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Bass Master XM100 Type:100B

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  • redkurn
    replied
    Haven't had time yet, probably won't be able to get to it for a while, I keep forgetting to order new fuses since I may need more than one got sidetracked with a new guitar and other things going on.

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  • redkurn
    replied
    Q9 and Q10?
    I'll have time tomorrow to check, but I don't have a fuse at the moment.

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  • g1
    replied
    Check the new output transistors for shorts.

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  • redkurn
    replied
    Originally posted by g1 View Post
    Can you be more specific, powered on as in connected power to the pedal with no signal going through the chain? Or engaged the effect at high volume? (if the latter, is it back to the stock fuse value?)
    Stock fuse, was playing through it with no pedals and it was fine for maybe 10 minutes, plugged in the VFE pedal and tried it for a couple minutes and then turned that one off and turned the boss pedal on, volume is set low and the gain is maxed, but it shouldn't be or have been the problem.

    I was plugged into the High channel, I think I may have strummed a string, but all I can recall is the fuse got bright and the amp cut out. I had the volume on the amp about half way up, maybe a little less.
    I had just got done dialing in a nice clean tone and messed with the scoop knob to see what it was about.

    22 minutes to break a amp again, got to be a world record there! Probably wasn't something I did though, this amp has seen better days and those resistors were toast, practically fell apart when I removed them.
    Last edited by redkurn; 04-29-2021, 05:52 AM.

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  • g1
    replied
    Can you be more specific, powered on as in connected power to the pedal with no signal going through the chain? Or engaged the effect at high volume? (if the latter, is it back to the stock fuse value?)

    Leave a comment:


  • redkurn
    replied
    Well definitely do not use a Boss DS-1 on this amp, the fuse just went, powered the pedal on and poof blown fuse, worked fine with my VFE Triumvirate I built though.
    So I guess it's got an issue still.

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  • redkurn
    replied
    I did it helped some, but not as much as I’d hoped and they aren’t the easiest kind to get the spray into.

    They are almost like alpha 9mm pots with the riveted plastic on them, it’s not scratchy really, but cutting connection until it’s at the max. A little wiggling and it works fine enough.

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  • The Dude
    replied
    If you haven't, try some Deoxit on the volume control.

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  • redkurn
    replied
    -60mv on the output, new resistors in place and J111 reversed, it sounds really nice.
    The volume knob seems like it will need replaced in the future, but for now it is working.

    Thanks to all, g1 you sir have helped so very much and taught me a few things.

    Leave a comment:


  • redkurn
    replied
    Go figure once the parts arrive things start happening and I am too busy to mess with the amp.
    One day free so far was today and I didn't really feel like opening it up, but instead spent most of the time trying to learn how to play better.

    If nothing is going on tomorrow I'll give it a go and see if it is finally fixed and no voltage on the output.

    Leave a comment:


  • redkurn
    replied
    Originally posted by g1 View Post
    Idiots at ON Semi have flipped the pinout again!!! This is brand new, April 2021. They have a new 'Rev.4' datasheet on their website that mouser doesn't even have yet. So maybe mouser are shipping the brand new part. The latest 'rev.4' pinout agrees with the old 2N5638 pinout. That seems to be what you have got.

    So, ON semi rev.2 (March 2006) DSG pinout looking at face (same as 2N5638)
    ON semi rev.3 (Sept.2020) GSD pinout (opposite of 2N5638)
    ON semi rev.4 (April 2021) DSG pinout (same as 2N5638)
    What a nightmare. At least they are back to what it should have always been.

    (edit: I see you had already posted the new one in post #55, sorry I missed it)
    Yea it's trippy when you see it like that. XD must have had some backlash over it.

    So I need to flip the fet around when I get it apart and replace the resistors, then probably fixed?
    I think I will test the original resistors again for giggles.

    Leave a comment:


  • g1
    replied
    Idiots at ON Semi have flipped the pinout again!!! This is brand new, April 2021. They have a new 'Rev.4' datasheet on their website that mouser doesn't even have yet. So maybe mouser are shipping the brand new part. The latest 'rev.4' pinout agrees with the old 2N5638 pinout. That seems to be what you have got.

