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Amp Camp Amp - ACA
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Old 2nd May 2018, 05:24 AM   #4171
MEPER is offline MEPER  Denmark
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Quote:
Originally Posted by ThermalAlchemy View Post
You’re correct there was no fuse in the 24 V line to the amp. I was impatient and just wanted to get things halfway wired together to see it up and running to work out the bugs because I have to manufacture a back panel to mount all my connections and I wasn’t ready for that yet. Thank you for giving me the fuse amperage size I will be installing those tonight I’d rather see a small flash have a fuse then a large flash and smoke of transistors and resistors . As for the Transformers they came with their own built-in fuses but they did not blow even though my wattmeter that I was plugged into show A wattage draw 416 W.

2A T fuse pr side should do it but 3.15 T has more limit agsint that fuse blows without a fault but gives less protection against a real fault.
I also use a vario transformer first time I apply power with an A-meter so I slowly apply voltage. If it draws much more current that it should I stop and nothing has been damaged.
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Old 2nd May 2018, 08:17 AM   #4172
MrBoat is offline MrBoat  United States
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Are they going to bring the older version PCB's back for the ACA? In hindsight, I had more fun building from those than I would have from a complete kit. Does anyone ever build these p2p?
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Old 2nd May 2018, 08:25 AM   #4173
coolnose is offline coolnose  Europe
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It's planned P2P on my side since I wanted to try one day anyway and this simple project looks like a nice candidate. Nothing to show though ....
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Old 2nd May 2018, 09:45 AM   #4174
ThermalAlchemy is offline ThermalAlchemy  United States
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Default part 2 Snap,Pop, Flash 4th time replacing transistors

this time I removed the possibility of a short to ground of the transistors. I placed each transistor on it's own heat-sink. Even without insulation pads it make no difference, transistors are not touching any thing and a fan is blowing cool air over the heat-sinks and circuit board.
As soon as I plugged in the power into my watt meter it spiked up to 200W and I immediately pulled it. the only heat developed was the resistors on the power supply, transistors and power resistors on the amp board just mild warm. The photo under the circuit board so you can see the quality of solder nothing bridged. This time looking at the insulating pads you can see they did not get hot, no brakes or metal filings.
1:What should my next step to test?.
2:Should I increase the voltage on C2 from 25V to 35V because i'm using 24V instead of 19V?.

By the way the sound difference between the 19V computer brick power supply and the separate toroidal transformers mono power into the DIY UPS is worth the extra time and money
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Old 2nd May 2018, 10:10 AM   #4175
adason is offline adason  United States
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If you are running 24 volts, i hope you added one extra resistor (2k2), and changed values of two other resistors as per post #105.
Its possible you exceeded limits of jfet, now even you added new good outputs, amp is not working right, current all over.
Check each transistor.
I built few ACA, even turbo version, but i have 5x the heatsink plus fans.
Good luck.
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Old 2nd May 2018, 10:41 AM   #4176
Zen Mod is offline Zen Mod  Serbia
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soldering is still all over the place , regarding quality

you simply can't beat the physics , especially if lacking in luck department

find someone skilled enough , to solve your problems

SF is big city , there must be some Greedy Boy near you

xperience shows , with cost of 6pack and some gasoline , there is a chance to find friend for life
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Old 2nd May 2018, 11:24 AM   #4177
Skylar88 is offline Skylar88  South Africa
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@ThermalAlchemy

Just a shot in the dark; Is -Out maybe connected to or touching ground? Refer to the schematic below.

I nearly made this mistake when I built my ACA and didn't have insulated RCA sockets available.

.
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Old 2nd May 2018, 11:45 AM   #4178
twocents is offline twocents  South Africa
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Quote:
Originally Posted by MrBoat View Post
Does anyone ever build these p2p?
Yes, check this one by X:
Amp Camp Amp - ACA
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Old 2nd May 2018, 01:49 PM   #4179
Eric is offline Eric  United States
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ThermalAlchemy - I agree with what everyone said above.

Edit: Apparently, I hit "reply" before I realized there was another page of discussion.... oops...

That irregular surface with the oval holes has many edges. If the mosfet is not *PREFECTLY* level with the mounting surface, or any of those oval holes have even the *SLIGHTEST* of a raised lip around the edges, you are likely to have cut-through in your SilPad and then the mosfet grounds to the sink and causes things to burn up.

The image you have where you removed this metal lattice work is a MUCH better approach, but I would go one step further. Remove this metal lattice from the sink that it is attached to. Then, take some 400 grit wet/dry sand paper, wrap it around a small flat metal block (never just use your fingers), apply some lubricant (water, oil) and do some sanding on that screw hole to make sure there is not a raised lip around the edge that will also cut through your next SilPad and ground the mosfet again.

Surface prep for mounting mosfets is *VERY* important.
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Last edited by Eric; 2nd May 2018 at 01:53 PM.
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Old 2nd May 2018, 02:10 PM   #4180
6L6 is offline 6L6  United States
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ThermalAlchemy

If your circuit is pulling 200W, you have a short somewhere, most likely a dead Mosfet. Hopefully the input Jfet is ok, but it will need to be checked as well.
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