NAD - sort of

Discussion in 'The Squawk Box' started by Leña_Costoso, Sep 19, 2017.

  1. Leña_Costoso

    Leña_Costoso Senior Member

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    Tomorrow the last shipment of parts arrives.

    Construction of another modified "tweed" Super will begin.

    Hopefully a cabinet pic or two tomorrow, if I don't get in too late. The 2x10 is done up in blackface style covering and cloth. I used to think tweed was great, but really, playing out... black tolex wins, and doesn't say steal me (as much).

    (to be continued)
     
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  2. Cjsinla

    Cjsinla Premium Member

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    I can't wait for the pics to start. The parts for my tweed 2 X 10 Super shipped from Weber today, get to me on Friday. Keep us posted on yours. Who did you order the parts from?
     
  3. Leña_Costoso

    Leña_Costoso Senior Member

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    Mojo Mouser Digikey Allied Amazon....
     
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  4. Cjsinla

    Cjsinla Premium Member

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    Ok, so multiple vendors. How is the build coming?
     
  5. Leña_Costoso

    Leña_Costoso Senior Member

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    I only was able to open up the boxes today. Everything looks good. The last of the shipment was the cabinet from Mojo. I don't think I'll start assembly until at least the weekend. I still have quite a bit of storm clean-up to do. But hopefully I can get some pictures of the cabinet and post those online shortly.
     
  6. Leña_Costoso

    Leña_Costoso Senior Member

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    I got going thru things today. Mojo sent the wrong tubes, but they're correcting immediately. I ordered four ATOM capacitors and two are on backorder? FTW? They say Sept 26 for the remaining ATOM's. I'm not gonna mention which vendor, they do me right all the time for my work stuff. Other than that, I've got a pair of Celestion G10-Vintage here that are getting lonely.

    Excuses excuses... but, my truck blew its water pump the day before Irma hit. Wunnerful. Been truckin' to work 12 miles on a gallon of water each way! When the cabinet arrived, I had no way to get it home, as the truck was (finally) in the shop. Could not get the parts (idler and tensioner for the serpentine) so they needed an extra day to get it done. Didn't want to strap things to my Harley (ahem)... so finally... hopefully...I'll have a home bench full of goodies to begin assembly on tomorrow, and be ready for the last of the ATOMs and the right tubes and playing this amp by mid next week.

    This is gonna be the 2nd to the last amp I build, so I went all out with some nice selected carbon comp resistors, and such. The 5f4 in a 4x10 cab I did for a bro had the same, and also was modded from a stock 5f4, as this one will be, and it has a really nice tone. That one had the last four Emi 10ALK's I could manage to get hold of at a reasonable price.

    In the mean time, a crappy pic of the cabinet, sitting on the floor of my shop at work. Its lonely....!
    [​IMG]
     
  7. Cjsinla

    Cjsinla Premium Member

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    I like the black tolex look on that cabinet. My Super's gonna be tweed, I've never really had any tweed amps so I decided to go traditional.
     
  8. Leña_Costoso

    Leña_Costoso Senior Member

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    No names or logos on this one. It will just be my amp.
     
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  9. Leña_Costoso

    Leña_Costoso Senior Member

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    Problem:
    [​IMG]
    The output transformer leads got crushed in shipping or along its life from the factory. Grrrr. The blue wire is hanging by the insulation, and actually, fell off after this picture was taken. Yes, I can fix it, but I contacted the vendor to let them replace it, before I start with the solder and shrink wrap.

    Got the cabinet drilled for the chassis, got the chassis drilled for the fiber board. Got the fiber board drilled and mounted in the chassis. Enlarged a few holes to accept grommets. Just piddly stuff. Tomorrow I can run down and get some finishing supplies for the bare wood inside the cabinet, make up my custom tube chart and get that pasted in there. Then get started on the board assembly. Gonna hold off on the rest of the mechanical until I get the transformer issue resolved.
     
