[PROJECT] Fender Twin

Discussion in 'The Squawk Box' started by Kuroyama, Jul 15, 2009.

  1. Splattle101

    Splattle101 V.I.P. Member

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    NO!!!! I take it back!!!! DON'T BUY THAT USELESS BOAT ANCHOR OF AN AMP!!!













    :naughty::naughty::thumb::thumb:Just send me the address of your music shop. I'll uh...sort it out.:naughty::naughty::thumb::thumb:
     
  2. Kuroyama

    Kuroyama V.I.P. Member

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    My bad. Late on the update. Im on vacation now and out of town. I BOUGHT the amp, but was planning to carry it 3 blocks by hand back to the train... THAT didnt happen. When I get back from vacation Ill call the shop, theyll ship to my home, where I'll airdust the mummified crust out of it and commence with the full on Amp Porn.

    Anybody got anything in particular they want to see pix of to help figure out what da deelio might be?
     
  3. dwagar

    dwagar V.I.P. Member

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    good for you man. I think you scored.

    one of the drawbacks to a Twin is noticeable when you try to pick the damn thing up.
     
  4. Mike60

    Mike60 V.I.P. Member

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    +1...
     
  5. Phil47uk

    Phil47uk Senior Member

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    Mike, check private messages.
     
  6. Kuroyama

    Kuroyama V.I.P. Member

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    Well, the amp arrived. Like a knucklehead I wasnt prepared with airdusters and contact spray. Went out to find em, but Japan doesnt have any Radio Shacks or anything really like it. Im gonna have to go to Akihabara and load up on parts.

    There is a LOT of reading involved here. At first the thought of a project like this didnt really appeal to me, but there seems to be a LOT of info out there!! Just a matter of me sitting down with it and reading. Provided I dont kill myself, this should be a lot of fun!

    Of course, getting a fully functional Twin out of the deal wont hurt either.

    BTW somebody guess from the pix above that I bought an "Evil" Twin. It looks like they were right. The red knobbed deal is called "THE Twin" Not to be confused with "Twin-Amp" (E34).
     
  7. Kuroyama

    Kuroyama V.I.P. Member

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    BTW, Most of what Im reading talks about pulling tubes from the amp WHILE ITS ON to check them / Isolate failure. If the interior of the amp is so gawdawful dangerous, and Im supposed to unplug it, and drain the caps before working on it... How does pulling tubes from a LIVE amp work out to be a safe action?? Whats more, arent tubes hard to pull??

    Anybody got a preferred method for grabbing and pulling tubes?
     
  8. Fracture

    Fracture Senior Member

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    It's a win/win.
    I have this amp, and it's the one I play most.
    The clean channel is super clean, the O/D is useless.

    For a $100 buy it, have it assessed.
    At worst, you could have to part it out (if unrepairable or out of your budget)

    Get a thick hunk of tempered glass and make an end table out of it.
     
  9. Splattle101

    Splattle101 V.I.P. Member

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    * You CANNOT safely pull out power valves or rectifier valves with the power on.
    * You should let power valve cool before mucking around with them. They're most fragile while they're hot and in the first stages of cooling.
    * Pre amp valves can be changed out while the power is on, but with the standby OFF.
    * They are tougher than the power valves (smaller), but they're still hot. A cloth or pot mit will be needed.

    At risk of telling you things you already know, when you look in the back of the amp you'll see a big open box with two speakers in it. At the bottom is a bag-like thing with a couple of leads coming out of it. This bag contains the reverb tray. At the top is the metal box from which all the valves, transformers, cables and controls etc are hanging. This box is the chassis.

    Inside the chassis there are deadly voltages and currents lurking. Do not fuck around inside the chassis at all unless you know exactly what you're doing.
     
  10. Kuroyama

    Kuroyama V.I.P. Member

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    Splattle, at the risk of winning the next Darwin Award I plan to airdust, the chassis, then clean the volume and tone pots with contact spray. From there I plan to check tubes for rattle with a drumstick. Still learning about draining filter caps though. As I understand it, Ill need a cap with two leads that I can bridge the filter caps with to drain them. That was just info from one source though. Im still reading and cross referencing the info I take in.

    [ame=http://www.youtube.com/watch?v=xkpoS4aZtuI&feature=related]YouTube - Tube Amps 101 repairs, maintenance and more[/ame]

    There are tons of example videos like this one. Plenty of opportunity for me to see what the amp looks like without actually disassembling it. In doing so Im better prepared to disassemble it. Still, one step at a time. If replacing tubes and cleaning pots resolves my problem, then theres no need to push farther! But before I replace multiple tubes, I need to understand biasing them. Keep in mind I knew nothing about this when this post began. So I still have lots of reading to do. I have nothing but time, and theres no rush to take anything apart. This isnt my main amp anyway! I normally practice into a line 6 Pocket Pod with headphones!! Best case scenario Ill only be rockin this amp on weekend days. No nights, no weekdays. I wont be gigging it. So if this education takes a long time, then so be it.
     
  11. dwagar

    dwagar V.I.P. Member

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    I think this should be the sub-title for the Amplifier section.

    But, be smart, take your time, read all the info you can find. When I have an open chassis I am very very careful. Even if I think it's drained I double check it with a meter.

    Don't rush anything. Stop and think. You don't want to make it worse than it is now. 'Woops' is a term you shouldn't be using.
     
  12. Kuroyama

    Kuroyama V.I.P. Member

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    Thanks for the advice Dwagar. Im treating this project like I paid full price for the amp. (As far as the wife is concerned, when I brought an amp that big into the house, I may as well have...) but on a more serious note, without death as an obvious downside to making a handling mistake, it would suck to invest all this time and effort just to blow something and turn the whole project into an end table. Or even worse... just have the amp sound like ass. I already own a multimeter and soldering equipment... Im guessing itll be cheaper to import tubes from the internet than it will be to buy local in Tokyo... Just have to figure out where to get them. In any case, Ive got time to read.

