Hi all,
I have two identical 500VA transformers (2x35V), which were handwound by a specialist a few years ago. Unfortunately there are no writings on it, primary wires have both same color, secondary as well - and I couldn't get in touch with the winding guy anymore.
I want to use them in a dual mono amplifier, but have to make sure that they are connected correctly.
Is there any way to see (or measure) which is the beginning of each wiring of both primary and secondary?
Thanks a lot
Dan.
I have two identical 500VA transformers (2x35V), which were handwound by a specialist a few years ago. Unfortunately there are no writings on it, primary wires have both same color, secondary as well - and I couldn't get in touch with the winding guy anymore.
I want to use them in a dual mono amplifier, but have to make sure that they are connected correctly.
Is there any way to see (or measure) which is the beginning of each wiring of both primary and secondary?
Thanks a lot
Dan.
Hi,
if you have a single primary winding then it is simple to find:
using a multimeter set to resistance (or a battery & bulb) find the pairs of secondaries that are connected. The primary ends are connected to the mains. Treat both ends as dangerous in case a wiring fault develops. Measure the voltage across each secondary (should be above 35Vac). Now connect one end from a secondary winding to one end of the other secondary winding. Measure the voltage at the two secondary free ends. If you have zero Vac then you have connected two secondary beginnings together. If the the voltage is above 70Vac then you have connected the secondaries in series using one beginning and one end.
if you have a single primary winding then it is simple to find:
using a multimeter set to resistance (or a battery & bulb) find the pairs of secondaries that are connected. The primary ends are connected to the mains. Treat both ends as dangerous in case a wiring fault develops. Measure the voltage across each secondary (should be above 35Vac). Now connect one end from a secondary winding to one end of the other secondary winding. Measure the voltage at the two secondary free ends. If you have zero Vac then you have connected two secondary beginnings together. If the the voltage is above 70Vac then you have connected the secondaries in series using one beginning and one end.
Ummm...
there are obviously 3 pairs of windings.
identifying the *primary* winding is the trick here.
that's easy enough for this tranny.
measure the DCR of each pair of windings (label them).
the two secondaries will have almost identical DCR (ohms).
the primary will be noticeably different.
usually I prefer to use a low voltage AC source for "sexing" the windings. one could just use a <12vac xfmr for this purpose. this keeps you from having nasty disasters and nasty shocks. use the 12vac as the source, then measure the voltages you get back. if you've done the DCR measurements correctly then all you have to do is to find the phase of the two secondaries as the previous poster noted.
when you go to hook it up as a + & - supply you'll want a "series" connection, putting them together effectively out of phase in that the windings work in parallel only in phase, but when you make the center tap that is the negative phase lead of winding one connected to the positive phase lead of winding two. which one you call winding one and winding two is arbitrary.
_-_-bear
there are obviously 3 pairs of windings.
identifying the *primary* winding is the trick here.
that's easy enough for this tranny.
measure the DCR of each pair of windings (label them).
the two secondaries will have almost identical DCR (ohms).
the primary will be noticeably different.
usually I prefer to use a low voltage AC source for "sexing" the windings. one could just use a <12vac xfmr for this purpose. this keeps you from having nasty disasters and nasty shocks. use the 12vac as the source, then measure the voltages you get back. if you've done the DCR measurements correctly then all you have to do is to find the phase of the two secondaries as the previous poster noted.
when you go to hook it up as a + & - supply you'll want a "series" connection, putting them together effectively out of phase in that the windings work in parallel only in phase, but when you make the center tap that is the negative phase lead of winding one connected to the positive phase lead of winding two. which one you call winding one and winding two is arbitrary.
_-_-bear
Using a 12Vac (low current) wall transformer as stated above is the most important advice unless one is very brave indeed.
If you just happen to hacve an inductance feature on you DMM, I think you can work out primaries vs. secondaries without applying power. Primaries will have more turns and therefore a higher inductance reading. If that's not true someone tell me, please.
Identifying primaries from secondaries by applyinf ac power is fairly easy. Find two wires that have continuity. Apply 12Vac and read AC voltage on other wires. If the the voltage is lower that means you've guesed right - you are applying power to the inputs. If the you get greater than 12vac that means you have it backwards.
The above assumes a step down transformer. of course. If it is supossed to be a step up like you might need when building a tubev amplifier the logic is the other way around.
The next step is fuguring out which wires to connect to form a center tap, etc. That was covered previously.
