D-LA2A Support Thread

[[silent:arts]]

check heaters & B+ without any tubes T4Bs.
insert the tubes, check again (still no T4B).
listen to it (still no T4B) with and without audio.
all fine?
plug in your T4B and enjoy.

 

[electrisizer]

nearly finished  ;D

 

[electrisizer]

problems:

i had a bit distortion + low cut on channel B when peak red. was going on. the v203 dosent like the JJ ecc83!

i changed to a vintage telefunken -> distortion gone. the crazy thing: v103 dosent distort with the JJ  :

second thing: at high gain level i have oscillation on both channels , but this gain ill never need. perhaps ill change to 100k pots/resistors.

input trafos are the haufe rk310, output edcors...

this thing smashes sounds in the front

 

[electrisizer]

ah - im going crazy, theres still a bug...

first question: does audio pass even if theres no power on? (mine does)

second question: days before i had really nice compression now theres nearly nothing...even if i have full limit resp.

i suspect the relays but cant measure any voltages right now...

 

[tomcat]

1: Yes, these are hw bypass relays, no power: bypass

 

[thestudio]

Question: Is there a reason that heater runs couldn't of been put on the pcb instead of using separate wire runs?  Did UA on their dual La2a use the pcb for heater runs???

 

[[silent:arts]]

Question: Is there a reason that heater runs couldn't of been put on the pcb instead of using separate wire runs?  Did UA on their dual La2a use the pcb for heater runs???

You can't twist PCB traces, and we are talking about AC heaters, 2 x 2A ...
I'm not aware of a UA dual LA2A, any link?

 

[Soeren_DK]

the reason why there is no C4 trimmer is: I didn't find any easily available in europe. the 300pF is a guessed estimate I read somewhere in the long LA2A threads, but can easily exchanged to other values.

On my pcb c104/c204 is marked with 150pf and I bought 150pf?

Cheers
Soren

 

[[silent:arts]]

... On my pcb c104/c204 is marked with 150pf and I bought 150pf?

and me (and most others) used 150pF ;D

 

[drgrateful]

I am almost done...

I fired up the D-LA2A without the T4B's. I measured the following voltages:

After D1: 340v
After R129: 250v
V101: pin1 105v, pin6 108v
V102: pin1 106v, pin7 112v
V103: pin1 81v, pin6 81v
V104: pin5 126v, pin6 114v

Voltages for the other channel are similar, except for v204: pin5 142v, pin6 98v.

Am I in the ballpark? Can I plug in the T4B's confidently?

The NE2 neon lamps don't light up: is this OK without the T4B's plugged in?

 

[Soeren_DK]

... On my pcb c104/c204 is marked with 150pf and I bought 150pf?

and me (and most others) used 150pF ;D

Thanks Volker.
I'm almost done but I need to adjust the unit. Anyone have guide other the little section in the manual?

Cheers
Soren

 

[Randyman...]

... On my pcb c104/c204 is marked with 150pf and I bought 150pf?

and me (and most others) used 150pF ;D

Thanks Volker.
I'm almost done but I need to adjust the unit. Anyone have guide other the little section in the manual?

Cheers
Soren

Ditto - Same boat.  Did you use the Arco trimmer caps?  How did you mount them to the PCB?  Or for that matter - if anyone has any handy tips for mounting the Arco trimmer caps - that would be great!  PCB is stuffed, just waiting on the chassis (any day now!).  I have a perfect project lined up to break this beast in, too!  

8)

 

[[silent:arts]]

I'm almost done but I need to adjust the unit. Anyone have guide other the little section in the manual?

do you think it is mis-adjusted?

 

[Soeren_DK]

No not really. But maybe there was a guide to adjust the RV137 and RV103?

Cheers
Soren

 

[Soeren_DK]

Finished
(almost, only need some knobs but I couldn't wait)














Cheers
Soren

 

[ilfungo]

great job!!!
I saw that you used for Sowter in and out
how do they sound?
thanks

 

[Soeren_DK]

great job!!!
I saw that you used for Sowter in and out
how do they sound?
thanks

Thanks.. 
We are relocating so I don't have the right fatalities to test this beast right now. I'm listening through a ghetto blaster with AUX IN but it sound great...

Cheers
Soren

 

[jrfred453]

Hey guys,
Just firing one of these up.
Right away with all the tubes in the fuse blows
I'm in the US and using a 1amp fuse. The Antec power transformer I'm using has 3.6v and 5 amps for the heaters. So I should use a bigger fuse????
I continued on to find the problem...
Inserted one tube at a time into the first channel. The 12BH7A blew the fuse, so I used the one from the other channel. No blown fuse and continued to check voltages.
after D1-340v
after R129-250.6v
V101 #1-92.1v #6-104.1v
V102 #1-85.1v #7-65.1v
V103 #1-78.8v #6-78.8v
V104 #5-116v #6-112.3v
Where should I look for the cause of the low voltage at V102

I also tried to insert tubes in channel 2..... but the fuse blew (1 amp fuse??)
all points without tubes show 340v on channel 2

 

[drgrateful]

The NE2 neon lamps don't light up: is this OK without the T4B's plugged in?

I will answer myself: I needed to adjust RV104 and RV204: now the neon lamps light up as they should.

 

[thestudio]

"You can't twist PCB traces, and we are talking about AC heaters, 2 x 2A ...I'm not aware of a UA dual LA2A, any link?"

 How about using different layers within the pcb?  ????