| kneadle |
Hi all,
There was a thread somewhere on this forum about salvaging transformers, but I can't find it.
I took apart my Pioneer VSX-402 (and it was a sad thing, too:bawling: college memories), hoping to re-use some of it. Problem is, all the stuff is integrated, but among a few things, the transformer seems to be salvageable.
I just don't know much about it, and I don't know where to find info for it, and not just the rating, but HOW to salvage it and use it again.
Thanks,
Dave |
|
|
| Stocker |
| If you still have the rest of it, you will have better luck. If you can spot where the secondaries connected to the rectifiers you will know where to measure from. If not, you can slap a voltmeter on all the secondaries relative to each other. If some of the outputs don't make sense, you know they probably aren't a proper secondary voltage. Another way is to see with an ohmmeter if the secondaries are all one wire or are they separate windings... |
|
|
| Evan Shultz |
once you have the Tx identified as Stocker suggests, remove the solder and pull the Tx off the board. make sure the keep the parameters with the Tx so you can keep track of it. The bridge from the second pic might also be worth taking.
There's no trick to reusing a Tx, if it has suitable secondary voltages, then put it in there. Since you may not know the VA or current limits [can we assume they are low since this is a commerical product?], I know of no sure way to determine the maximum rated current. Good luck! |
|
|
| tg3 |
| What was the power rating on the back of the amp chassis? This will give you some idea of the VA rating of the transformer. |
|
|
| kneadle |
| quote: | Originally posted by Evan Shultz
once you have the Tx identified as Stocker suggests, remove the solder and pull the Tx off the board. make sure the keep the parameters with the Tx so you can keep track of it. The bridge from the second pic might also be worth taking.
There's no trick to reusing a Tx, if it has suitable secondary voltages, then put it in there. Since you may not know the VA or current limits [can we assume they are low since this is a commerical product?], I know of no sure way to determine the maximum rated current. Good luck! |
This is what I was afraid of. There was no "rest of it." When I said "integrated," I wasn't kidding; the board pictured was soldered directly to the housing of the transformer, as though the two were manufactured only for each other. No gangly wires were there or anything. It seems the primaries and secondaries are accessed through that board.
Power rating: 230 watts. I'll do some googling now.
Oh well, I need a nice 20 pound dumbell for exercise.
Thanks,
Dave |
|
|
| Stocker |
Come on now, don't give up so easily!
Measure the secondaries and find out what's what. Solder some wires to the primaries to get them to a mains socket and see what the secondaries give you. Then divide that voltage by 230 for your favorite secondary voltage, and you will have a (probably optimistic) voltage and current rating.
It's easy. |
|
|
| mcs |
| quote: | Originally posted by Stocker
Solder some wires to the primaries to get them to a mains socket and see what the secondaries give you. |
Don't forget a fuse!
I would probably just connect 12V AC to the primary for more safe measuring...
Best regards,
Mikkel C. Simonsen |
|
|
| Stocker |
Actually, in the first typing I had both a fuse and a GFCI socket. In my own testing I used very fine wire to go to a GFCI power strip. Either way, if the unit was not non-functional because of the power section, the transformer should need nither.
You know, if you just want it to be used and don't care to work at it, you could always ship it to me...
...for the cause, of course! :D |
|
|
| kneadle |
How do I determine where the mains and secondaries are if there are no wires to play with?
Dave |
|
|
| mcs |
Measure the DC resistance of the different windings. There will probably be two windings (or a center-tapped one) with very low resistance. That's the main secondary.
What mains voltage did the amp run on? 120V only, or 100, 120, 220, 240 etc? If it's 120V only, it much easier to find the primary... You will then have a winding with higher resistance than the secondaries. You may also have other windings with even higher resistances, but they may be low-current windings for preamp stages.
When you have found what you think is the 120V primary, connect 12V AC to that. You should then be able to measure the different secondary voltages (/10). But be careful! If what you thought was the primary wasnt, there could be 100-200V at the winding that is...
Best regards,
Mikkel C. Simonsen |
|
|
| Stocker |
| Looking at the pictures again, I say hook up to the side of the transformer with the lower number of wires. If I saw correctly there is a side with three wires, and two of them had different insulation on them from the third. Those two are probably your primary for 120V. |
|
|
| kneadle |
I think you're right, but here, take another look from a better angle.