If you just happen to hacve an inductance feature on you DMM, I think you can work out primaries vs. secondaries without applying power. Primaries will have more turns and therefore a higher inductance reading. If that's not true someone tell me, please.
Identifying primaries from secondaries by applyinf ac power is fairly easy. Find two wires that have continuity. Apply 12Vac and read AC voltage on other wires. If the the voltage is lower that means you've guesed right - you are applying power to the inputs. If the you get greater than 12vac that means you have it backwards.
The above assumes a step down transformer. of course. If it is supossed to be a step up like you might need when building a tubev amplifier the logic is the other way around.
The next step is fuguring out which wires to connect to form a center tap, etc. That was covered previously.
sam9 said:
Hi there.........this unknown tranny wasn't one of my favorites.....any form of physical ident is a good start before putting any volt/current into it..........primary on EI types is usually closest to core.... use ohmmeter to tabulate resistance/ wiring colours/ then one can establish what part of winding it is.
--> A temptation is to put LV AC into a heavy current secondary winding....and see what comes out of the other wires ...beware......I did this with a transformer from a Yamaha DC player and later found this was 2.5-0-2.5V (which was for 3V logic) and got stung with 600V AC from the primary...the dangers cannot be overestimated.
(unknowingly, I thought I was playing safe so I'd put 6.5VAC across a 2.5V winding with 92:1 step up ratio!)
A variac and isolation tranny makes life safer and a darned sight easier.....
Watch it ?? never complete a circuit with two fingers doing the same thing....
rich
Transformer connection trouble
Thanks guys, I have to state something indeed I wasn't precise enough in my inquiry.
It is a toroidal step down tranny, with 2 primary windings 115, which in my case I'd connect in series - which was done by the manufacturer already (the centre tabe is connected within the insulation and couldn't be split). I recon the primary by the fact that the wires are thinner, although they have the same insulation color than the secondary.
As most of you know, using an amplifier is crucial with the correct position of the power plug - luckely in continental Europe we can use the smart german Schuko outlets, where the earth is connected from both sides an thus the plug can be flipped 180° easely.
In my other regular gears, I can hear the difference, without using a phase tester or such device.
The phase on my trannies are not visual, so I have to check them by listening: but in my case the trick is - what if I would connect one transformer IN PHASE and the other OUT OF PHASE (it's a single housing dual mono amp using Hypex UcD's) ...
So I was looking a way to get the phase from my primary, but also form my secondary, where the centre tab is again already connected, but both ends are not identified (both have red insulation).
So, on my secondary which one is the "beginning" and which one is the "end" - because I need to connect both trannies in the same way.
The sound is OK, but the image "walks" a little and is streched the both left and right ends, which I didn't have with my old Class AB Mosfet.
So, any way to check this?
Thanks,
Dan
Thanks guys, I have to state something indeed I wasn't precise enough in my inquiry.
It is a toroidal step down tranny, with 2 primary windings 115, which in my case I'd connect in series - which was done by the manufacturer already (the centre tabe is connected within the insulation and couldn't be split). I recon the primary by the fact that the wires are thinner, although they have the same insulation color than the secondary.
As most of you know, using an amplifier is crucial with the correct position of the power plug - luckely in continental Europe we can use the smart german Schuko outlets, where the earth is connected from both sides an thus the plug can be flipped 180° easely.
In my other regular gears, I can hear the difference, without using a phase tester or such device.
The phase on my trannies are not visual, so I have to check them by listening: but in my case the trick is - what if I would connect one transformer IN PHASE and the other OUT OF PHASE (it's a single housing dual mono amp using Hypex UcD's) ...
So I was looking a way to get the phase from my primary, but also form my secondary, where the centre tab is again already connected, but both ends are not identified (both have red insulation).
So, on my secondary which one is the "beginning" and which one is the "end" - because I need to connect both trannies in the same way.
The sound is OK, but the image "walks" a little and is streched the both left and right ends, which I didn't have with my old Class AB Mosfet.
So, any way to check this?
Thanks,
Dan
Hi,
The phase that comes out of your transformer matches the input phase. So you can connect the transformers round any way once you have series connected the primary and secondary windings.
The rectifier then converts the output into a stream of half wave pulses. Again phase does not matter.
The phase that comes out of your transformer matches the input phase. So you can connect the transformers round any way once you have series connected the primary and secondary windings.
The rectifier then converts the output into a stream of half wave pulses. Again phase does not matter.
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