DOUK EAR834 by Marek GRANDE FINALE

[Marek]

Being inspired I joined as well

So mine set  arrived from Doukmall China. Shipment from China via Luxembourg ca 3 weeks all together.
PCB with standard elements. Next challenge opened. WIsh me good luck.
 


First comment: as first option will start from delivered set to have a possibility to find differences doing changes upgrades later on.

First remark I have is about coupling capacitor between 2nd and third tube. On board and schematics it is 0,01 uF  but delivered one is  ,1  K  400V green MKT  1822  so I guess it is 0,1 uF
explained already by Jessica and friends

Second is bipolar transistor delivered MJE 13005 instead of 13009 marked on PCB - difference is current 4A(13005) vs 12A(13009). Can I leave delivered 13005 (4A) ?? DONE Explained

Next smal capacitor rated 100 pF but should be 110 pF _ 10% difference - DONE EXPLAINED

I think that is all for now. Thanks in advance. MArek
Progress will be updated here

Transormer ordered from TOROIDY https://sklep.toroidy.pl/pl/p/TSTA-0060002-Transformator-sieciowy-do-urzadzen-lampowych/639 cost ca 70 € plus transport version audio #07 filled by epoxy

Hammond choke ordered instead of resistor
1% caps for RIAA ordered from https://www.ebay.co.uk/itm/CD15FD331FO3F-Cornell-Dubilier-Capacitor-330Pf-500V/133176802202?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649






SO my case arrived and looks very, very proffesional. It is professional case I have to say.
Great execution and extremally fast by https://www.modushop.pl/  costing with components painting drilling etc ca 115 € with local DHL delivery




2020.11.19

For V1 SPAX7‑A ordered
For V2/V3 E83CC JJ - the newest 12AX7 lamp from SLovak JJ ordered.

[Jessica_K]

All looking good, the case looks lovely.

Jessica xxx

[Marek]

So final assembling is coming. Transformer sent by supplier so MOnday should be here. To make in out signal interconnections I went for silver single core 0,5  wire 999 as I have some rest from other project in PTFE tube double shielded so hot/cold in separate 2 mm tube covered by bigger one A bit non flexible but I have some space.

[Marek]

Transformer arrived from TOROIDY

[Marek]

Preassembled, transformer+switch connected to power supply. Tomorrow first start up. Wish me good luck.

[Marek]

So nothing exploded yet. First success.

Data from "wall" = AC 220 V - strange as should be 230 V but OK still in range of old voltage

output #1 - 260 V - so seems to be accpetable as I found - transformer data is showing 250 V so I have 10V more
output #2 - 6,6 V - should be 2x3,15 = 6,3 V - I hope in acceptable range

SO now lets go for DC challenge.

[ropie]

I used Toroidy toroids in my last couple of Gainclones. Very nice guys to deal with!

So nothing exploded yet. First success.

[Marek]

Hi all friends Please help with grounding. I have some doubts or misunderstandings. Look below.

1. 230 V EU side seems to be clear yellow/green from power socket has to be connected with yellow/green from transformer if exist - in my case exist and grounded to chasis. Like on picture right ? Correct ?



2. GND points on preamp PCB and power supply PCB - should they be connected as well together and grounded separatelly on chasis ? What about GND from tonearm/deck. Of course I have screw on input side on chasis - but should it be also connected by wire to whichever place. Sorry this is a bit unclear for me - I have seen photo with all green/red arrows but something is not fully clear for me. Nobody is perfect

[Jessica_K]

Hi Marek,

Grounding is not a one size fits all science. It depends on how it suits your build. There is one rule that is important that of a star point. From your first picture you have connected transformer gnd and mains gnd to the chassis, this will make a good ground point, connect all other gnds (PSU, amp) to this point too.

There another option that moves the star point to the PSU gnd, but that would require extending the transformer gnd to meet with the PSU and then wire mains gnd to the PSU and take another wire to the chassis gnd and another to the amp.

I hope you are seeing the star configuration, wherever you make it all wires come from it

Jessica xx

[Marek]

Hi Marek,

Grounding is not a one size fits all science. It depends on how it suits your build. There is one rule that is important that of a star point. From your first picture you have connected transformer gnd and mains gnd to the chassis, this will make a good ground point, connect all other gnds (PSU, amp) to this point too.

There another option that moves the star point to the PSU gnd, but that would require extending the transformer gnd to meet with the PSU and then wire mains gnd to the PSU and take another wire to the chassis gnd and another to the amp.

I hope you are seeing the star configuration, wherever you make it all wires come from it

Jessica xx

SO something like this ?

As I have separateted PCBs I connected also power B+/- and 6,3 V as per below diagram. Is this OK against loops for "0"-GND cables ?

[Jessica_K]

Hi Marek,

That should work well,  and add the external ground post ( for arm etc) to the same point.

There are no guarantees when it comes to grounding as it depends on other parts of your system but this is good

Jessica xx

[Marek]

Hi Marek,

That should work well,  and add the external ground post ( for arm etc) to the same point.

There are no guarantees when it comes to grounding as it depends on other parts of your system but this is good

Jessica xx

Super. Thx so next small step ready for execution.

[Marek]

SO something like this ?

As I have separateted PCBs I connected also power B+/- and 6,3 V as per below diagram. Is this OK against loops for "0"-GND cables ?

Done as adviced. all greens grounded in star. All wired as well so ready for powering. Still stressed but not today.

Maybe one day will do it better but I placed all cables on top of chasis. 

[Marek]

START UP story

First of all thank you all supporters SPECIALLY BIG REGARDS THANKS to Jessica for all support I got

So unit assembled tested as dry run (no signal - no power amp - no tubes installed) - some doubts about Voltages 6,3 as I had less 6,15 - OK left as it is

Suggested by Jessica I installed tubes - short power on. No explosion no fire - second for longer time and Voltage B+ check

All in chain crosschecked by Jessica on acceptable level - PERFECT - my face was smiling

SIgnal from TT and out to power amp

Left channel playing Beethoven - right ..................... HUUUUUUUUUUUUUUUUUM

THree days discussion with Jessica looking for this that etc BUT all seems to be correct. Tubes checked on my MingDa no problem nice music

So disassembled preamp PCB cleaned in detailes by EtOH and needle all disputable soldering some soldered again DONE

Finally final check of few points with magnifying glass and surprise

V1,2,3 soldering point no6  on reverse side is very close to long path. Distance is less than 1mm and feet 6 (anode) was shortened with neigbour path by rosin with tiny ball of tin giving 500 mV on grid of V2. Cleaning removing ball (checked all three tubes) reassembling and

BEETHOVEN FROM BOTH CHANNELS no hum. EXCELLENT. Show time is coming tomorrow.



PS Of course RCA positioned correctly (red white - crossing on photo)  trying to be faster than necessary.

Now I can step back to LENCO restoration https://www.lencoheaven.net/forum/index.php?topic=36239.0. Tomorrow missing parts are coming

[Tomcat1969]

Brilliant Marek. Well done!