Plinius III 80 watt p/c class AB Amplifier - Page 2 - diyAudio
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Old 11th January 2012, 07:28 AM   #11
Butcher is offline Butcher  New Zealand
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Check your email RSK
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Old 11th January 2012, 07:32 AM   #12
RSK is offline RSK  Malaysia
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Many thanks Tony -)))
I got your mail.
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Old 11th January 2012, 09:05 AM   #13
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Hi Butcher,
Thanks for the schematic
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Old 11th January 2012, 09:38 AM   #14
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Quote:
Originally Posted by Butcher View Post
There ya are you other two chaps, check your email.

tiefbassuebertr thanks for the info.

Tony.
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AudioEnz - Sound history: New Zealand's history of audio
I read:
The first Plinius II preamp and III power amp (the Plinius III pictured) looked like an electric fence controller.
I doubt, that the designations for the model numbers "II" and "III" are really correct, because nothing informations outside of NZLD are to find online by this model numbers, also not by the Arabic numeral "Plinius 2" and "Plinius 3", as written about
http://www.pliniusaudio.nzld.com/history/index.asp

What is exactly to read on the rear pannel of both devices (mayby a Arabic numeral with the Roman numeral II and III, e.g. like "The Preamp MK-II"/"Plinius 200W MK-III") ?
It also raises the question, which audio amplifier device was "Plinius I" if "Plinius II" and "Plinius III" would be complete as model number.

Last edited by tiefbassuebertr; 11th January 2012 at 09:51 AM.
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Old 12th January 2012, 01:53 AM   #15
Butcher is offline Butcher  New Zealand
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Hi tiefbassuebertr. They are known as read. The Plinius II is the preamp. The Amplifier supplys it with +- 15 volts DC to power the preamp.

The Amplifier is the Plinius III.

My amp is brown. My friends one is black.

Twin toroid transformers. Twin bridge rectifiers. Two DC resovoir caps at 8000uF each. Totalling 16000uF per channel.

Power supply = +- 50 volts. 100V p-p.

Bloody good power supply if anything!

VAS into darlington driver stage then into MJ15003, MJ15004.

Bias. I set mine to 150mA. 0.033V (33mV) across emmiter resistor (0.22 Ohm)

Amp runs quite warm! but not hot.

This is higher than Plinius set it to. It is safe to set this high (NO AUDIO! wait 30 mins for warm up) Then check. Readjust again for 150mA.

My amp completely rebuilt. New transistors except for metal ones (are low noise anyhow).

I replaced ALL caps with polyethylenes OR Polystyrene. Input coupling 10uF p/c. Some Plinius III amps have this, some don't.

I fitted a stereo Alps volume pot to the front of mine. Bypassed twin level pots at back.

Rewired with 50 ohm double shielded coax (foil).

Gold RCA sockets.

Beefed up wiring on power supply boards. REPLACED caps on dethump (was not working when I got her!)

Heat sinks on bridge rectifiers.

Metal oxide resistors or 5W wire wound)

Argh, she kicks **** now fellas!

Any more info, just ask...

Tony.
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Old 12th January 2012, 01:56 AM   #16
Butcher is offline Butcher  New Zealand
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Oh, one afterthought. These amps have blimin' problem with s**t PCB traces. Replace with wire etc.

Tony.
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Old 12th January 2012, 02:00 AM   #17
Butcher is offline Butcher  New Zealand
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Oh, one mod I'd reccomend is to to with DC offset.

Solder a 22K variable resistor across R12 (4K7). Adjust for zero voltage across the speaker output terminals.

Alternativly replace R12 (4K7) with a 5K6 and solder a 47K variable resistor across it.
Adjust for zero voltage across the speaker output terminals.

One channel of my amp had 45mV. My poor speakers! Speakers don't like the extra heat dissipated by DC across them! Now it is 0V!

(p/c = per channel . Just to clarify one of my previous posts).

Anyway, enough for now, enjoy yer stereos guys! Not how big it is, only the way it's used! Go vintage amps!

Tony, New Zealand.
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Old 12th January 2012, 02:01 AM   #18
Butcher is offline Butcher  New Zealand
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Should read = 40W per channel!

Tony.
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Old 12th January 2012, 07:01 AM   #19
Butcher is offline Butcher  New Zealand
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Power supply update:


200VA
33-0-33V
3.0 Amps

Also bypassed the 10uF polyethylene input coupling cap, what a difference!!
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Old 12th January 2012, 07:18 AM   #20
srh is offline srh  New Zealand
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Hi Tony, would you please send me a copy of the schematic. Thanks.
tonyhopkins-at- xtra.co.nz
Regards, Steve.
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