I bought a broken HK AVR-65 off of ebay for like 35 bucks US and cannibalized some parts off of it for other projects.
But I still have the mains transformer and was thinking that, even though it's an E+I, I could save myself some major cash by using it in an amp. The problem is, I don't know what the specs on the transformer are. The amp it came out of was a 65w/channel @8ohm, 5-channel amp. So I'm sure the VA is pretty high, but I don't know what the secondaries are.
I've searched online for the specs, but I can't find them. Does anyone happen to know the specs on this trans? If not, what's the easiest way to test it? I'd rather not build an entire power supply to find out what the secondaries are.
PS. I've tried searching the net using every number code on the transformer and came up with nothing.
But I still have the mains transformer and was thinking that, even though it's an E+I, I could save myself some major cash by using it in an amp. The problem is, I don't know what the specs on the transformer are. The amp it came out of was a 65w/channel @8ohm, 5-channel amp. So I'm sure the VA is pretty high, but I don't know what the secondaries are.
I've searched online for the specs, but I can't find them. Does anyone happen to know the specs on this trans? If not, what's the easiest way to test it? I'd rather not build an entire power supply to find out what the secondaries are.
PS. I've tried searching the net using every number code on the transformer and came up with nothing.
I thought about that, but I've never done it before and I wanted to make sure I wasn't going to blow it up or anything. I'll try that... which brings me to stupid question number 2:
The transformer has no markings indicating which side is the primary or the secondary. On one side there are 6 wires (two red, two blue and two black). The other side has 5 wires (two yellow, two black and one blue). So how do I know which side is primary? Will it hurt the trans if I put the mains on the wrong side temporarily? I would think that it would... but then again, what do I know?
If they follow convention, the black leads are the primary. And it may be a split primary, i.e., one that can be wired in parallel for 220 or in series for 110.
Before hooking up any voltages, use an ohmmeter and trace out what's connected to what and at what resistance. Draw out a little map. Then pick the highest resistance winding, connect a signal generator across it (set the gen for 50-60 Hz and a few volts output), and measure the voltages on the other windings so you can determine ratios. The ratios will scale to mains voltage.
Before hooking up any voltages, use an ohmmeter and trace out what's connected to what and at what resistance. Draw out a little map. Then pick the highest resistance winding, connect a signal generator across it (set the gen for 50-60 Hz and a few volts output), and measure the voltages on the other windings so you can determine ratios. The ratios will scale to mains voltage.
Actually, I just emailed Harmon Kardon and they sent me a complete service manual in .pdf. Go figure... It obviously didn't tell me the voltages or anything, but it mapped out which wires were which. It seems that it has 3 sets of secondaries for the various circuits in it. I must say, I was kind of surprised that they so readily sent it to me though.
Anyways, I'm still going to practice what you all have suggested, so I know what to do if I run into this problem again. Thanks again.
Anyways, I'm still going to practice what you all have suggested, so I know what to do if I run into this problem again. Thanks again.
Well, I've looked thoroughly through the 89 page manual and found the voltages for all three secondaries. #1 is +/- 50.3v after the regulators and #2 is +/-47.6v after the regulators. I don't really care about #3 because it's low voltage for the digital components.
However, it doesn't give a current rating or VA for the trans. The service manual shows that a 6 amp fuse is used on the mains line. So am I correct in assuming that 6 amps is the current rating for the trans?
However, it doesn't give a current rating or VA for the trans. The service manual shows that a 6 amp fuse is used on the mains line. So am I correct in assuming that 6 amps is the current rating for the trans?
Fuse
No, a 6A mains fuse means the primary will draw at most 3A. WHich is all the current that can be drawn without the fuse popping from a fatigue failure during the warranty period. The transformer would at most have a total VA rating of 360W. The 6A fuse just means that in case of a catastrophic failure, the transformer will take 6A for a short period until the fuse blows. Remember the fuse is sized for fire prevention and to minimize nuisance blowing. It has little to do with the power rating.
