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post #1471 of 1670

Well welcome back! Thanks again for your help! I'll look into those tubes, and pointy feet thingies :)
 

Quote:
Originally Posted by holland View Post

You're very welcome.  It's been a long time since I've been on these forums, over a year I think.  It's good to see these projects still rolling.

 

"pointy feet thingies", lol.  They are just spiked feet for amps and such.  I can't remember where I got mine.  It's been over 2 years since I built this amp!

 

I am using the Tungsram ECC82.  I like it very much.  It's a bit different than the more common 12AU7s.  I also very much like the Amperex 8416 tubes.

post #1472 of 1670

This can't be right?

C3P and C4P gets really hot, really fast.

And they has expanded on the top.

IMAG0093.jpg

I don't dare to reconnect it before I know it is right.

 

 

edit: oh crap. i tried again, and this time magic smoke from lv-

 

please help me :(

 

Could it be that i have reversed the P2L:R P1L:R and P1P s?

could this have done this?


Edited by egotrip - 11/30/10 at 2:39pm
post #1473 of 1670
Quote:
Originally Posted by egotrip View Post

 

Could it be that i have reversed the P2L:R P1L:R and P1P s?

could this have done this?



Yes.  Your caps are dead.  You need to order new ones after you fix the diodes.  It's a common mistake, so no worries.  While you're checking your diodes, double check *all* of them.

post #1474 of 1670
Quote:
Originally Posted by holland View Post



Quote:
Originally Posted by egotrip View Post

 

Could it be that i have reversed the P2L:R P1L:R and P1P s?

could this have done this?



Yes.  Your caps are dead.  You need to order new ones after you fix the diodes.  It's a common mistake, so no worries.  While you're checking your diodes, double check *all* of them.



I thougth P2-1 L:R where resistors. oh well.. then a potmeter is as a diode then?.

all other diodes and caps are installed correctly. and i need a HV- too..

is it common to fry this one too? (fried it when i detached the caps and tried again to mesure voltages.

Havent had the posibility to messure anything yet. :S

 

have to tur thos trimpots, order a nec hv- and 2 new caps.

post #1475 of 1670
Quote:
Originally Posted by egotrip View Post
I thougth P2-1 L:R where resistors. oh well.. then a potmeter is as a diode then?.

all other diodes and caps are installed correctly. and i need a HV- too..

is it common to fry this one too? (fried it when i detached the caps and tried again to mesure voltages.

Havent had the posibility to messure anything yet. :S

 

have to tur thos trimpots, order a nec hv- and 2 new caps.


A potentiometer is a variable resistor.  Sorry, I wasn't clear.  I think you placed the diodes incorrectly and may have over-volted your caps.

 

I'm not sure what you mean by detaching the caps.  You can measure voltages by flipping the board over and checking it.  Be careful of the HV side.

 

Measure the voltages at the + pin for C3P and C4P.

post #1476 of 1670

I have desoldered the C4P and C3P.

I have to order another pair.

 

2x Aluminum Electrolytic 2200μ 35V

1x 15V 1A Fixed Negative Regulator TO220

 

These three componets has been damaged.

I am trying to find replacements nearby, becouse i dont want to wait 14 days for replacements.

post #1477 of 1670

I think you should find out why the caps blew up.  Just replacing it may mean having to replace it again.

post #1478 of 1670

The problem is that all the uprised diodes d1-12 is backwards.

The cavalli site says that positive end is always upwards, this is ok.

I know that both diodes and pcb is marked with a band to represent the direction.

I just assumed that the circle on the upright diodes ment that the where supposed to be mounted with the cathodes pointing towards the circle.

 

By investigating further on all of the photos postet in this thread, I now know I was wrong.

It where an marking for where the bottom of the diodes was supposed to go.

 

Oh well, I just have to turn them then.

 

New parts is ordered, and i will begin desoldering a lot of diodes to prevent future f**k-ups :D

Thanks for the help so far.

 

Don't be supprised if i ask more novice q's since I am pretty new at this.

 

I can make this work. :)


Edited by egotrip - 12/1/10 at 10:30am
post #1479 of 1670
Quote:
Originally Posted by holland View Post


A potentiometer is a variable resistor.  Sorry, I wasn't clear.

Then you made my head spin. I thougt a pot was a variable resistor. You cought me off guard when i asked about the pots, and you mentioned diodes.

No harm done. :D

 

Quote:
Originally Posted by holland View Post
 
Be careful of the HV side.

