So did one stk amp. Did two chip amps.
Was at friends shop and he had this crappy looking woostock sa4000.
He sold it to me for 10$.
I purchased it because I loved the sound. It sounded just like my dads akai amp from the late 70s.All I cant tell you is that it uses 4x 2N3055HV transistor which seems quite common so I am hoping that I can fix it even if I dont have the schematic.
Starting from the power supply. There are 4x 1000uF 35v caps. All are bulged.
Simple question should I replace with the same or should I got with larger values.
i.e. how about 4700uF 50V. Is there a reason why they used lower values ?. Like maybe lower ESR ?. The Transformer is a 24-0-24 unit.
Was at friends shop and he had this crappy looking woostock sa4000.
He sold it to me for 10$.
I purchased it because I loved the sound. It sounded just like my dads akai amp from the late 70s.All I cant tell you is that it uses 4x 2N3055HV transistor which seems quite common so I am hoping that I can fix it even if I dont have the schematic.
Starting from the power supply. There are 4x 1000uF 35v caps. All are bulged.
Simple question should I replace with the same or should I got with larger values.
i.e. how about 4700uF 50V. Is there a reason why they used lower values ?. Like maybe lower ESR ?. The Transformer is a 24-0-24 unit.
4700 will pull too much power from the supply.
Put 1500 / 63V at most.
Those must be UR / Usha / BEL transistors!
https://www.google.com/url?sa=t&rct...sing-2n3055/&usg=AOvVaw0eG7uNu50bhW9tTMrrerhW
https://www.google.com/url?sa=t&rct...t-amplifier/&usg=AOvVaw2-TmR4NpD1c_0qTnoPANiT
https://www.google.com/url?sa=t&rct...with-2n3055/&usg=AOvVaw3MCDAObr24yvuOX2xk09EH
Enjoy
Put 1500 / 63V at most.
Those must be UR / Usha / BEL transistors!
https://www.google.com/url?sa=t&rct...sing-2n3055/&usg=AOvVaw0eG7uNu50bhW9tTMrrerhW
https://www.google.com/url?sa=t&rct...t-amplifier/&usg=AOvVaw2-TmR4NpD1c_0qTnoPANiT
https://www.google.com/url?sa=t&rct...with-2n3055/&usg=AOvVaw3MCDAObr24yvuOX2xk09EH
Enjoy
Since this amp was made in India. I strongly suspect its a rip off from some earlier design.
Anybody know of a Phono Stage that uses 6 0.47 Uf PP caps ?.
There are no op amps on this board. Only transistors. Will start off by looking at Rod Elliot's schematics. I got it for the case and the knobs and the Phono section.
Anybody know of a Phono Stage that uses 6 0.47 Uf PP caps ?.
There are no op amps on this board. Only transistors. Will start off by looking at Rod Elliot's schematics. I got it for the case and the knobs and the Phono section.
Attachments
Ok so Im documenting this here just in case somebody else tries to restore one of these. They are super popular in my country. Even though the company has shut down. This amp was made in the 70s or 80s as per what somebody told me.
You see them coming up for sale on Youtube and various 2nd hand sites like olx.in
Part of the charm of its sound for me is the transistors.
It uses 4 x 2N3055HV NPN. The good news is that these transistors are still made in India by BEL. And its used in the defence sector. Even better news. They use the old manufacturing process. And they are cheap.
Since this amp predates all the existing sites like Rod Eliot I dont think Ill find any info there.
Did find some info that its based of an old Philips design. And a company called Vega used to sell kits to build these amps.
My hunt continues. I did find brand new BEL 2n3055HV and 2n3773 at Vishal in Bangalore.
Not sure if I should switch up to the 3773 if I do that means I can beef up the transformer.
But then to ensure everything works and what components need to be changed I would need to enter up the complete circuit in Tinia TI or Proteus. If I do land up doing that I will share the file. Who knows I may get lucky and find an existing project.
I did find this schematic though. Lets see how close it is
https://img1.wsimg.com/blobby/go/f39bc628-876b-4f23-ac52-17d69a2277f4/downloads/150W Quasi Complementary Amplifier circuit dia.jpg?ver=1641558632341
You see them coming up for sale on Youtube and various 2nd hand sites like olx.in
Part of the charm of its sound for me is the transistors.
It uses 4 x 2N3055HV NPN. The good news is that these transistors are still made in India by BEL. And its used in the defence sector. Even better news. They use the old manufacturing process. And they are cheap.
Since this amp predates all the existing sites like Rod Eliot I dont think Ill find any info there.
Did find some info that its based of an old Philips design. And a company called Vega used to sell kits to build these amps.
My hunt continues. I did find brand new BEL 2n3055HV and 2n3773 at Vishal in Bangalore.
Not sure if I should switch up to the 3773 if I do that means I can beef up the transformer.
But then to ensure everything works and what components need to be changed I would need to enter up the complete circuit in Tinia TI or Proteus. If I do land up doing that I will share the file. Who knows I may get lucky and find an existing project.
I did find this schematic though. Lets see how close it is
https://img1.wsimg.com/blobby/go/f39bc628-876b-4f23-ac52-17d69a2277f4/downloads/150W Quasi Complementary Amplifier circuit dia.jpg?ver=1641558632341
getting hotter on the trail.
https://frank.pocnet.net/other/Phil...icationBook_AudioAmplifierSystems_1970-09.pdf
https://frank.pocnet.net/other/Phil...icationBook_AudioAmplifierSystems_1970-09.pdf
Replace electrolytics with Keltron capacitors, they are good.
Keltron is a local company with technology from Sprague, and little chance of fakes.
And almost same / slightly higher price as junk Chinese stuff.
And I have heard that some people have faked BEL transistors, so buy from a reputed person like Vishal, Universal and others.
I was at MSRIT, Mathikere, behind Tata Institute.
Keltron is a local company with technology from Sprague, and little chance of fakes.
And almost same / slightly higher price as junk Chinese stuff.
And I have heard that some people have faked BEL transistors, so buy from a reputed person like Vishal, Universal and others.
I was at MSRIT, Mathikere, behind Tata Institute.
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