problem with this clone
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problem with this clone
hello good to all and congratulations for the forum.
I have this clone of plexi I think of 18 watt made up of two 12ax7 and two el84
with its four send-return inputs
the problem is that when the channels are bridged and I use the bass pickup on the 6 and 5 strings the sound drowns out.
I have changed valves and it remains the same.
if I use the return it sounds good.
where can the fault be?
I had thought to fix it or even make a new board taking advantage of the rest of the components.
I attach photos.
Thanks .
I have this clone of plexi I think of 18 watt made up of two 12ax7 and two el84
with its four send-return inputs
the problem is that when the channels are bridged and I use the bass pickup on the 6 and 5 strings the sound drowns out.
I have changed valves and it remains the same.
if I use the return it sounds good.
where can the fault be?
I had thought to fix it or even make a new board taking advantage of the rest of the components.
I attach photos.
Thanks .
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- Bieworm
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Re: problem with this clone
Hey.. I think you need to give us more information. If it's a 4 input 18W there is likely no bridging the channels. It will be out of phase and that's the thin sound you hear.cisatracurio wrote: ↑Tue 04/20/21 10:39 amhello good to all and congratulations for the forum.
I have this clone of plexi I think of 18 watt made up of two 12ax7 and two el84
with its four send-return inputs
the problem is that when the channels are bridged and I use the bass pickup on the 6 and 5 strings the sound drowns out.
I have changed valves and it remains the same.
if I use the return it sounds good.
where can the fault be?
I had thought to fix it or even make a new board taking advantage of the rest of the components.
I attach photos.
Thanks .
Also.. don't re-use components from a turretboard. That's screaming for problems. If I were to rebuild an amp I'd only reuse the existing transformers .. heck I even throw away the tube sockets. In my understanding a rebuild is a situation where you can't find the problem in the amp and start over... so it's not smart to use components again. You gave a big chance of reintroducing the same problem in the new build. But likely there is nothing wrong with your amp..so why rebuild it?
Post pictures so we can see what we're dealing with.
Thanks .. and welcome
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Re: problem with this clone
Hello, thanks for the answer
attached several photos of the team
the truth is not a great idea to rebuild it just solve the problem
Thank you
attached several photos of the team
the truth is not a great idea to rebuild it just solve the problem
Thank you
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Re: problema con este clon
I don't know if they will be well uploaded
You do not have the required permissions to view the files attached to this post.
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- Bieworm
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Re: problem with this clone
Do you have a schematic of THAT amp? Not a standard plexi schematic, but the one from the amp you have. With the pcb board it's nearly impossible to see how it's wired. It's not traceable if it's wired to be jumpered. I don't think it's any high suality amp, but it should be fun to play anyway.
Can you post a sound clip of it with and without jumpering. The without jumpering channels should be one of each channel separately.
Can you post a sound clip of it with and without jumpering. The without jumpering channels should be one of each channel separately.
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Re: problem with this clone
That seems to me from the little I know about it
I do not have the scheme and I can imagine that looking at the plate it is difficult to get an idea
tomorrow I will record the audios and upload them
Thank you
I do not have the scheme and I can imagine that looking at the plate it is difficult to get an idea
tomorrow I will record the audios and upload them
Thank you
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Re: problem with this clone
is the potentiometer at the right side of the input jacks for blending the inputs rather than a jumper cable?
look at those screw terminals on the boards,tweakers delight!
look at those screw terminals on the boards,tweakers delight!
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Re: problem with this clone
that potentiometer on the right side of the inputs is a basic master volume.
I will look at the cables that come out of the inputs and go to the plate in case there is a bad connection because at first glance you cannot see any capacitor in bad condition
as soon as I have the sound samples I will attach them
the amplifier has a decent sound and a lot of volume so my intention to solve the problem
Thank you
I will look at the cables that come out of the inputs and go to the plate in case there is a bad connection because at first glance you cannot see any capacitor in bad condition
as soon as I have the sound samples I will attach them
the amplifier has a decent sound and a lot of volume so my intention to solve the problem
Thank you
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Re: problem with this clone
Hi ,Another thing I can think of if I couldn't fix it.
With the transformers that I have, could I mount a plexi?
Thanks
With the transformers that I have, could I mount a plexi?
Thanks
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- Bieworm
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Re: problem with this clone
Normally yes. It's the same kind of amp right now so..cisatracurio wrote: ↑Wed 04/21/21 3:22 amHi ,Another thing I can think of if I couldn't fix it.
With the transformers that I have, could I mount a plexi?
Thanks
But you need to check the specs of the transformers to be sure.
Anyway... this is no plexi. It's 1 tube short and the output stage of a plexi is way more powerful with EL34s.
