DIY LA2A (P2P)

Posted Posted by DibS in DIY     Comments 4 comments
Nov
28

I’ve started my DIY LA2A. I’ll be posting details as I go.

IMG_1135

The faceplate was created using SSLTech (Keef)’s “Super 77 Method” The design was passed on to me by Nate Kahle which I modifed. I will not be using a 3 way switch as of now so I simplified that part of the design. I’m pretty happy with the results. There are some imperfections, but I’m chalking that up to “antiquing” the look.

IMG_1104

Here is the turret board populated and wired. I’m currently using a 100uf cap for C4 in place of the vari-cap that normally goes there. All known sources of those vari-caps seem to have discontinued it. I’ll change that out if I need to when I’m all done. I’m using all metal film resistors and Orange Drop caps with a Nichicon on C10.

IMG_1137IMG_1142IMG_1146IMG_1163 IMG_1165 IMG_1171 IMG_1174 IMG_1175

So when I fired her up, no love… No smoke and fire, but barely passing signal. I found a few mistakes and omissions in the wiring and tried again and whalah! It distorted unpleasantly at peaks and when I poked the wiring with a drumstick (output wire and cap) I was able to get it to go into full motorboat mode. I put some grid stoppers on the 12BH7 and Bobs yer uncle.

Man, does this thing sound good.

Edit:  I’ve since opened her back up to chase down what little hum there was coming out of this thing.  I was able to get it absolutely quiet by tying up the wires that are coming from the left side of the front panel and moving them away from the input transformer.

I replaced the fixed capacitor I put in C4 with an Arco 42.

Also, I replaced V1 with a 12AY7 and changed R9 and R13 to 100K in an attempt to lower the input gain a bit.  It helped a lot.  I’m now able to bring my knobs past 10.  I’m still thinking I might replace the 600/10k input transformer with a 600/5k to give me even more room to play.

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4 Comments to “DIY LA2A (P2P)”

  • December 8, 2009 at 3:04 PM
    Danny says:

    How did you make the faceplate?

  • December 8, 2009 at 3:21 PM
    DibS says:

    It’s called the Super 77 Method. From The DIY site:

    Avery laser labels backing paper… throw away the labels, print (reversed) onto the ‘slippy’ side of backing sheet, then spray on the super 77 and LET IT DRY FOR 5 MINUTES!!!
    Once it’s nice and tacky (do this in a DUST-FREE environment!) align and rub-down the labels with a sharpie lid.

    If the labels get out of whack, you have to start over with the panel. -To remove EVERYTHING from the panel, just wipe it with a clioh soaked in naptha (Zippo lighter fluid..same stuff but MUCH cheaper if you buy it from a paint supply place by the quart) then THOROUGHLY dry it off, re-spray with Super-77, let it dry for another 5 minutes, and start again.

    Once it’s correct, let it dry IN A DUST-FREE ENVIRONMENT(!!!!!) and after 24 hours, apply a coat or two of Krylon clear. There’s a skill to this where the temperature of the can makes a differnece to the ‘smoothness’ of the final coat, but it’s not too difficult.

    Search Super-77 and I think you’ll find another write-up somewhere…

    Keith>

    Or this description:

    http://www.prodigy-pro.com/diy/index.php?topic=27107.msg325175#msg325175

    And Here:

    http://www.prodigy-pro.com/diy/index.php?topic=26632.msg317542#msg317542

    And more hints here:

    http://www.prodigy-pro.com/diy/index.php?topic=991.msg12976#msg12976

  • December 10, 2009 at 10:45 AM
    Danny says:

    Awesome! It looks great!! Good job on it for sure! Thanks for the info! I will give it a shot!

  • December 10, 2009 at 10:50 AM
    Danny says:

    Where did you get the graphics? Sorry for all the questions, yours turned out so well I want to try and duplicate it.:)

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