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Aragon 4004 converted to MK.ll and maybe other mods

KNielsen

KNielsen

Well-Known Member
Hey AK.

I want to share this project as this might inspire others to either restore or make the fully rebuild.

It should be mentioned that the Aragon 4004 in this thread is built by request, soo..... -some parts cannot be selected otherwise, as this is a request by the customer.
The most common parts selected are Dale, Nichicon, Kemet and Wima. So should be ok, even if "we" like other stuffing.....

But for now, this is our plan:
4004 restoration throughout including converting to 4004mk.ll (schematics are available for this step, and added in this post as PDF), and a 8008 PSU regarding e.caps size (not xformer).
A new thermistor will accommodate the bigger e.caps.
All 1/4w resistors are changed to Dale RN60, all driver transistors changed and maby the powertransistors is replaced. This last part with the powertransistors I'm not that big of a fan of; the emitter shows a differences of maximum 1mv in the original condition, but the owner feels that these MJ21xxx should be replaced while the amp is here for a restore, and this I fully understand.... Please comment on this if you have second thoughts, and find this a good investment regarding powertransistors or not?? :)
Other inputs is also very welcome, so please share while building this one.
I'll post as progress
IMG_20220119_192506.jpg
 

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Text to pictures above:

-The e.caps has been changed before. A suitable size of caps that'll fit the original capholders is no option as these sizes are obsolete. So the PCB on top (rectifier and power/ground board) of the e.caps has to be drilled and new coppertraces added to make contact to the wider connection on the newer caps. This has been done by previous owner, and looks quite good, so this I don't need to fix this, but we're changing the e.caps anyway. The caps installed now is 4x22.000uf Epcos.. We are aiming for the 4x35.000uf-region if sizes that will fit in hight are available.

-Looking at the capholders, previous owner went for a rather funny solution, I think I'll order some decent holders for the new caps that'll fit without the charm of a metal strap to keep things tight.

-I did a closeup pic of the DC-PROCTECTION board to show how the wires are connected to this circuit. They are extremely tight, but adding some heat and pulling without bending(!) makes the wires come loose.

Best regards
 
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The groundlifter between the PSU and chassis-GND in 4004 is a 10ohm wirewound resistor pr channel as pictured.
My initial plan was to follow the example of Aragon 8008 with 10ohm wirewound in parallel with two back-to-back diodes pr channel.
Would it be a better choice with a suited 10ohm inrush current limiter instead of the 10ohm resistors? I plan to keep the back-to-back diodes as pr 8008
IMG_20220128_140131.jpg
 
First PCB desoldered.... Two coppertraces needs some attention, but otherwise everything went OK. The PCB has been lightly cleaned to remove old grease around the powertransistors and that's about it for now
IMG_20220128_160413.jpg
 
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The first order, 304euros (including tax) so far for a fully rebuild all new (except powertransistors, we keep the original) 4004 with mk.ll mods.
Some of the RN60D resistors I had in stock, but most parts I needed to order.
I added a AS35 10018 inrush limiter to install near chassis ground.
I still need to order new insulation for the powertransistors as the old ones weren't as good as thought, and some of them literally broke apart when removing the powertransistors from the PCB. Also need to source 4x36.000uf/100v Kemet and clamps to go with the 66mm diameter e.caps.. and new drivers and BIAS-transistor (MJL15030/31)...
I ordered new heatsinks for the drivers also. Two of the heatsinks were quite poor near the soldering to the PCB, and one already had a broken leg at the PCB before I started desoldering them.

The order includes all new parts for the DC-proctection, except for the RH4V2 relay, that is in good condition. I'll post a schematic for this unit later, as these are not provided by Mondial for the mk.l.... only the mk.ll DC-schematic can be found in the PDF attached in this thread, but in really poor condition. If someone has the time to redraw this with correct values/transistor-symbol and post, I would be quite happy :)


Best regards
 
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Is there anyone interest in this thread showing a full makeover, obsolete parts changed to new or better? Or I'll just continue in private not sharing my findings as I'll proceed...

Best regards
 
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I'm definatly interested! I'm also sure it will be of great value down the line when these amps receive the respect they deserve. Eeventually the price of components and avaliability will normalize and then DIY-ing of this sort will gain interest agan.

