Hi rope,
I'm assuming ETI 477 is a project from the now defunct magazine Electronics Today International.
ETI material is now owned by Silicon Chip and I believe they can provide copies of old articles. Try these links and email address.
http://www.siliconchip.com.au/
http://www.electronicsaustralia.com.au/
silchip@siliconchip.com.au
I'm assuming ETI 477 is a project from the now defunct magazine Electronics Today International.
ETI material is now owned by Silicon Chip and I believe they can provide copies of old articles. Try these links and email address.
http://www.siliconchip.com.au/
http://www.electronicsaustralia.com.au/
silchip@siliconchip.com.au
Eti-499
Hi Rope,
I found the March 82 copy of ETI. It has a 150 watt MOSFET PA amp design. The project number however is 499. You said June 82 and project 477 . I am not sure I have that copy. If you want 499 I can scan it and email it to you if you give me your email address.
The circuit uses two pairs of 2SK134/2SJ49 per channel.
Cheers.
Hi Rope,
I found the March 82 copy of ETI. It has a 150 watt MOSFET PA amp design. The project number however is 499. You said June 82 and project 477 . I am not sure I have that copy. If you want 499 I can scan it and email it to you if you give me your email address.
The circuit uses two pairs of 2SK134/2SJ49 per channel.
Cheers.
Hi Rajeev & rope
Why do you want this circuit?
I built it some 20 years ago and tossed it after poor (sonic )performance and instability (culminating in pcb fire)
I used the lefover bits to clone a Hafler dh-200 which has worked faultlessly since...
Just my 2 cents worth, hopefully others had better luck than I.
Why do you want this circuit?
I built it some 20 years ago and tossed it after poor (sonic )performance and instability (culminating in pcb fire)
I used the lefover bits to clone a Hafler dh-200 which has worked faultlessly since...
Just my 2 cents worth, hopefully others had better luck than I.
Eti477
Hi Gheorge -may i ask you few questions.
First-did you use the original PCB with all the original parts on it ?
Second -did you try to understand what caused the fire ,because
there are fuses which will blow long before the PCB gets on fire?
I have build myself Two of them but didnt try them and sold out 20 years ago.
To Rajeev - Ill try to scan the issue and send it to you -give me the e-mail. But i have no scanner so it can take some time.Meanwhile i can send you the Australian Issue in PDF files which i received from M-r Paul Cambie from Australia.
Hi Gheorge -may i ask you few questions.
First-did you use the original PCB with all the original parts on it ?
Second -did you try to understand what caused the fire ,because
there are fuses which will blow long before the PCB gets on fire?
I have build myself Two of them but didnt try them and sold out 20 years ago.
To Rajeev - Ill try to scan the issue and send it to you -give me the e-mail. But i have no scanner so it can take some time.Meanwhile i can send you the Australian Issue in PDF files which i received from M-r Paul Cambie from Australia.
Hi
Yes I did use orig PCB's
Amplifier was oscillating badly, after the fire (at reletively low volume) I placed some caps (a couple of pF) accross the 200ohm resistors to the output mosfets (or something like that).
This made themstable enough to use but sound was very very dull. Not a path on the Hafler
Mosfets were effectively on the PCb via the design layout.
Yes I did use orig PCB's
Amplifier was oscillating badly, after the fire (at reletively low volume) I placed some caps (a couple of pF) accross the 200ohm resistors to the output mosfets (or something like that).
This made themstable enough to use but sound was very very dull. Not a path on the Hafler
Mosfets were effectively on the PCb via the design layout.
HI
Actually I have made a power amp similar to the Eti project-499 from the mar1982
issue of eti., I have used 2+2 Irf240 & Irf9240 in the output ,to get more output at
8ohms I have increased the supply voltage to + - 58v , 41-0-41V transformer , the
amp is working fine , good sound , good punch , but the output mosfets really get
hot inspite of a extra large heatsink , short wiring and filter caps near the mosfets ,
I was wondering if the heating of the Mosfets was due to any ultrasonic osclations
which are inaudable and above the audio frequency band ?is that possible??
In the same issue of
eti there is mention of the Eti -477 project , hence I was wanting to see the same
for referance.
Actually I have made a power amp similar to the Eti project-499 from the mar1982
issue of eti., I have used 2+2 Irf240 & Irf9240 in the output ,to get more output at
8ohms I have increased the supply voltage to + - 58v , 41-0-41V transformer , the
amp is working fine , good sound , good punch , but the output mosfets really get
hot inspite of a extra large heatsink , short wiring and filter caps near the mosfets ,
I was wondering if the heating of the Mosfets was due to any ultrasonic osclations
which are inaudable and above the audio frequency band ?is that possible??
In the same issue of
eti there is mention of the Eti -477 project , hence I was wanting to see the same
for referance.
ETI477
Hi Gheorge ,there arent 200 ohm in the gate are used 100 Ohm
resistors,you didnt answer if you used the orirgrnal parts or not. What about the .22 Ohm source resistors, which must have low inductance?
To Rajeev- Ill compress all the pages to one RAR archive and ill send them to you-You must use osciloscope to be sure what happens with the amp!
Hi Gheorge ,there arent 200 ohm in the gate are used 100 Ohm
resistors,you didnt answer if you used the orirgrnal parts or not. What about the .22 Ohm source resistors, which must have low inductance?
To Rajeev- Ill compress all the pages to one RAR archive and ill send them to you-You must use osciloscope to be sure what happens with the amp!
Hi Rajeev,
The original transistors had a negative temperature coefficent whereas the IRF devices have a positive tempco, with the possibility of thermal runaway. So you need some thermal compensation in the bias generator, which I am guessing is simply a pot (variable resistor) You need a sense transistor bolted to the heatsink which would tell the circuit to draw less power when it gets hot. See the thread on the IRF540 for this.
If this is the problem you can tell your friends that you have a Class A amp
The original transistors had a negative temperature coefficent whereas the IRF devices have a positive tempco, with the possibility of thermal runaway. So you need some thermal compensation in the bias generator, which I am guessing is simply a pot (variable resistor) You need a sense transistor bolted to the heatsink which would tell the circuit to draw less power when it gets hot. See the thread on the IRF540 for this.
If this is the problem you can tell your friends that you have a Class A amp
Hi consort,
You could be right,
I have 2 amps rated at 75w made with original transistors , which I made 22 years ago , working fine till now, but this with Irfp devices I tried now, but I think all mosfets have negetive temp properties , however the gate voltages are different in these and the original Hitachi mosfets
You could be right,
I have 2 amps rated at 75w made with original transistors , which I made 22 years ago , working fine till now, but this with Irfp devices I tried now, but I think all mosfets have negetive temp properties , however the gate voltages are different in these and the original Hitachi mosfets
eti 477 fan`s
i have every circuit for this amp and also a deatailed article on fail safe reabuilding.....sparkey@hotkey.net.au
i have every circuit for this amp and also a deatailed article on fail safe reabuilding.....sparkey@hotkey.net.au
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