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Thread: egnater rebel 20 sounds like a ring modulator

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    egnater rebel 20 sounds like a ring modulator

    Good day,

    I have this rebel 20 which I bought online from a used store in Japan. I was aware of the buggy issue which I thought was only a leaking filter cap. I have a jcm2000 that sounded like this and fix it with a recap job.
    Well Ive changed most of the filter caps in this egnater, next to the power transformer and even swapped out the resistors, but the weird ring mod tones are still there.
    Here's what it sounds like

    https://youtu.be/uE11nLgKLT0

    There's also this low hz hum. I checked the grounding of the filter caps and they were ok.

    Also Ive tried using the preamp section by sending it out on the return of my classic30. Awesome tones.. but I wish I could make the egnater's power section work by itself

    https://youtu.be/P5NyuDVcN-c

    I havent checked on the bridge rectifier going to the filaments since the preamp is working just fine.

    I thought of checking the big resistors near the power tubes next, but posted here instead since it might be futile. Is the power transformer busted? What else could be the culprit for this ring mod sound? Or is this what they call wolf tones? Thanks!

    Schematic i got is from elektro tanya

    https://elektrotanya.com/egnater_reb.../download.html

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    What effect if any to the controls have on the problem?

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    Experience is something you get, just after you really needed it.

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    There is this 6v6/el84 mix knob and a wattage knob(attenuator?) They both seem to affect the tone/pitch and hum, but never totally remove the weird sound

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by severthee View Post
    There is this 6v6/el84 mix knob and a wattage knob(attenuator?) They both seem to affect the tone/pitch and hum, but never totally remove the weird sound
    ..and the other controls do what? Please answer the questions full else we will never get there.

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    Old Timer J M Fahey's Avatar
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    Shotgunning didnīt work, now youīll have to troubleshoot.
    You got a complex/weird amp to service.

    Crazy EL84/6V6 output, crazy "Watts" control which works by starving/misbiasing the LT phase inverter, weird "Rebel Mix Mod V2" ... all of which may create that ring modulator type distortion, yet not be "broken" in the conventional sense, simply misadjusted.

    Just for starters, inject 100mV 1kHz at "Power amp input" or "loop return, donīt know how itīs labelled" , set all 2?/4? rebel mix pots to 10 , set "Watts" to 10 or maximum and scope speaker out: what do you get?
    Post scope screen.

    As a side note, your YT videos do not help at all, you do not speak, pluck ... twist some unidentified controls ... pluck ... twist ... pluck ... twist .... useless and annoying.

    Explain what you are doing, as in: "I set xxx control to yyy, this is how it sounds ..." , rinse and repeat.
    Show front panel so we clearly see what you are doing.

    But in any case, for now leave guitar aside and inject a sinewave, constant and predictable.
    Your guitar plucking? ... not that much.

    Last note: download schematic and attach it here , instead of sending us to Elektrotanya to go through their weird "acceptance" ritual.

    Here, I am attaching it for you:Egnater rebel20 sch.pdf

    Hereīs a simplified black and white version:

    Click image for larger version. 

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    or the colour version:

    Click image for larger version. 

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    Juan Manuel Fahey

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    My apologies, that video was initially intended only to exhibit the ring mod tone, I sent that vid link to egnater but never did got a reply. That's why it was more of fiddling than explaining, I was trying to find usable tones real quick.

    As for the knobs, all the preamp related knobs are working from mastrr ,treble ,middle ,bass and gain, they affect the normal guitar tones. That is either as a "preamp only" like exhibited in video 2 where it was send out to the fx return section of classic30. Or as standalone in video 1, the preamp knobs works normally. But the Tube mix knob and watts knob of the powersection are the ones changing the pitch or tone of the hum and ring mod sound.

