Building the amp5

[heady 0]

hmmm...so maybe heady is the one who is the one who will be our SLT runner in future....

Buying is not a problem, the problem will be how to pass it to you. You stay in west and ck and I stay in the east. Seriously, if you need stuff from Farnell, can collect for you if item below amount for free delivery.

Edited September 19, 2006 by heady

[heady 0]

Thanks to CK's advice on using a bench vice. I did the toroids, hope the winding is good enough, anyway got 44 coils around the inductor. Read some advice on the diy forum about not letting the first and last turn touching each other, so I place a short heat-shrink tube on one wire to see if it will do just that.

[ckng 0]

Thanks to CK's advice on using a bench vice. I did the toroids, hope the winding is good enough, anyway got 44 coils around the inductor. Read some advice on the diy forum about not letting the first and last turn touching each other, so I place a short heat-shrink tube on one wire to see if it will do just that.

Looks pretty good! I don't have a bench vice so I had to do the toroids of my AMP3 by hand. Not very fun.

 

Regards

CK

[heady 0]

Did the caps on the back of the board. The BOM missed out C441 which should be 0.1uF, so all 12 pieces of 0.1uF 50V caps will be used up.

 

Also took some time to discover where C44 and C45 are, since the instructions said to omit them first. Turn out they are white lines and circles between C41 and C442, one line is diagonal to the long edge while the other is parallel.

 

Maybe tomorrow got time to do the resistors. Anyone know why most of the resistors are 1/8W type?

Edited September 21, 2006 by heady

[ckng 0]

Did the caps on the back of the board. The BOM missed out C441 which should be 0.1uF, so all 12 pieces of 0.1uF 50V caps will be used up.

 

Also took some time to discover where C44 and C45 are, since the instructions said to omit them first. Turn out they are white lines and circles between C41 and C442, one line is diagonal to the long edge while the other is parallel.

 

Maybe tomorrow got time to do the resistors. Anyone know why most of the resistors are 1/8W type?

 

I think Jan wanted to keep them as small/short as possible. You know, a bit like SMT components.

 

Regards

CK

[heady 0]

I am surprised that only 1/8W resistors are used in most parts. Surprising because the transformer is huge and the power rating is 100W per channel, this is a really different beast from most amps. Anyway, I know nothing much about Electronics, only what I learned in Physics lessons so many years ago.

[ckng 0]

I am surprised that only 1/8W resistors are used in most parts. Surprising because the transformer is huge and the power rating is 100W per channel, this is a really different beast from most amps. Anyway, I know nothing much about Electronics, only what I learned in Physics lessons so many years ago.

 

Those portions probably run on fairly low current. The huge transformer is more for the output stage to have enough power to drive your speakers at the desired volume

 

Regards

CK

[kross 0]

hi guys, so heady started liao huh...too bad i also don't have a bench vice so maybe I'll have a hard time donig it.maybe need you guys' help next time.

[heady 0]

Using the BOM as a guide, I have finished almost all the resistors. Here are some gotcha's that I faced:

1. Bleary eyes no good for soldering - I soldered a 220ohm resistor into a position for a 220Kohm. After removing it, I realised that the 220ohm was supposed to go into R60 which is 1W resistor position, ie the holes are far apart. Now that resistor won't fit, cos I already cut the legs.

 

But the good news is that, with the 20-0-20 transformer we used, R60 should just be jumpered (I think). Phew.

 

2. R201-R204, 1K - voltage divider for volume control:

Do not solder the 1K resistors! Leave these positions un-populated, otherwise there won't be enough 1K resistors. Almost did this, lucky I vaguely remember reading something about this on the 41Hz forum and checked it out.

 

3. R43&R44:

In the BOM, these are marked as 39K. There are no 39K resistors in the kit. Reading the built instructions, I realised these should be 22K.

 

BTW - after finishing the small caps (tantalum or ceramic?), there should be 4 pieces of 1000pF left over which will be used for the output later.

 

[heady 0]

Finished the caps with a big boo-boo. According to the built instructions, the huge power caps should go into position C61 and C62.

 

I did C61 first and then C62, into the same position holes as C61 in the pcb - big mistake. I did not flip the pcb to check that C62 cap is now too close to L11 and U4. So now I have to remove the cap. Problem is, the power caps are soldered to pads which are connected to huge amount of copper in the pcb and the soldering iron I have cannot melt the solder completely. All the heat goes into the pcb board.

 

# edit on 24 Sep - managed to remove the C62 cap. My solder station from Koba has died. Need to get a new soldering iron. Sigh. #

 

Other things to note are:

- C150 on the BOM is 220uF 50V but the supplied cap is 330uF 50V

- C34 on the BOM is 100uF 35V, supplied cap is 150uF 35V

 

As usual, it is easier to solder the caps from smallest to largest.

 

Forgot to mention - I did not solder in the Solen caps, I used the supplied Panasonic FC caps. First reason is that the Solen caps are huge, I want to have everything in and working before putting them in, so as to adjust for space. Second, there are people who say Solen is too bright, so I am taking more time to think about it.

 

Edited September 24, 2006 by heady

[heady 0]

23-0-23 toroid on ebay:

http://cgi.ebay.com/23-23V-400VA-Toroid-Tr...0QQcmdZViewItem

[heady 0]

Hi guys, need some help. I am about ready to check the 5V supply. Any idea where to check it? I know J10 is the + side but where is the negative side?

 

Thanks.

[ckng 0]

Hi guys, need some help. I am about ready to check the 5V supply. Any idea where to check it? I know J10 is the + side but where is the negative side?

 

Thanks.

 

Look for any ground point on the PCB. E.g. the negative side of the big bulk capacitors is a good starting point. Be careful not to short out anything!

 

Regards

CK

[heady 0]

Thanks CK. Problem with no schematics is that we have to guess.

[kross 0]

Hi guys, just read through the notes last night. I think we have to change some resistors value if we are using the =/-20V transformer right?

 

and heady, what input stage gain you choose to use? for 'general use' or for use with preamp?