Connect with us

electronic drummer / transformer wiring / capacitor rating

Discussion in 'General Electronics Discussion' started by Donr, Jun 2, 2011.

Scroll to continue with content
  1. Donr

    Donr

    12
    0
    Jun 2, 2011
    Hi folks, I am not only new to this forum but am also new to electronic repair. First I would like to impress you with my intelligence by telling you that I bought TWO mti auto orchestra drum machines on ebay and ----- well, you know the rest of that story. Seeing as how I broke the bank buying these I would like to get one working the way it should and I intend to tear into one and try my luck. I had a tech look at one and as long as it powered up he didn't want to go any further. It may be that he just didn't feel capable but I think the real reason was because it would be too labor intensive and he felt the machine was not worth it. But I have the time and the interest so what do you guys think my chances are? They both work but just not properly. By learning how to test different components and asking questions on this forum maybe, huh? Appreciate your thoughts.
     
  2. kwoolsey94

    kwoolsey94

    22
    0
    Feb 14, 2011
    Donr, ill be glad to help where I can. Fist your best bet is to good the P/n and serials of your drum machines ( i also play drums ) and find any schematics where you can. Next once your in the machine you can test things several ways. The biggest thing that fails on electrical drums is the contact point of where you hit the stick to where it hits a relay making the circuity compute the noise. If theres a bad Capacitor it will bubble up or pop when its faulty to test resistors you will need a multi meter and test the electrical flow in and out and see what the resistors rated for to what it should be putting out. ( theres aids and calculators online that help with that because of color codes and ect. ) a good aid would be the tutorials on this site and youtube !
     
  3. Donr

    Donr

    12
    0
    Jun 2, 2011
    transformer wiring

    I have a Triad trans. f-57x. It has 117 volt pri. and 28 v sec. It has a center tap. Is the center tap a ground picked up from trans.or does it go to a grd? This is in an electronic drummer and my sch. shows several places to check volts and they register on the digimeter without touching the grd. prong. Two of the trans, out leads go to one dist. plug and the center tap goes to another. Is that center tap furnishing my ground as I can touch gound prong of my tester to grd. and it makes no difference on the reading? Ideas? Thanks, donr
     
  4. shrtrnd

    shrtrnd

    3,808
    510
    Jan 15, 2010
    Somebody on this site will probably look for the exact transformer you listed.
    Don't ground any of the wires coming off the transformer, none of them are grounds.
    Someone will have to check the drawing on your transformer to be sure:
    TYPICALLY, that 'center-tap' will provide 12VAC (Hence 'center'- tap), for anything
    else in a circuit that might require 12VAC.
    I'm posting this poste-haste, because grounding any wires from the transformer, will
    be a short, causing the winding to overheat. Don't do it, and somebody else here
    will probably be on to help you. I gotta go to work right now.
     
  5. Donr

    Donr

    12
    0
    Jun 2, 2011
    electronic drummer/ transformer wiring

    Thanks for the help guys I appreciate it. My main concern is why and how my test meter showed voltage with only the positive prong touching test point. Also shrtrnd, I don't doubt what you said but in my book by Kybert it says with a center tap trans. to grd. center tap. ?????? Like I said I am new at this and know nossing.donr
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
    2,830
    Jan 21, 2010
    Ground may refer to several things.

    It almost certainly does not refer to "earth"

    There are circuits where the centre tap of the transformer can be come the circuit ground.

    Grounding "any" wires from a transformer isn't necessarily a bad thing, but it may be the wrong thing, and we need to know what you mean by "ground" :)
     
  7. poor mystic

    poor mystic

    1,068
    31
    Apr 8, 2011
    Hi Donr
    The transformer type you quoted is available in a lot of different wiring configurations as a quick check through the usual google shows.
    Depending on the intentions of a designer, any component might appear in many different roles, and there is certainly no hard-and-fast rule about grounding centre taps or anything else. That'd be like saying that all wheels in a machine must be touching the ground.
    As for your voltage measured from nothing, you are seeing the effects of the electric field which exists about every charge. Remember how electrical forces can in principle be detected at any distance whatever? That's what you're seeing.
     
  8. shrtrnd

    shrtrnd

    3,808
    510
    Jan 15, 2010
    Ok Donr, I was worried you were going to 'earth-ground' one of the transformer wires.
    Transformers have primary windings, where the input voltage is applied, and secondary windings which can increase or decrease the input voltage: 'Transforming'
    the voltage to what you want. In your case 117VAC in/28VAC out. Most transformers have
    at least the center-tap of the secondary. Which would be 14VAC, and it's there just
    because it's useful in running other circuits in equipment. Although it's not always NEEDED, (and often not connected to anything).
    depending on your machine.
    'Grounding' the center-tap as of your transformer, means tying it to one of the other secondary
    wires (NOT an earth ground). That means that even though you have a 28VAC secondary,
    they're telling you to use it in the circuit at the 14VAC value of the centertap. Because
    when you 'ground' the centertap, you're electrically 'short-circuiting', or disabling, half of the secondary winding output,
    reducing the output voltage to 14VAC, instead of the 28VAC.
    However: it sounds like your book is talking about electronics in general, and not in
    reference to the machines specifically, that you bought. That directive, may not apply
    to use in the machines you bought. When the manufacturer made your machines, they wired the circuit for what they needed. If you replace the transformer with the same
    type, wire it the same way.
    All these other smart guys have valid points about using technically correct terms when
    discussing electronic topics, but you said you weren't a techno-nerd, so I'm trying
    to speak in general terms.
    Your confusion about the voltage you read on the transformer is because of the way
    reading AC is done. You have to be tied to the actual AC ground of the circuit under test, the voltage almost
    always reads higher out of an unloaded transformer than one connected to the circuit it
    runs, and depending on how everything is connected, you can get some pretty wild
    readings.
    Anyway. Was your question just about the unexpected readings on your volt-meter,
    or are you wondering about the replacement of your transformer?
     
