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Fender Ramparte - Schematic

Discussion in 'Amp Tech Center' started by GERPUD, Feb 8, 2015.

  1. Joshbailz

    Joshbailz TDPRI Member

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    Thanks, before i go pulling my amp apart can i just check whether you mean version A or B of my attachment? Thanks for the advise on the OT i will fit the filter first then hopefully have ago at some of your other mods :D. I have to say i went on holiday last week and spent the week following all of your forum posts and they have inspired me to turn this little amp into a beast!:lol:
     

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  2. GERPUD

    GERPUD TDPRI Member

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    What I did is Version B, but with 2x47uF in the first cap..
    Version A would also work. It is the equivalent of doubling the second cap instead. It may give the same result, but doubling the first cap increase filtering of the B+.
    I dont' know if the difference would be hearable. Probably not. The important thing is the added filtering stage and choke.
    More filtering cap decrease the voltage sag. I like that. Better punch and responsiveness. Different overdrive sound.
     
  3. Joshbailz

    Joshbailz TDPRI Member

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    Perfect thanks! i will get the caps ordered and give it ago.
     
  4. Joshbailz

    Joshbailz TDPRI Member

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    Ok i have the parts and i think i have located where to attach the extra filtering stage, can you just check that i am adding it in the correct place please (see circuit attachment). Also did you keep the two wires on the back of the pcb that fender added to try and correct this problem or did you remove them? (see second attachment). Finially is there a reason that you used 2 x 47uF caps as opposed to 1 x 94uF cap (or a close equivalent) ?

    Thanks :p
     

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  5. GERPUD

    GERPUD TDPRI Member

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    For the black wires on the back (and one on the front), they were added afterward to modify the original pcb (continuous ground path) to make "star" ground pattern instead. I would keep that this way because there is surely a reason why they would do that after the pcb have been done. Star pattern is a better ground scheme.

    You showed the right place for the extra filtering stage. But don't forget to break a pcb link behind. Otherwise, first filtering stage will be bypass and useless. Scratch it with a scewdriver, screw, nail or anything else.

    You could use 1x94uF-450V, but good luck to find this huge cap!
    You could use 3x33uF if you want, as long that they are 450-500V.
    Whatch out to install them in the right direction. I've blew some fuses and caps when putting them in the wrong way.
     
    Last edited: Aug 17, 2015
  6. Joshbailz

    Joshbailz TDPRI Member

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    Help!

    SO i have added 2 47uf caps in parallel then taken the positive line through the inductor and broken the track on the underside of the board all before b+. But now I'm getting some very strange noises coming out of the amp, any obvious ideas that i'm missing?
     

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  7. GERPUD

    GERPUD TDPRI Member

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    Did you tested it with the PCB out of the housing?
    You've added a lot of wires and your new diy pcb is adding possible connection for ground loop or other ground problems.
    Otherwise, I have no ideas.
    You broke the right link. You have the right schematic.
    I have put the new cap directly in the original PCB. It takes less space. see post #45.
     
  8. Joshbailz

    Joshbailz TDPRI Member

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    Yes it was tested with the PCB out of the housing, i don't understand how you've added in your cap directly into the PCB as the + leg has to go to the choke? then the choke returns to the - of the cap unless i'm mistaken?
     
  9. GERPUD

    GERPUD TDPRI Member

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    The earth connection is on the housing. All the grounded connections to the housing are missing (pots and guitar cable). The ground reference to earth is also missing.That is probably your noise problem.

    I've put all negative legs on the existing negative cap leg. I make a hole in the pcb to solder the positive leg on the back of the pcb. I was more solid this way. I've put the new caps over the rectifier (need to fold the C10-C13 caps). It's very squeezed, but it worked well.
     
  10. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Just curious if anyone else has encountered (or heard of) this situation - He picked up a supposedly-new Ramparte at GC (unboxed); not having any significant noise issues for a single-ended amp (i.e. it's noisy with single coils and pretty quiet with humbuckings, with a low latent hum not noticeable when playing).

