D-LA2A Support Thread

[firfe]

thank you for the reply.
i think my solver work in this case.
i would just to be sur that not a bd idea.
next step...the wiring.
the pcb is just perfect...

 

[salomonander]

hey
id like to use some big 10uf pio caps for c105 and c205. most come in 400v though. is this sufficient for this build? the ones in the bom are rated 450v. cheers

 

[firfe]

hello
i've a problem with my voltage.
i've a big noise with modulation in the gain pot.
no action for peak red  pot.
the vu looks working but nothing in gr mode.
my voltage are little strange.
i've found -15V diference beetween the good value and mine everywhere on the pcb.
I ve check my resistor...
i use a rondo trafo.
thank you in advance for help.
you can find my voltage in attachment.
Best

JF

 

[firfe]

hi
ok i've check all my resistor again...everything is ok.
but always same voltage problem...if it's a problem i'm not sur.

i've made a mistake when i 've put the tube.
i've exchange one 12AX7 with the 12BH7 .i hope the tube still working.(light is ok).

in the second channel i've the signal ( no strange modulation and noise) but zero gain reduction.
only the gain pot working.
all the other command look inactive.
and my voltage measure are same as the first channel.
i will solver my molex connection.
and have you an issu for check if the T4b work?
sorry about my fantastic english.
best and thank you .
jf

 

[dipfrik]

Just finished my build a few minutes before. But i can't get any compression on the baby? Gain works fine, bypass fine, tubes and NE2 are glowing (checked the heater wiring triple times). If i dial in the peak reduction fully clockwise nothing happend. Maybe a tiny little bit in my imagination , but the meter is not moving any mm in GR mode. (both channel acts the same)

Exchanging all tubes and T4B with different ones has no effect.

Any hints were i can start my search?

Thanks, Sven

 

[[silent:arts]]

Play around with RVX03 and RVX04 ...

 

[dipfrik]

Hi Volker,

thanks for 1st quick hints, but we are talking about the "STEREO ADJ" and the "ZERO ADJ" 1M VR's on the board right?
I definitely need to get a better understanding of the whole circuit, but how can these affect the compression (peak reduction) from nothing to "working"?

Many thanks, Sven

 

[[silent:arts]]

Look at the schematic: if RVX03 (STEREO ADJUST) is set to "linksanschlag" it is set to ground = no compression.
The "ZERO ADJ" can be set to show no compression too (even if it does compress).
Sometimes the trimmers need some for and back movements to work / to conduct after long time storage.

 

[dipfrik]

Ok, i will try that later at home. If RVX03 is not linked at all (dual mode with no wires between the molex pins and the switch) it has still an effect on the compression for each channel?

Thanks, Sven

 

[[silent:arts]]

Yes. It is like a second "Peak Reduction" control.
Stell den auf Rechtsanschlag.

 

[dipfrik]

Yes. It is like a second "Peak Reduction" control.
Stell den auf Rechtsanschlag.

Ok, i got my right channel working after a few heavy rotations on all three guys RVX04 - RVX03 and RVX37 and i see and hear a good amount of gain reduction.
Then i checked the left channel again and again but no gain reduction. Maybe a tiny little bit if i crank it all up, but far away from the right channel and again no sign of any movement in GR on the meter.

I tested everything from the left on the right to make shure nothing is damaged on the left channel and also moved the "working" parts from right to left.

- T4Bs both fine in the working right channel
- all tubes fine in the working right channel

(all from the working right channel in the left channel has no effect)

Ok fine or not

I measured the whole pcb on both side, but found at any point identical/very similiar voltages. I also replaced RVX03 and RVX37, because RVX04 is the only one on the left channel, that responded to trimmer movement (needle is moving and i can totally dim out NE2) and works like the one on the right channel. I checked both later and there were fine. I switched all the meter, front panel potententionmeter with no effect.

So what can i do now with my left friend? It's a stereo frontpanel.

Cheers, Sven

 

[firfe]

hello
noboby can't help me...

 

[dipfrik]

Hey firfe, i would if i could but captured with my own problems

 

[[silent:arts]]

Sven, if the Cable length does allow it: cross check the peak reduction pot and look if the failure follows.

Mr. Firfe, did you cross check the tubes from left to right?

 

[dipfrik]

"Ohje"… did that the last three hours in any possible combination including all i/o transformers with no luck  :-\ (right = fine, left = no GR)

How should a channel sounds/act if:

(input/output = with transformers in the chain)

a1) only input  is connected - tubes - T4B
b1) only input is connected + tubes - T4B
c1) only input is connected - tubes + T4B
d1) only input is connected + tubes + T4B

a2) only output is connected - tubes - T4B
b2) only output is connected + tubes - T4B
c2) only output is connected - tubes + T4B
d2) only output is connected + tubes + T4B

a3) only input & output is connected - tubes - T4B
b3) only input & output is connected + tubes - T4B
c3) only input & output is connected - tubes + T4B
d3) only input & output is connected + tubes + T4B


e.g. on the working right channel i have in combination a2) massive!!! hum. If i did the same on not working left channel the hum is there but way-way quieter.
Do i need more hum on the left?

OMG..this baby will drive me crazy..i know it

Thanks again for any hints, Sven

PS: after so many successfully built units as "rookie" in in the last 2 month with no problems, Holger told me again and again: "the time will come my son…" yes, now!

 

[dipfrik]

Update: please forget the hum stuff right now. i found out that the heater wiring was not optimal regarding "drilling" and i can get control of the hum on both channel with repositions the wire away from the gain molex connection. So the unit should be dead quit with no audio at the input in all combinations from a1 - d3.

 

[dipfrik]

…another update from my workbench.

I didn't solve the problem, but i completed a second pcb a few minutes before. An exact copy of the "no left GR" 1st problem board.
What should i say? Works like a charme from minute zereo

What is wrong with the 1st board and the GR on the left channel? damn it...

This is not the way how i want to solve problems

Night, Sven

 

[dipfrik]

"all clear"

Ok, it was the heater wiring. I renewed the complete heater wiring on the 1st unit and now the left channel is back and i can start calibrating two units.

Thanks for all the help!

PS: will come back with finished assembled unit

 

[frazzman]

"all clear"

Ok, it was the heater wiring. I renewed the complete heater wiring on the 1st unit and now the left channel is back and i can start calibrating two units.

Thanks for all the help!

PS: will come back with finished assembled unit

That's some epic wiring there!

 

[desol]

I built my unit years ago and I still have not been able to figure out why I'm unable to calibrate it like everyone else.

It seems to work and compress flat with the trimmers all the way to the left. I've looked at it under freq analysis and
the trimmers are mounted according to the silk-screening on the board. I have no idea.

According to the trimmer data sheet (on BOM), it looks like resistance is increased with clockwise rotation?