I recently got an et-3400a and there is no model for it online, there is one for the et-3400 though, I was wondering what the spots marked AA, AB, ST1, ST2, etc.. do or just the raindrop shaped holes in general, I look at the picture and it seems like there is something soldered underneath but I have no idea what and don't have the proper manual for the 3400a.


It didn't come with a manual.

It's probably a stupid question as I am very new to soldering.

  • \$\begingroup\$ Is there a schematic or a manual? \$\endgroup\$ Jan 17, 2016 at 6:51
  • \$\begingroup\$ There are some links here with a PDF manual and a schematic for ET-3400A. There's also a dedicated yahoo group if that helps. \$\endgroup\$ Jan 17, 2016 at 8:08
  • \$\begingroup\$ @RogerRowland: That looks like the best answer. Why don't you post it? \$\endgroup\$
    – JRE
    Jan 17, 2016 at 11:26
  • \$\begingroup\$ @JRE Well, it was only superior Googling that led me to it, but I've posted the comment as an answer for posterity anyway, thanks. \$\endgroup\$ Jan 17, 2016 at 13:18
  • \$\begingroup\$ What does soldering have to do with anything?? \$\endgroup\$
    – DerStrom8
    Jan 17, 2016 at 13:45

1 Answer 1


There are some links here with a PDF manual of the original ET-3400 but also with a schematic for ET-3400A.

There's also a dedicated yahoo group if that helps.

  • \$\begingroup\$ Yeah, i've seen those, I just didn't really feel like trying to interpret the schematic but I suppose ill go for it. \$\endgroup\$
    – Rhezner
    Jan 17, 2016 at 16:39
  • \$\begingroup\$ its also strange that the schematic doesn't match my board, neither does the picture I posted, but it definitely is the 3400a. For example the spot above the keys where it has C, D, E, F, H, J, K just isn't there, but it definitely is not the 3400 as it has 3400a written on it and matches the picture of the 3400 even less. It also has different capacitors, im a bit lost. \$\endgroup\$
    – Rhezner
    Jan 17, 2016 at 16:47
  • \$\begingroup\$ d8apro.com/ebay/ET-3400A_Db.JPG It looks like this one \$\endgroup\$
    – Rhezner
    Jan 17, 2016 at 16:52
  • \$\begingroup\$ @Rhezner - According to the schematic, AA, AB ... AF, are taps off the secondary of the transformer and I can't see what problem you see with those. ST1 and ST2 are labelled "Segment test" and page 35 of the ET-3400 manual says to short those pins to light all segments of the LED. Maybe you need to clarify what your problem is? \$\endgroup\$ Jan 17, 2016 at 16:54
  • \$\begingroup\$ Im sorry, I have trouble interpreting a schematic, what am I supposed to do with the single letter holes like X and R. They don't seem to be bridges, just holes. I am new to this but I am able to solder pretty well as long as I know what to solder. \$\endgroup\$
    – Rhezner
    Jan 17, 2016 at 17:20

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