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Thursday, 24 May 2018

Rostex Turbo Metal

I've heard that in 1991 former Lell engineer went on to form a new company called Rostex. At least that's the rumor and i have no other information about the brand or the pedal. You know anything about these (or have a demo clip/video), please do post it in the comment section.

For the layout, in addition to adding series polarity protection and input pulldown, i subbed the output buffer FET to common 2N7000 pinout.

4-knob version:
And the  3-knobbed version:

(Edit 25.5.2018 23:31: fixed a fault with low wiring and added the 3-knob layout
Edit 29.5.2018 20:35: Fixed 3-knob layout that had a misplaced cut on board image)
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26 comments:

  1. Dexter24 May 2018 at 23:04

    thanks Miro!

    KP303B is a N-ch Jfet.

    Datasheet link

    And I've seen another version with 3 knobs.

    ReplyDelete
    Replies
    1. mirosol25 May 2018 at 05:34

      For the FET, as it's only an output buffer, i personally see that as a waste of JFET :) - and thus, the 2N7000 would perform the same. As would basically any n-channel FET or MOSFET. One can use what they want. Just mind the pinout.

      I've seen the 3-knobbed version as well. For the floater schematic, that seems to be exactly the same circuit. Except for the Low control fixed on maximum setting.

      I do find these russian circuits interesting as they rarely are just clones of the western designs. With an open mind and one could possible tweak many of those to perfection.
      +m

      Delete
    2. mirosol25 May 2018 at 05:39

      I'll see the 3-knob schematic in the evening and possibly tweak the layout accordingly for another version.
      +m

      Delete
  2. Unknown25 May 2018 at 12:07

    there seems to be a mistake with the low knob, according to the schematic low 1-2 should be switched with low 3 and a 4k7 resistor should be added between the new low 3 to ground

    ReplyDelete
    Replies
    1. mirosol25 May 2018 at 21:32

      Thanks for noticing! My bad. Now fixed.
      +m

      Delete
  3. Unknown25 May 2018 at 22:24

    Cheers for this! Love these mystery builds. Just cut my board to size...

    ReplyDelete
  4. Blorvak28 May 2018 at 08:49

    Let me know if I'm crazy here... I'm populating the 3 knob version and I think there may be a stray cut in the wrong place on the bottom row on the non-component image? I'm guessing that the correct cut should be 6 holes from the left of the board, instead of 4?

    ReplyDelete
    Replies
    1. Elijah-Baley28 May 2018 at 16:29

      I think you're right.
      I guess the two non-component sides of the version layout have been confused.

      Delete
    2. mirosol29 May 2018 at 18:25

      Nowh fuck :) I'll fix them asap... Sorry. been of from doing layout for a while and that's what i get..
      +m

      Delete
    3. mirosol29 May 2018 at 18:39

      Fixed. *Should* be ok now.
      +m

      Delete
  5. Elijah-Baley28 May 2018 at 16:29

    This comment has been removed by the author.

    ReplyDelete
  6. Buke Lorley29 May 2018 at 09:47

    This forum thread has some photos of this and a YouTube demo, not of this, but of a Rostex Delay: http://guitar-gear.ru/forum/topic/4570-%D0%B3%D0%B8%D1%82%D0%B0%D1%80%D0%BD%D1%8B%D0%B5-%D0%BF%D0%B5%D0%B4%D0%B0%D0%BB%D1%8C%D0%BA%D0%B8-rostex/

    There's also a schematic on there for a Rostex Turbo Overdrive:

    http://guitar-gear.ru/forum/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=42117

    ReplyDelete
  7. Buke Lorley29 May 2018 at 10:06

    A couple more schematics on this Soviet Guitars thread, including a Rostex Distortion and an Anta Fuzz: http://sovietguitars.com/e107_plugins/forum/forum_viewtopic.php?103421.150

    ReplyDelete
    Replies
    1. mirosol29 May 2018 at 18:45

      Nice! Thanks Luke!

      Do note that the Distortion is pretty much 1:1 with the Turbo Metal.
      +m

      Delete
  8. Andrea C.6 September 2021 at 15:50

    My 3 knob version doesn't work.
    All seems to to be ok (first round of classic debugging routine is not giving results), but when I switch on I can hear only some low rustle moving the pots. But if I touch the top of the 4.7 electrolitic caps with my finger, I can hear the distorted sound of the guitar, but very very low and far away...
    The caps are ok, the 2N7000 is ok, the IC is ok. The ground is well connected.
    It's may 33rd pedal... never happened such a strange thing...

    ReplyDelete
  9. Andrea C.5 October 2021 at 15:18

    Now, using my audio probe the pedal sounds very good, with a nice distortion, at the Gate of the mosfet, the central pin: after this point the signal disappears.
    The cut at the fourth hole from the right of output is right..?

    ReplyDelete
  10. Andrea C.5 October 2021 at 15:22

    Someone more prepared than me can tell me the path of the signal from Gate pin to Output on the pcb?. Maybe I have the 4,7uF cap faulty..?

    ReplyDelete
  11. Andrea C.9 October 2021 at 21:33

    FIXED!
    With the help of a diyer on the web, I understood that the problem was really what I wrote some days ago: the signal was blocked in the gate of the mosfet.
    The gate wasn't properly biased, because in the schematic a resistor was missing: so, I just added a 1M resistor (on the back of the pcb) from drain to gate of the fet, and now all is perfect!!!

    Now you can consider it (the three knobs version) as "verified"..!

    ReplyDelete
  12. harly_wake18 August 2024 at 23:23

    Hi, don't take it as impudence, but can someone please check me? It just so happens that it is more convenient for me to make a print layout. The circuit works, but veeeeery quietly, I checked it several times and I can't see the problem.

    https://harlywake.blogspot.com/2024/08/blog-post.html

    ReplyDelete
    Replies
    1. harly_wake19 August 2024 at 12:06

      swap j201 on 2n5457 and volume appear

      Delete
    2. harly_wake19 August 2024 at 12:16

      It seems like my j201 isn't working...

      Delete
    3. IvIark19 August 2024 at 13:18

      No great surprise there. For maybe 10 years now J201s have been either dubious quality, or straight up fakes. Fortunately I bought a stash from a known Fairchild supplier before that happened, but if I wanted any more now I'd stick to surface mount J201s (MMBFJ201) and adapters ike this to make them through hole compatible:

      https://www.bitsboxuk.com/index.php?main_page=product_info&products_id=3144

      These are within the through hole J201 specs and are probably more consistent that the old TO92 form factor

      Delete
    4. harly_wake19 August 2024 at 13:26

      Wow, that's clever, thanks for the info. I'm new on campus, every day is a discovery)

      Delete
  13. harly_wake19 August 2024 at 14:01

    By the way, on 5457 it sounds quite fuzzy, different from the original. I have a distortion clone from soviet on к157уд2 and it sounds as a distortion literaly, similar to DS1. But on 201 does fuzz grain appear? I don't know when I'll get 201.

    Apply schematic diagram is not for this particular unit, but it is something very similar.

    https://harlywake.blogspot.com/2024/08/blog-post_19.html

    ReplyDelete
    Replies
    1. harly_wake19 August 2024 at 15:39

      oh, and there кп303в

      Delete
    2. harly_wake19 August 2024 at 17:42

      oh, and others similar schematic says that leds АЛ307ВМ, that's 5mm green

      Delete