  10. Leña_Costoso

    Leña_Costoso Senior Member

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    [​IMG]

    Thought I'd share the tube chart
     
    Last edited: Sep 23, 2017
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  11. Leña_Costoso

    Leña_Costoso Senior Member

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    Before I go cut big logs into smaller logs.... all from Irma, I thought I'd give a little first impression review of some of the components.

    I got chassis and "kit parts" from MojoTone. They made the cabinet too. Other parts I got from Mouser, from Allied, heck... I ordered the speakers from GC because they were in-stock and nobody else had 'em.

    Two cabinet makers I've use in the past were Larry Rodgers and Mojo. Larry has passed on, and gosh he was a lot younger than me and looked a lot older. Larry had a humidity problem. Depending on exactly when and where his stock was stored, you'd get humidity in the wood, shrinkage, Tolex bubble-up. He did good work, but his shop was miniscule and he'd roll his wood and power tools outside in order to work.
    Mojo on the other hand makes outrageously nice cablnets. Never had a joint or bubble-up issue with them. The fasteners are top notch and the placement of fastener holes and such appear to be jigged, not measured. That is - baffles interchangeable, through the same holes, same with back panels. Not that I change things around, but it shows they have a real production line going on, with some engineered precision involved.

    One thing Mojo did really nicely - was mostly all carbon comp resistors, and orange drops. Been said they don't belong in a tweed circuit, and maybe so. I used Mallory 150's in a 5F4 (still modded), and its owner says "It nails the tone I've heard in my head for 35 years". The best part - is every item comes in a cubbyhole in a parts tray, and the lid of the tray has all the color codes for each and every resistor, printed out in full color on the inside of the lid, representing each cubby. Assemblers should still verify, but gosh it makes it easy for the newbie.

    On the downside, it did take some mental gymnastics to figure out the hardware. This could be my own fault. In the past, i'd run down to West Marine with list in hand and pickup all stainless hardware for the cabinets and transformer mounting, even the tube socket fasteners. Now I've got - a certain amount of 8-32 screws, some more 8-32 with different heads, some 6-32 screews, some 4-40 screws. Small screws easy - on the small sockets. Bigger screws, easy - for the chassis. Medium screws...er... but I got it figured out. Their choices are good, but my choices probably would have been different. Again, this is my past work conditioning me into one mode of thinking, and I'm having to re-think again (hard to do at my age!).

    Mojo, I'm sure, sells chassis made by outsourced vendor, and that vendor probably caters to more customers than just Mojo. As such, there are holes in the chassis that suit many different applications, And the holes that need to be enlarged to get grommets and screws through. Mr DeWalt is happy with that. Not a pain, just a reality. In the past I'd used Weber chassis. That was before Ted kicked the bucket. Every one had bad welds. I'm talking ten outta ten, you could bust the spot welds with hand pressure. Three reverb chassis, three deluxe chassis, three champ chassis and a 5F4 chassis. Had to drill and pop rivet each end to prevent them from bustin loose. Ted's ink also smeared, like it hadn't been baked well. Mojo has no such problems with their chassis. To be fair, I have no idea if Weber has improved, and this was back in the 1990's when he was just getting started. He never did make 'em right (Thank, Ted) and told me to bring my business elsewhere among other things (when I complained about the bum welds). I hope they're doing better these days.

    So there ya go for MojoTone. They seem to have the "kit" concept packaged well. On the other hand, a sheet that says, "use this hardware for this application" would have been nice. They also have some parts in the kit that are not used in a 5F4 Super, but might be used in a 5F4 Bandmaster or such. I got a standard layout and a redrawn 5F4 schematic, both of which I really didn't need... but the layout is nice looking and in color.

    Chainsaw time.... more build later!
     
  12. Leña_Costoso

    Leña_Costoso Senior Member

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    [​IMG]

    No chainsaw work today. Still more to do, but thought I'd take a break and work on the Super.
    Got the cabinet almost nearly done the way I like it. Notice the beauty washers used for support, and the "third screw" on top, for the support of the PT's weight. The bare wood inside (a very clear white pine) has been given a finish and the only thing left is to replace the copper colored screws they used to hold the baffle to stainless (like I fit the rest of the cabinet with).