    Thanks for uploading the schematic, I will try to find and upload the ones with values

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    Senior Member SoulFetish's Avatar
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    Quote Originally Posted by severthee View Post
    Good day,

    Also Ive tried using the preamp section by sending it out on the return of my classic30. Awesome tones.. but I wish I could make the egnater's power section work by itself
    you can. input a signal into the return jack in the effects loop. If it's a full interrupt loop it should isolate the PI and output section.
    One, and very quick way to eliminate a noise issue is to remove the tubes and try a some other tubes you know to be functional. Tube noise/problems and can show up in so many different ways. Often in exhibiting behavior you may have not come across before. But you can save yourself HOURS of troubleshooting by quickly swapping out tubes.

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    If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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    Yes i have tried using classic 30 preamp and a sansamp preamp to the egnater's return, the ring mod tone is there. I've also swapped the el84 since i have a bunch of them , same sound. What I dont have are spare 6v6 since most of my amps run on el84 and 6l6, i have to buy or borrow some fresh 6v6. Was wondering if i can run the amp without the 6v6 in place just to test?

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    Old Timer J M Fahey's Avatar
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    Please inject a sinewave and show output, sound is what weīre after of course but waveforms tell *a lot*.

    As of "Egnater" , I know him through other Forum and heīs a great guy, but sold Company, brand, designs, etc. to a group of raw investors who only care on ROI (return on investment) and have NO CLUE on Electronics, Music, and anything non finantially related so in general they canīt help you even if they want to.

    Notice schematic is written in Chinese and mentions a third party OEM contractor who must have been the lowest bidder.

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    Juan Manuel Fahey

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    Senior Member SoulFetish's Avatar
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    Quote Originally Posted by severthee View Post
    Yes i have tried using classic 30 preamp and a sansamp preamp to the egnater's return, the ring mod tone is there. I've also swapped the el84 since i have a bunch of them , same sound. What I dont have are spare 6v6 since most of my amps run on el84 and 6l6, i have to buy or borrow some fresh 6v6. Was wondering if i can run the amp without the 6v6 in place just to test?
    Yes, it’s fine for testing. In fact, you should pull the 6V6s and test the original EL84s. Then pull the EL84s and test just the 6V6s. See if you can isolate the source of the problem.

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    Senior Member SoulFetish's Avatar
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    But it is sine wave-scope time. You have acess to a signal generator (use a phone app tha’ll give you a 1kHz sine wave if not), dummy load, and oscilloscope?

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    Ok I will try to borrow a scope.

    i was tracing the board and making sure every wire and grounds goes to where it should.
    I checked on the continuity of qc208, qc104 and qc107 from the power transformer. the schematic shows that those 3 quick connects are tied together. the qc208 going to the bias and the qc107 (grounding the filter caps) have continuity, but the qc104 (connected to the first 1n4007) does not. should it be a concern that qc104 doesnt have continuity with them?

    Attachment 52956

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    Supporting Member Jazz P Bass's Avatar
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    Quick Connect QC104 must connect to diode D101.

    REBEL20sch 8-09 with Values.pdf

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    Schematic with values:
    (double post )
    Attached Files Attached Files

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    Quote Originally Posted by Jazz P Bass View Post
    Quick Connect QC104 must connect to diode D101.

    REBEL20sch 8-09 with Values.pdf
    yes qc104 is connected to d101. but does qc104 needs to be grounded? as per schematic, qc104 is grounded via qc107. but when testing my qc104 is not connected to any ground

    ThanksClick image for larger version. 

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    Lifetime Member Enzo's Avatar
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    as per schematic, qc104 is grounded via qc107
    No. Look at the schematic. The two spots next to the winding where the wires cross SHOULD NOT HAVE DOTS. That is a drawing typo. Think about it, if those wires were connected together, there would then be a dead short across the transformer winding. Any "grounding" you find at QC104 to QC107 is through the low resistance of the transformer wiring, NOT a direct connection. QC208 and QC107 are connected on the board. QC104 is NOT connected to them.

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    thanks! that's what I thought but was not sure. because the qc107 and qc208 coming out of the pt, even when not connected to the board made a beeping sound on the dmm. just read now there is a low resistance of only 6ohms between qc107 and qc208 that's why I had a continuity beep.

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