How Much Is Too Much...

Discussion in 'Marshall Amps' started by SHREDNECK, Jul 21, 2018.

  1. SHREDNECK

    SHREDNECK New Member

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    ...WHAT?!??

    LoL -- didn't quite know how to take that one... :p:p

    The answer to your question is No.

    This allows me to be more concise:
    Two 8x12 full stacks.
    Two vintage tube heads:
    * A 1992 100 watt three channel 30th Anniversary over (2) 4x12 A/B Anniversary cabinets.
    -- Head and cabinets can be configured in a number of ways, and are Mono/Stereo, 4, 8
    or 16 ohm impedance, 300 Watts RMS handling capacity on each cabinet.
    * A 1984 JCM 800 Lead Series 2204 50 Watt Head over (2) 1960 A/B 4x12 Cabs;
    260 Watts RMS each 4x12 Cab handling capacity.

    =======================================================

    The heads are currently configured as Master / Slave:
    * 6100 is, of course, Master
    * 2204 Mains Input 40/60 Hz, 175 Watts Alternating.
    * Feed for the 2204 Low Sensitivity Input is Slaved via the 6100's Uncompensated Link Line Output. The D.I. is not utilized in this configuration.
    * Front Panel Settings are Lean on Pre, Fat on Gain.
    * Both Heads run into 8 Ohm loads.
    =======================================================

    The rig has been configured in this manner since buying the Master 6100 new in 1992.
    She is simply the most Badass setup I have ever had the privilege of playing through / hearing.
    I just happen to be lucky enough to own her.

    Later on, in The Great By and By, I'll address my axes a little, and a bit concerning the studio.

    - Bruce
     
    Last edited: Jul 23, 2018
  2. SHREDNECK

    SHREDNECK New Member

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    Quoth anitoli:

    Ok this is what i measured for temps on my 6100 after 4 hours of playing into an attenuator with the MV on 12 O'clock:

    Top of power transformer: 107
    Top of chassis by PI: 111
    Top of switches on front plate: 98

    Bruce if you could get a temp reading from your amp the comparison would be invaluable.

    =========================================================

    I'm running both Master / Slave; after powering up both stacks, starting on Standby:
    This is what I've measured:

    * Ambient room temperature: 80 degrees.
    * Face plate next to rocker switches: 98 degrees peak.

    After rig was taken off Standby, I placed the thermometer on the left front panel again:
    * Surface temp: 102 degrees peak.
    -- Edit: Real Feel is closer to 140 surface temp. The thermometer did not reflect this; not the best application with this particular thermometer.
    The top thermal vent temperature is closest to Real Feel @ 122 degrees.


    Temperature following 10 minutes playing on channel 2 Crunch @ high dBspl, with
    thermometer placement across top thermal vent grill: 122 Degrees

    This held steady at the loud volume setting; channel 2.

    =======================================================

    So that's how she shook out.

    Questions / suggestions encouraged.

    THANKS! -- Bruce
     
    Last edited: Jul 23, 2018
  3. SHREDNECK

    SHREDNECK New Member

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    *edit: Duplicate Post
     
    Last edited: Jul 23, 2018
  4. ampmadscientist

    ampmadscientist Well-Known Member

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    107 C or F ? :lol:

    The ambient temperature would be a big factor in this.
     
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  5. anitoli

    anitoli Well-Known Member

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    Fahrenheit. The room temp was approx 72.
     
    Last edited: Jul 23, 2018
  6. ampmadscientist

    ampmadscientist Well-Known Member

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    107 C = 224.6 F (wire will melt...)

    :lol::lol::lol: It was a joke, hope you got the joke. I was being absurd.

    But ambient temperature is the baseline, so you need to measure that also.

    The real question is:
    How far above ambient temperature does each amplifier operate?
    There could be 20 degree difference in ambient temperature, easily between 2 locations.
     
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  7. SHREDNECK

    SHREDNECK New Member

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  8. SHREDNECK

    SHREDNECK New Member

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    Duplicate post
     
    Last edited: Feb 1, 2019
  9. SHREDNECK

    SHREDNECK New Member

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    Okay All -- here are some updates: @ampmadscientist : From your provided list of amp technicians, I am now working with a new outfit for me; Tom Boffa @ Sound Electronic Services, Arvada, CO whom has been in business for decades. This guy is SHARP, He had the head for three weeks, as this is his backlog time. He re- tubed and re- biased the tubes (third time this was done) and ran the amp on standby for a few hours while under load, and had no heating issues. When I got the head back I called him, I had run the head cranked for 20 - 30 minutes, and the overheat conditions reappeared. I formerly only used a meat thermometer, so exact heat measurements taken off the front of the chassis were hard to get.

