All things LA2a related

[The Kid]

Like I said, that resistor is wrong, for the parts listed. That 135 volts at the plate only holds for the 1968 schem. Do the math! :wink: :sam:

 

[CJ]

What math is this?

Just plug it in, make some noise, compress the noise, then bow to the west. :razz:

 

[The Kid]

Hmmm, well, I like the first part, but I'm not Muslim, so not sure about the bowing. Unless Led Zep is back in LA! :grin: :sam:

 

[CJ]

I invented the T4, you idiot!
Now down on your dirty knees! :razz:

And do it right. I don't want to have to call Shaggy. :grin:

 

[The Kid]

1000 pardons, oh great one!

Speaking of Shaggy, I saw some Scooby Snacks at the store the other day. Seriously! In the pet section, but that made me wonder if that was an accident waiting to happen, on account of Shaggy used to eat 'em too! (impressionable young kids?) :grin: :sam:

 

[CJ]

I was talkin bout the cypress hill shaggy, but that's alright.
Jus kiddin on the T4 raz, ya know.
It was really Lawrence.
It's a 3 day weekend for bonzo, so ....

 

[The Kid]

Yeah, I know you were razzin'; (if you think I was actually bowing, well. . .!) As far as Shaggy, the only new rap I know of that I actually kinda liked was that 99 problems and a bitch ain't one. And, of course, by that I mean the voltage on pin 5 is definitely too low. (Trying to segue back into the topic!) :grin: :green: :sam:

 

[CJ]

Dude, do you know how many people get freaked by that AQ5 screen?

Every dang one of them!
I would like to split the forhead of one Dr. Lawrence, the nut who messed that simple screen circuit up so bad that it looks like a monkey on a typewriter invented it.
If you don't believe me, read this whole thread.
Then head over to the LA2 pc bord thread and read that.
Then do a search on LA2 and read that.
There is more stuff on the LA2 in this forum than in the darn patent office and the UA files combined!

Then there's the stuff at the "other" place, but we don't go there no mo becuase this is a Happy place, right?

Sing it, everybody:

"Evrything is beautiful, in it's own way..."

I sing that every time I pass a really knarly car wreck with body parts all over the place.

 

[The Kid]

Dr. Lawrence messed it up, but, according to what I just read, the guy you wanna blame for the T4 appears to be RE Halsted! (1958, 8 years before Lawrence!) Well, 4 before he filed.

:shock:

 

[CJ]

There's an old saying,

"The first guy dosen't have a chance..."

 

[The Kid]

You got that right! Halsted must not have been into audio! Well, that's the first I've heard of him!

 

[CJ]

Actually, if you read up, you will discover that most inventions we use in our modern society came from ideas meant to kill people.
The T4 is no exception.
It comes from proximity fuse type technology, Lawrence was using his brain to make weapons, like most of the bright minds were back inthe cold war days.

 

[The Kid]

Yeah, readin' it right now. There's a show on cable about that, how military intended stuff becomes civilian. What the hell's it called?

 

[HappyTom]

Thanks!
To clear things up, i built this unit using the Blootech-manual. The kit comes from Blootech. I followed the instructions and was not aware i had to follow a schematic aswell.
I read this thread before i found my problems, that was like 12h work...
The manual might be unclear or I might be Swedish and got a hard time understand what's written in the manual.
Steve: Is there anything in the manual that I don't understand? :grin:

[quote author="AnalogPackrat"]

If you are using 22k for R34 and 1k for R36 on V4, you shouldn't have R38 and C13 installed. Those two were added with a later rev that changed R34 to 10k and R36 to 470R. These details are in this thread, so search it. This may well be what is making your V4 voltages a bit wonky. Someone posted a table of revisions to the LA2a somewhere--probably also in this thread. Use Ohm's law to calc current through R34 and R36 and you'll a) learn something and b) determine whether your V4 is behaving within the realm of happiness.

As for your last table of voltages--check that you did not wire R3 and/or R37 (or any of the pots, for that matter) backwards. Otherwise, it looks close. I think you could safely install the T4b and give it a try.

A P[/quote]

I'll take out R38 and C13 and link V4 pin6 to C7d and see what happens.

Thanks guys!

HT

 

[The Kid]

not aware i had to follow a schematic aswell

Well, that's what's great about electronics; it has a universal language, so it doesn't matter what country you're from. It's great to build by the numbers (kits), but schematics are an important part of the process, especially in one like this with various revisions.

Schematics are not always correct, either, but a good understanding of electronics, (basic circuits, what each part does) will usually help you find the problem. And, as you have learned here (hopefully) they come in really handy for troubleshooting! (Because even if you get really good at this, you'll still make mistakes, like everybody!) :thumb: :sam:

 

[ytrehalf]

Can anyone recommend a 2 pole 3 position switch for the LA2a?

I'm also looking for vari-caps.

 

[babyhead]

I am just about to piece together my LA2As was thinking of a mod and I wanted to bounce the idea off of the forum before I commit it.

I have a couple of Cinemag 150:10k mic inputs and was thinking of putting one in place of the HA100x and a JLM Go between to make a mic input for the LA.

Will the 40db of gain from the LA with the step up be enough?

Would there be problems with the signal being too weak at the T4 attenuation point or the 100k pot?

What do you guys think?

:guinness:

 

[babyhead]

Shameless, self-serving bump!
:guinness:

 

[Bluzzi]

I am starting to wire my LA2A (finally) and I am using Cayocosta's layout.

The T4B comes with a matching resistor that is supposed to replace R25 on small turret board near meter.

Right now R25 is 33k. Does anyone know if should I be replacing it with the one that comes with the T4B? Or do we ignore it?

Thanks.

Jim

 

[CJ]

Use it.

Calibrating is the last thing you will do. Have fun first, then worry about your meter reading 1% accurate db.

I dial it by sound, so meters are usually fun to watch, but ignored.