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Re: problem with this clone
Ok I understand that it depends on the specifications of the transformers.
What if I wanted it to be with the 84 so that it had 18 watts or can it also be with the 34?
And what scheme should I follow with diodes in the rectifier?
Thanks
What if I wanted it to be with the 84 so that it had 18 watts or can it also be with the 34?
And what scheme should I follow with diodes in the rectifier?
Thanks
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- Bieworm
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Re: problem with this clone
Stay with the EL84. An EL34 will draw 2x the current and might not work with those transformers. And the OT will likely be 15 or 18W output...so there would be nothing to gain with EL34scisatracurio wrote: ↑Wed 04/21/21 5:15 amOk I understand that it depends on the specifications of the transformers.
What if I wanted it to be with the 84 so that it had 18 watts or can it also be with the 34?
And what scheme should I follow with diodes in the rectifier?
Thanks
6V6 would be fine too.
Assuming your build runs with 2x 12ax7 and 2x EL84 the heater current is at least around 2.2 A. So with 2x 6V6 and 3x 12ax7 you should still be fine and make it a more similar preamp to plexi specs. There are several 6v6plexi schematics online and here in the download section available. Do you have experience in building tube amps?
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Re: problem with this clone
Thanks Bieworm I understand that you tell me that due to the characteristics of my amplifier the transformer should ensure the power supply for the 3 12ax7 and 2 6v6 and thus make a more reliable scheme to a plexi.
I have very little experience in tube amplifiers if I have done other types of electronic assemblies and I understand a little about the operation of the valves
I have very little experience in tube amplifiers if I have done other types of electronic assemblies and I understand a little about the operation of the valves
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Re: problem with this clone
I think my amp can correspond in schematic to a superlite tmb from what I have been able to see?
Thank you
Thank you
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- Bieworm
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Re: problem with this clone
That is possible, but without a schematic or reverse engineering it's impossible to say that. There arelots of combinations with that same tube layout..cisatracurio wrote: ↑Wed 04/21/21 7:03 amI think my amp can correspond in schematic to a superlite tmb from what I have been able to see?
Thank you
It would be wrong to advice you to start rebuilding it without proper soldering experience. Tube amps are dangerous to work on. If you're really erger to do it you should study amp works in advance
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- Bieworm
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Re: problem with this clone
Btw, I don't think you can jumper channels. It looks like you have one normal channel with 1/2 12ax7 and the lead channel will likely be the 2nd triode in parallel or series to fatten up the signal. This means the triode of the normal channel can only be used separately OR in series/parallel with the 2nd triode.
Maybe somebody else here with more knowledge says a different thing... but that's what I can derive from the photos.
Maybe somebody else here with more knowledge says a different thing... but that's what I can derive from the photos.
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Re: problem with this clone
if it can be that it works like that, with which the problem would be in the second channel.
Attached audio file the first two are from the first channel and the second part of the file corresponds to channel 2, first bridge pickup and then neck pickup where the problem with the Bass
Attached audio file the first two are from the first channel and the second part of the file corresponds to channel 2, first bridge pickup and then neck pickup where the problem with the Bass
You do not have the required permissions to view the files attached to this post.
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- Bieworm
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Re: problem with this clone
Wow.. I think you need to check some voltages. This is with the amp fully dimed?..
The low end is out of balance...
Maybe Josh or someone else here knows where to start looking?
The cathode bypass cap seems rather small..try clip a large value in parallel with alligator clips. At least 1000uf 63V. It's the cap at V4. Watch out for the polarity when testing that... negative to ground
You could have more control over that by reducing the cathode bypass cap on V1, but with the pcb that's a pain in the a$$ when you don't have the know-how and skills
The low end is out of balance...
Maybe Josh or someone else here knows where to start looking?
The cathode bypass cap seems rather small..try clip a large value in parallel with alligator clips. At least 1000uf 63V. It's the cap at V4. Watch out for the polarity when testing that... negative to ground
You could have more control over that by reducing the cathode bypass cap on V1, but with the pcb that's a pain in the a$$ when you don't have the know-how and skills
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- zaphod_phil
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Re: problem with this clone
Where's the schematic for whatever amp this is?
Bieworm wrote: ↑Wed 04/21/21 3:58 pmWow.. I think you need to check some voltages. This is with the amp fully dimed?..
The low end is out of balance...
Maybe Josh or someone else here knows where to start looking?
The cathode bypass cap seems rather small..try clip a large value in parallel with alligator clips. At least 1000uf 63V. It's the cap at V4. Watch out for the polarity when testing that... negative to ground
You could have more control over that by reducing the cathode bypass cap on V1, but with the pcb that's a pain in the a$$ when you don't have the know-how and skills
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Nature abhors a clean tube amp