D-AOC PCBs - the building and help Thread

[silent:arts]

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THE PSUs

as mentioned before the PCB contains 3 PSUs:
PSUs.jpg


all components colored red are part of the
High Voltage PSU
CAUTION: Mains or High Voltages are lethal, you have to work very carefully here.
it is a good idea to always have a separate Voltmeter constantly connected to the High Voltage when working, this can be easily done at R128 or R218.

since this is an adaption of the Gyraf G9 High Voltage PSU, please read the Basic safety rules Jakob wrote on the Gyraf G9 site.

R2 & R3 are setting the B+ voltage, I used some sockets on my prototype to empirically find the "right" values:
PSU-R2R3.jpg

with 470R + 47R resistors (silkscreened values) I get 238V after Rx28, close enough.
if you want to come closer to the 243V from analags schematic you can use a single 510R and a jumper, this gives me 241V (again, after Rx28).

don't forget to mount the TL783 insulated to the heat-sink, otherwise you will have a short from the regulator's output to ground !!!

!!! be aware that this PSU needs a load to work properly, with no tubes inserted you will have more than 350V !!!
!!! with no tubes inserted the High Voltage caps need a very long time to discharge, read the safety rules again !!!
if you are unsure and afraid of the tubes, test with only one channel fitted first.

and yes, you need a power transformer with a 220V - 250V secondary @ 0.1A even living in a 230V country.
DON'T KILL YOURSELF

all components colored yellow are part of the
Heater PSU
the power transformer needs to have a 9V - 12V secondary @ 2.5A, and the LM350T gets hot.
you need a good heat-sink here !!! the SK129 38.1 I used in mine (and which is silkscreened on the PCB) is not enough in my opinion.
PSU-Heatsink1.jpg

may be a SK129 50,8 or SK129 63,5 will work, but I don't have one of either to test.
with a larger heat-sink and the regulator mounted off board to the chassis the regulator stays quite cool:
PSU-Heatsink2.jpg

like the TL783, the LM350T must be mounted insulated to the heat-sink, otherwise you will have a short from the regulator's output to ground !!!

before inserting the tubes adjust the heater voltage to 6,3V using RV1.
there are two test points next to C8.
after inserting the tubes check again and readjust.

all components colored blue are part of the
universal PSU
use this PSU for relay bypass, meter lamps, VU buffers, what you want.
if you don't plan to use any of the above you can just let this components out.
the output voltage is chosen by the 78XX you use.
take 7805 if you want 5V, 7812 for 12V, 7824 for 24V.
of course you need a matching secondary on your power transformer, and C11, C12 and C13 should be in the right voltage range.
if you want a real true hardwire bypass take very low values for C11 and C12.
at the moment my PSU3 holds the power for 4 seconds after switching off the unit, using 2200uF and 100uF (24V).
will have to change this since I want the compressor to be immediately in bypass after switching it off.

it is not necessary to insulate the 78XX from the heat-sink, but more elegant.
the PSU3 has its own ground path, you can use it floating, or use a little jumper (provided on the PCB) to connect the PSU3 ground to the main PCB ground.

hope this is helpful,
more to come
 

Purusha

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Very excited about this project. Thanks!!! :thumb: :thumb: :thumb:

Volker, like many others I would also love to hear about the best possible meter option in this one, of course when you find the time.
 

laiben

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What will happen with the sound if I use a 600ohm:600ohm transformer for the 1:1 tranny?
 

[silent:arts]

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don't know what they are called in english, I used one of each:




laiben, I used a 600R:600R Haufe for some tests and measured good results.
haven't compared it sound wise yet
 

bernbrue

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Hi,
I just wanted to mention that www.musikding.de has almost all parts for this project in stock. Besides Vactrols and solen fast caps a suitable power transformer (primary 2x115V, sec1 250V 0,1A, sec2 9V 2,5A, sec3 24V 0,5A for EU and US members) is available as well.
regards
Bernd
 

Jim50hertz

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[quote author="bernbrue"] Besides Vactrols and solen fast caps a suitable power transformer (primary 2x115V, sec1 250V 0,1A, sec2 9V 2,5A, sec3 24V 0,5A for EU and US members) is available as well.

Bernd[/quote]

Where? I can't see it listed on their site

Thanks for the tip though. :thumb:

Cheers

Jim
 

pyjaman

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Hi everybody,
Since I get more and more interested by this project, I've been studying the schem and pcb's PDFs (thanks a lot for these files!) And a question (may be a stupid one) comes to my mind ... for the GR metering, are BOTH the zener and the neon bulb necessary? I'm not familiar with the use of those little neons and don't know where to source them (France)...
I may be a little out-of-subject talking PSU, but if someone could help...
thanks,
Laurent.
 

pyjaman

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Talking parts supply, Banzaieffects in Germany also sells vactrols and various film and electro HV caps (Solen fast, wima and more expensive hi grade caps) They have tubes too, various brands for cheap...
 

bernbrue

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Laurent,
you can use either the 1N5371 or the NE2 neonlamp. There is a footprint for both on the pcb. For reasons of temperature stability I would take the 1N5371, though NE2 is working fine in my prototype. The advantage of the neon light is that you see that the board is under power. The risk of touching something and getting an electrical shock is somehow lowered. Greetings to France, I´m on holiday there next week.
regards
Bernd
 

pyjaman

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thank you for such a fast answer, I suspected something like that looking at the pcb traces...
Have nice holidays...
 

sinestaraudio

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Hi bernbrue,

you mention earlier about the mains transformer at Musikding, but i cant see the one you mention, could you be so kind as to point it out?

Thanks for your help

Best
Pete
 

[silent:arts]

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according Musikding:
since I had a phonecall from my transformer winding company - they are not amused to wind the same "custom transformer" every few days - which I can very much understand. they asked me if we could do it another way.
for myself, you guys are getting me crazy with the PCB orders, no way to handle a group buy with PSU transformers at the same time.
I thought about a solution, and one of my ideas was to get someone else to handle this, like a shop who sells to DIYers anyway.

bernbrue was kind enough to handle this.

we have discussed this "behind the scenes" for a time, since this should be a "no go commercial project", and Musikding will of course earn some money with kits, transformers, or anything else. I don't know if the main transformer is from the same source I do.

if Musikding offers all the parts I'm fine with it, since you DON'T have to buy there. for some people it would be easier and cheaper to have all from one source.

but may be Musikding don't have (the parts) on there website yet.

we will see.
 

bernbrue

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in addition to Volkers statement, which I totally agree with: The needed parts will be on their site soon. In the meanwhile, just send the partlist to Musikding and they will make you an offer with all available parts. Everything else is none of our business, since we don´t do any business here. You can buy there, but you don´t need to.
regards
Bernd
 

OneRoomStudios

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What is the reason for having such a high secondary for the filament? Would a standard 6.3 VAC secondary work with this circuit? Could the larger voltage differential be the cause for the LM350T getting so hot?

If a standard 6.3 VAC secondary would work, it would make it a lot easier to find transformers. For example, a Hammond P-T269AX (125-0-125 @ 0.1A, 6.3 @ 2A) could be used along with a cheap, smaller transformer for the universal section.
 

[silent:arts]

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[quote author="OneRoomStudios"]What is the reason for having such a high secondary for the filament? Would a standard 6.3 VAC secondary work with this circuit?[/quote]
the LM350 voltage regulator needs a minimum of 3V difference between the input and output terminal to work.
yes, 9V is a bit on the high (but safe) side, thus the heat.

have not tested this for hum or noise, but of course you can leave out the whole heater PSU and use AC heating.
 

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