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Aragon 4004 converted to MK.ll and maybe other mods

mondialfan said:
There's has to be an error in this schematic. Q101 & Q102 should be tied into the circuit to trip the relay (base of Q104) but they're not.
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Correct....! My fault.... I edited the schematic a couple of times to make the layout more readable but forget to tie these up again... I correct this and post the schematic again :)
 
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The 4004mk.ll mod schematic suggest 47uf/0.1uf(100v) on the backside of the board as decoupling to both rails.
For this build I used 100uf(100v) Sprague Atom and 1uf(400v) Vishay 1839mkp.
IMG_20220204_170008.jpg IMG_20220204_165551.jpg
 
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The 4004 ground lifter... I desided to go with the Dale wirewound that I ordered together with back-to-back 1N5408 diodes like the Aragon 8008...
Before/after pictures
IMG_20220128_140131.jpg IMG_20220205_200702.jpg IMG_20220205_200927.jpg IMG_20220205_200855.jpg
 
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Bodgeangles said:
Really nice work, and great thread. Thanks for posting it.
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Thanks. It's a fun build, and listening to the amp before I took it apart, I'm really excited to hear the final result when finished.
Progress is gonna be a bit slower then normal due to lack of parts, but the owner @palmqvist99 and I desided that "the right parts" is worth waiting for.
The relay can be the biggest issue to source, without we'll have to wait 2-3month for stock to raise..!??
We see what happens :)

Best regards
 
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2SA1837 and 2SC4793, now made by UTC has arrived, ordered from profusionplc.com... I ordered 30 of each, so enough to replace Q3/Q6 (2SA968/2sc2238) on each board in the 4004, but like to have some extra in stock! :)
Now I only need two more packages, where one of them will arrive tomorrow with MJE15xxx-series of transistors ;)
IMG_20220208_174645.jpg
 
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One little trick:
The screw at Q3 and Q6 can be a little hard to loosen or tighten on it's heatsink... The pictures shows how to do this; find a suitable small screwdriver that will pass through the hole of Q1/2- and Q7/8-heatsink and into the screw at Q3/6... This will make it a lot easier to deal with :)
IMG_20220208_211159.jpg IMG_20220208_211320.jpg IMG_20220208_211347.jpg
 
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The schematic doesn't show any Zobel???
Is it the one located underneath the heat shrink between the speaker binding posts?
And if values are NOT according to the normal 1.5ohm/0.22uf that Mondial uses in their later models, should I change this to the newer standard?
Do you know @mondialfan ?

Best regards
 
KNielsen said:
The schematic doesn't show any Zobel???
Is it the one located underneath the heat shrink between the speaker binding posts?
And if values are NOT according to the normal 1.5ohm/0.22uf that Mondial uses in their later models, should I change this to the newer standard?
Do you know @mondialfan ?
Click to expand...

There should be no Zobel from the factory. If there is one it was added by a previous owner. The presence of a zobel is not a bad thing. This thread at diyaudio discusses the lack of a zobel in the Aragon and the possibility of adding one. Many amps use a more generic value for the output zobel of 5ohms and 0.1uF and sometimes 10ohms and 0.1uF. In fact if you pull up enough schematics of various other manufacturers amps you'll see those values on the output a lot. Mondial must've come up with their values on the Acurus amps with some experimentation as to what worked best. Also see section 3.4 in this article from Rod Elliot.
 
mondialfan said:
There should be no Zobel from the factory. If there is one it was added by a previous owner. The presence of a zobel is not a bad thing. This thread at diyaudio discusses the lack of a zobel in the Aragon and the possibility of adding one. Many amps use a more generic value for the output zobel of 5ohms and 0.1uF and sometimes 10ohms and 0.1uF. In fact if you pull up enough schematics of various other manufacturers amps you'll see those values on the output a lot. Mondial must've come up with their values on the Acurus amps with some experimentation as to what worked best. Also see section 3.4 in this article from Rod Elliot.
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Thanks for reply... I opened the packed and did find a Dale 5ohm, 5watt/0.1uf, 200vdc Zobel... The amp seams to work well with this setup, so I'll leave it intact.

Regards
IMG_20220210_162540.jpg
 
To the pic above:
The powertransistors aren't fully mounted yet.. But I cleaned them and and the holes at their position also, so my OCD tells me to put them in place to avoid dirt in-between, untill I get the mica insulation for a final install.
All soldering on the boards it done. Just need to power each of them slowly up with my PSU, to check that everything functions the way it's supposed to before installing in the chassis. The rails in this 4004 is roughly 68vdc and I have up to 64vdc on tab at my PSU, so testing can be really close to the final layout...
I'll post a fully partslist when the amp is build and tested, for inspiration or a direct copy

Regards
 
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palmqvist99 said:
I was thinking we might be able to improve on the cap in the zobel. any thoughts on that?
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Looking at the post by @mondialfan and reading the links he provided, I do not see any point in altering the values.
The resistor is high quality, so we should keep this. At some point, I would add a Wima MKP .1uf/250v instead of the yellow unknown cap, and resolder with a "nicher touch" then the oversized heat shrink look?:)
 
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The axial cap is a lot easier to implement in a zobel arrangement like that so I'd probably leave the whole thing in place. It doesn't affect sound quality only high freq stability.
 
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