    However, his has JJ 12AX7's and a Ruby 6L6, which I didn't think were stock (I have an Excelsior, which came with quickly - removed Chinese tubes).

    His only issue is pretty odd, and he's opened it up and looked around inside (has enough knowledge not to kill himself!) - no apparent mods, but the "cool" channel has more gain than the "hot" (or whatever it's called) channel.

    I suggested preamp tube subs (he had spares) and there was no change. It'll probably be here tomorrow - just trying to get a head start if this is a known situation.
     
  11. Joshbailz

    Joshbailz TDPRI Member

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    Cool thanks I will give it ago today, so you have tAken all the grounds that don't seem to go anywhere on the pcb, (presumably it's a ground fill?) and connected them to the 47uF cap?
     
  12. GERPUD

    GERPUD TDPRI Member

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    I didn't do anything with the grounds.
    If you what to do something with them, I guess you can connect them to the 47uF cap, but can't see why you would want to do that.
     
  13. GERPUD

    GERPUD TDPRI Member

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    My stock amp had both 12ax7 and 6l6 Ruby.

    The hum cannot be heard when playing. It is very annoying in a small room when not playing.

    The way the schematic is done, it is not possible that the cool has more gain. There is three preamp stage for hot channel and two for the clean. The tone cap are very different on both channel. The hot channel cuts the bass and the treble. The gain from the cool channel is 100% from power tube and bright cap on the volume. The gain of the hot channel is ~60%? from power tube, but mostly mids.
     
  14. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Well, the amp was dropped off - and as the owner had left the country and I'd just fixed his Marshall (that I used to own) for just parts cost, it was GIVEN to me!

    Personally, I think it's really cool - and I own a lot of vintage amps!

    It's bare-bones - like an Uber-Champ. The design is pretty stupid, but DOES work -

    If the parts values are right!

    I found the problem with this one in 10 minutes (thanks GERPUD for drawing up a linear schematic like Fender used to - it helped me check parts values).

    R16 is supposed to be a 100k resistor. This one had a 1k resistor in it. Dumb mistake. I've seen similar mistakes in original tweeds though!

    Replacing that one resistor fixed MOST of the issues. The "Hot" channel was still a little strangled on the high end. Not a volume problem - just not a lot of highs.

    Clipping C19, which bridges the volume control, was obvious.

    I ran it through a 2x12 loaded with special Hendrix-cab "Greenbacks" (Celestials). Damn, is the Hot channel loud! And clean, and controlled perfectly using guitar controls.\

    And the Cool channel is now all-headroom, perfectly clear and distinct.

    This one - even with the chassis out of the box - has very little hum for a single-ended amp. It's perfectly usable as-is.

    I loaded the cab (glad I read about the mounting bolts - it now has T-nuts) with a Vintage 30 and replaced the V1 tube with a NOS Tung Sol 12AU7. Tamed the gain of the Hot channel to a little more practical level, and the Cool channel sounds incredible. Subbed a NOS RCA 12AX7A in V2 - like it better than the JJ. And am using an RCA blackplate 6L6 instead of the Ruby. The tubes made more subtle than drastic differences.

    I love the look, and especially the weight (I have a 35-pound lifting limit). the size and being a little over 20 pounds, plus the volume of the Hot channel make it a perfect small club amp. Use your guitar and maybe a pedal or two for tone shaping - no need for a bunch of unnecessary mods. An A/B switch and a few pedals is perfect.

    Kind of amazing that I have boutique amps, a '62 Concert, '64 Champ and '55 Deluxe - yet have and really like all the Pawnshop-line amps (I have the Excelsior and TWO Gretas as well - only mods are tube changes and a tone pot on the Excelsior!)
     