 

By HV side, do you then speak of High Voltage-side?

 

I won't reconnect power untill i have visually inspected every cap and diode.

Been inspecting a lot of photos from finished builds from this thread.

I am pretty sure I have located the problem..  friggin' diodes.....

post #1480 of 1670

Yes, you may want to touch the caps with a power resistor to drain them, before doing any work.  It can sting a good bit if you don't and you swipe it by accident.

 

Sorry for the confusion.  When you showed a pic of the caps, it was immediately clear the diodes were put in wrong, causing over-volting of the caps.

 

I may be wrong, but I think the prototypes had a mix of diode positioning (up and down), so it was not an unheard of problem.  It's good that it's a fixed position now...unless my memory recollection is failing and it always up band up.

post #1481 of 1670

The thing that tricked me, was there where no positive (+) marking on the pcb.

So i thougt that the circle (where the bottom is supposed to be) was the line to represent the band on the diode.

I acually placed the diode posisitioned upwards, but the bottom of the diode outside the circle. since i thougt it represented the band of the diode.

I am clearly no electronics expert :D

 

(btw, bleeding the caps with a 10k resistor should do it?)


Edited by egotrip - 12/1/10 at 11:33am
post #1482 of 1670

For something of relatively low voltage, something like that should work if you go up in wattage.  I generally use a 100k/1W resistor at least (higher wattage the better).  Light bulbs work too. ;)  A 100W light builb or a string in series is a nice discharger.

post #1483 of 1670

Hi all!

 

I've run into some problem with a power supply:

 

The SOHA II requires 2x15v 1a PS with 300ma tubes. 30v*1a = 30VA.

All i have are:

15x2 18va x7

15x2 25va x1

 

And i plan to use russian tubes (6.3v 600ma heaters).

Therefore i need to get 1.5A PS for the whole board, or separate the heaters PS from the board PS.

The heaters PS is straightforward: 600mA @6.3v = 600mA 12v in series = 600mA 15v = 9VA minimum requirement.

 

Then, how much current do in need for the board alone (without heaters)?

My calculation shows the following:

300ma heaters take 5va (600ma = 9va).

Therefore the board requires 25va. (30 - 5) :) 

Something is wrong here... Why should we change to 1.5A PS when going for 600mA tubes? All we need is additional 5VA, not 15...

post #1484 of 1670
Quote:
Originally Posted by S3TUP View Post

Hi all!

 

I've run into some problem with a power supply:

 

The SOHA II requires 2x15v 1a PS with 300ma tubes. 30v*1a = 30VA.

All i have are:

15x2 18va x7

15x2 25va x1

 

And i plan to use russian tubes (6.3v 600ma heaters).

Therefore i need to get 1.5A PS for the whole board, or separate the heaters PS from the board PS.

The heaters PS is straightforward: 600mA @6.3v = 600mA 12v in series = 600mA 15v = 9VA minimum requirement.

 

Then, how much current do in need for the board alone (without heaters)?

My calculation shows the following:

300ma heaters take 5va (600ma = 9va).

Therefore the board requires 25va. (30 - 5) :) 

Something is wrong here... Why should we change to 1.5A PS when going for 600mA tubes? All we need is additional 5VA, not 15...

 

You just need the proper power transformer.  You basically need another 0.5A (AC) for the heater.  Voltage and current, though related, are not the same thing.  You are deriving your 12.6V from a 15V AC source.  It is the AC rating you need, not the VA relative to 12.6V.  If you had separate transformers for every voltage needed, you would need 3 transformers.  Heater, buffers, and tube.  To save space, a single transformer is fine, but you lose out on the current demands relative to the transformer.  We can't create power from nothing.  The tubes, though by default drawing 1-2mA each, is through a voltage multiplier, which in turn multiplies the current from the transformer (can't create voltage for free).  The same can be said of the heater.  The regulator consumes some current, and burns off voltage as well.  We can go down in voltage but must spec the VA relative to the 15V AC coming into it.  Also note, that the heater regulator is on the negative rail.

post #1485 of 1670

After a looong loooong time I finally managed to finish my Soha II. There's an strange noise problem that I still need to solve, but it will take a bit more until I can find some time to work on the amp. Anyway the noise lasts only for less than 10 minutes from power on and the amp is dead silent after that.

 

Soha2.jpg

 

More pics here: http://www.head-fi.org/forum/thread/85561/post-pics-of-your-builds/7635#post_7163318

Happy new year!!!!!! beerchug.gif

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