Thanks,
Dave |
|
|
| Stocker |
I am extraordinarily tired so nobody bite my head off if my answer is a little muzzy, please!
With that picture, I have to revise my previous comment. The secondary is almost 100% going to be the side with the many pins out. The primary is a little different that what I am used to seeing but not unusual per se, if I am correct. The reason for 3 wires on the primary side is so you can use it for 110 or 220... if you want to use 220, you need half as much primary wire to get the same volts out the secondary. Wind on another approximately equal number of turns and you can get the secondary voltages... Split the primary in two (center tap) and you can use it either way, depending on where you are going to sell it. The 2 pins on the primary side look to be on single wires each, and the non-pin wire looks like the connection in the middle. Hook those two pins up and see what you get out all the other ones on the other side of the tranny. |
|
|
| kneadle |
| quote: | Originally posted by Stocker
The reason for 3 wires on the primary side is so you can use it for 110 or 220... if you want to use 220, you need half as much primary wire to get the same volts out the secondary. |
This is something I've been suspecting all along. I think I'll take it to my local electronics supplier and see if he can help me accurately figure it out because the more I think about it, the tireder my brain gets, too.
Dave |
|
|
| planet10 |
Cab you snap a pic (or scan) the foilside of the circuit board and draw in the components on the other side? (is the black rectangle a bridge rectifier?)
I suspect the side with the board is the secondary.
A variac, a voltmeter, paper & pencil, plus some deduction will tell you what you have...
dave |
|
|
| kneadle |
I can, and did. I'm a little confused by the two "AC Mains." The tracings are quite easy to see in the pictures. I couldn't see them with the naked eye.
...and the other side....
 |
|
|
| planet10 |
I can't make them all out, but it is pretty clear what most everything is. Yellow is 110 in (green is ground), red is secondary, purple is recified AC... if that one big fat trace is secondary ground then you have a bipolar supply, if not you have only one rail.
Normally you would connect the output of a variac to the yellow.. If you are VERY careful you can connect 120 V. Then measure the voltage across the red... also between red and the unmarked fat trace between the 2 reds. (if it is secondary ground it will be 1/2 of red-red).
Report back
dave |
|
|
| JasonL |
| quote: | Originally posted by kneadle
I think you're right, but here, take another look from a better angle.
Thanks,
Dave |
have yo figured this out ? If not let me know i know the answer..
little hunt Thermal / Protection fuse on the main of that tranny : O ) ill draw it on the pic of you still need to figure out witch side is ac in
Jason |
|
|
| kneadle |
I am making progress, with a great step toward figuring it out with that tracing by dave (planet 10). First, I need to work up the courage to hook voltage up to this mama. Passive electronics is one thing, but adding amps and volts to a circuit proves me to be a newbie. Would someone like to suggest a safe way to get 120V to this naked Tx?
Is that what a variac is for?
Thanks,
Dave |
|
|
| JasonL |
can you get me a better picture with light of the top of the tranny ?
ill mark out what goes where for you.. as i have done it lots..
My method..
1st Disconnect all caps from the tranny
2nd take a old lamp cord and keep the ac plug on one end.
3rd install a inline fuse of 1amp i used a fuse with a button top to add and remove replace the blown fuse.. at the other end where there is no plug add alligator clips. to it.
get me a better pic ill draw it on the tranny for you..
Jason |
|
|
| Zero Cool |
| quote: | Originally posted by kneadle
Is that what a variac is for?
Thanks,
Dave |
Thanks EXACTLY what a variac is for! apply the power slowly and monitor current draw!
For example, i was testing a new transformer, Big mama! there was nothing connected to the secondary side except my meter, BUT, one of the leads had accidentally touched another lead. I power up my variac, raised the voltage to about 2-3V and the current meter SPIKED! I know right away something was wrong! i powered down, checked everything, found the 2 shorted leads, seperated them and power up again, this time, no current draw and i could raise the voltage to full line potential and take my readings.
a variac is an essentail to in a DIY workshop. they can be purchased used cheaply! and there a great and fun first DIY project!
Variacs come in all sizes. I found a nice 1Kva unit for about $20.00 at a swap meet. I searched ebay and found a 0-150V meter and a 0-10 Amp current meter, slapped them into a project box with fuses for the primary and secondary sides and WallA! instant Home brew Variac! Total cost. $38.50
Zero :Pumpkin: |
|
|
| kneadle |
| quote: | Originally posted by Zero Cool
Thanks EXACTLY what a variac is for! apply the power slowly and monitor current draw!