    Hopefully wire up the board tonite.

    More to come....
     
  13. Leña_Costoso

    Leña_Costoso Senior Member

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    I got hold of Mojo today, they took a look at the picture, and said no problemo, we'll send another OT, and also sent a prepaid label to return the old one.

    Great, great customer service.

    I didn't shop much, just for the individual components (like caps, speakers, a few odds and ends components). Have not dealt with them in 8 years or so, but they never cease to impress with service.

    Getting close to the finish line. Caps and tubes should be in tomorrow. Replacement OT in by Friday. Should have a playable instrument for the weekend!
     
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  14. Leña_Costoso

    Leña_Costoso Senior Member

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    Reviving things a bit here, as I had to take time off from building the Super.

    Went over to Hobby Lobby today... and they have perfect plate copper for a control ground/chassis ground buss plate, if you're so inclined to use one (I am). Measures 12x24 inches at .015 inches thick. Cuts easily with a paper cutter. I found a 12 inch strip about 2-1/4 inches wide makes a good fit (actually just an RCH under 2-3/8 inches wide would have fit the Mojo chassis, other chassis may vary a bit. Price on their plate is right at twenty bucks, or about two bucks per long chassis tweed amp, since you can get 10 cuts from it. For a Champ... you'd get twenty plates!

    Its easy to mark with a scribe, then drill. I taped my plate in place, marked an input jack hole, took out the plate, drilled it with a narrow step drill. Back in place, I secured the plate with an input jack, then scribed the rest of the holes. Did it that way so the plate wouldn't wiggle much. You can easily "walk" a hole over a tad with a dremel if you get one off center a bit.

    One "trick" I always do is drill two small holes in each corner of the plate, then turn up the corners. Makes it easy to solder a ground wire to. Can do the same at strategic locations by bending up a little hump in the plate after drilling a hole for ground wire. Works perfectly, especially if you're soldering with a smallish iron.

    I also know some chassis providers include a plate (like Weber) and some don't, so I'm just passin this along for general info.

    *on a better note, I'm getting roof estimates and doing battle with insurance on Irma damage, but the 60' tree that hit the house is almost all cleared and I got a pile of oak all cut up for the firepit! Only stump grindin' to do now. Not bad for a sixty year old geezer, if he does say so hisself.
     
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  15. Leña_Costoso

    Leña_Costoso Senior Member

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    [​IMG]

    [​IMG]

    Some shots of the copper ground plate that I made to fit the Mojo Super (5F4) chassis. Its very easy to spot the holes with a sharpie from the front, drill one, insert a jack (or pot), then drill the others having complete registration. I start on one end with a jack, then the other end with the presence pot, and that way nothing will shift. The steel of the chassis is much harder and tougher than the thin copper, so a long narrow Unibit (step drill) will self center easily. The only thing left after drilling is to remove the plate and do a quick "deburr" with the step drill and you're good to go. Corners folded up for easy ground attachment, as well as a few insertion holes along the way.

    Although I've used supplied brass plates before, this method has always worked well for me, and have had no noise issues, hum, motorboating, squeal.... just quiet amps.

    ...more to come...
     
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  16. cherrysunburst00

    cherrysunburst00 Senior Member

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    This is such a cool project. Thanks for sharing
     
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  17. Leña_Costoso

    Leña_Costoso Senior Member

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    [​IMG]

    Just got the board in, after checking each component, each flying lead, and each underboard connection.

    [​IMG]

    And about half wired.

    Discovered that my PACE soldering machine is not up to the task of soldering the copper while laying on steel. Gotta go dig out my big 900w Weller iron. No biggie, just a little time snag. The PACE will do the bent corners, pot bodies, etc... just not copper with the huge heat sink behind it (the chassis).

    And... the middle ATOM capacitor is high on purpose, to allow it to fold away if needed, to gain access to the screw that holds the board and backer to the chassis. As it is, I've got a star washer under the head of the screw, then a keps nut behind it as a "spacer" between the board and backer. Then another keps nut outside the chassis holding it all.

