Hi,
No, I did not drill any holes, I use the holes for rectifier diodes that are on the PCB, although it is a bit difficult to mount the diodes using those holes
Ncc
Ncc,
I've just seen this now.
I'm sorry you are in difficulties!
When you have huge current flows like this, routinely check the following:
1. You have the correct output devices mounted, 1058 on left, 162 on right, not wrong way around.
2. Secondary #1 connected to LEFT side, positive rail, and Secondary #2 connected to RIGHT side, negative rail.
3. Diodes D1 and D2 correct way around.
4. Bias string connections all correct; D4, D5, D6 and P1. Check all these vital parts for continuity.
The problem is 95% likely to be in the output stage. The rectifier diodes have a common cathode at the center terminal, so can go in the board either way, tab forward, or tab rearward. Doesn't matter at all!
This is a ridiculously simple power amplifier and should not be too difficult to get going.
Good luck!
Thanks guys for helping NCC, he is being very patient, careful and calm!
Cheers,
Hugh
I've just seen this now.
I'm sorry you are in difficulties!
When you have huge current flows like this, routinely check the following:
1. You have the correct output devices mounted, 1058 on left, 162 on right, not wrong way around.
2. Secondary #1 connected to LEFT side, positive rail, and Secondary #2 connected to RIGHT side, negative rail.
3. Diodes D1 and D2 correct way around.
4. Bias string connections all correct; D4, D5, D6 and P1. Check all these vital parts for continuity.
The problem is 95% likely to be in the output stage. The rectifier diodes have a common cathode at the center terminal, so can go in the board either way, tab forward, or tab rearward. Doesn't matter at all!
This is a ridiculously simple power amplifier and should not be too difficult to get going.
Good luck!
Thanks guys for helping NCC, he is being very patient, careful and calm!
Cheers,
Hugh
Hi Hugh and everyone,
After reading your advices, I dismounted the PCBs from the heatsinks and carefully checked everything and I could not find anything wrong:
- Output devices mounted correctly. I don't have 2sk1058/2sj162 so I use what I have on hand which is BUZZ900/905 pair, BUZZ900 on left, BUZ905 on right of the PCB
- Diodes D1 and D2 orientation is correct
- Bias string D4, D5, D6 connections all correct
I could not find anything abnormal, so mounted one channel on heatsink to test. I used a variac to increase voltage from about 50V to 220V and things seemed to be ok this time, I could set the bias and voltage across bootstrap resistor and output offset to about 5mv. Then I was able to do the same to the other channel (one channel at a time).
I puzzled me because I did not know what was wrong and I did not correct anything then everything seem to be fine.
After that I put everything back to the chassis then power on again and I got the same short like before. It took sometime for me to find out the problem:
I use only one transformer with two 25V secondary windings. Secondary #1 connected to LEFT side, positive rail of left channel but I inadvertently connect it to the RIGHT side negative rail of right channel, the same apply for the Secondary #2, that's should be the problem.
After correcting the problem, I could power two channels with out any problem. The amp is making beautiful music right now.
Thanks Hugh and everyone for helping
However as an inexperienced Diyer I do not understand why it has happended like that. If I power only one channel at a time it's fine but if I power two channels at the same time with my original wiring then I get a short.
I should be very grateful if you could explain it for me.
Thanks,
ncc
After reading your advices, I dismounted the PCBs from the heatsinks and carefully checked everything and I could not find anything wrong:
- Output devices mounted correctly. I don't have 2sk1058/2sj162 so I use what I have on hand which is BUZZ900/905 pair, BUZZ900 on left, BUZ905 on right of the PCB
- Diodes D1 and D2 orientation is correct
- Bias string D4, D5, D6 connections all correct
I could not find anything abnormal, so mounted one channel on heatsink to test. I used a variac to increase voltage from about 50V to 220V and things seemed to be ok this time, I could set the bias and voltage across bootstrap resistor and output offset to about 5mv. Then I was able to do the same to the other channel (one channel at a time).
I puzzled me because I did not know what was wrong and I did not correct anything then everything seem to be fine.
After that I put everything back to the chassis then power on again and I got the same short like before. It took sometime for me to find out the problem:
I use only one transformer with two 25V secondary windings. Secondary #1 connected to LEFT side, positive rail of left channel but I inadvertently connect it to the RIGHT side negative rail of right channel, the same apply for the Secondary #2, that's should be the problem.
After correcting the problem, I could power two channels with out any problem. The amp is making beautiful music right now.
Thanks Hugh and everyone for helping
However as an inexperienced Diyer I do not understand why it has happended like that. If I power only one channel at a time it's fine but if I power two channels at the same time with my original wiring then I get a short.
I should be very grateful if you could explain it for me.
Thanks,
ncc
Hi NCC,
Since you write (and presumably speak!) English about 1000 times better than I do Vietnamese, it will be a pleasure.