Zero :Pumpkin: |
I suddenly understand very much. I need to go get me one of them thar variacs real quick. I'll post back on Monday.
Seriously, understanding "variac" as a concept in the ideal realm has opened many doors very suddenly. This is good. I feel confident about active electronics today. Too bad I won't have a variac till Monday.
Thanks,
Dave |
|
|
| planet10 |
| quote: | Originally posted by kneadle
I am making progress, with a great step toward figuring it out with that tracing by dave (planet 10). First, I need to work up the courage to hook voltage up to this mama. Passive electronics is one thing, but adding amps and volts to a circuit proves me to be a newbie. Would someone like to suggest a safe way to get 120V to this naked Tx? |
I have an AC cord with substantial alligator clips on them... (i also usually plug that into my variac, but before i got that i'd just plug it into a switched powerbar). You could also just solder the AC cable to the board -- what you don't want os the live AC connection moving on you...
| quote: | Is that what a variac is for?
|
A variac plugs into the AC mains at one end and supplies a fused variable AC supply out the other... this is where the 12 VAC suggestion came from... connect the AC mains to the output of the variac, set it to zero, switch it on, and then while measuring turn it up until you have 12 VAC. Then measure the secondaries & multiply by 10... if something goes amiss, much less drama happens with 12v than 120V.
If connecting to 120V just be VERY careful, and make sure nothing is going to short anything or connections come loose etc.
Slow, methodical, careful.
dave |
|
|
| planet10 |
| quote: | Originally posted by Zero Cool
Variacs come in all sizes. I found a nice 1Kva unit for about $20.00 at a swap meet. I searched ebay and found a 0-150V meter and a 0-10 Amp current meter, slapped them into a project box with fuses for the primary and secondary sides and WallA! instant Home brew Variac! |
My variacs are unmetered -- how did you hook it all together? I can probably dig relevant meters out, and with them in place the variac would be much more powerful.
dave |
|
|
| kneadle |
| quote: | Originally posted by planet10
Slow, methodical, careful.
|
I like beer a lot, and I would hate to miss out on years of tasting beer while I sleep in a grave of my own digging.
I have the method, now; I'll go slow, and I'll be careful, especially with the above-mentioned motivation.
Dave |
|
|
| JasonL |
| quote: | Originally posted by planet10
I have an AC cord with substantial alligator clips on them... (i also usually plug that into my variac, but before i got that i'd just plug it into a switched powerbar). You could also just solder the AC cable to the board -- what you don't want os the live AC connection moving on you...
A variac plugs into the AC mains at one end and supplies a fused variable AC supply out the other... this is where the 12 VAC suggestion came from... connect the AC mains to the output of the variac, set it to zero, switch it on, and then while measuring turn it up until you have 12 VAC. Then measure the secondaries & multiply by 10... if something goes amiss, much less drama happens with 12v than 120V.
If connecting to 120V just be VERY careful, and make sure nothing is going to short anything or connections come loose etc.
Slow, methodical, careful.
dave |
what board.. there is no board. DONT solder any ac wires to the board with all the parts on it that is the secondary not the primary.
Get me a picture of the top of the tranny ill draw the ac in pin's for you.. |
|
|
| kneadle |
Jason,
I appreciate this. However, since it seems to be contradicting some other stuff, would you mind explaining a couple of things?
How did you know that those are the mains and what each wire is?
Why does the board say "AC Main" in it?
Thanks,
Dave |
|
|
| planet10 |
| quote: | Originally posted by JasonL
what board.. there is no board. DONT solder any ac wires to the board with all the parts on it that is the secondary not the primary.
Get me a picture of the top of the tranny ill draw the ac in pin's for you.. |
You can't read on the board where it says AC Mains? The other side has no-care connections, perhaps allowing the factory to swithc between 110 and 220V
dave |
|
|
| kneadle |
And I must add, I don't think anything was plugged into the Tx at those points. All wiring was indirectly routed to the Tx via that board.
It's entirely possible that I am remembering incorrectly, but I'm pretty sure that I was surprised enough by that to bring it to this forum.