    Also have T-nuts on the baffle, instead of little 6-32 keps nuts. I've had both come off from bouncing around in transit. Taking no prisoners here!

    ...more to come...

    (edit in)
    This is the first amp I've built "from a kit". Everything before this, four champs, two deluxes, another super and a 5f4 super as a "Bassman" 4x10.... were all from parts purchased, wire included.

    What I used to do... and I wish I still had my push back wire rolls.... was use yellow for grids, blue for cathode connections, and red for plate and B+ connections. Even under the board I'd keep that color code. Made for easier assembly, and REAL easy repair (or mod) if needed. You could just go by the color code. When I converted black or silver Champs to dual 6V6's (with diode rectifier and Princeton transformer set) I'd do the same thing. Having done this amp in all yellow wire, I can say - go color code!

    One other thing I've learned from this "kit" is the small terminal connectors. They don't say what to do with 'em! But, I'll tell ya that one is gonna be used to make for a neat filament "false center tap". I've always had problems getting to come out neat on the pilot lite. Its just me, as other folks have no issue. But, this amp will have the filament wires going to the terminal ends, with the 100ohm resistors soldered to the center "ground" terminal. Then wires up to the pilot, and filaments, so all I have are two wires at the pilot light.

    And this amp will also have to extra fuses. One on the B+ center tap, and one between the "death cap" and ground (just in case the cap blows shorted). Normally for a 3 wire ground, the death cap is superfluous, but... if you're ever in a position to use a 2 prong adapter (ha! can you say old parking lot connections used as "stage" power? ;) ) In those cases, the death cap comes into play to reduce hum.

    Ok... thru for tonite!
     
    Last edited: Oct 16, 2017
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  18. Leña_Costoso

    Leña_Costoso Senior Member

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    Moving along a bit...

    [​IMG]

    The 9 pin sockets all wired up. Not seen are the B+ ground, the ground for the filament "false center tap", and the various grounds on the copper plate completed. Left to do - Connect the choke, wire the rectifier and output tube sockets. Wire the filaments and pilot lamp. Wire the mains supply.

    A little testing, progressively. First the rectifier, then with the output tubes, and finally with the preamp tubes. And last is to connect speakers.

    Then its "hit the switch and start the bitch". And a coin toss chance of horrible squeal. Ya never know about that squeal, but once you hear it the first time, you'll always know what it is.....

    Somehow I've lost my pot for the bias adjustment. Great. Gotta get a new one. So, I'll just go with what's there as a resistor, for now, unless its really terrible.

    [​IMG]
     
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  19. Leña_Costoso

    Leña_Costoso Senior Member

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    Well folks.... I'm sitting here tonite, and doing nothing on the amp, except sending off an email to Mojo to tell 'em that their "diagram" and the schematic are showing the same thing when it comes to the 6L6 screen grids.

    That is to say... Mojo's diagram is "Fender 5F4 correct", while the schematic shows something different.

    All this came to me while I was driving back from a customer locale about 150 miles away. Lots of steerin' wheel time. Time to think.

    The Fender way (and Mojo's diagram) is to feed the screen grids after the choke, with nothing fed before it. Put another way, the screen grids and the CT of the output transformer are both supplied from the output of the choke.

    Their schematic shows the CT of the output transformer being fed before the choke, and the screen grids being fed after the choke - and no screen grid resistors.

    I think what I did on that killer "5F4 Bassman" was to put in the usual 470 ohm resistor, and wire it with plates fed (through the OT) from before the choke and the screen grids after the choke. I think I've got some 470ohm 5w ceramic body resistors at the shop.
     
  20. eslover

    eslover Senior Member

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    Hi Lena_Costoso, I am very interested in these tweed super builds as of late. Between you and Cjsinla, I am now saving up for this kit. But I am confused about your latest post: when I look at the mojo schematic the screens and the center tap are to the left of the choke...isn't that **before** the choke in the traditional sense of the signal path (signal moving left to right)...help??

    I'm on a novice builder please be gentle.
     

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