Star Earth implementation for monoblock AKSAs?

Lost81 · « **on:** 11 Jul 2004, 12:01 am »

To the monoblock constructors out there,

How did you implement the star earth since the hole in the center of the Power Supply PCB is missing?

I thought of locating the star earth off-site from the PS PCB, my EE housemate said that that's not "daisy-chaining." He did caution me to use a thicker wire (10AWG) running from the PS PCB to the off-site star earth though. I guess I am going to tack-solder the cable to the PS PCB. Either that or I will take a risk and drill through the trace for a more secure connection.

Should I drill a hole on the PS PCB and implement the star earth like the dual-mono version?

Thanks in advance.

-Lost81

EchiDna · « **Reply #1 on:** 11 Jul 2004, 12:23 am »

you can drill through the trace no problem....
this would be better than a tack solder mechanically and likely electrically as well.

andyr · « **Reply #2 on:** 11 Jul 2004, 12:25 am »

The normal AKSA power supply PCB is two mirror-halves - one for R channel and one for L.

Scribe a line down the middle of the PCB to separate the earth on one side from the earth on the other (I used a Stanley knife/carpet knife for this) and drill a hole for the star earth bolt in each side.

Regards,

Andy

AKSA · « **Reply #3 on:** 11 Jul 2004, 12:39 am »

Benny,

Exactly as Glen and Andy have suggested; scribe that line down the center, and mark out a point 3/16" to the left and right of the line at the mid-point and drill two 1/8" holes. Then you can mount a 1/8" bolt in each monoblock half as formed, and use it as a dedicated star earth for each channel.

Just be sure that the head of the little bolt clears the capacitors beneath, to avoid any mechanical damage to the cap.

Cheers,

Hugh

Lost81 · « **Reply #4 on:** 11 Jul 2004, 03:37 am »

Thanks for the tips, guys.

Will be doing what you suggested in a bit.

I hooked up the transformer to check voltage and made the mistake of shorting the secondary windings (i.e. Black and Orange got together. I mistaken it for Ground, while connecting Red and Yellow to DVM).

The entire house went dark.

I heard a lot of crinkling sound from the transformer.
I actually thought it was going to burst into flames...
Much later, when I touched it (after disconnecting everything), it felt very warm.

I thought it was toast and was about to order a replacement from Avel Lindberg when I decided to check the transformer for shorts with the DVM.

I think I got lucky. The primaries and secondaries are still isolated from each other. The plastic shrinkwrapping are now much tighter around the windings though.

Anyways, I did a search on this forum and found the correct circuit hook up diagram that Hugh provided sometime back:
I.e.
http://avellindberg.com/transformers/y23_range_connections.htm
(The 1st diagram).

So, I hooked up the transformer and its reading fluctuates between 36 to 38V AC.

Man, for a while there, I thought I was out $60 + shipping for a replacement 330VA toroidal transformer!

Whew!

-Lost81

AKSA · « **Reply #5 on:** 11 Jul 2004, 04:00 am »

Benny,

Mein Gott you were lucky!!

This is the connection from Hell........ But you survived the Rubicon......

Are you a pussy cat? You have about five lives to go, I'd guess.....

Check twice, connect once, breathe easy!

Cheers,

Hugh

Lost81 · « **Reply #6 on:** 11 Jul 2004, 09:17 am »

Heh,

Thanks, Hugh...
I guess I better treasure my remaining 4 lives left.

Ok, weird, weird, weird problem here.
Anyone can give me a take on this?

My AC mains voltage is 118.7V.
After the transformer, it is 37.8 AC.

Here is the weird one:
After the Power Supply PCB it is 25.3 VDC on the +ve rail, and 26.1 VDC on the -ve rail.
And for ALL 4 monoblock Power Supply PCBs!

What gives?

With such voltages, trying to bias the amps is futile (I tried):
The dismal results are:

Voltage at minimum bias:
R25 = 1.89VDC
R26 = 1.91VDC

Voltage across Speaker Output and Earth at minimum bias = 43 millivolts

Voltage between R5/R6 and Earth = 22.3V DC

---
Bias trim pot turned to maximum = 4.31 VDC across R25 (100R)
Voltage across Speaker Output and Earth at maximum bias = 10+ VDC
---

All these measurements are probably useless since the voltage after rectification is barely 50% of the supposed values.

Where did I go wrong?

Truly lost,
-Lost81

AKSA · « **Reply #7 on:** 11 Jul 2004, 09:33 am »

Benny,

Do you have documentation with your transformers?

Can you scan it and send it to me?

It's possible you have 2 x 120V primaries, and instead of being in parallel, they are in series...... That would do it!

Cheers,

Hugh

Lost81 · « **Reply #8 on:** 11 Jul 2004, 10:09 am »

Quote from: AKSA

Benny,

Do you have documentation with your transformers?

Can you scan it and send it to me?

It's possible you have 2 x 120V primaries, and instead of being in parallel, they are in series...... That would do it!

Cheers,

Hugh

Hi Hugh,

You are a godsend!

My transformer model is the Avel Lindberg Y23 Range.
It's model part number is Y23 6752.