Dave |
|
|
| planet10 |
| quote: | Originally posted by kneadle
And I must add, I don't think anything was plugged into the Tx at those points. All wiring was indirectly routed to the Tx via that board. |
Jason was concerned enuff that my deductions were contrary to his that he called me...
Above answers Q1/ there was nothing connected to the other side....
Q2/ A double check... where did the ribbon attached to the AC Mains marked inputs come from -- the power switch?
Other points:
I have never ever seen AC Mains mean anything other than the wall. (Jason says those are heading to another -- a third rectifier in a cheap receiver?-- rectifier elsewhere)
And anytime i've seen these types of trafos, and the primary was on the other side, there is always a little vestigial circuit board connected to the trafo and wiring is connected to the circuit board.
This is where the variac does come in handy -- if Jason was right (which in the face of mounting evidence he is not) then the possibility exists that if you put 120V AC across what he thinks is a secondary you might exceed the insulation voltage rating (doubtful)
dave |
|
|
| JasonL |
| I could be wrong but why would they put the main fuse on the opposite side ? |
|
|
| planet10 |
| quote: | Originally posted by JasonL
why would they put the main fuse on the opposite side ? |
Inscrutable japanese...
and if it was the primary how does the AC get into the trafo with no wires connecting to that side?
dave |
|
|
| kneadle |
Let me get some proper test equipment and all mysteries will be solved. I'll post back just BEFORE I apply voltage ;) Like I said, probably Monday.
Dave |
|
|
| kneadle |
Here you go. This is the top (it broke while dissembling):
And here's the tracing (the input is top right)
 |
|
|
| JasonL |
| wow looks like im right seeeeeeeeeee!!!!!! |
|
|
| kneadle |
Okay,
Would you please elaborate after you finish celebrating?
Dave:rolleyes: |
|
|
| JasonL |
| sure.. also .. do yo have the make and model of this amp ? |
|
|
| kneadle |
Pioneer VSX-402
Early Dolby stuff. Cheapest on the market 12 years ago or so...college...pomp and circumstance...Cerwin Vega! Re series attached...
I googled the amp, and I found a ton of stuff in Russian, but that was about it.
Thanks,
Dave |
|
|
| JasonL |
| so there are 2 power amps in this amp 5 channels 2 for main and 3 for center and 2 for rear ? right.. so this proves me right.. when i get home ill use photo shop and draw it out on your pictures provided.. |
|
|
| kneadle |
I'm not sure that's right. It's early surround sound technology, so be careful in your analysis. There is no provision for a center channel, and I'm not sure how the channels were powered.
There are outs for 4 main speakers, Left and Right A&B. There are two outs for rear speakers, Left and Right.
Dave |
|
|
| planet10 |
| quote: | Originally posted by kneadle
Would you please elaborate after you finish celebrating? |
Yea annoying him acting 10 yrs younger than he is... but he may be right, which creates the mystery of how the AC gets into the mains transformer (and what the purpose of the transformer on the main board is)....
in the pic i have circled two connections... if the red one goes to the AC mains connection then Jason is right. The yellow one would be the 120VAC from the wall... where did it go?
dave |
|
|
| planet10 |
oops the pic...
The black block next to the transformer on the board is likely a relay that acts as the power switch.
dave |
|
|
| JasonL |
the yellow goes to that little tranny sitting beside it as it is the soft turn on. the amp is on but not fully on. Meaning the power amp part is off but the rest may be on. this is how these recievers work..
so.. when i get home ill outline how this is setup.
J |
|
|
| kneadle |
| quote: | Originally posted by JasonL
the yellow goes to that little tranny sitting beside it as it is the soft turn on. the amp is on but not fully on. Meaning the power amp part is off but the rest may be on. this is how these recievers work..
J |
That makes sense. When it was plugged in, it was in "Standby" mode if the amp wasn't powered up.
Will post more pics in a sec. I'm terribly intrigued by all this, and it started only as passing interest...
Dave |
|
|
| kneadle |
Here are all the boards inside the Pioneer VSX-402, except for the one attached to the front face, which I presume is the switching module or whatever.
Let me know if you want to see one of these boards in better detail, and I'll post it.
