Amp Camp Amp Kit 1.6/1.8

Hello. This is my first post to the forum. I'm having trouble with my ACA 1.8 build - no sound on the left channel. Resistance and voltage reading for the left circuit board are virtually identical to the right circuit board but there are discrepancies on both boards from the voltage values listed in Step 56 - Troubleshooting. I'm hoping that listing these values here will enable a knowledgeable person to give advice on how to proceed.


Right Channel


Q1 - S 15.2mV, D 8044V, G 4.59V,

Q2 - G 13.7 V, D 23.67V, S 9.25V
Q4 - D 23.66V,

R5 - 13063 V, R9 - 4.56V, R10 - 4.26V, R15 - 8.91V



Left Channel


Q1 - S 16.1 mV, D 8.13 V, G 4.56V
Q2 - G 13.49 V, D 23.69 V, S 9.00 V
Q4 - 23.72 V
R5 13.46 V, R9 4.56V, R10 4.39 V, R15 8.72 V


I don't know if this helps, but this is where I am right now and any guidance beyond this point is need and appreciated.
 
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Hmm. Both channels look pretty close from those readings and both look a little out... but I suspect that is not what is causing your problem here.

Q1 and Q2. This this tells much.

24v on the drain of Q2 means the supplies are OK.

9 volts on the source. This is low for both. The voltage here should adjust with the preset and you are aiming for about 12 volts. Although low it would not stop the amp working.

So that is one thing to check. Does the voltage adjust correctly with the preset.

If you have no sound at all then I would be looking at a basic connection error in either the input wiring or the speaker feed. Switch it OFF and check continuity from the input sockets all the way through to R11.

Also make sure you have not got a short circuit across the input socket.

Other clues... can you hear the dead channel produce the same 'thump' in the speaker as you power it on and off?
 
Up and Running!

Thanks for your advice Mooly. Adjusting the voltage solved the problem. I was aware of this step but some how glossed over it and became distracted by the lack of sound on the left channel and didn't make the adjustment. Thanks again for putting me on the right track.
 
When assembling the ACA, does anyone ever attach the various leads (power, signal, speaker, LED) to the board before mounting the board to the heat sink? In reading through the instructions before attempting the build, it just seems it would be easier to solder the leads while still having access to the back of the board. Thanks for any thoughts.
 
I did this, and for me it helped. The last things I soldered were the legs of the fets, which were already mounted on the heat sinks.

Interesting… you delayed the final joining of the circuit boards to the heat sinks even later than I had been considering.

Speaking of the FETs, are there any tricks to getting the bends in their leads in the right place so that they align with the through-holes of the mounted boards? The instructions seem vague enough in this area to potentially be a problem.
 
Sent the wrong parts (I think)

Hi guys,

I bought a couple of amp camp amps. My first one was perfect and works great. But I started my second one last weekend and noticed that I've been sent the wrong transistors. I'm talking about the little small ones. I'm meant to get two of each but have three of one type and one of the other. Can anyone tell me who to contact? Thanks.
 
Speaking of the FETs, are there any tricks to getting the bends in their leads in the right place so that they align with the through-holes of the mounted boards? The instructions seem vague enough in this area to potentially be a problem.

I bent them as per the instructions, from memory at the shoulder on the legs, doing a dry fit before proceeding too far.
 
ACA 1.8

Hi, This is my first post to this forum. I’m building two ACA 1.8 amps. Started with just one to see how it would go. Checked all my values prior to installing. All checked out. Put it all together, powered up. Adjusted voltage to 12ish, all looked good. Connected it to my preamp, speakers and CD player. Fired it up and nothing but dead silence. Put it back on the bench and started troubleshooting.
Here’s what I got.

Red Board

Q4 D=523k. 24.5v
R10= bottom 336k 4.26v
R9= Top 522k 4.58v
R15= bottom 4.36k 11.8v
R5= Top 10.4k 17.3v
Q1
S=0k 15.4 v
D=4.67k 12.08v
G= 620k 4.57v
Q2
G=10.61k 17.29v
D= 624k 24.06v
S= 4.68k 12.68v

White Board

Q4 D= 530k 24.05v
R10= Bottom 336k 4.2v
R9= Top 522k 4.6v
R15=Top 5.8k 12.5v
R15= Bottom 5.2k 11v
R5= Top 10.6k 17.3v
Q1
S= 0k 11.4v
D=4.8k 12.10v
G= 620k 4.63v
Q2
G=10.62k 17.3v
D=524k 24.0v
S=4.85k 12.71v

It’s my first DIY project so this is mostly foreign to an old man. Could someone share their wisdom and guidance to get this running? I’d really like to build the second one without as many issues.
Thanks So Much