Here are it's general specifications:
http://avellindberg.com/transformers/y23_range.htm

Here are my transformers' exact specs:
Load (VA) 330
Secondary Voltage (V) 35 / 35
Secondary Current (A) 4.71
Regulation (Typical) 6.0
Temperature Rise (°C) 52

(Source: http://avellindberg.com/transformers/y23_range_specs.htm )

Thank goodness for your reply, I was contemplating desoldering my PS boards already. And then I stopped and thought that it is statistically impossible that I could have 4 identical failure modes across 4 Power Supply PCBs with identical voltage shortfalls.

Thanks, Hugh!

Cheers,
-Lost81

Lost81 · « **Reply #9 on:** 11 Jul 2004, 10:11 am »

For what it's worth:
I followed the 1st wiring diagram on this page:

http://avellindberg.com/transformers/y23_range_connections.htm

Is that the wrong one?

-Lost81

AKSA · « **Reply #10 on:** 11 Jul 2004, 12:33 pm »

Hi Benny,

Yup, you used the wrong one!!

Primary is just fine, secondary is the problem. You must use the secondary connections on the right side of the MIDDLE diagram; you have your secondaries in parallel, not in series, and this is the reason for the low voltage.

Your transformers appear to be undamaged. You've been REALLY lucky!

Cheers,

Hugh

Rhythm Willie · « **Reply #11 on:** 11 Jul 2004, 10:28 pm »

RE: Star earthing monoblocks.

I bent a bit of copper strip at right angles,drilled a hole in it then soldered it to the large earth strip on the 1/2 power supply PCB. The earth leads then just bolted to it - a good neat strong connection.

Lost81 · « **Reply #12 on:** 11 Jul 2004, 10:46 pm »

Quote from: AKSA

Primary is just fine, secondary is the problem. You must use the secondary connections on the right side of the MIDDLE diagram; you have your secondaries in parallel, not in series, and this is the reason for the low voltage.

Just to reconfirm this by being pedantic:
So that essentially means that I can leave the primary connections as it is, but the secondary connections will be:

Black / Yellow wires together

Red / Orange wires together

Correct?

Quote from: AKSA

Your transformers appear to be undamaged. You've been REALLY lucky!

Whew! Yep, I thought I would double confirm this important step with you before doing anything. I don't think the transformer can survive another mis-wiring...

A thousand thanks!

-Lost81

AKSA · « **Reply #13 on:** 11 Jul 2004, 11:22 pm »

Hi Benny,

Quote

So that essentially means that I can leave the primary connections as it is, but the secondary connections will be:

Black / Yellow wires together

Red / Orange wires together

Not quite! Red/Orange together is fine. This goes to star earth.

BUT!!!

Black goes to AC1 on the ps pcb, and Yellow goes to AC2 on the pcb. DON'T CONNECT THEM TOGETHER, THIS WILL SHORT OUT THE TRANSFORMERS AND DESTROY THEM!!

Hope this helps,

Cheers,

Hugh

Lost81 · « **Reply #14 on:** 11 Jul 2004, 11:52 pm »

Woah!
Escaped another near disaster...
(Won't want to use up all of my 4 lives left...)

A side question:
Since these AKSA 100W modules are built as Nirvana from the ground up, do I follow the stock procedure for setting up bias, or the Nirvana procedure for setting up bias.

Thanks a lot!

Cheers,
-Lost81

AKSA · « **Reply #15 on:** 12 Jul 2004, 12:16 am »

Benny,

Either procedure will work fine. The operating points are not the same, but very close, and in terms of output stage bias, identical.

Cheers,

Hugh

Lost81 · « **Reply #16 on:** 12 Jul 2004, 02:11 am »

Woah!
Awesome!

Rail voltage at the power supply PCB output is 51.8V DC, with reference to earth.
Identical on the +ve and -ve PCB sides.

Going to do the rest of the monoblocks now.

I'm stoked!

-Lost81

AKSA · « **Reply #17 on:** 12 Jul 2004, 02:20 am »

Hey Benny,

You're home free!

Now, sail through the biasing, you should be fine now, but need any more help, just email me privately.

Nearly there!

Cheers,

Hugh

Lost81 · « **Reply #18 on:** 12 Jul 2004, 03:19 am »

Thanks, Hugh, I really appreciate it!

Cheers,
-Lost81

Lost81 · « **Reply #19 on:** 12 Jul 2004, 03:23 am »

Quote from: Rhythm Willie

RE: Star earthing monoblocks.

I bent a bit of copper strip at right angles,drilled a hole in it then soldered it to the large earth strip on the 1/2 power supply PCB. The earth leads then just bolted to it - a good neat strong connection.

That sounds like a neat idea.
Did you use eyelets for bolting?
Or did you solder the earth wires directly to your ground strip?

I followed the advice of the others and managed to carefully drill a 1/8" hole in the center of the thicker Earth PCB trace. It looks neat. I would have to use eyelets though, or else the bolt end up being too long and stress the PCB board.

The eyelets and spades I have found so far are all of the cheap, horrid, galvanized metal / aluminium sort.

Copper spades and eyelets would be so nice...
Anyone know where to get them?

-Lost81