Dave |
|
|
| planet10 |
| quote: | Originally posted by JasonL
the yellow goes to that little tranny sitting beside it as it is the soft turn on. |
No the yellow goes somewhere else -- it could well feed the mains transformer (it is after the on/off relay)... it can clearly be seen on the trace side of the board where the standby tranny gets its AC.
dave |
|
|
| planet10 |
Dave,
can you take a pic of the trafo in the same orientation as post #2 but zoom out... also a pic such that the text on the top & bottom of the trafo circuit board can be seen.
dave |
|
|
| planet10 |
Also, what is mounted on the heat sinks?
dave |
|
|
| JasonL |
| quote: | Originally posted by planet10
No the yellow goes somewhere else -- it could well feed the mains transformer (it is after the on/off relay)... it can clearly be seen on the trace side of the board where the standby tranny gets its AC.
dave |
that is what i ment. the yellow goes to the mains on the *BIGER* tranny : O ) |
|
|
| kneadle |
First, the requested angle of the tf
 |
|
|
| kneadle |
Now, when I first took it apart, I thought the heat sink was attached in some sort of heatsink "extended" way, never thinking that the chips were bent backwards....
So I figured out how to unscrew them from the heatsink and bent them up. There are SIX chips, 2 each of these (=4)
And these two:
Do you want to see the board they are mounted on?
Dave |
|
|
| kneadle |
Missed that request till just now
 |
|
|
| planet10 |
| quote: | Originally posted by kneadle
First, the requested angle of the tf |
What i was trying to see was the other side of the pic below... but when i adjusted the gamma on the pic the two bright spots turned into pins... perchance do you have a cable that connects these pins to the yellow pins on the main board? |
|
|
| planet10 |
Is the bridge on the trafo board smaller (or the same) as the one on the main board? What voltage ratings are the 2 sets of caps on the main board?
dave |
|
|
| kneadle |
| quote: | Originally posted by planet10
What i was trying to see was the other side of the pic below... but when i adjusted the gamma on the pic the two bright spots turned into pins... perchance do you have a cable that connects these pins to the yellow pins on the main board? |
I was hoping you wouldn't ask that one. I have two wires which I certainly disconnected from something--the only two wires in the whole blasted amplifier, but I can't for the life of me remember if they went from those two pins to the two pins we observed on the main board earlier. They're still shaped so that they do fit the pins without my manipulating them; so that's a really good guess, eh?
Those pins, by the way, have the op-amp "triangle" symbol near them, identical to the symbol on the tracing side of the Tx board.
| quote: | Originally posted by planet10
Is the bridge on the trafo board smaller (or the same) as the one on the main board? What voltage ratings are the 2 sets of caps on the main board?
dave |
The bridge is much smaller on the trafo board than the one on the main board.
The voltage ratings are: 71 V and 8200 mF for the biggies, 42V 3300mF on the smaller set.
Dave |
|
|
| kneadle |
and by "bridge," we mean that gangly-looking black thing, like a tall waterfowl, attached to the board at 4 points, with straight-line demarcations on the outside pins and squiggled-demarcations on the inside pins?
Dave |
|
|
| JasonL |
| yeah i think i'm beginning to think i'm right after all because A the whole amp does not run off one secondary. way to hi of a voltage for the amp. 2nd it costs to much to put in a regulated psu for the amp to run into a lower voltage.. so my best suggestion is to use a set of alligator clips with a inline fuse 2 amp. it is not going to blow a breaker or any thing just connect it. if i'm wrong it will blow if i'm right you can use your dmm to check the voltages.. |
|
|
| kneadle |
| quote: | Originally posted by JasonL
yjust connect it. |
connect it to...? Those pins you identified several pages ago? |
|
|
| planet10 |
| quote: | Originally posted by kneadle
I was hoping you wouldn't ask that one. I have two wires which I certainly disconnected from something--the only two wires in the whole blasted amplifier, but I can't for the life of me remember if they went from those two pins to the two pins we observed on the main board earlier. They're still shaped so that they do fit the pins without my manipulating them; so that's a really good guess, eh? |
As far as i can see those are the only connectors of that type... so jason is right, those 2 pinsa are 115V AC in, and you have 2 secondary voltages... from the cap ratings 50-60V & 30-35V, both centertapped.
| quote: | The voltage ratings are: 71 V and 8200 mF for the biggies, 42V 3300mF on the smaller set.
|
The higher V will have the higher current rating , but the voltage is somewhat high. It might be possible to rewire the secondary for 230V in (there are those 2 extra wires) and still run it off 115V & halve the secondary voltages.