In the misc section of www.schematicsforfree.mattsoft.net is an article of determining the ratings of unmarked power transformers. I think you wil find what you need there.
However, in the case of multi winding transformers, it is next to impossible to determine the amperage rating of the lower voltage windings. However, it is almost impossible to make them capable of less than 1/2A. The VA rating you determine by measuring core size applies mainly to the highest voltage winding. Assme the lower ones are only good for 1/2A each.
Regardless, look up the article I refer to on my web site.
No, a 6A mains fuse means the primary will draw at most 3A. WHich is all the current that can be drawn without the fuse popping from a fatigue failure during the warranty period. The transformer would at most have a total VA rating of 360W. The 6A fuse just means that in case of a catastrophic failure, the transformer will take 6A for a short period until the fuse blows. Remember the fuse is sized for fire prevention and to minimize nuisance blowing. It has little to do with the power rating.
In the misc section of www.schematicsforfree.mattsoft.net is an article of determining the ratings of unmarked power transformers. I think you wil find what you need there.
However, in the case of multi winding transformers, it is next to impossible to determine the amperage rating of the lower voltage windings. However, it is almost impossible to make them capable of less than 1/2A. The VA rating you determine by measuring core size applies mainly to the highest voltage winding. Assme the lower ones are only good for 1/2A each.
Regardless, look up the article I refer to on my web site.
I have a kenwood ka-127 amp. The rating on the back says 120v 5 amps. The mains fuse is 6 amps. The amp is rated to drive 8-16 ohm speakers. I am driving two 3 ohm subs (one on each channel). I'm getting 700-750 wrms to each sub (measured with multimeter), so that's ~1400 watts out of the amp plus a lot of heat (have a fan on it). 1500 watts at 120v comes out to 12.5 amps. Remember that the fuse is 6 amps. Never had it blow. The wire inside the fuse is streched out and bent, but it never blew. I changed most of the wiring inside the amp, and replaced the speaker output relay (the contacts melted).
My 6 amp fuse handles 12 amps continuously without blowing....
My 6 amp fuse handles 12 amps continuously without blowing....
6A Fuse
Hi:
A 6A fuse is designed to blow within 10 seconds if subjected to a 100% overload and within 1 hour at a 135% overload.
However, running with audio is not the same thing as sine wave power, thank goodness. In reality, your average current is within the rating of the fuse, or it would have blown. Readings with a multimeter are not that accurrate. To get good measurements, I have to use an oscilloscope. To be really good, I also use an Audio Precision but lets face it, how many of the people in this forum can afford one.
The fact that the fuse wire has sagged means that you have pushed the limits though, and that you will have a nusiance disconnect some time in the near future.
If it were indeed true that you were able to get 1400W of power through a 6A fuse without it blowing, you would either have invalidated over 100 years worth of industryexperience in designing fuses or discovered a way to get more power out of an amplifier than you put in.
The reality is that if you measured the average power from the AC line, you are within 6A though you may peak above that for short times. Hence the sagging of the fuse wire when it had a near death experience.
Hi:
A 6A fuse is designed to blow within 10 seconds if subjected to a 100% overload and within 1 hour at a 135% overload.
However, running with audio is not the same thing as sine wave power, thank goodness. In reality, your average current is within the rating of the fuse, or it would have blown. Readings with a multimeter are not that accurrate. To get good measurements, I have to use an oscilloscope. To be really good, I also use an Audio Precision but lets face it, how many of the people in this forum can afford one.
The fact that the fuse wire has sagged means that you have pushed the limits though, and that you will have a nusiance disconnect some time in the near future.
If it were indeed true that you were able to get 1400W of power through a 6A fuse without it blowing, you would either have invalidated over 100 years worth of industryexperience in designing fuses or discovered a way to get more power out of an amplifier than you put in.
The reality is that if you measured the average power from the AC line, you are within 6A though you may peak above that for short times. Hence the sagging of the fuse wire when it had a near death experience.
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