D-LA2A Support Thread

[herrmann]

Output cap needs to be loaded with the transformer to actually measure no DC... So, I guess in the beginning all my Solen caps were ok, and that was just the carnhill who was already faulty. Looking for problems, I have actually created them !

 

[Randyman...]

I have a troubleshooting inquiry:

I just finished my D-LA2A, and both channels pass audio.  CH1 works and compresses fine.  CH2's gain works fine but it doesn't show any gain reduction, and sounds a tiny bit distorted when I crank the Peak Reduction knob.

If I engage Stereo Link, I can tell CH2's detector is feeding a signal to CH1 (CH1 shows gain reduction from CH2 when linked).  So CH2's detector appears to be working fine, just no actual GR happening on CH2.

I already swapped T4's and tubes with the "good" channel, but the problem remains on CH2.

Any pointers on where to start looking?


Thanks to Volker and the DIY Forums!  ;D

 

[Randyman...]

Bump for any tips on my above issue (CH2 passes audio, but no GR).  I know the CH2 Sidechain is getting audio because CH1 responds to CH2's Gain Reduction when "Stereo Linked".  CH2 just doesn't do any GR, and sounds a little distorted when I crank the Peak Reduction control.

Tubes and T4B's were swapped between channels and the problem remained on CH2.  I'm a bit hesitant to start poking around with the unit powered on - so I'd LOVE to get a shove in the right direction before I go poking around the 250V hazards that lurk inside...

Thanks so much!  8)

 

[[silent:arts]]

Randy:
- check if RV203 & RV213 are fully open
- look for bad solder joints at V201, C211, T4B

 

[Randyman...]

Will do.  I'll have some time on Sunday.  I'll take a peek and get back to you.

Thanks for your input, kind sir!!!  8)

 

[electrisizer]

hi,
im still having a fault: theres too much gain in my sidechain. especially on percussive sounds im getting distortion on both chanels as soon as im cranking up the peak red. pot.

my first idea it is that theres something special with the impedance of the 1:1 input tranny...

what do you think about changing the R105 to an lower and the R106 to an higher resistor value?

 

[Randyman...]

Randy:
- check if RV203 & RV213 are fully open
- look for bad solder joints at V201, C211, T4B

Hello again,

I checked RV203 & RV237 (I don't see a RV213), and they seem OK.  Adjusting them has no impact on CH2's lack of GR.  Solder joints look good at the other points mentioned as far as I can tell.

Any thing else I can try?  I might just have to use the one channel for a while as I have a Vocal session coming up and I was planning on using this box for obvious reasons


Also - Would the Limiter Response trim-pot be the one that would be moved to the "Side-Chain HP Filter" located on the rear of Tat's D-LA2A case?



Thanks for your continued help - I do appreciate it.  8)

 

[MicDaddy]

Mouser is all out of Molex: 97-00-0445  or  538-97-00-0445  what is a suitable substitute that will work with the connectors?

Thanks! 

 

[electrisizer]

hey there,
still dont have a glue to get rid of distortion in sidechain...

description:

on both channels i have an high frequencey distortion as soon as peak red. is cranked up

it sounds similar to overdrive with line levels. example: one hit in bypass on hit in sidechain http://snd.sc/faxgXg

so it seems to be an simple overdrive in the path. the only things that are not like in the stock build: 1:1 input trannys (haufe rk310-2)
datasheet: http://www.mikrocontroller.net/attachment/70260/www.kubarth.de_54_.pdf

the distortion exists before the stereo adj. (RV103). even at lowest RV103 and so with nearly no compression i have a distorted signal in the sidechain. my guess is that perhaps the T4 is driven too hard...

has someone an idea  ???

 

[Randyman...]

Your problem sounds oddly familiar to my CH#2 issue mentioned above (no GR, and slight distortion as the Peak Reduction is cranked up).  On mine, CH#1 works fine, and CH1 responds to CH2's Peak Reduction control when stereo linked - so I know I'm getting good sidechain audio out of CH#2 (just no GR on CH#2).  Very similar to your issue from what I can tell...

I'm hesitant to go poking around a powered D-LA2A (I was fearless with my 1176's and a "Poor Man's Scope"!) - so I'm kind of stuck ATM.  Watching your progress closely

I wish I would have fitted my chassis with the PCB Rails like Hairball's 1176 enclosure.  Then you can easily remove the bottom for troubleshooting w/o yanking wires out and ruining the nice wiring job (I'm not a fan of terminal blocks - I hard wire most everything)!  I guess I'm over-confident in my builds 

Best of luck to us both 

 

[horvitz]

All done.  **** to share 

Best friends!!  ;D ;D

 

[Randyman...]

Small update on this older post of mine from Page 21:

Same here!  I ordered these and am also curious if they will work:

http://www.mouser.com/ProductDetail/Omron/G6A-274P-ST40-US-DC5/?qs=ISjK4nnpKfFgGVuxsXPgBw%3d%3d

They have an 80ma coil current and 400ma consumption rating instead of 100ma coil current and 500ma consumption like the ones on azone's BOM - but are both 5V, seem to have the same 2A switching capability and same footprint.

Anyone know if they will work properly?

The substitute relays I used had the +/- swapped (they are polarized) - so they didn't work at first.  I swapped the +/- 5v wires feeding the relays, but then the 4 small Diodes were shorting out the +5V regulator  .  So I snipped the diodes out, and it works fine minus some popping when switching the bypass in/out.  So if anyone uses these relays based on my previous post - make sure you are aware of this fact!