    [ame=http://www.youtube.com/watch?v=Rg3-dZC5Fww&NR=1]YouTube - MORE Tube Amps 101 - Draining Filter Caps - DVD on Repairs, maintenance and more![/ame]
     
  13. Kuroyama

    Kuroyama V.I.P. Member

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    Saturday is AIRDUSTING DAY!! Though Im sorry to say this weak-ashed can of airduster is NOT up the task of REALLY cleaning the filth from this amp. I will have to go get brushes. BUT here are some pics in the sunlight, and a question about 1 SOVTEK 6L6 tube!

    The tube on the far right. The white crust... is that normal? The other three tubes dont have it.

    [​IMG]

    Then heres some grime. I dont know what kind of storage facility this thing was kept unused in (maybe someones garage?) but there are signs of rust on some of the metal. I havent pulled the chassis yet. Going to Akihabara this weekend to get a resistor wires and cable so I can build my own little Filter Capacitor Drainage System.

    I also need to pull the other tubes to see if theres obvious need for replacement there. There are TWELVE TUBES in this thing!!! I dont think my parents TV console from 1975 had that many tubes!!! Wow.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  14. Torren61

    Torren61 Senior Member

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    5881 (6L6 tubes) Classic American sound, I have some vintage Brimar 6L6 tubes...but only 2, you're going to want a matched set of 4 and vintage is the way to go to get a great sound.
     
  15. Cygnus X1

    Cygnus X1 Senior Member

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    White crust inside the tube usually means it has lost vacuum.
    Meaning it is dead.

    I would do this:
    Pull the tubes, remove the chassis, put it guts-up on the bench.
    Look and sniff for anything obvious.
    Cracked diodes?
    Burnt resistors?
    Pregnant looking capacitors?
    Does it have a high V fuse on the board?

    Use alligator clips to clip meters on to the first B+ set at 600V.
    So that is neg lead on the minus side of the first big capacitor closes to the power transformer, positive on the positive side of the same cap.

    Stand back and power it up.
    I use a long extension cord and wall switch, or a multi strip that has a power switch on it
    in case anything wants to go "Boom".
    See what you get (DC voltage).

    If that looks ok, then let the voltage bleed off the caps for a few minutes.
    This is where any remaining high voltage may remain, so still be aware of working around those caps!

    Then clip to pins 2 and 7 of any of the power tube sockets and check for 6.3V AC.
    Looking at the socket upside down, pin one is the first clockwise from the rectangular index tab. Count clockwise for next, etc.
    You can also probe from top top side of the socket to do this.

    Report what you get.

    And be careful!!!!
     
  16. Splattle101

    Splattle101 V.I.P. Member

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    For this amp the the Groove Tube 6L6GE would be excellent. New manufacture in the US and some sub assemblies in China. Great sounding valve, very much like the late 70s GE 6L6GC it's based on. Copied from. Made on the same machines with the same feed stocks, etc.

    The valves in those pics are Sovtek 5881 WXTs. These are 6L6GC equivalents, NOT like old US-made 5881s. These valves take 500 Volts or more on the plate, where old Tung Sol 5881s are designed for 350-450 V.

    Your lovely old Brimars would die beautifully in this amp. They're 6L6GAs or GBs aren't they? I'd love to hear them in my Bassman, but I can't afford to go buying more spare valves right now. I've already got three spare pairs of old US Tung So 5881s, so I think another purchase would have very poor SA coefficient right now. :hmm:
     
  17. Cygnus X1

    Cygnus X1 Senior Member

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    Did I miss something?

    Why are we discussing buying hundreds of dollars worth of tubes before he even has it running?

    Troubleshoot with known good cheap tubes.
    Then start tweaking after it is known to be safe to operate.
     
  18. Kuroyama

    Kuroyama V.I.P. Member

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    I think Cygnus is on point for this. Lets get the amp up and walking before we try running. Lets Keep it Simple. If you have a list of various tube and their attributes... Im open to all that information to store for later reference. But for now, lets get the obviously broken stuff repaired without killing me in the process.

    Cygnus. I read somewhere that running the Twin on just 2 (of these 4) tubes is an option. Ill need to go back and source my info, but... The key to doing it was the order in which you placed the tubes (or rather, which tubes you pulled).

    If I had a dead tube, is that the same as having a pulled tube? My first big mistake here. I did not label the tubes before I pulled them. (Thinking that it didnt matter because one dead tube would mean a required matched set of 4 anyway) BUT knowing which socket the bad tube came from wouldve told me if it was part of the problem or not. Im guessing yes, but Ill go back to that source on "running on 2 tubes" to see what the effect SHOULD be if the wrong tube is pulled (or goes dead).

    To all members, if you understand Tube amps or better yet, understand Fender Twin amps... by ALL MEANS drop whatever knowledge you want here. Its all welcome.
     
  19. Cygnus X1

    Cygnus X1 Senior Member

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    I believe it's the two outside tubes, or the two inside, just not odd skips.
    Regardless, there are many steps to take before we get the tubes back in there.

    Get those readings, and follow the safety rules.
     
  20. Splattle101

    Splattle101 V.I.P. Member

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    No, you missed nothing. I was simply discussing what I think would sound best in there when it is running. And also pointing out what would not work in there.:D

    I think we veered onto this tangent in answer to the query about the state of the valve with white stuff in it.
    I quite agree.:thumb:
     

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