BAJA Real Tube Drive pedal project

bajaman · Post by **bajaman** » 06 Nov 2015, 09:43

OK
You definitely have a fault condition around the dual opamp and it looks to me like you have a short between pin 3 and pin 4, because pin 4 is the correct voltage - pins 1, 2 and 3 should measure 0 volts DC.
Not sure how you are measuring the op amp but the correct pin order is 1 2 3 4 down one side and then 8 7 6 5 down the other side (pin 8 directly opposite pin 1, pin 7 directly opposite pin 2, pin 6 directly opposite pin 3, and pin 5 directly opposite pin 4

). I think you are referring to pin 8 as pin 5 in your list of measured voltages - this pin (8) should be +15v DC and all the other pins on that side of the chip should be 0 volts DC.
The op amp may still work but you definitely have a direct short between pin 3 and pin 4 - use the ohms x 1 setting on your meter ( without the power supply connected of course) and I think you will find these pins are connected together either through a poor etch or solder bridge etc.
If you manage to remove the short it should work correctly and won't sound bassy on bypass - if you still get +15v DC on pin 1 then you will need to replace the op amp.
Let us know what you find

bajaman

jesven · Post by **jesven** » 06 Nov 2015, 16:10

Thank you guys , I won't give up with this, i measured the ic voltages just in the way it's pleaced on the socket (from left to right pin 1 under pin 8, pin 2 under 7 etcetera) I will take a very closer look at this section triying to find the mistake .

thanks

jesven · Post by **jesven** » 06 Nov 2015, 16:48

DrNomis wrote:quote="jesven"]Well I checked all and i found nothing, but this time i measured the tube pinout and it measures :

1: 9.70 D.C.v
2: -12.73 D.C.v
3: -12.81 D.C.v
4: 0.01 A.C.v
5: 12.4 A.C.v
6: 5.73 D.C.v
7: -12.72 D.C.v
8: -12.82 D.C.v
9: 0.01 D.C.v
I'm using a 15vAc/1100mA power pack , are these numbers right or need to modify something.
Thanks

Most of the voltages look about right except for the voltage on pin 1, it looks a bit high, check to see if you used the correct value resistor, go back to where I posted a list of voltages for my build and write them down on a piece of paper, you could also try substituting a known good tube too.....hope that helps....

Just so you don't have to read through all the posts to find the list of voltages here they are again:

IC 1 (8-pin Dual Op-Amp):

Pin 1: 0.01V.

Pin 2: 0.01V.

Pin 3: 0.01V.

Pin 4: -15.01V.

Pin 5: 0V.

Pin 6: 0.01V.

Pin 7: 0.01V.

Pin 8: +15.03V

Tube Socket Voltages:

Pin 1: +4.0V.

Pin 2: -11.6V.

Pin 3: -11.3V.

Pin 4: 0V.

Pin 5: 12.4 V AC.

Pin 6: +1.07V.

Pin 7: -11.51V.

Pin 8: -11.26V.

Pin 9: Not Used.

Power Supply Voltages:

Input : 17.4V AC.

+V Supply: +15.03V.

-V Supply: -15.01V.

+VV Supply: +11.29V.

-VV Supply: -11.28V.

Thanks Dr Nomis measured the supply voltages :

V+=15.11D.C.v
V-=-15.01D.C.v
V++=12.95D.C.v
V--=-12.85D.C.v
Input (at tube board)=12.1A.C.v
(At main board)=17.1A.C.v

jesven · Post by **jesven** » 06 Nov 2015, 18:33

Well i checked and checked and checked with the multimeter set as continuity as it hasn't ohm x1 I found continuity on every track will keep doing this till I find something , will try with a new opamp too ,also, I would like to know if a faulty diode or electrolitic capacitor could be causing this issue as I can't find any kind of bringe or short-circuit , or may be a faulty ic socket .?
(I'm not convinced with the last theory but anything could happen... I guess).

bajaman · Post by **bajaman** » 06 Nov 2015, 20:39

OK - supply voltages and tube voltages are fine.
1. Remove the op amp
2. Check that the pads for pin 3 and pin 4 on the PCB are not connected (shorted) with an ohmeter.
3. If they are not connected, replace with a new opamp.
4. Measure the DC voltage on pin 1 - if it is not 0 volts DC, replace both the 1N4148 diodes.
5.Report back with your findings

cheers
bajaman

bajaman · Post by **bajaman** » 06 Nov 2015, 20:46

How to read the pins of the dual op amp

: dual op amp.jpg (26.83 KiB) Viewed 2688 times

jesven · Post by **jesven** » 08 Nov 2015, 07:42

Mr. Bajamaaaaan , Dr. Nomiiis, I have it working you're the best of the best, it was a faulty diode , I'm so exited .! Lol , thank you so much for helping me through this project, I really appreciate it , yo the best .!

bajaman · Post by **bajaman** » 08 Nov 2015, 08:08

excellent news

- how do you like it now it is finally working for you

cheers
bajaman

jesven · Post by **jesven** » 08 Nov 2015, 08:43

it sounds a little bit fat , but actually, i like it, anyway I have a very fat sounding pickups (chinesse ones) I guess it won't sound that fat with any other guitar, also, I think it may need a little bit more gain ... Not entirely sure about that .... I think I like it as it is (it sounds really good , even using the cheapest and worst tube brand on the market ) , may be ussing the correct power supply will make the difference even when it's only one volt.