Question - Is the point of these diodes by the relays to prevent the relays from discharging back into the +5v path (pretty much back-EMF off the coil, correct?)?  Any harm in leaving them out - or should I replace them but install them "backwards" for my backwards relays?


PS - electrisizer - Any luck with your problem?  I'm hoping your solution will be very similar to mine for my CH2 issue...

horvitz - Purdy!  Hope to get some pics of mine up soon, but I want to wait until it's 100% "in the can".  I didn't use any headers, only the terminal blocks for the power transformer connection.  I like the cleaner look w/o headers, but it is making troubleshooting a PITA 

PPS - I also saw drgrateful's post on how to mount the Arco's - makes sense!  Just add some makeshift leads and make them fit directly on the PCB.  I don't know why I couldn't see that w/o someone poking me with a stick.  I was about to mount them off-baord with some shielded wire and some silicone adhesive! 

Thanks  8)

 

[poctop]

Hello All,  I have this problem where the audio signal is always bypassed,  but the wierd thing is that i did make sure my ground was connected and there actually a pretty normal 5V on the really and the diode is reversed biased like it should, no wrong connection or bad solder  i checked evrything i could think of and everything should be working so i removed the relay and wired it manually and it works,  so my question here since i cannot put the 5VDC relay backwards and it is connected with 5Volt on it , why both relay on both channel are doing the same thing wich is with 5VDC on it its seems that the thing is bypassed anyway,  logically 4 realy cannot be bad, 

is this happened to anybody else ,  this should logically work and it is not,
is there something stupid i am missing , 

Thanks all,

 

[poctop]

Oh btw this is the realy is have been using
653-G6A-274P40-DC5

there must be an answer for this , seems so simple 5DC on the relay will put the unit in operating mode and 0VDC will bypass the unit ,
this is so wierd,
Dany,

 

[electrisizer]

hi randy

no luck here  :-\

i changed the r105 to 11k as mentioned at jensen site for 10k:10k input transformers. theres no difference to my ears (havent looked at scope, but distortion always there).

perhaps the input tranny is my fault because its on both channels. and there was another thread times ago with someones impedance problem about 10k input trannys.

i have still an oscillation when gain rises too much (i never need that gain but the gain pot mod dosent change that behavior). so this indicates perhaps the trannys.

ive checked audio signal at several points in the circuit and hear that the signal on T4s pin 3 is very loud and distorted. same at r133. but this musent be a fault...

next weeks i visit my fahter as he is a real "vintage man". building things since the 70s. not studio gear but hifi... has a scope and signal processors  perhaps he finds a solution.

 

[Randyman...]

Oh btw this is the realy is have been using
653-G6A-274P40-DC5

there must be an answer for this , seems so simple 5DC on the relay will put the unit in operating mode and 0VDC will bypass the unit ,
this is so wierd,
Dany,

Sounds like the EXACT same issue I posted about above yours!  I also had to substitute my relays from Mouser (see my above post for the ones I used).  My relays' +/- 5VDC connections are backwards from the D-LA2A PCB.  Compare the Relays in Azone's BOM to yours and see if they are also "backwards".

I had to swap the +/- that feeds each channel's relay traces.  Then the problem is that the diodes are backwards and cause a direct short on the +5 regulator.  You'll need to snip out the diodes above the relays and install them backwards (or leave them out like I did so far).

hi randy

no luck here  :-\

I'll keep my fingers crossed for you.  Sorry I'm not of any help...

8)

 

[poctop]

thanks Randy Man i will triple check again ,  after a trace fix festival i will keep you posted ,
for sure because i wont sleep well tonight ,
Dan

 

[alexc]

Horvitz, that's some beautifully built unit(s) there.

I'd be very well proud of such high assembly quality.

Well done!

 

[horvitz]

Thank you very much, Alex!  I was hoping to get more than just test tones through the box this weekend, but the snow messed that up.  It does work fantastically though, and was a good fun build.

Randy/Dan - I assume you are looking at that relay due to the fact that the proper relay for the build is out of stock just about everywhere?  In mine, I wound up building the 5V section as 12V since the 12V version is in stock and my meters also have 12V lamps.  Maybe that would be easier than jamming that other one in there?

  Brian

 

[poctop]

Hi all,  some very important things that all should be awared,
1) C8 on the board is not on the Bom make sure you order C8 as well, think it is 0.1uf wima,
2) the use of polarized relay will not work on the board well depend on the convention i had an omron relay PN
653-G6A-274P40-DC5  and he did not work cause had the 5Volt backward to the polarity of my relay ,  it can be mounted backwards to the bottom of the board i guess,
3) i had a problem where compression would not occur before very too much gain and the reason was that i turned the stereolink fully clockwise and it should have been turn fully counter clockwise,  so depends on how you mount the trimmer there !,
4) i strongly suggest that you put some dip socket for the relay as well , just cut the pin you dont use on the sip,  so if you have a bad luck with those relay you will save the board and a lot of time been there done that got the T-shirt,
5) at some point in the developpement i had a channel noisier than the other one and i tried swapping 12ax7 arround the noise dissapaered,
6) make sure you put the jumper to the board to make your 5V relay gnd. this one pretty obvious but still !,
7) the zero GR meter adjustment and the GR tracking adjust are interrelated so you need to do it a couple of time to satisfy both condition,
8) please use a 100K trimmer on the board to replace the tracking resistor R125 and R225 so you can proceed to the GR tracking adjusments so easy, 


Well so far so good both channel compress and respond like they should more testing to come Zapppppsssss

Sincererly
Dany,