D-AOC PCBs - the building and help Thread

[living sounds]

Has anyone build a unit with electronically balanced I/O?

Would the GSSL (de)balancing circuitry work without modifications?

Also, I've modded mine with the Kubi mod and am running it unbalanced right now. The Threshold is very sensitive (turning the pot a little counterclockwise gets a lot of compression already) - is this normal?

I like the sound of the compressor a lot even running it unbalanced.

Thanks!

 

[Blackout]

Hello everybody. I just finished up my other D-AOC and while double checking everything I found some troubling issues. First, a few resistors are reading the wrong values even though the part itself is correct. for example: the R124 & R224 330K resistors both read about 42k. There are others that are WAY off as well. I truly don't understand it. All of the resistors besides the 2watt ones are the brown metal film Vishays, so they are good quality, although it is my fist time using them. Are they easily damaged by heat or something? They have the value printed right on them so its not like they're just misplaced on the board. Second, I am getting voltages that are entirely TOO high. Above 300v all over. The are tubes inserted and when measured at the input terminals I get 9.34vac, 24.9vac, and 260vac. I am using the Edcor XPWR055. On a little side note, the 24v and 9v winding were reversed. 9v was supposed to be orange and 24v yellow, but it ended up the other way when I tested the Xformer. Crappy QC. Anyway, When using the test points and comparing the voltages that were kindly posted by SilentArts mine were way off. I get around 330v on all except R122 which is nearly zero and R127 which correct at 60v. Any Ideas? Something is terribly wrong. The regs ARE isolated from the heatsink, but I get continuity from the LM350t's middle leg and the metal area that screws to the heatsink to the case. I used nylon screws, washers, nuts and thermal paste to attach them if you were wondering. When I use the test points to set the heater voltage it starts up reading correct and soon drops off. The tubes filaments also cease to glow at this point as well.  I reflowed all parts on the board. check all diodes and found one to be off: D14 1n4004. Will replace now and report any changes. Any help would be greatly appreciated. I will try and include some pics, but just to warn you they will be taken with my phone. I lost the battery charger for my camera. Thanks for any help and even more thanks for such a wonderful circuit.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

 

[Blackout]

Inside:

EDIT: Update..... Replaced D14 1n4004 diode that was measuring off and replaced the resistors that were off. R101 which is lables 15k and has a 15k resistyor in place is still measuring about 500ohm. This happened as soon as I reconected the input xformer molex (ch1). Since is measured fine before that I have to assume the change is due to the these being connected by a trace. If so that will also explain the other resistors that share the same "wrong" reading despite changing the part. Despite all this I am still encountering the same problems with high voltage and heater voltage dropping off after a few seconds. Reg overheating? I'm at a loss right now. any help would be great. Thanks!


*****EDIT:***** I tried removing the tubes and while keeping a meter on Rx28 I proceeded to reinstall one tube at a time. V103 (12au7) then V101(12at7) - correct 242V @ test point while each was in, but as soon as I installed V102 (12au7 closest to faceplate) the voltage started to rise until it was back at about 332v. I tested at both R128 and R228, but there was no difference. I think this is the most significant clue so far , but alas, I don't know what it means as far as where the problem may lie. Also, with ONLY the two tubes in place, the heater voltage stays at a steady 6.3v. It drops as the other voltages rise when the last tube on ch1 is inserted. Grrrrrr.    :'( 

 

[Blackout]

So with the first two tubes on ch1 installed, rhe comp passes audio, the input and output knobs work and I think the compression is working, but it is SUBTLE. No action on the VU no matter how hot a signal I send. For this quick test I ran dynamic mic --> 1073 --> DAOC. Signal was certainly louder and fuller , but without real compression. Most likely due to the last tube not being installed. Since the voltage would spike if the last tube in ch1 was inserted or ANY other tubes in Ch2 that channel would not pass any audio. FYI: I have all the Kubi mods done and i'm not using the bypass boards right now because, well, I don't have any. I plan to get them soon though. Not even thinking about that until this is sorted out. Cheers.

 

[Blackout]

Well, it seems this thread is not frequented very often anymore. I removed the board and checked again for bad solder joints, mistaken connections between joints etc and when I powered up again I now have about 240-244v with all the tubes in place. Sigh of relief  . But...now the heater voltage is stuck at just above 9v at the test point. Taking measurement at the regulator in on the PCB I can see the voltage adjust down to 6.3v when using the trimmer. I also get that voltage at the + side of the diode and resistor below it as well as on the right leg of the trimmer. But at the test point and at the heaters in the tube sockets I get just over 9v still!  Any clues, ideas or thoughts? I am so close now. Is there some where I can use a resistor to drop the 3v I need to get rid of? Of course I would rather have it work properly. Help a brother out. Thank you and have a great day.
-Blackout Audio & Engineering-


EDIT: This sucks. I now have the high voltage and dropping heater. Didn't change anything to make this happen, but that the deal now. When this happened I replaced the LM350 and the electrolytics in the High Voltage section, but no change. I gues I will try new tubes, but all this blind changing of compnents and such is rather frustrating and not the best way to go about this in my opinion so Im not going to do anything else until I can get some sort of feedback or pointers. Anybody out there? I keep trying , but am not arriving at a sollution. Thanks and hopefully will hear back soon. Cheers.

 

[G-Sun]

Just looking at the units displayed in the first post.
You guy's are making insane good-looking DOACs Keep rocking!

