Noob Question - Lectrolab R200B Repair

Discussion in 'Amp Tech Center' started by mikestearns, Oct 18, 2019.

  1. mikestearns

    mikestearns Tele-Meister

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    I need to replace the power tube socket on my old Lectrolab R200B, and while I had the chassis out of the cabinet I could see that the caps all need to be replaced. It has one of the old can caps in it, should I replace that with individual caps, or would it be better to find another can?
     

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  2. Wally

    Wally Telefied Ad Free Member

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    If there is a multi section cap can available with the values needed, that would be my choice. If not, then I would leave thenoriiginal cap can there..disconn3cted...and recap with single caps.
     
  3. Bendyha

    Bendyha Friend of Leo's Silver Supporter

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    20/20/40/40µ they exist, they are not cheap. FT make one.

    You don't get to see amps with that tube line-up very often - a 50L6, 35X5, and two 12BF6.....50+35+12+12 = 109, near enough to 117V , heaters run straight from the mains.

    Half-wave rectification, field-coil speaker.........Hows it sound ?
     
  4. mikestearns

    mikestearns Tele-Meister

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    Sounds good, and replacement tubes are easy to find and cheap. It’s very Champ-ish but not quite as good. Plug in a telecaster and it’s instant stones, give it a boost and it’s communication breakdown. It was also a hundred bucks, so it’s safe for me to try to repair without risking destroying a really expensive amp.
     
  5. mikestearns

    mikestearns Tele-Meister

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  6. Wally

    Wally Telefied Ad Free Member

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    If that fits physically, then the voltage is of no concern. That isolation transformer sends wall voltage to the rectifier, so as long as the voltage capacity of the cap can is 150vdc or higher it is good to go.
     
  7. mikestearns

    mikestearns Tele-Meister

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    I successfully changed out the tube socket and replaced the old paper caps. This is my first time attempting any kind of amp repair, so I was insanely ecstatic that I managed to get it working again. I've decided to hold off on replacing the filter caps. I think I'm reading the schematic wrong - the filter cap can only has 3 tabs so I think its a 40/40/20? And the other 20uf cap below those three in the schematic pic thats obscured a little I think is a coupling cap that looks like whoever had it before me already replaced.

    I think the next time I go to work on it I want to change how the speaker connects so that I can also run an extension cab to give me options to use a 12inch speaker instead of the 8 that it currently has.
     
  8. Wally

    Wally Telefied Ad Free Member

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    Pics of your actual circuit would help. The schematic, which I take it is stapled inside the amp, shows 4 filter caps and two electrolytic bypass caps....one of which is a bypass for the power tube bias resistor.
    All electrolytics need to be changed, imho. But....if the amp goes down due to a failed electrolytic, it is a small loss, I suppose.
     
  9. mikestearns

    mikestearns Tele-Meister

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    Wally likes this.
  10. mikestearns

    mikestearns Tele-Meister

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    I would think the resistors have all drifted at this point. The bypass to the power tube resistor looks like the blue cap in that photo, its just on the other side of the power tube socket and not in this pic. They both look like they've been replaced at some point. I replaced all the yellow .01uf caps. It looks like the death cap was also removed, I'm assuming that was all done when the 3 prong power cord was installed.
     
  11. Wally

    Wally Telefied Ad Free Member

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    Mike, sorry for the assumption. There is a different schematic for another version of that amp. You can find it at Schematic Heaven under Bargain Bin amps or at EL34 World under Lecteolab. It has a different power supply circuit than does the schematic you show above.
     
  12. mikestearns

    mikestearns Tele-Meister

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    Thanks! I just assumed the whole time I was reading that one wrong.
     
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