    So, ON semi rev.2 (March 2006) DSG pinout looking at face (same as 2N5638)
    ON semi rev.3 (Sept.2020) GSD pinout (opposite of 2N5638)
    ON semi rev.4 (April 2021) DSG pinout (same as 2N5638)
    What a nightmare. At least they are back to what it should have always been.

    (edit: I see you had already posted the new one in post #55, sorry I missed it)
    Attached Files
    Last edited by g1; 04-19-2021, 03:18 AM.

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  • redkurn
    replied
    Originally posted by g1 View Post

    Yes. The low resistance reading should be between drain and source. Just a guess, but I think what confuses people about jfets is that they are 'on' in their non-powered state. They require a voltage applied to the gate to turn them off.
    The jfet is most commonly used as a switch. The switch is between the drain and source terminals and the 'command' is applied to the gate terminal. When the jfet is 'on' there is a low resistance between drain and source. This is the switch 'closed'.
    When you apply the correct voltage to the gate, the switch goes 'open', you have high resistance between drain and source, and the jfet is in it's 'off' state.
    The J111 is an 'n-channel' type, so it needs a negative voltage at the gate to turn it off. A 'p-channel' type jfet requires a positive voltage at the gate to turn it off.

    The 2 different datasheets for the J111 part are both correct, but only for their respective brands. ON Semiconductor decided to build their own version of the part recently that had the face pointing the opposite direction from all other J111 jfets that had come before. This was a very irresponsible thing for them to do. So their datasheet is correct, but only for their own version of the part.
    The Fairchild J111 datasheet I posted in post #47 is correct for all other brand J111's, and also matches the pinout for the 2N5638. That is why Yorkville has the J111 listed as a sub for the 2N5638. I think if you ordered a J111 from Yorkville, you would get the older style part (not from ON Semi).
    So based on the readings it must be installed backwards, I installed it based on it being listed as a GSD, but it appears to be a DSG.
    I think when I have it apart, I'll try getting a reading from the resistors again out of circuit and compare to the new ones.
    Also thinking I will flip the fet before I do any of that and see what it does, unless it could damage the output again.

    Just trying to be careful, I know I probably seem like an annoying idiot and I likely am a idiot, but one that is learning. XD

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  • g1
    replied
    Originally posted by redkurn View Post
    Because the measurements I got have me thinking it is a DSG since pin 1,2 had the lowest resistance 23.3R, am I catching on now?
    Yes. The low resistance reading should be between drain and source. Just a guess, but I think what confuses people about jfets is that they are 'on' in their non-powered state. They require a voltage applied to the gate to turn them off.
    The jfet is most commonly used as a switch. The switch is between the drain and source terminals and the 'command' is applied to the gate terminal. When the jfet is 'on' there is a low resistance between drain and source. This is the switch 'closed'.
    When you apply the correct voltage to the gate, the switch goes 'open', you have high resistance between drain and source, and the jfet is in it's 'off' state.
    The J111 is an 'n-channel' type, so it needs a negative voltage at the gate to turn it off. A 'p-channel' type jfet requires a positive voltage at the gate to turn it off.

    The 2 different datasheets for the J111 part are both correct, but only for their respective brands. ON Semiconductor decided to build their own version of the part recently that had the face pointing the opposite direction from all other J111 jfets that had come before. This was a very irresponsible thing for them to do. So their datasheet is correct, but only for their own version of the part.
    The Fairchild J111 datasheet I posted in post #47 is correct for all other brand J111's, and also matches the pinout for the 2N5638. That is why Yorkville has the J111 listed as a sub for the 2N5638. I think if you ordered a J111 from Yorkville, you would get the older style part (not from ON Semi).

    Leave a comment:


  • redkurn
    replied
    Originally posted by g1 View Post
    Yes, it was stupid for ON semi to reverse their pinout. There are a few other instances of that with different transistors, it's very rare but extremely troublesome.
    So the different datasheet shows how they have reversed their pinout for the ON semi part. You put it in reversed from what was there before so it should work.
    I put it in reverse of the original part because the datasheet, maybe I got a little lucky and the whole datasheet thing doesn't matter as much as I originally thought.

    I keep going back to it in my head though, if the resistance is lower on source and drain than source and gate, it would make it DSG or GSD?
    Because the measurements I got have me thinking it is a DSG since pin 1,2 had the lowest resistance 23.3R, am I catching on now?

    Leave a comment:

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