  15. GERPUD

    GERPUD TDPRI Member

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    I will simply said that is your very personal opinion and that my opinion, based on the differences I heard on my amp, there is few other mods that are worth it.
    The drive channel and footswitch I've done are not worth it, but I had fun doing it.
    Good mods are in priority order:
    - speaker
    - negative feedback pot (more headroom, cleaner)
    - Choke, more filtering cap (no more noise, no more voltage sag, more headroom)
    - 5k primary OT (more headroom, smoother sound)
    - Bigger OT (more bass, bigger sound)

    Useless mods (but high fun!):
    - Orange drop caps
    - All overdrive mods (master volume, footswitch, tone caps)
    - Wood cab.
    - Standby switch
     
    Last edited: Sep 1, 2015
  16. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Yeah I was going to mention the standby switch - those are very rarely necessary. If you get deep into tech info written by electrical engineers cathode-stripping (which a standby switch is supposed to prevent by allowing the tubes to warm up slowly) is a very minor problem, and other issues will cause tubes to fail or have problems for before cached stripping (I really laugh when I read advice stating you need to turn the two switches off in some specific order - ridiculous!)

    The overdrive and Master volume mods are just personal preference. I agree absolutely about the speaker (I settled on a 16-ohm Celestial Greenback in mine).

    But the Cool channel needs no more headroom - it's ALL headroom unless I push it with a boost pedal!

    And surprisingly, mine makes less noise than any of my other single-ended amps - Champs, Magnatones and other amps with similar output stages. I initially thought the OT and PT position would cause a problem, but in my case there is absolutely none.

    A lot of that can be the power source. My previous house had an ambient noise issue and I had to use filters and voltage regulators to clean ANY amp's sound up.

    But where I live now the ground is good, voltage stable and there's just no issue - unless I plug in a single coil pickup guitar and hold it close to the amp - but that's true with every amp, singe ended or not.

    What I finally did end up with: the Greenback, removed C19, use a Tung Sol 12AU7 for V1, a Sylvania 12AX7 in V2 (after trying a dozen or so) and an RCA blackplate power tube.

    I also use a Morley A/B/A+B switch so I can blend the channels, and that sound is absolutely wonderful! Each channel individually is fine - blending them is incredible (and again, I have a bunch of very high0-end amps). This little spud surprises me!

    One tip - R16 is the key to relative channel levels, as it essentially serves as the mix resistor that controls the amount of each channel that goes to the grid of the last stage. With the 100k stock resistor the Cool channel is clean all the way to the top (with normal guitar signal, not with any boost pedals); the Hot channel has more gain and more highs, but not piercingly so.

    I may play with that value a bit - try an 87k, then a 68k (actually I'll use a decade box to change values in seconds) and try to get the cool channel to the point that it barely starts to break up when dimed when hit with PAF's. That should make the higher levels of the Hot channel more usable (it's a little too loud for practical purposes.

    There's no need for a tone stack - the guitar controls work just fine on everything I've plugged into it, from a Les Paul to Tele to Casino to Kay archtop with a monkey-stick D'Armond.

    Oh - and when changing the speaker installing T-bolts is mandatory - and don't forget to pain them...or use a Sharpie...to make them black like the baffle.(10-32's fit perfectly if the holes are drilled to 15/64" and the cane gill cloth removed - takes 10 minutes to remove and another 10 to reinstall it with a stock staple gun). Another pleasant surprise was the screwed (not glued!) baffle.

    As far as the overall circuit - it's really dumb, with all kinds of self-canceling parts that could be removed and jumpers installed. But It *works*, and the tech mantra is "if it ain't broke, don't fix it"!

    Great little amp - and 29 pounds with the Greenback!

    Here's my footswitch layout (normally it would be next to me, not behind the amp). The control settings, by the way, provide just a slight increase in volume when switching to Hot, and a really fat sound when blended:

    [​IMG]
     
  17. GERPUD

    GERPUD TDPRI Member

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    ?!16ohm!? You end up with a 14.8k primary. SE 6L6GC are theoretically optimal at around 5k... Your amp should sound very punchy, treble, with low mids. That should drop also the clean volume.
    We do not have the same amp... You're lucky, because the noise seems to be a common problem to a lot of people.
    I don't see why the voltage regulator and house ground should help the noise. The noise I hear is 120hz. Everybody has a 60 or 50hz supply. Voltage regulator does not change that frequency. A more stable voltage should not has an impact on that frequency.... I'm not an expert, but seems odd to me.
    Cutting C19 is perfect, but I find the overdrive lacking bass compared to the clean. Try increasing C4 and give me news!
    I agree!
    I agree!
     