 

[jsefer]

Well, it seems this thread is not frequented very often anymore. I removed the board and checked again for bad solder joints, mistaken connections between joints etc and when I powered up again I now have about 240-244v with all the tubes in place. Sigh of relief  . But...now the heater voltage is stuck at just above 9v at the test point. Taking measurement at the regulator in on the PCB I can see the voltage adjust down to 6.3v when using the trimmer. I also get that voltage at the + side of the diode and resistor below it as well as on the right leg of the trimmer. But at the test point and at the heaters in the tube sockets I get just over 9v still!  Any clues, ideas or thoughts? I am so close now. Is there some where I can use a resistor to drop the 3v I need to get rid of? Of course I would rather have it work properly. Help a brother out. Thank you and have a great day.
-Blackout Audio & Engineering-


EDIT: This sucks. I now have the high voltage and dropping heater. Didn't change anything to make this happen, but that the deal now. When this happened I replaced the LM350 and the electrolytics in the High Voltage section, but no change. I gues I will try new tubes, but all this blind changing of compnents and such is rather frustrating and not the best way to go about this in my opinion so Im not going to do anything else until I can get some sort of feedback or pointers. Anybody out there? I keep trying , but am not arriving at a sollution. Thanks and hopefully will hear back soon. Cheers.

Try checking your voltages with load. The voltage regulators need load to operate properly, if you  check your voltages with out load you might get weird readings.

 

[bernbrue]

When this happened I replaced the LM350 and the electrolytics in the High Voltage section, but no change.

Might be a misunderstanding, but high voltage section needs a TL783 regulator and the heater (6,3V) uses the LM350. Did you check your ground connection? There is a connector next to the LM350 that needs to be connected to main (earth) ground. Trim your heater voltage to 6,3V with all tubes inserted.
regards
Bernd

 

[Scrappersa]

I just received a stuffed board with one of the Antek power transformers (I'm in the United States). I'm having a little trouble figuring out where the secondaries attach to. It's marked like this:

1. 115V    RED-BLACK
2. 115V    RED-BLACK

1. 250V-0V-250V
YELLOW-WHITE-YELLOW
2. 6.3V
BLUE-BLUE
3. 6.3V-0V-6.3V
BROWN-GRAY-BROWN

I understand that the two red and two black wires go to the IEC plug/switch but I'm confused where the other ones go.

 

[Scrappersa]

Hey guys, I am really struggling with hooking up the power transformer.

http://www.antekinc.com/pdf/AN-1T250.pdf

 

[zayance]

Well referring to Schematic of PSU's your power trasnsfo should do i guess for HT and heater, but won't do for Relay's etc...
You'd need another small transformer for the relay's....

You can just use one 250VAC winding, and one 6.3VAC Winding, Try to avoid having Transformer tips flying around, isolate them. Or parralel both 250VAC and 6.3VAC, will give you same voltage but will double the Current capability.
Up to you.

Maybe this will help? And you can check your connections on the transformer powered up alone, before plugging in the circuit BUT PLEASE BE CAREFULL!!!!!!!!!!

 

[zayance]

Oh and one important thing, go with the color code written on the toroidal and not the pdf of his specs, maybe it's the same but good practice is to stick with infos ON the transformer

 

[[silent:arts]]

This PSU transformer is better used with a D-LA2A, not with the D-AOC 
For both: no relay power etc,

but for the D-AOC the heater just don't fit.
6,3V isn't enough for the (regulated) heater voltage.
2 x 6,3V in series regulated down = a **** load of heat

unregulated AC heaters with this: never tested

 

[Scrappersa]

Thank you. I love all of you. I'm going to use this transformer for an LA2A build from you at some later point in time Volker.

Edit: Found this one. http://www.edcorusa.com/p/649/xpwr055_120-240

Does anybody know where I can find one that is not built to order and preferably in the United States? I would like to use this on a session I have in two weeks if possible.

 

[nielsk]

There is no reason why 12 volts can't be regulated down to 6, worse case scenario use a power resistor to drop the voltage a bit. The regulator wants to see at least 9 volts...

 

[[silent:arts]]

not build to order, but outside the us:
http://www.musikding.de/Passive-parts/Transformers/Toroidal-transfomer/Toroidal-transformer-230V-250V-9V-24V::1361.html

 

[zmgwg]

hi,
I've got "droping heater voltage with tubes inserted" problem that some people described.
I can have any pair of tubes inserted, but when I insert 4 or 6 the voltage starts to slowly drop.
it can't be solder joint cuz any tube can work but not all at the same time, right? or does it have to do with anything how voltage is distributed between 3 tubes, and I should check for bad solder joint?
power transformer have required 2.5 spec. for 9v, that's for sure.

 

[[silent:arts]]

might be the regulator needs better cooling?

 

[zmgwg]

could that be the issue?? voltage slowly dropping when it's not cooled properly?
I have 6.3v without tubes inserted. I've used heatsink size printed on pcb, so it may be it, but I though there was some people that had luck with heatsink this size or did everyone upgrade to the bigger recommended size?
you can feel heat over regulator with pair of tubes for sure!
with ether pair of ecc82s voltage is stable, pair of ecc81 voltage drops in few minutes, and with all the tubes voltage drops to 0.40v in like 6 seconds.

what would happen if there was short from regulator to heatsink, because I'm not quite sure of insulation I used there?

I didn't leave much space for bigger heatsink, would chassis mounted be better?

 

[bernbrue]

That looks like a thermal shut down. The regulator MUST be isolated from ground. Not only do you need a small isolation washer (plastic film) between regulator and heatsink, but also an isolation for the srew that fixes the regulator to the heat sink. Use heat conductive paste between regulator and heatsink! If you haven´t switched on power for too long, there is a good chance that the regulator is still working, provided you have a proper isolation and cooling.
regards
Bernd