electronic drummer / transformer wiring / capacitor rating

[Donr]

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.

 

[kwoolsey94]

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 !

 

[Donr]

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

 

[shrtrnd]

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.

 

[Donr]

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

 

[(*steve*)]

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"

 

[poor mystic]

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.

 

[shrtrnd]

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?

 

[Donr]

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

 

[Donr]

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

 

[shrtrnd]

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.

 

[Donr]

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.

 

[Resqueline]

For reference about what Donr is talking about here's his previous thread: https://www.electronicspoint.com/electronic-drummer-transformer-wiring-t235519.html

For reference to Donr here's Radio-Shack's 0.047uF 50V ceramic disc capacitor: Catalog #: 272-134 (2 for $1.89). I don't know what voltage rating you require though.
http://www.radioshack.com/product/i...Name=Type&filterValue=Ceramic+disc+capacitors

 

[Donr]

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.

 

[Resqueline]

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.

 

[Donr]

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.

 

[Resqueline]

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.

 

[Donr]

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.

 

[Resqueline]

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.

 

[Donr]

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