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Marshall 2203x HT Fuse blown. Should I check the Screen Resistors?new tubes?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by daneswede1, Dec 1, 2005.

  1. daneswede1

    daneswede1 Member

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    I blew the HT (High Tension) Fuse on my reissue 2203x Marshall JCM800. I know a little about this but im still pretty green with tech stuff~!!
    ?
    I heard that when this happens the tubes are now out of balance and need rebias and replacement. My main question is that I heard that this could SOMETIMES affect the SCREEN RESISTORS that are in line with the output tubes I believe>? If the screen resistors are burned ill have them replaced? Is there anything else that might be affected by this blown out HT Fuse? It is under warranty and I have brainstormed with the tech momentarily but id like some outside advice here.

    I am no tech. I know a lot of things about the parts on JCM800 2203s in particular. Im still learning about the 2203x reissue however. I do like the tone of it .I was also going to throw the Mercury Output Tran and choke in their but this will void the warranty. EWll Ill get it fixed or REPLACE IT WITH A NEW AMP FIRST!! Thanks for any and all info! VERY VERY MUCH appreciated as always!
     
  2. pfrischmann

    pfrischmann Member

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    I'm assuming you traced down why the HT fuse blew to begin with?

    It could just be a weak fuse......it could not.
     
  3. daneswede1

    daneswede1 Member

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    Actually, After I opened the HT fuse and saw it was blown, thats as far as I got. I was told by a tech that it caused the Output tubes to be out of balance. I dont know if the Screen resistors are burnt or not? GUess ill take it in. I was wondering why this happened. I plugged it into my Furman power conditioner when this happened? I have another 2203 from 1981 in mint that works fine through the same FUrman? No problems. I dont know. :confused:
     
  4. pfrischmann

    pfrischmann Member

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    I had this happen. It took out a brand new Mercury Magnetics OPT in the process. In my case a tube socket was arcing. I don't think popping an HT fuse can cause your tubes to go out of balance. You can't really say that until you know why the HT fuse popped.

    Who ever you take it to, it's important they test the tubes and find out the root cause.
     
  5. Swarty

    Swarty Member

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    The most common reason for a HT fuse to blow is a bad output tube. A fuse blowing will not cause tubes to go out of balance (whatever that means?).
     
  6. TheAmpNerd

    TheAmpNerd Member

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    Raising the Bull **** flag here.
    What probably caused the tech failure was something else,
    resistor cap etc. Then one tube probably started running away.
    Finally the fuse blew. When ever the tech fixed the problem
    and tested or measured the current when the amp was
    working again...it was drawing more or less current then
    it used to.

    OR

    Something upstream of the tube was still slightly faulty and
    he didn't bothter to check it, leaky cap or resistor value change.

    ANYWAY

    Plug another fuse and see if it blows. Over time on perfectly functioning
    amps, I've had a number of fuses blow.

    IF

    It blows again, check output tubes. Replace. If again or you are concerned
    take it to a tech.

    Good luck and let us know what happens.
     
  7. daneswede1

    daneswede1 Member

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    Im gonna take it in under the warranty next week. Ill have him test the output tubes and see if its something "up stream" as you say! The screen resistor may be the culprit. ??

    Dougstubes sold me some RUBYTUBE BSTRs and 9th Gen chinese 12ax7s. He has a lot of feedback on his site where people have said some good things about these tubes so ill give them a shot.Gonna throw a NOS RFT ECC83 in the V1. I love those RFTs. Anyone else use the RUby BSTRs?
    ___________________
    THE RIG!
    81 Marshall 2203 minty!Siemens-- EL34s NOS and --RFT NOS 12ax7s
    04 Marshall 2203x
    Bogner Ubercab #1
    Bogner Ubercab #2
    71 Les Paul Custom
    01 PRS Single cut birds
    05 Taylor 714CE (pyments-still owe 1000!)Originally was going to buy the 314ce but it was sold and my buddy at Sam Ash gave me 40% off this one on a layaway which they arent supposed to do so i said what the fuc* you only live once right?
    TC Electronic G Force
    Furman Regulator
    SKB 6 spce flght
    Klon Centaur
    Analogman TS9 808 brown mod
    Analogman BOSS OD-1 3403d chip-->
    --> and push/pull asymmetrical-symmetrical mods
    Digitech Whammy pedal red reissue. (Now i see why Vai and Satch use this thing. Good things!)
    Morley Bad Horsey wah II
    Monster cables

    _______________________
    wants and needs:
    pay off my 714ce Taylor of course over the next month or two
    GROUND CONTROL PRO Ftswtch systm:
    :from Voodoo lab. Good system with the TC ELect. G Force.Vai uses it so its gotta be reliable IMO.
    Fender Strat:Corona Cali model. Maple neck w/ sperzels-EVO's and a sustainiac. I love that tubeyt midrange bite!
    Fender Twin or BLckfce model for clean tones
    Lynch triple amp switcher pedal
     
  8. donnyjaguar

    donnyjaguar Member

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    Here are the best ways I know to blow the HT fuse:

    - output tube shorted
    Interestingly enough I've had this happen but when the tube cooled it became unshorted. Still had to trash the tube though. :(

    - output tube(s) lose bias voltage
    This is caused by a fault in the bias circuit, particularly a coupling cap that is flakey. When this sort of meltdown happens its usually a good idea to replace all components if you're not 100% sure which one is the culprit. Check also the Sgrid resistors to see if they've been fatigued.
     
