How to downgrade from Firmware 6.38 to Firmware 6.xx

Works on PSP 1000, 2000, 3000, 4000 (newer 3000) or PSPgo!

You can downgrade with this downgrader from Firmware 6.38 to Firmware 6.20. From Firmware 6.35 to Firmware 6.20. And from Firmware 6.31 to Firmware 6.20.

Supported models:
PSP1000 [01g], PSP2000 [02g], PSP3000 [03g / 04g], PSPGo[05g]

Unsupported models:
PSP 3000 = 07g / 09g, etc. Can not be used (with error display) 

I tested it by myself on a PSPgo with Datecode 9C and Firmware 6.38 ;=).

For this, you will need:

- PSP 1000, 2000, 3000, 4000 (newer 3000) or PSPgo

- a supported PSP model

-6.38/6.35/6.31 -> 6.20 Downgrader By Davee, ported to 6.38 by some1
-Official PSP Firmware 6.20 for PSPgo or normal PSP

Tutorial

1.Extract the downloaded archive.

2.Ms0: (ef0 / PSP / GAME / copy the Downgrader to this folder.

Ms0: (ef0 / PSP / GAME / UPDATE / copy the official Firmware 6.20 Updater (EBOOT.PBP) to this folder.

3.It should look like this: 

4.Launch the Downgrader from your XMB.

5.Press X to start the SCE Updater.

6.The 6.20 updater will appear, update as always.

7.Now a BSOD (blue screen) will appear:

8.Press O to solve the problem and you're done.

Source: pspslimhacksforum

Also, thanks to "flofrucht" for the great tutorial