(I receibe some 6N17B and i have everything ready to begin with the mini version.)

Thanks Mr. Bajaman, I'll prepare the enclosure soon and post some pics.

DrNomis · Post by **DrNomis** » 08 Nov 2015, 10:02

jesven wrote:Mr. Bajamaaaaan , Dr. Nomiiis, I have it working you're the best of the best, it was a faulty diode , I'm so exited .! Lol , thank you so much for helping me through this project, I really appreciate it , yo the best .!

No worries at all, I had a feeling that it would turn out to be something relatively simple......

DrNomis · Post by **DrNomis** » 08 Nov 2015, 10:15

jesven wrote:it sounds a little bit fat , but actually, i like it, anyway I have a very fat sounding pickups (chinesse ones) I guess it won't sound that fat with any other guitar, also, I think it may need a little bit more gain ... Not entirely sure about that .... I think I like it as it is (it sounds really good , even using the cheapest and worst tube brand on the market ) , may be ussing the correct power supply will make the difference even when it's only one volt.

(I receibe some 6N17B and i have everything ready to begin with the mini version.)

Thanks Mr. Bajaman, I'll prepare the enclosure soon and post some pics.

Provided that you use tubes with the same pin-outs as the 12AX7, you'll find that different tubes will give different distortion characteristics, the higher the voltage-gain (mu) of the tube the more distortion you will get, a 12AU7 typically has a mu of about 19, a 12AT7 about 60, and a 12AX7 about 100.....

You might need a larger value heater current limiting resistor if you want to use a 6N17B tube, that's because the 6N17B needs a 6.3V/400mA heater supply whereas the BRTO was designed for tubes that need a 12.6V/150mA heater supply, so, you might need to change the 33 Ohm/5W resistor to something like maybe a 68 Ohm/5W resistor to get 6.3V on the 6N17B's heater......

theodorus · Post by **theodorus** » 30 Nov 2015, 18:20

Hi, I just made two of these because I was looking for an alternative for my GGG tube-driver which is a bit noisy and big , I stumbled on this thread (took me a while I must admit ) and decided to make on ( actually two

)
I'm very pleased how they work and sound and want to thank you for designing and sharing the info on this great pedal

Some pictures (yes ,it needs some paint and lettering) :

Greetings from Holland
Theo

bajaman · Post by **bajaman** » 01 Dec 2015, 02:10

Hello Theo

Very nice build pictures - glad you like it too!
cheers
bajaman

287m · Post by **287m** » 01 Dec 2015, 13:13

hello bajaman
where layout for 1590BB? look missing/move in your photobucket
thanks

vmaxvmax · Post by **vmaxvmax** » 05 Jan 2016, 15:05

I have just built this using one of bajaman's pcb combo's.

It sounds great! Really nice boards - thank you bajaman. This unit beats all of the overdrive/distortion pedals I have built and owned over the years. It has replaced my Klon clone, and Timmy on my board.

It compliments a tube amp driving the power stage hard. I use an 18watt clone I built.

Do not hesitate to buy the boards from bajaman!

It is very quiet and has no real switching noise.

I have an OPA 2134 Burr Brown in there - I tried various op-amps and with my cloth ears didn't discern much difference other than mild changes in background hiss.

It seems to be punchier with an ECC 81 in there. I tried several ECC 83's including JJ's, an old Mullard, a heap of 'Marshall' '83's and a heap of GT's (inc their so call M for 'Mullard). All of the ECC83's seemed somewhat softer with more distortion.

The ECC 81 has more punch and plenty enough distortion (to my tired old ears).

I did not change the bias voltage - anybody offer comments on resistor values for the ECC 81 as opposed to the stock 47k values?

bajaman · Post by **bajaman** » 06 Jan 2016, 00:26

yes - still my go to drive pedal after all these years

bajaman · Post by **bajaman** » 06 Jan 2016, 00:28

latest OSH park boards available now

DrNomis · Post by **DrNomis** » 06 Feb 2016, 05:21

Those new PCBs look great, are they priced the same as the original, bajaman?

I might see if I can order a PCB set this coming fortnight......

Mbas974 · Post by **Mbas974** » 07 Feb 2016, 13:49

In adding a tone-stack to this pedal, what should fit as the best solution ?
A solution like BB-Preamp can be a good option ?

Any suggestion ?
Thanks is advance.

bajaman · Post by **bajaman** » 07 Feb 2016, 21:06

In adding a tone-stack to this pedal, what should fit as the best solution ?
A solution like BB-Preamp can be a good option ?

Any suggestion ?
Thanks is advance.

Don't do it

BAJA Real Tube Drive pedal project [documentation]