Also, this could really stand out as a great documentation of the love and dedication given to the process of restoring this iconic piece.

@mondialfan @IndyAudio @acurusav @aragonav @KNielsen
 
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Had some spare time this evening and went through the first output circuit for potential leaks in the copper mask (hope my rather poor English is understandable here :) ). Most newer PCB's don't need that much attention, but since age is a factor I thought this were time well spend. It's worth to mention that this 4004 PCB is quite sensitive to heat from the soldering iron and the copper will lift quite easily if heated to much, even at a decent temperature on the iron, so be careful.
I do not know exactly when Aragon changed their production to the better, but my guess is when they switched to the Yellow/gold PCB in the later models or 4004mk.ll..?! Other might now better on this subject :)
I didn't find corrosion due to bare coppertraces, but there were some open spots in the mask, and I treated these with an epoxy overcoat called CW2500 from Chemtronics... An amazing product when restoring old amplifiers.
IMG_20220131_213657.jpg IMG_20220131_213935.jpg
 
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StuartB said:
Man, I wish I was smart enough to do this sort of work. Very impressive.
Click to expand...
I'm not educated in electronics, but hope to Inspire others in this matter :)
I have restored a decent amount of amplifiers to jump into this project, still a lot of research though before I opened this thread with my goals for this amp.

Thanks for reply. Very appreciated
 
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Sorry I'm a bit late in showing up for the party. You can install 80V caps in the main PS as well. Most 4004's should be in the low 70VDC range on their rails.
 
KNielsen said:
The groundlifter between the PSU and chassis-GND in 4004 is a 10ohm wirewound resistor pr channel as pictured.
My initial plan was to follow the example of Aragon 8008 with 10ohm wirewound in parallel with two back-to-back diodes pr channel.
Would it be a better choice with a suited 10ohm inrush current limiter instead of the 10ohm resistors? I plan to keep the back-to-back diodes as pr 8008
View attachment 2466475
Click to expand...

I would replace the ceramic resistors with 10ohm/10A rated inrush protectors.
 
KNielsen said:
The order includes all new parts for the DC-proctection, except for the RH4V2 relay, that is in good condition. I'll post a schematic for this unit later, as these are not provided by Mondial for the mk.l.... only the mk.ll DC-schematic can be found in the PDF attached in this thread, but in really poor condition. If someone has the time to redraw this with correct values/transistor-symbol and post, I would be quite happy :)
Click to expand...

You may want to at least remove the plastic cover and use a relay contact file to clean the contacts. The nice thing about those types of sealed relays is that they can be opened and cleaned. I would however consider sourcing a replacement relay if you can find one. Here's a thread I just posted about hidden protection relay failures.
 
mondialfan said:
You may want to at least remove the plastic cover and use a relay contact file to clean the contacts. The nice thing about those types of sealed relays is that they can be opened and cleaned. I would however consider sourcing a replacement relay if you can find one. Here's a thread I just posted about hidden protection relay failures.
Click to expand...
Relay with matching partnumber Vs the original is available.
Thanks for reply
 
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DC-proctection relay in 4004:
https://www.digikey.com/en/products/detail/idec/RH4V2-UDC24V/8344266?s=N4IgTCBcDaIEoAsAsA3EBdAvkA

Looking at pictures online I'll suspect this relay to be used in 4004mk.ll ect ect ect also......, and 8008...
8008 might be the 12vdc version due to one relay pr outboard instead of one single unit pr amp... It very much depends on the DC-protection layout in the 8008, and schematics isn't available for newer models.
-If someone has knowledge about this, please respond to this post

Regards
 
KNielsen said:
DC-proctection relay in 4004:
https://www.digikey.com/en/products/detail/idec/RH4V2-UDC24V/8344266?s=N4IgTCBcDaIEoAsAsA3EBdAvkA

Looking at pictures online I'll suspect this relay to be used in 4004mk.ll ect ect ect also......, and 8008...
8008 might be the 12vdc version due to one relay pr outboard instead of one single unit pr amp... It very much depends on the DC-protection layout in the 8008, and schematics isn't available for newer models.
-If someone has knowledge about this, please respond to this post

Regards
Click to expand...
Zero stock though while I do this post...
 
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