  18. Silverface

    Silverface Poster Extraordinaire Platinum Supporter

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    Mids didn't change at all between a 2x12, 8 ohm Celestion cab and the 16 ohm single speaker. Pretty common in single ended amps like Champs and tweed Princetons to be able to use higher impedance speakers without noticeable affect on tone or volume (the math may say one thing but it boils down to the individual parts when combined in a complete package). FWIW 4 different 6L6's, a Mullard EL37 and 50's Tung Sol 5881 yielded similar results - the RCA is a tube that happened to be a single.

    120Hz hum can be picked up through shielding of other items in the house, dimmers, fluorescent bulbs (which I refuse to use anywhere) and external sources of RF interference. The AC power supply I use does help with external sources, which is why I've carried the 25 pound monster around for 15 years.

    We have the same amp, and I don't doubt you have hum or that some others do - but others have also told me they don't notice anything worse than that of any single - ended amp. Im my case there's less than my old Champs and Magnates as the Ramparte is shielded far better. 120Hz hum is very commonly environmental.

    Removing C19 isn't cutting any bass - partially because of the significant speaker upgrade. No need to mess with C4.

    I did make ONE other change:

    I got out my decade box, clipped out R16 and tried various values - and there were significant differences in the relative volume levels of each channel depending on the value of that single resistor.

    I finally settled on a common 68k. It tamed the Hot channel enough to make it not outrageously loud/distorted when cranked, and the Cool channel now is louder and will break up just bit in a smooth, saturated way when dimed - so it can be completely controlled both tone and volume/drive-wise just by using the guitar's controls.

    It also fattened up the blended channel sound even more - despite the difference in topology, speaker and cabinet construction it sounds very close to my '55 5D3 (the first ones with miniature preamp tubes) Deluxe! That was a real surprise to me! I flipped back and forth between both for several hours today with about 10 guitars and it was pretty darned amazing.

    And my buddy still doesn't want it back! Fine by me!
     
  19. Joshbailz

    Joshbailz TDPRI Member

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    After having a rethink i decided to ditch the extra strip board and added the cap straight onto the legs of the other cap, i also re-flowed the solder on several joints that looked a little dodgy and the results...................a completely silent amp, to the point where you can't tell its on.

    On checking the board i did notice that i have R31 missing, on my board this is just a piece of wire and from looking at the schematic it looks like it would have formed a tone filter, has anyone else got R31 missing?

    I also found that the clean is now very clean throughout the entire volume range but it has also increased the presence of the amp so i may look to add a filtering stage to control this as it can be a little too much with my strats. The hot channel still needs some work as its very muddy, by that i mean not enough highs! the distortion is more like a subtly overdrive.

    For anyone with hum problems i would recommend the mod that Gerpud mentions, 47uF cap in parralell with a 4H choke in series.
     
  20. GERPUD

    GERPUD TDPRI Member

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    I'm glad it worked!
    R31 is missing on my amp also. It would have decrease the effect of the bright cap. So, if you find there is too much presence, you could try to remove C21, or use your tone pots on the guitar.
    I found the drive channel very muddy also. Removing C19 is a must. Then, it will lack (to my taste, Silverface will not agree) bass frequencies. This can be corrected with C4 by increasing its value (this is a hi pass filter). The right value is a matter of taste. Putting C19 1000pF at the place of C4 470pF would help. But if I remember, that was not enough to my taste. 0.033uF was a bit too high. Something around 0.02uF would do I think. Replacing C4 is a hard job. Need a lot of accuracy and skills because it is so badly placed on the pcb...
     
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