  9. Donr

    Donr

    12
    0
    Jun 2, 2011
    electronic drummer/transformer wiring

    You guys have just made my day because with the way things were shaping up I probably would have grounded that transformer to the case which has an earth grd. right from the power cord input. At least I was smart enough to get on this forum and ask questions. And shrtrnd, I was asking two questions, trans. wiring and the reading on my meter and you guys have answered both. I will now spend more time reading my schematic and moving with great caution. I will probably be back with more questions providing I can see through the smoke to type. Once again, thank you much. donr
     
  10. Donr

    Donr

    12
    0
    Jun 2, 2011
    capacitor rating

    This is a continuing project that I have already had help from here on my transformer. I have that now but there is a suppression cap between hot and neg. feed to the trans. I tested it and it is dead. I finally found a place that converted the number over to theirs. Original # is 2b-437m. Changes to b32022b3473m289 of their #. It also has ecq-ue on it. My sch. says it is rated at .047uf. Problem-- these companys are not overjoyed at selling one cap. which is completely understandable. Another problem is I live in a small town that has no electronic supplys and the Radio Shack within 25 miles says they have .47 uf, .oo47uf but no .047uf. They also have other caps and my question is do I dare change rating some? This machine I am working on is a auto orchestra rythm machine and has a BUNCH of componets in it I would rather not send to electronic heaven if I can help it. Your thoughts would be appreciated. donr
     
  11. shrtrnd

    shrtrnd

    3,808
    510
    Jan 15, 2010
    I don't know where you're at, but you've got a computer.
    My suggestion is to find a couple catalog places that stock electronic parts, that
    can ship inexpensively to your house. You can usually get the parts you want in a
    few days, and with the catalogs on-hand, you'll be ready the next time you need parts.
     
  12. Donr

    Donr

    12
    0
    Jun 2, 2011
    Thank you shrtrnd, for the answer. I tried the company that changed my orginal # over to theirs ( the one in my post) and they had a minimum and Mouser sold the trans. okay but wanted to be called about the cap so I figured they had a minimum too. I will find a catalog from someone that sells small parts.
     
  13. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
  14. Donr

    Donr

    12
    0
    Jun 2, 2011
    Thank you Resqueline for the info. Also not being familiar with the forum do I detect a suggestion that I should have used original post for my inquiry? If so please let me know, I want to do things right.
     
  15. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Hope the info turns out helpful, but if that cap sits on the AC mains then you'll need something better.
    Yes, it's usually very beneficial (for all parts involved) to keep one "project" in one thread - for better understanding of the full picture. It often results in better help.
    This question seemed a little out of the blue though it refers to a project - but which one only finds out about by happening to check out your previous posts.
    I can easily merge these two threads if so desired.
     
  16. Donr

    Donr

    12
    0
    Jun 2, 2011
    Yes you are right about the cap being too low of rating because it is on the main but I am in the process of getting the right one. If you can combine the posts it would be better because I will be on this project for awhile. Sorry about the mixup, I will keep it straightend out in the future.
     
  17. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Threads merged, no worries. :)
    Noise suppression cap's values are not critical btw. (-20% to +100% is ok) but on the mains they should be X (or X2) rated. They should be Y rated if connected to ground.
     
  18. Donr

    Donr

    12
    0
    Jun 2, 2011
    PCB jumping

    This post is to get an explanation as to why someone put jumper wires on this board. I will attempt to post a picture of it. I have removed the wires and have used a continuity test on all circuits. I realise this is not going to put a load on but just check for track interuptions. With the exception of one track which had an obvious cut. This auto or. I am working on has a total of six circuit boards and this one is the mixer board where everything begins, such as all three legs from the center tapped tran. connects here, center leg becoming circuit ground. I just need to find out why the wires would be put on if the tracks are all good except for the one. It would seem they were trying to jump over some bad components which doesn't make sense to me either. One other question: is there any way to check IC units? This board has four, all the same part#. Thank you.
     

    Attached Files:

  19. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Those jumpers are indeed confusing, and most of them seems to modify the circuit. We'll need a shot of the other side too though. A circuit diagram would also help a lot.
     
  20. Donr

    Donr

    12
    0
    Jun 2, 2011
    pcb jumpers

    I have no way to copy these to my computer other than by camera but maybe you can see enough to help. I guess my picts didnt load, try again
     
    Last edited: Jun 26, 2011
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-