• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Poll..anyone interested in an Aikido linestage PCB group buy?

Jump to Latest
#861
Thks Ron,

I just read an article for National Union 6X5 that it recommends a 16uF for the reservoir cap!

Now I'm using Bas's psu. Which cap would be the reservoir cap?
C1 is the variable cap but I'm unsure if this is the reservoir cap as they mention.
I was recommended to start with a 0.47uF cap for C1 which I have.
 
#862
Brit,
You are correct, the C1 is the reservoir cap. Starting at .47uF is only the starting value to determine the voltage of the B+.
Raising the value of C1 will increase the B+. It's OK to go lower than the 16uF, but you might shorten the life of the rectifier if you go over the recommendation of the manufacturer. Reason is too much in-rush amperage on the anode of the valve before it's ready to conduct full B+ voltage.
As I understand the principles..................If I'm wrong someone will correct me as to the principles.

Ron
 
#863
I have non CT transformers and would like to know how to handle to Heater Bias connection and ground connection.

Couldn't find the answers on this thread. If I missed the post please point me in the right direction.

I have 2 tranny's non CT:

0-275 V (200mA)

0-12.6 V (4 A)
0-6.3 V (1.5 A)

Where is the Heater Bias point on Bas's psu connnected to?

Also I am planning to build a chassis out of wood and plexiglass so I have no point to earth. How do I handle the ground? One thick copper rod on the base as a common ground???
 
#864
Think I've got it now:

quote:
And, how do I connect the 80V bias to the 6.3V 3A heater winding, anyway
You should connect it to the center tap of the 6,3V supply.

The 6,3V center tap is either real if the (3,15-0-3,15V) in that case you should connect the 80V bias to the 0.

Or a "virtual" center tap. Created by 2 resistors of say 50ohm.

6,3V
50R
0
50R
6,3V

see attached diagram

Bas Horneman has attached this image:
Click the thumbnail to see the original image.
 
#866
Pin information of the 5687 board.

Looking at my new board I see a difference in the manual.

JB mentions using J7 to connect the ground to the chassis through the stand off.

I believe it is J4.

Also going back to information earlier on this thread it mentions using J1 and J7 for a 6N1P/5687 set up. (J3=no,J4=yes,J5=no,J6=yes).

For a 12.6 V heater i believe I need to use J2 (not J1 or J3) and not J1 for a series set up.

Also J5 and J6 are only used if you want to hard wire caps C1 and C2.
I'm planning to use a 3 way switch to change between C1 and C2 so these jumpers are left out.

Anyone had the same experience?

Also what is the purpose of floating the ground with a small cap?
 
#867
Brit01 said:
Pin information of the 5687 board.

Looking at my new board I see a difference in the manual.

JB mentions using J7 to connect the ground to the chassis through the stand off.

I believe it is J4.

Also going back to information earlier on this thread it mentions using J1 and J7 for a 6N1P/5687 set up. (J3=no,J4=yes,J5=no,J6=yes).

For a 12.6 V heater i believe I need to use J2 (not J1 or J3) and not J1 for a series set up.

Also J5 and J6 are only used if you want to hard wire caps C1 and C2.
I'm planning to use a 3 way switch to change between C1 and C2 so these jumpers are left out.

Anyone had the same experience?

Also what is the purpose of floating the ground with a small cap?
Click to expand...


Brit,
Damn it, I think you will get your Aikido built before I do! LOL

OK, here goes:
I too looked for a long time at the circuit and board trying to figure out what the H#ll those jumpers did and how to configure them. (J1-J6) Then, Blamo. It was very clear how they work as either heaters in // or series. Keep looking at it, it'll come to ya.

The "floating" ground cap is just another way of defeating hum in a ground loop to chassis. Can't hurt to use it.

The 3 way switch on the output caps is a cool idea of JB's. I too will set it up to be used as intended. I purchased some 2.0uF Obbligato Film in Oil to use as the secondary caps, JB provided a set of Auricaps 2.2uF with my build. I also plan on bypassing the Obbligatos with a .1uF Russian teflon after the caps and tubes settle in. (lets not start on weather or not caps have a break-in period) I also want to try a bypass with a westcap PIO .1uF Military spec. These will come later, after I learn my Aikido's sound.

Did you buy an attenuator for your Pre yet? if so what value?

Merry Christmas,
Ron

edited Jumper #s
 
#868
Well I've got the heaters and B+ up and running smoothly.

Can't progress any further until beginning of Jan now because I'm out in our summer beach house. Have to wait until I get back to the city.
i just brought the essentials with me. Those 2 tranny's were kind of heavy on the bus!!!!

Yes it's clear that if you use 6.3 Volts tubes then use J2 only for a series set up.

C5 and C6, 0,33 and .68 Wimas.
The board is quite different to the manual JB sent me. Have to send him an email.

I picked up a cheap stereo logarithmic 100K pot last week but testing the 2 channels, one side is 83K and the other 100K!!!
Get what you pay for I guess. I will return it in the new year and test the next one in the shop.

I see JB is selling a 3 stage attenuator for 29 USD. That's new.
 
#872
Hi Ron,

All the caps seem ok on the psu. The arrows showing the negative side. I'm using IL electrolytics axial.

I know sometimes the heat can be normal. In a SS amp of mine there are a couple of heat resistant resistors that do get very hot and all is normal.

Cheers
 
#874
Just some pics of the amp on my breadboard. Playing music nicely but with some hiss and a lot of gain. I need to build the chassis, connections, grounding etc.
 

Attachments

  • aikido small 3.jpg
    aikido small 3.jpg
    76 KB · Views: 419
#878
How do I measure the plate current with my DVM? I'm not 100% sure and don't want to measure across the wrong points as this can have rather nasty surprises.
Click to expand...
Calculate it. I.e. measure the voltage across the cathode resistor.

R=V/I

So if you need I

I=V/R

V=what you just measured...say 3,5V
R=value of the resistor say 1000 ohm

= 0,0035A

times 1000 to get mA.

3,5mA is running through the plate.
 
#879
Thanks Bas. That's pretty straight forward.

Another question.

If the Aikido has too much gain and I want to lower this without changing the input tubes (currently running 6N1P with 5687), what would be the best way?

Do I increase the value of the cathide resistor of the 6N1P so less current passes or do I need to increase the resistor R15?
At the moment I'm using 470 ohms as cathode resistors and R15 is 78K.

Thanks
 
You must log in or register to reply here.
Top Bottom