalAlchemy is offline ThermalAlchemy  United States
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Default I want to donate ACA kit To my college Electronics 101 class

My first community college is underfunded and understaffed where I took my basics electronics classes at laney College Oakland. I would like to donate my time and some ACA kits to the class, already have approval from my Former instructor.
I do know the majority transistors from eBay Chyna are knock offs or lesser known Chinese companies that are not Semi South ON , Fairchild or Vichy. And well aware 100% of the ToshibaĎs are fake counterfeit but do they work good enough for a free kit to students or does anybody know of dropping replacements without doing the math to change resistors because thatís where I am very weak.

The attached photo files of resistors IRFP240, IRFP450, 2SK170
Iím willing to spend the money on the fake resistors Or third-party not so well known semiconductor company (they donít always have to be a big well-known brand name do they ?) as long as they work. Canít beat the price probably donít sound as good but I will have a authentic demo in the class to show the difference and Iím willing to experiment.

For the class I was going to provide to demo options one (point the point construction ) and the other on Perfboard.

I was going to link the amp camp amp V1.6 build guide link to the students from there they can make up their mind if they want the homemade donated kit for free and they have the option to purchase the boards if they want.

The IRFP240 were $24 to $37 for 50 PCS One even claims they are Fairchild.
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