    Different story at the top right of the vent grille -- temp was hot enough to burn my hand. I'm going to take the entire full 8x12 stack into him next week, to duplicate the head under cranked conditions played from an '85 BC Rich Bich with Dimarzio SD 2 pickups and active boosters / electronics. Never had overheat problems for decades, until this past year. This all started from a cascade failure in the middle of the night originally when I may have left the amp on and the Bich plugged in before bedtime. This is unlikely and out of routine for me. Why did this happen in the first place? It IS POSSIBLE that a bad actor having keys to the house / home studio entering in the middle of the night resulting in an ear piercing squeal, then cut out before I was able to take it off standby. Blew out all of both heads' tubes and both output fuse group failure LEDs at the back of the Anniversary head .

    The JCM-800 2204 fifty watt slave head was repaired with no further problems the first time.

    @anitoli : I am going to remove the back panel and cranking the 30th Anniversary 6100 100 w. head for 20 -30 minutes again shortly, will continue in an upcoming post after I do more temp readings. Will have to get Tom @ Sound Electronics to get another full range of internal temp measurements. In the mean time, I remembered that my Klein digital multi- meter / clamp- on ammeter has a plug in temp test probe that will suit the task better than a meat thermometer.

    I will perform the tests and follow up with the readings in an upcoming post, and compare to those you've taken at the test points you've listed. (Thanks again!)

    -- SHREDNECK BRUCE
     
    Last edited: Feb 3, 2019
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  10. SHREDNECK

    SHREDNECK New Member

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    Here's the latest:

    Pulled off the back panel to expose internal components at the chassis top. Tubes look to be fine, all EL34s cathode base filaments have a nice, healthy glow, as well as the top anodes / plates.

    The kicker: that's as far as she got since the only 20 - 30 minute test when she would crank out at high volume, everything then sounded great but wayyy overheated as previously stated.

    The outputs from the head only produces a light hum in the cabinets, but with high gain and high volume on standby (on line) the guitar would not play, and the familiar Marshall light hiss on crunch and lead (channels 2 and 3) was absent.

    I guess that last time I played through her when she was cranked for that 20 / 30 minutes apparently just damaged her further. Never had the chance to do temp testing.

    I even plugged the Bich in to the JCM-800 and ran to the Anniversary speaker cabs -- that test went fine.

    Plugged the guitar input back into the Anniversary head and ran the speaker outs into the JCM- 800 stack speaker cabinets -- nothing. That light hum is back again -- no more beyond that though.

    I'm calling Tom of Sound Electronics and shouldn't need to bring in both 4x12s after these tests revealed the described conditions -- only the head itself once again (I hope).

    The repairs are costing me over a grand now. Should be put to the front of the line as warranty work -- Will keep y'all appraised of the state of repairs going forward.

    Thanks, all -- SHREDNECK BRUCE
     
    Last edited: Feb 1, 2019
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  11. SHREDNECK

    SHREDNECK New Member

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    Here's a possible cause for the 6100 head malady -- I discovered that the 6960 A and B 4x12 cabinets were both cabled for 4 ohms each and the impedance switch on the back of the head is set at 8 ohms collectively.

    Shouldn't that result in a 2 ohm cumulative demand on the head? I'm thinking so.
    The Anniversary 4x12 cabinets are now cabled for 16 ohms each and the head remains set to 8 ohms.

    I just got off the phone with Tom, and I laid it out for him as written on this thread. It was not until after the call that I'd discovered the mismatch. I knew from the start it could be something simple, and I think this is the most likely culprit of my woes. Thank God the Anniversary cabinets tested out now and appear to be undamaged -- don't know for sure yet but the JCM- 800 cabs are only wired @ 16 ohms each, and that culminates to an 8 ohm load demand on the 2204 head as it should.

    The JCM- 800 stack is performing as it should as well, this is my 2nd go- to in the absence of the Anniversary head and sounds great!

    The head goes back to Sound Electronics Services Monday or Tuesday, and will likely not be covered under warranty.

    He'll have it for a bit over a week, he agreed to work me into his schedule rather than having to wait another 3-4 weeks ordinarily.

    Man, I feel pretty humbled by this oversight, a.k.a. "dumb-assery".

    I don't care if I caused it or not -- I just want it FIXED and I have learned a valuable but painful lesson from it all.

    The final checks on the Anniversary cabs will be performed from the JCM- 800 head for performance and whether or not it overheats the JCM- 800 head when cranked for another 20- 30 minutes.

    Speculation at this point, but we'll see.
    I think we're on the road to salvation at last. We'll see what the tech turns up, and I'll keep you posted!

    SHREDNECK BRUCE
     
    Last edited: Feb 1, 2019
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  12. Mitchell Pearrow

    Mitchell Pearrow Well-Known Member

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    I know this is late to the party but question are the cabs you mentioned (anniversary cabs have the mono / stereo switch) I would get rid of them and go hard wired 16 ohms like your others , it may have saved you in the future, as I myself don’t trust those stupid things! Cheers Mitch
     
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