dave |
|
|
| JasonL |
| you can rewire this tranny to use 220 you have to cut that copper band that goes around the tranny then remove the black cap. then under that you'll see.. this is also not a serviceable thing as it has that big copper band... |
|
|
| planet10 |
| quote: | Originally posted by kneadle
and by "bridge," we mean that gangly-looking black thing, like a tall waterfowl, attached to the board at 4 points, with straight-line demarcations on the outside pins and squiggled-demarcations on the inside pins?
|
A bridge is 4 diodes in one package... the squiggles (sine waves) are AC in, the +/- are the (unfiltered) DC out.
dave |
|
|
| kneadle |
| quote: | Originally posted by planet10
A bridge is 4 diodes in one package... the squiggles (sine waves) are AC in, the +/- are the (unfiltered) DC out.
dave |
Oh, a RECTIFIER....
duh... |
|
|
| Stocker |
Too much talking, not enough experimenting!
I turned a little (2cmx2cm) transformer into smoke one time without so much talking, but this thing surely could withstand 120V on the two lonely pins or the "ac mains" pins on the other side. Hook it up. See what happens! |
|
|
| kneadle |
Too chicken. I don't like electricity enough yet, so I have to work up some courage on something in which I have a little more inherent trust. Kinda like catching a fly ball over against fielding a sharp grounder. Eh?
Dave |
|
|
| JasonL |
| do what i said about the aligator clips and fuse you wont get shocked that way at all.. trust me i do it and have never gotten shocked that way.. the worst was a flash from the fuse poping |
|
|
| Stocker |
What he said.
Being shocked isn't as big a concern for me as seeing the safety (fuse, GFCI, circuit breaker etc. ) pop. it always makes an awfully sudden, sometimes loud noise and you realize that you were
--> . <-- that close to a LOT of juice. :hot:
And, to be perfectly honest, the first couple of times you see that fuse blow out of the corner of your eye, it will scare the poop out of you! :bigeyes: with your project!
If you blow several in a row (like *some* of us have :dead: ) you may be a bit shaky for a while and not want to play for a while
Trust me, we have all been right where you are before and hopefully will be again. Everybody blows stuff up sometimes. BUT (and this is a big but) you are extremely UNlikely to do any damage to anything except your cheap-or-free part.
Go for it.
:D :D :D
/edit: I don't think anybody really likes plugging in untested transformers. |
|
|
| kneadle |
Okay okay okay....
...just don't let my mom know, ok? Promise? ;)
Other things to do....will post back BEFORE I risk my life for a stinkin Tx in a day or so. There's this thing I do called WORK, and it occupies me for many hours at a time this part of the week.
Dave |
|
|
| kneadle |
| Oh, and what am I doing AFTER I plug the thing in? Which pin gets which pole? Neg or Pos? then what, do I lick my finger and touch the posts on the other side? |
|
|
| JasonL |
| quote: | Originally posted by kneadle
Oh, and what am I doing AFTER I plug the thing in? Which pin gets which pole? Neg or Pos? then what, do I lick my finger and touch the posts on the other side? |
YOu must lick all fingers not just one. |
|
|
| kneadle |
| quote: | Originally posted by JasonL
YOu must lick all fingers not just one. |
Touche
:D |
|
|
| Stocker |
touche = touch. :D
toungue is easier.
Put your AC voltmeter on the secondaries and see what you get relative to whatever else there is. Looks from the pictures like you may have two center-tapped secondaries. Measure from one pin to all the others and make a chart. At least a couple of outputs will make sense. Be sure to check for two sets of very-close voltage secondaries lined up like this:
sec1a centertap sec1b sec2a centertap sec2b
if this is the case, the transformer is useful for voltages of
sec1a-sec1b
sec1a (or b)-centertap
sec1a-CT-sec1b
and similar for secondary #2.
recording the primary voltage at the time of measurement is useful if you have plans to rewind it for a different combination of volts and amps, but it sounds unlikely at this point! :D |
|
|
| kneadle |
You know what? I don't know what "center-tapped" means. I was just about to do a search on that, but would you mind just telling me?
