Mistakes you Learnt from! (might be helpful for beginners)

[Rixsta]

Today I was thinking about mistakes I made in the past building amplifiers, things that today i would do differently.

I thought if we keep this thread nice, simple and to the point it will be helpful for those creating their first amps and help them hopefully not blow the thing up!

Im not one for making guidelines as Im still a newbie myself but ill let you lot do that lol


1: Long wires from Mosfets to PCB in my case didn't help, my ZenV4 amplifier build Was close to oscillation. Im not sure but i think the Gate resistors need to be close to the Mosfet too ?

2: Audio Input Wires want to be kept away from Power supply wires to avoid interference.

3: when drilling Heatsinks if using a hand held Drill make sure you use a Tap first as one of the holes i drilled i slipped a bit. and for drilling the right positions for the Mosfets in some situations you get one chance to drill it right.


Ok, ill post some more of my experience soon

 

[AndrewT]

Multi-meter probes with exposed metal.

Insulate the probe tips so that only the last 1mm is exposed to accidentally touching other components.

 

[AndrewT]

Add test loops to your PCB layout.

Saves having to probe deep into crowded spaces.

 

[AndrewT]

Orient electrolytics in same direction on your PCB.

 

[AndrewT]

Where should this be located?
Construction tips, or design Threads?

 

[jhsjhs99]

Multi-meter probes with exposed metal.

Insulate the probe tips so that only the last 1mm is exposed to accidentally touching other components.

This is really clever; I will do this, thanks. A fuse gave its life due to this issue.

Does anyone have tips around neatly preparing cases for these projects? I have had problems making clean holes without bending the metal around them.

 

[budwiser]

Place a block of wood under where you are drilling.

This is really clever; I will do this, thanks. A fuse gave its life due to this issue.

Does anyone have tips around neatly preparing cases for these projects? I have had problems making clean holes without bending the metal around them.

 

[tool49]

If drilling before tapping, I like to have extra sharp bit, so a sharpener does a really good job and reduces the pressure required to actually punch metal through Drill Doctor

Also sometimes when making panel holes that are quite large and the panel quite thin, the regular twist bits will make oval holes, for this I like to use steppers which give you perfectly rounded holes with no vibrations: Irwin Unibit

 

[sakellogg]

setup 2 meters when you are testing for voltage and current. use one for volts and one for current.
ive killed parts before, forgeting to swap back using 1 meter.
stupid move on my part i know but, i havent done it again after i got another fluke!

 

[tool49]

Don't rely on harbor freight multi meters for measuring current. Out of three different units, I was seeing over 2 amps of difference with my Fluke.

 

[Danger Mouse]

double or triple check correct position of your parts at PCB

doing this a liitle bit careless costs me a matched pair of 2sk170 at input of a SYMASYM. At my pass clones all goes easy till now
may be i take more care at pass

 

[tool49]

I'd go one step further ask someone else to double check your placement before powering the project. A fresh eye will often see something that you will miss (even multiple times!)

 

[Zen Mod]

mistakes

I made them all

learned nuttin'

 

[Pemo]

Twisted pairs.
Power Ground
Audio Ground.
Is that right Andrew?

 

[Mr. dB]

Twisted pairs.
Power Ground
Audio Ground.
Is that right Andrew?

Or dirty ground and clean ground, to keep rectifier noise out of the audio ground.

Which one do you connect to the speaker ground? I've seen both...

 

[vdi_nenna]

Measure all resistors with multi-meter before soldering to PCB.

 

[Andersonix]

Before switching on for the first time, check for open circuit between heat sink and middle (source) pin on output transistors to ensure that thermal pads are in fact electrically insulating.

 

[Rixsta]

Before switching on for the first time, check for open circuit between heat sink and middle (source) pin on output transistors to ensure that thermal pads are in fact electrically insulating.

Thanks, yes this is one of them Iv'e not forgotten, mostly that im scared of blowing a Mosfet when it can fry them all like dominoes and cost you a bit.

Will read what you all put when I have time, Cheers i needed to see some of this stuff myself!

 

[Floric]

- Before applying voltage for the first time, check for short circuits with your Ohmmeter.

- Never apply voltage to a pcb without spacers to the desk.

Not that I already did it...

 

[HIPCHECK]

1. Read the pin out on the datasheet (IE 7812 and 7912 voltage regs have different pin outs) my first project and first error!

2. make sure you connect the proper ground to the circuit in a dual mono amp (when I cased up my dual mono Mini A, DUH!)

3. be VERY CAREFUL with Caps, Goggles are your friend...be Careful if you did not buy them BRAND spanking new. Build yourself a isolation area to apply voltage to them slow.

4. Dont pull an "all-nighter" and then try to power up your build, walk away comeback after lunch and double check the basics first!

5. Get a Variac, Bulb Tester, Fuse board, and make a test rig.