[build] Dripelectronics.com LA2A pcb v3 (atoms) build thread.

[TornadoTed]

My components turned up today and I have stuffed the board, it looks fantastic and is so easy with the excellent instructions.

I have a few questions if you don't mind answering them. I apologise in advance as I am really new to electronics and some of these may be stupid questions!


I ordered exactly what was on the BOM. I have several parts left over.

1x .022uf Orange Drop, the BOM says 4 but I can only see 3 on the PCB

2x 3.9k Resistors, I used one at R24 above the Zero adjust trimmer.

1x 6.8k Resistor. I can't find this on the PCB anywhere.

1x 1k 1/2 Watt Resistor, I used 7 of them at R20, Grid/1k, R18, Grid 1k, R36, R31 and R32. The BOM says 8, where do I use the other one?

2x 1M Resistors. Where do I use these?


I currently don't have anything at,

NE-2 What do I need here?
R7/2k A bit confused as there is no 2k on the BOM.
J2 Do I jump or use a 1k?
J3 Do I jump or use a 1k?
R38/22k Do I jump or use a 22k?
.1 400v C-Cap Ceramic It says optional, should I use something here.

The diodes I have are these,

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=651-6135

Are they ok as I notice they are different to the ones in the instruction manual?

 

[dripelectronics]

sorry , ive been meaning to update the manual ,
as feed back and questions arrive.

spare .022 was for the power switch rc network (anti pop) if not using the
mallory quench arc .

one of the 3.9 resistors was intended , if you wanted a bit deeper
limiting , (replace R7)

6.8k was a total typo

spare 1k , typo

2 x 1m resistors are for the ground lifts on xlr in and out.
(refrence manual)

NE-2 is a NE-2 neon light needed for regulating the meter

i missed the 2k on the bom , it is normally a 2.7k for R7

for all the jumps , just use wire , unless stated 1k (grids on 12bh7a)
i add things like this for troubleshooting . just incase.

r38 , use a 22k (some original versions have it , some dont)

go ahead and add the x-cap , it can help filter junk out of the
power going in . (ref. audiophile scourcebook)
some times has no effect what so ever.

your diodes are supposed to be in a TO-220 package,
those say DPAK and are surface mount .

one of the pins is actually connected to nothing ,
in that configuation , the metal base is the cathode ,

best to return them and get a TO-220 package ,

sorry about the leftovers .

g.

 

[TornadoTed]

Awesome Greg, many thanks.

I'm loving the build, it is so well laid out. I can't wait to finish it and run some stuff through it.

 

[thehazardharke]

Got mine today! Thanks greg!!

I'll have pictures posted soon!

 

[peters]

I am just getting prepared to build this project, and am wondering if it can easily fit into a 2U (3-1/2") enclosure if tubes are mounted sideways on a length of angle bracket, over the PCB. Am I risking adding significant hum by having jumpers from the board to the sockets (say 2" long)? Would using the DC heaters help?

thanks,
--Peter

 

[Bill Kahler]

The following came from Gregory's replies to a couple of my emails:

On the bottom of the caps page the BOM lists 1) 68pf and 2) 150pf caps. Should be the other way around.

BOM says 1 47uf @25 volt, manual and board say 50 V for C10. 25 will work - only 10V passes so either are OK.

Also in the manual C11 says axial leaded cap, but it's not listed in the BOM. Orange drop works fine.

3 1@1kilovolt ceramic 500 v minimum for optional ground lifts
for the lifts - use poly pro caps like the orange drops - only need 2 for ground lifts - the other was for the x-cap. Do not use the x-cap (it was mainly added for trouble shooting )

Part number discrepancy : the Quencharc snubber listed as Mouser part 504M02QA220 should be 539-104M06QC100.

 

[T-rex]

Sorry for the newb question, but I didnt see this anywhere.  About what is the total cost (approximate) for this project.  I am getting ready to do a Gssl for the experience but I would much rather build an LA2A if the cost isn't too much greater.

 

[cwalcott]

i spent about $900 on mine.  that included the case which was about $350.

- chris

 

[thehazardharke]

spent $400.00 on mine. I got my transformers free.

 

[T-rex]

Thanks for the info, that gives me a ballpark.

$350 for the case?  That must be one sweet case!

 

[cwalcott]

sorry, my bad.  it was $350 for 2 cases.  that's still expensive but i needed cases and i'm not much of a metal guy.  but to answer your question, yes they are really nice cases.  the transformers were the next most expensive part.  it's not a cheep project to make from scratch but it's worth it. 

- chris

 

[Whoops]

The Hexfred diodes aren't easy to order in small quantities.
Mouser's minimum order is 715 and Digikey is 1000.

RS only seems to offer the TO-220 package in 600v max. You need 1000v minimum.

Found an alternative here: (pics are illustrative only both are TO220)

http://www.newark.com/vishay-formerly-international-rectifier/hfa06tb120pbf/fast-recovery-power-rectifier/dp/63J6640

http://www.newark.com/vishay-formerly-international-rectifier/hfa08tb120pbf/fast-recovery-power-rectifier/dp/63J6645

These are the specs you need to look for:

type: Diode Hexfred / Fred
Package / Case: TO-220AC
Minimum values: 1000V (Reverse Voltage)  and 1A


if my info is right , this will probably save you some time.

 

[fazeka]

I don't know why you couldn't just get it at digikey? I just checked out their site on my iPhone. 462 qty. @ $1.93 each. I thought it was a 220 package...?

 

[fazeka]

Yep, double-checked Digikey:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=VS-HFA06TB120PBF-ND

Also, Allied:

http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=5030305&MPN=HFA06TB120PBF

 

[Whoops]

Cool,
more alternatives are always better.

Although the price in Newark is $1.14

can't beat that!

 

[fazeka]

Nice, yes!

 

[buschfsu]

any word on the dc version?

 

[jeerzee]

Well how does the ver3 atom SOUND and stack up to the previous versions?
Not a good sign seeing the thread just kind of drop out!

 

[jeerzee]

WELL????????????!!!!!!!!!!!

 

[rrs]

Is the manual still available.

Clicked the link and all I got was a pretty girl.  ;D