Thanks,
Dave |
|
|
| Stocker |
Kneadle is wheedling.
a transformer is two pieces of wire. they are wound around the core a zillion times or less. usually less. if there is an electrical contact to the wire in the center of the length, it is a center tap. it will (for secondaries) have half the voltage across it relative to one end, that the ends have to each other.
it is a tap
in the center.
use it for a 0V reference
or not.
lucky I am tired or you would have to spend 2 minutes on google.:whazzat:
/edit: you have the same name as my grandfather's only son gave his only son. |
|
|
| kneadle |
Two Val-uable minutes saved. Thanks.
Dave |
|
|
| kneadle |
...I worked up enough nerve. Here is the voltage assignment using this picture as reference:
From top to bottom are pins 1-8.
Here's the voltage I could get out of them:
1+??=0
2+3=47
3+4=47
2+4=94
5+6=20
5+7=40
6+7=20
1+8=3
Every other combo yielded 0 volts.
Now...
What can I build to accomodate this Tx?
Dave
PS--and I didn't die! |
|
|
| Stocker |
Be happy. This is a useful transformer. To me it looks like you have output secondaries of:
47-0-47
20-0-20
3
or
94
40
3
rectified, roughly
66-0-66
28-0-28
4.2
The 28V taps are good if you want to do the chip amps forum's darling, the gainclone. A simple amplifier that can be built in an afternoon for less than $20 (by far) and that will sound, quite possibly, amazing. The higher voltage taps could also be used for a single supply gainclone.
The nice thing about DIY audio: think about what you want to do, and then design or copy a design and do it how you want. Almost any power amp design can be adapted to use this tranny!
If the output devices from the old amp are any good still (not hard to check) then you may be able to reuse them as well, with their heatsinks if they prove adequate.
Consider it useful to maybe 80% of the input power rating of the device it came from, or be optimistic and say it can give you 100% of the output power rating!
/edit:
The 4V output can be for indicators or low-level logic if you want. Or some crazy biasing scheme i guess but... :xeye:
And go easy on the output transistor leads. Bend them too much (as few as once or twice more) and they will break! |
|
|
| kneadle |
I'm building a BrianGT right now. Of course, I had already bought the necessary transformers from Avel for both the amp and one of Nuuk's preamp designs (at decdun.com somewhere).
HOWEVER, this amp and preamp will be powering the HohlFlutes I just built for my dear bride, so now I have the Transformer taken care of for BOTH an additional BrianGT kit and a Nuuk preamp for myself.
I'm very happy; 47 and 20. Well, 47 might be a little hot for an LM3875. I'll have to look into that. Still, very feasible, I should think!
Dave |
|
|
| Stocker |
reg
u
lat
ed
anyone? |
|
|
| DSP_Geek |
| quote: | Originally posted by kneadle
I'm building a BrianGT right now. [...]
HOWEVER, this amp and preamp will be powering the HohlFlutes I just built for my dear bride, so now I have the Transformer taken care of for BOTH an additional BrianGT kit and a Nuuk preamp for myself.
I'm very happy; 47 and 20. Well, 47 might be a little hot for an LM3875. I'll have to look into that. Still, very feasible, I should think!
Dave |
Check the winding resistance, just for grins. Anything below about 0.2 ohm from either hot to the center tap should be fine. 1.0 ohm would get you into substantial losses and heat.
Cheers,
Francois. |
|
|
| kneadle |
| quote: | Originally posted by Stocker
reg
u
lat
ed
anyone? |
But I'm an expert now! I don't wanna learn anymore!:o
Dave |
|
|
| kneadle |
What kind of regulators should I use for the 47-0-47 (66V rectified) tap if I wanted to build a single-supply GC? I mean, that's high voltage. I don't see any regulators rated to handle more than 60V input.
I've got the heatsink...
Dave |
|
|
| Stocker |
You may be forced to use
Zener
regulation. And perhaps some pass transistors eh? ;)
I too have been thwarted in my half-hearted attempt to find high voltage monolithic regulators... I am sure they exist, but I am pretty sure I don't want to search hard enough to find them, and then pay for them!
Zener regulated supplies are not that complicated. Google is your friend! |
|
|
| kneadle |
Well, I've thought about that. A zener diode circuit is simple enough, and--theoretically--I'd need only one circuit to get to a more manageable voltage.
Voltage in through a nice power resistor (say, 5w at 10 Ohms) to a zener diode of some significant power rating (??), with voltage out tapped by some load resistance, joining the anode of the zener at ground.
Yeah. I need to learn a little more, eh?
Google is my friend? Fie! I'll work on it, and report back for those interested |
|
|
|