  9. Erik

    Erik Member

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    I've used Ruby BSTR's before...I liked them a lot.

    As for the fuse problem...as mentioned previously, I'd just replace the fuse and see if it happens again. I've blown fuses in the past from doing pretty silly things. :eek:
     
  10. daneswede1

    daneswede1 Member

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    I wrote down what you said about the "fault in the bias circuit/ coupling cap. Ill mention that to him along with the screen resistor possiblity. Tx.
    As far as the RUBY TUBE BSTRs. Yeah, I have heard nothing but good things on these tubes. Ill go ahead with those then when I take this 2203x in. THe other head goes in after the reissue gets out. I want to make sure the 81 was originally an EL34 model. IT has the EL34s in it ans sounds unreal! I think it was an original EL34. Tx!
     
  11. VintageJon

    VintageJon Member

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    I would pull the output tubes and see if it blows fuse.

    No Blow?
    Then install tubes and if it blows it's a bad tube...

    -Jon
     
  12. Swarty

    Swarty Member

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    Or a bad socket.
     
  13. VintageJon

    VintageJon Member

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    Arcing socket is a possibility, I've seen it.
    Usually doen't manifest at idle, but these are unusual times...

    -Jon
     
  14. daneswede1

    daneswede1 Member

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    An arcing socket in an 8 month old amp? Highly unusual wuoldnt you say? ANyway TOday is Sunday and she goes tomorrow! It will be interesting to see the final verdict.

    In all the years of owning JCM800 2203s in particular ive NEVE rhad this happen? Funny it would happen to a reissue! hehe! For anyone thinking of buying a reissue 2203x I would recommend one. I like the tone of this amp. It doesnt have the stock gain that the 1981 2203 i have has but its still pretty good. I would say however NOT to buy a NEW MArshall Cabinet. I traded mine away after owning it for a few months. Just didnt sound the same as the 80s version of the same cabinet. Ive been told that the Celestians inside are now made in Japan? What the Fu**!! I dont know cause I didnt open her up!

    I was going to buy a couple of circa 1980s Marshall slant 1960a cabs with the old Ipswich, England Made G12T75s but I had a happy accident happen to me! A Bogner Uberschall and Ubercab fell on my lap for $1200 dollars! What a price hugh. I didnt care for the Uberschall to much gain for me but a very cool amp! I sold that for $1600 to a lucky person! I ran my Marshall 2203x through the Ubercab and it sounded so nice and warm I had to keep her! If you own a Marshall JCM800 or similiar amp I recommend this Bogner Ubercab to you highly. THis comes from someone who has used JCM800s and their cabs for 20 years~!If not at least go buy a circa 80s Marshall cab and do your self a favor! Just a thought!
     
  15. daneswede1

    daneswede1 Member

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    UPDATE .
    I cant believe this! Marshall actually put a wrong value/ screen resistor in there! Unreal. My tech caught it and replaced it with the correct value resistor. All is well! That is covered under warranty. My RUBY TUBE BSTRS tested bad So they get shipped back to "----" . Its not the tube guys fault. Probably happened in the mail or something. I wont mention names. (Unless I already did in a previous post but its all good) Im gonna try the Mulalrd Reissue EL34s and the TUng SOl 12ax7s. I know the reissue Mullard ARENT MULLARDS at all but ive heard them in a friends Marshall before and they do their job. Midrange and spongey I guess. WEll see. Never tried TUng Sols. Ill have it back in a few days or so.
     
  16. daneswede1

    daneswede1 Member

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    WEll THanks guys for all the posts to my original thread about the HT fuse. I have actually learned quite a bit. I have gotten the amp back and it sounds really good. MY tech tightened up some of the parts in my 2203x that Marshall had not taken the time to do before its initial shipment to S. Ash. Also the new screen resistor part/ value and correct bias along with the Mullard Reissues sound really warm and spongey as I thought it might. Ive come to learn its not only the tubes you use but its really the tech thats working on your amp and how much pride they take in making sure your 110% up and running. THis guy really knows his stuff! I highly recommend John and www.industrialamps.com
    Thx all
    JH
     

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