A single transformer has two secondaries.
One secondary must be wired for POSITIVE rails on each module, and the other secondary must be wired for NEGATIVE rails on each module.
If one secondary supplies both a pos and a neg rail, then the negative of one output will be the positive of the other, and this will make for a dead short at the common, ground connection.
This is a real trap using two, full wave rectifiers for each module, one for pos, one for neg.
It delivers much better sound quality, but requires careful wiring. This is the reason I urge people to use two transformers, each of 160VA, in the instruction to avoid this problem.
Happy listening! It is a late night, half sleepy amplifier, don't you think?
Cheers,
Hugh
Since you write (and presumably speak!) English about 1000 times better than I do Vietnamese, it will be a pleasure.
A single transformer has two secondaries.
One secondary must be wired for POSITIVE rails on each module, and the other secondary must be wired for NEGATIVE rails on each module.
If one secondary supplies both a pos and a neg rail, then the negative of one output will be the positive of the other, and this will make for a dead short at the common, ground connection.
This is a real trap using two, full wave rectifiers for each module, one for pos, one for neg.
It delivers much better sound quality, but requires careful wiring. This is the reason I urge people to use two transformers, each of 160VA, in the instruction to avoid this problem.
Happy listening! It is a late night, half sleepy amplifier, don't you think?
Cheers,
Hugh
After using the Fetzilla for a while I can say this amp will never leave my house.
Thursday a neighbour came to visit me and took his DIY speakers(bookshelf) with him.Hooked them on the Fetzilla and listen to music for a while.He used his cd's with songs he knews best where to pay attention to.His conclusion was ; very muture sound,tight and strong bass,very good midrange and the hight with lot of detail.He told me,I know the music we are playing very well but there were details in the music I'd never heard before not even with a headphone.Is this a 2x50watt amp,I've the impression of a more powerfull amp he said.We played for serveral hours also at high volume and the amp keeps going and stays rock-steady and the sound keeps sounding wonderfull.Now where are the Fetzilla designers I'm in a need of a 250Watt Fetzilla?
Thursday a neighbour came to visit me and took his DIY speakers(bookshelf) with him.Hooked them on the Fetzilla and listen to music for a while.He used his cd's with songs he knews best where to pay attention to.His conclusion was ; very muture sound,tight and strong bass,very good midrange and the hight with lot of detail.He told me,I know the music we are playing very well but there were details in the music I'd never heard before not even with a headphone.Is this a 2x50watt amp,I've the impression of a more powerfull amp he said.We played for serveral hours also at high volume and the amp keeps going and stays rock-steady and the sound keeps sounding wonderfull.Now where are the Fetzilla designers I'm in a need of a 250Watt Fetzilla?
Ours has been powered on since it was built - back in June from memory. It continues to please the family and astound anyone that comes over with its rich powerful sound. I have some pretty solid gear and a wide choice of amps but the Fetz is solid and perfectly suited to its role. I had assumed it would be underpowered - driving 86db stand mounts in an A/V 2.1 setup with NAD M51 as the DAC/pre and Oppo/apple TV/HTPC as sources, but it belies its 50W rating and never seems to run out of punch. I don't think I've ever driven it to clipping - not that I could hear anyway.
Man, I'm pleased about this......
However, how many people have built their FetZillas? I sent 192 pcbs out, so there must be around 96 stereos out there!
It is wonderful to be living - I probably had a 15% survivable from my 'accident', I really am a lucky guy, and I see the world through different eyes. I lived only 1 mile from the largest hospital in Melbourne, and with a fast ambulance and world class Surgeons definitely I get through.
But I do badly miss driving my car and Kawasaki ZRX; I have to wait until January before the doctors giving me permission to drive again. Until then my wife drives me around, or I walk......
Cheers,
Hugh
However, how many people have built their FetZillas? I sent 192 pcbs out, so there must be around 96 stereos out there!
It is wonderful to be living - I probably had a 15% survivable from my 'accident', I really am a lucky guy, and I see the world through different eyes. I lived only 1 mile from the largest hospital in Melbourne, and with a fast ambulance and world class Surgeons definitely I get through.
But I do badly miss driving my car and Kawasaki ZRX; I have to wait until January before the doctors giving me permission to drive again. Until then my wife drives me around, or I walk......
Cheers,
Hugh
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I thank God for sparing your life and giving you another chance. As you have said, perhaps, this incident has helped you see beyond Audio and delve into the deeper aspects of life. Hope you discover the greater purposes of your life. Take care, Hugh.
Hi Hugh,
fantastic to see you are out and about and getting involve on these forums
. I've been following you on SNA and then I heard what had happen. Like to really catch up with you in person. I caught up with Andy a month ago. Anyway, if you have got any of these Fetzilla pcb left I'll be interested, but I'm more into the higher wattage version.
cheers
ML
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