All things LA2a related

[dissonantstring]

hi steve,
o.k., i'm retarded! for the benefit of others i'll post this...
i left the wire which is connected to the + and - lugs on the beede vu meter and that is why i couldn't get my vu to zero out. took it off and i can now zero out my meter in GR mode with the zero adjust pot. do they put that wire in for stablizing the posts on the meter during shipping?

anyway, when i did the test you suggested (sending +4 dBU 1KHz sine wave into the unit with +4 selected on the meter switch) there was no reflection or movement on the meter. it just sits to the left at -20. i triple checked my rotary switch/ mini turret board/ front panel pot wiring and all looks as it should be though as i stated before i'm retarded so i could definitely be wrong. i tried to adjust my peak reduction and the needle on the vu does not reflect compression, though the signal level does become audibly softer when i increase PR. oh, i have an extra T4 i got from JBL and tried to stick that in to see if my bloo T4 was wired wrong, but got the same results.
i'm at a lost now. any suggestions?
thanks.
-grant

 

[Scenaria]

I have no doubt that something is wrong in the rotary switch wiring...

sounds like the compressor is working... the only place you can really be having a problem is in that area..

remember sometimes when we look things over its easy to assume that something is right after having looked at it a billion times.

 

[dissonantstring]

thanks for the quick response steve!
yes, as i stated before, i am retarded so i'll look into it more carefully and
if worse comes to worse, i'll redo all the wiring in that section and maybe something will stick out or hopefully i'll do it correctly this time.
one question though, i grounded A5 on the mini turret to the rivet point on the tabs which mount onto the meter, is this correct?
thanks.
-grant

 

[Scenaria]

yep!

thats correct

 

[dissonantstring]

cool!
thanks steve!
-grant

 

[yodermr]

I just wanted to thank everyone for putting all this experience down in one spot. Took me a while but I have sucessfully built an LA2A. If you have read any of my posts this should surprise you. I know I could handle making it pretty but pulling off the rest was a challenge.

Few minor things left to do but it works great and sounds great.

Finally got it together so I thought I'd throw a few pics out there.

http://www.demofactory.biz/Front.JPG
http://www.demofactory.biz/Back.JPG
http://www.demofactory.biz/Inside.JPG

While Jahansen's book was a great start, I couldn't have completed it without this site.

:grin:

 

[AnalogPackrat]

Nice one, Mark! Real man's point to point and a chunky style front panel. Looks good. Sowters?

:thumb: :guinness:
Analog Packrat

 

[CJ]

Coolsville!

You might be able to straighten out the T4 by seeing if there is a tension clip inside the octal case. If there is, sometimes you can rotate the octal plug within the base to make it come out right. This way you do not have to re drill the tube socket mounting holes. And don't feel bad, every single DIY LA2 I have seen here has had CTS. Crooked T4 Syndrome.
I cheated. I used a round can.

 

[Siegfried Meier]

The meter in the Bloo LA2A has a small clip across the - terminal and the + terminal. In the manual, it does not state to remove this, but I've been advised by a very knowledgable person to do so. Anyone?

Thanks,
Sig

 

[Scenaria]

yes you need to remove it...

think about it for a sec.. if you keep the clip inplace.. this would short out the two leads... your meter would not work :wink:

 

[yodermr]

Thanks for the complement. I was stealing the look from DW Fearn. The knobs and dial plates were from an antique radio shop in NY. They got lots of really cool stuff.

I used Jensen transformers. This was the only option that I knew at the time I was sourcing parts.

The T4 was from ADL - the bracket for the housing seems to be glued to the pin socket. Feel bad? Hell I'm so excited about just pulling this off it makes me horny. Tell me that's not messed up :wink:

 

[dissonantstring]

wow mark! :thumb:
that is a very cool looking LA-2A and that meter has got to be the hugest one ever. where did you get the chassis? it almost looks like a guitar amp chassis. great work!

i feel like i'm coming in last in this race, but i'm still in it. i'm not giving up damn it! with that i need help again steve!
i re-wired my rotary switch which brought up more problems which i won't get into. anyway i re-did the +4dBu 1kHz sine wave input (no T4) with +4 meter selection and noticed that when i turn the gain all the way up the needle moves up ever so slightly (from rest at 0 to a smidge over -20). then when i increase PR the needle moves down towards 0. so i have hope...right? :grin:
please help.
-grant

 

[Scenaria]

im a little confused....

you said you have no T4b in it?

but your seeing the needle deflection downward?

 

[dissonantstring]

[quote author="Scenaria"]well it sounds like you might have more than one problem... if in fact your EL is not lighting at all..

the first thing I would do

pull the T4b module.. this is only needed for compression but the unit will pass audio and add gain without it.

send +4dbu into the input of your XLR jack with a 1Khz osc

switch your rotary switch to +4 position

make sure your peak reduction is tured fully counter clockwise

bring your Gain knob up and look at the meter

does the VU meter move at all?

do you hear the level getting louder as you bring the gain up?

if you hear the level getting louder but the meter does not reflect this then you have something amiss in your meter and rotary switch wiring

if the meter does show the gain as you bring up the gain pot then we can move on...[/quote]

i actually did this test with both the T4 out and T4 in with the same results.
the gain does increase volume and PR does decrease it.
since it does the same thing with and without the T4 am i in worse shape?

:shock:
-grant

 

[Siegfried Meier]

Got one working. Careful with the wiring description of the Power Transformer - mine was wired permanently on because of this. Also, watch the grounds on the last few steps of the twin shielded wiring - this was making the Gain Reduction not happen. Things get really messy near the end. All in all, it seems okay on the bench. Next test is the studio. Hopefully it's okay. BTW, all my voltages were 99% accurate to what was posted in the manual.

Working on seeing if the second one makes it now. Will keep you posted.

Ignore the meter thing I said before - it obviously needs to be removed, even though not mentioned in the manual.

One last question - what does C4 do and how what do I adjust this to??

Sig

 

[CJ]

What happened to Paul B? We either fixed him, or he jumped off a bridge somewhere.
:?:

 

[dissonantstring]

[quote author="Scenaria"]im a little confused....

you said you have no T4b in it?

but your seeing the needle deflection downward?[/quote]
yeah, what the hell? if my T4 isn't in how can my unit be compressing?
:? is my rotary switch wiring still messed up? what could be causing
this?
-grant

 

[Siegfried Meier]

And the second one is working now too. Again, a few shorts in the tube sockets - I find that popping in a tube at a time, firing it ensures that each tube socket is properly wired. This time, no ground problems and the unit appears to test out great. Voltages are a little different from the last one, but still in the ballpark.

Thanks to everyone that helped out. I'm sure I'll have more questions as time goes on.

Siegfried

 

[yodermr]

Grant,

The chassis was from par metal. My next door neighbor is an Mold Maker. He has some machine (EDM) that uses a wire and some plasma arch for cutting metal. It was quick, easy and left perfect cut outs.

I searched for sometime on Ebay for a meter that would stand out. Nice focal point I thought :thumb:

 

[dissonantstring]

[quote author="yodermr"]

I searched for sometime on Ebay for a meter that would stand out. Nice focal point I thought :thumb:[/quote]

focal point?! i'd say. your unit is very unique looking (even if it is colored red like D*W*Frn). IMO it says, "here i am, use me!" great job mark!

hey steve,
sorry for being a nag, but could you point me an a direction here.. my LA wants to make sweet, sweet music. :wink:
-grant