SA-3A (LA-3A Clone) Support Thread

[scott2000]

Any idea where the "manual" you speak of might be located?

Maybe the LA-3A service manual??

UA's service manuals are usually pretty detailed.....

Although I'm not sure if this "clone" is different in many ways....

 

[Blackdawg]

Hi everyone,

Here is a google drive link to the Original BOM, Schematic, and a new BOM provided by RJS plus the notes of this thread: https://drive.google.com/file/d/1WLyVLz20jv8eB4c_JBKH0iZbfet6My52/view?usp=sharing

I have imported RJS text file into a spread sheet, you can just import it into Mouser if you want the molex parts. There is a link in there as well for a cart already with NO molex connectors. I hate molex stuff and never use it is why



RJS great to see you figured it out! haven't been on here in a while but it is common to put a small piece of foam or something under input transformer cans to ensure they aren't flush with the PCB. But now you know!


Cheers!

 

[Howard007]

Hi everyone,

I'm building this beautiful SA-3A and i'm reflect about the T4B, can I use 2 T4B IGS by Don audio or it's better to insert 2 matched
necessarily like the Stereo Matched Pair of Kenetek?

Thanks for your help!

Take care!

 

[JMan]

Hi everyone,

Here is a google drive link to the Original BOM, Schematic, and a new BOM provided by RJS plus the notes of this thread: https://drive.google.com/file/d/1WLyVLz20jv8eB4c_JBKH0iZbfet6My52/view?usp=sharing

I have imported RJS text file into a spread sheet, you can just import it into Mouser if you want the molex parts. There is a link in there as well for a cart already with NO molex connectors. I hate molex stuff and never use it is why



RJS great to see you figured it out! haven't been on here in a while but it is common to put a small piece of foam or something under input transformer cans to ensure they aren't flush with the PCB. But now you know!


Cheers!

I went ahead and pulled the trigger on this project, since I know Mike is getting out of the DIY biz and I didn’t want to miss out on this while it was still available.

Blackdawg, for some reason, when I click your link, it only takes me to the BOM.  I don’t see the schematic or anything else.  Any chance you could share again, or we could communicate via PM to get the rest?

Thanks, looking forward to this build!

 

[theposterkid]

I have attached the schematic.

 

[JMan]

Oh man, thank you!  I can't tell you how much I appreciate it!

 

[theposterkid]

I just finished wiring the switches and toroid transformer for my 3rd LA3A. It is the mono one pictured on the top. Below that is the stereo version with the Serpent panel that I made last year.

 

[BerndVP]

So, there is no way anymore to get this one ?

 

[JMan]

So, there is no way anymore to get this one ?

Bernd, you can still order the boards from the Serpent Audio website.  He just got a new batch in.

 

[theposterkid]

Bernd, you can still order the boards from the Serpent Audio website.  He just got a new batch in.

I emailed Serpent around May and again a couple months later, trying to buy more boards, and he never replied to me.

 

[JMan]

I emailed Serpent around May and again a couple months later, trying to buy more boards, and he never replied to me.

I find Mike extremely difficult to get ahold of.  But the boards are in the web store.  I know because I placed an order for them in June and heard nothing.  Finally got ahold of him a month later asking where my order was, he said he was waiting on a new shipment of boards that would arrive in early September and asked if I would like to cancel my order or wait...  I opted to wait and I kid you not, the boards showed up TODAY.  Like two hours ago.  They are sitting in front of me as I type, still snug in the cling wrap.  So, they're there -- and hopefully for you it won't be such an ordeal to get them.  (I'm just being whiny, though.  In reality I had plenty to keep me busy while I waited and I'm just glad they're here now.)  ;D

 

[BerndVP]

Hi JMan,
thanks for the information !
Do you have the BOM and Manual ? because the dropbox links in the original post doesn't work anymore.

 

[JMan]

BOM for a stereo build

 

[JMan]

Schematic

Cheers!

 

[JMan]

As far as I'm aware, there is no manual or build guide.  Just the documents above and this thread, but it should be enough to get you through it, I think.

 

[deadpoet]

Hi,


While assembling a stereo unit for a friend I revisited and re-calibrated my two units (from a long time ago)


One of the channels has developed a little problem which I think I've narrowed down to a problem in the output gain.

(MOD, 50dB, Compress)
Feeding a -18dBFS signal into it I get one side to Gain +/-6 for a 0dB(VU) reading while I need the other side to be at 7. Around 6 the signal gets distorted (while reading about -2.7dB(VU)).
When I turn up the peak reduction the volume lowers (obviously) and the distortion goes away.
When I compensate for the lost volume the distortion returns at the same VU reading.


Looking at the schematic logic tells me to try and replace Q3, Q4, Q5 and/or Q6 to see if the problem goes away or am  I wrong here?


Thanks in advance,
Herwig

 

[theblastedman]

Hey everyone! I just received PCBs for this project, and am trying to figure out where, if possible, I might get my hands on a front panel? They are out of stock on the serpent audio store. If anyone here has one they want to sell, or knows of someone who might have a few, let me know! Thanks a bunch

 

[JMan]

I've been eyeballing this project, which I have the boards and components for but have yet to officially start on, while I wait for some very slow shipments for other builds to arrive.  I've run into a question that seems important, yet hasn't really been addressed except by one post years ago that didn't get any attention.

The board silkscreen shows the comp/limit switch connection as [pin 1 - N/O; pin 2 - COM; pin 3 - S], but the schematic clearly shows [pin 1 - COM; pin 2 - N/O; pin 3 - S].  Which one is correct?   

I'm assuming the schematic is right and those connections must be swapped, yet so many people seem to have built this without mentioning this issue that I have to wonder...

 

[fallout]

The board silkscreen shows the comp/limit switch connection as [pin 1 - N/O; pin 2 - COM; pin 3 - S], but the schematic clearly shows [pin 1 - COM; pin 2 - N/O; pin 3 - S].  Which one is correct?   

I'm assuming the schematic is right and those connections must be swapped, yet so many people seem to have built this without mentioning this issue that I have to wonder...

It really doesnt matter. When set to 'compress' the switch is shorting/bypassing R3. All you're doing is shorting pin 1 to 2 on J3.

Hope this helps

 

[JMan]

It really doesnt matter. When set to 'compress' the switch is shorting/bypassing R3. All you're doing is shorting pin 1 to 2 on J3.

Hope this helps

Oh my gosh, you sure are right.  I was so caught up in “why don’t these match” that I didn’t even think through the simple mechanics of the switch.  *facepalm*