BAJA Real Tube Drive pedal project

jesven · Post by **jesven** » 29 Oct 2015, 11:16

Well. I can't get it work ,

don't know what to do now, any help .? Must say I'm using 15vA.c/ 1.1.A PS, I changed the led resistor with 1.2k as 1.5 is hard to find in Mexico.
I want to upload images but it says that archives are too big.

Bypassed sound OK
tube gets red when I plug the PS (it remains red when the effect is bypassed)
33k/ 2w resistor gets hot (not burning hot but hot)
status led working OK , (when I touch the track that goes to the long terminal of the led, it turns on.!)
Pedal works bypassed even unplugged and even unplogged when I turn it on, it turns on ! (I mean the status led turns on..
Well may be that's because of the electrolitic capacitors.)
Only little bit of hum noise can be heard when the pedal is on but, no guitar signal.

I suspect that the tl082 might be the problem, as i only own one , i can't tell.
First time I turned it on , a 470uf 35v dropped some juices, may be it got damaged but, if this one gets damaged, the pedal should be turning on and just get muted.?

Hope you can help me, thanks .

DrNomis · Post by **DrNomis** » 29 Oct 2015, 13:21

jesven wrote:Well. I can't get it work , don't know what to do now, any help .? Must say I'm using 15vA.c/ 1.1.A PS, I changed the led resistor with 1.2k as 1.5 is hard to find in Mexico.
I want to upload images but it says that archives are too big.

Bypassed sound OK
tube gets red when I plug the PS (it remains red when the effect is bypassed)
33k/ 2w resistor gets hot (not burning hot but hot)
status led working OK , (when I touch the track that goes to the long terminal of the led, it turns on.!)
Pedal works bypassed even unplugged and even unplogged when I turn it on, it turns on ! (I mean the status led turns on..
Well may be that's because of the electrolitic capacitors.)
Only little bit of hum noise can be heard when the pedal is on but, no guitar signal.

I suspect that the tl082 might be the problem, as i only own one , i can't tell.
First time I turned it on , a 470uf 35v dropped some juices, may be it got damaged but, if this one gets damaged, the pedal should be turning on and just get muted.?

Hope you can help me, thanks .

Sounds like you may have soldered that 470uF/35V cap the wrong way around, when that happens electrolytic caps can go short circuit, what you might want to do is go through all the components on the boards and check that they are all soldered-in correctly, especially the two power diodes in the power supply, it's possible that the TLO82 might have been damaged, have a good close look at the solder-side of all the PCBs, are there any un-intentional short-circuits?, are all the solder-joints good?, are any of the two voltage regulators getting very hot? the 33 Ohm/2W resistor should not get too hot.....

jesven · Post by **jesven** » 29 Oct 2015, 18:06

Well I double checked and then I double checked again , diodes and electrolitic capacitors are soldered as shown by Mr Bajaman on the layout , I thought about bridges so I passed an exacto all the way out and in between all tracks, I'm looking for those horts with a Magnifying glass and I can't find anything yet, I'll check it again , voltge regulators 7815 and 7915 are not getting hot , the resistor gets hot but not too hot , solder joins ... Well, not good but not bad, I use flux every time I solder, that help me not to have those cold solder spots, all of them are shini. I'm not saying I did everything perfect (obviously not) what I'm saying is that I can't find the mistake or mistkes.

*just to make sure about the diodes, the one closer to the power jack is looking upside , the next one just the opposite, on the knob board, the one closer to the tl082 is looking upside, the next one (in the left) is opposite*

Im ussing the left over wires of the components to solder all the boards to the main board (I don't think that should be a problem but anyway) also the in and jack sockets are a little bit bigger than the ones described by Mr Bajaman (I don't think that's wrong too)

Potentiometers are A100k, B10k, A500k from left to right (just to ensure those are not the problem) also I test them with the multimeter they're working OK, when i turn the effect on, the ground sound is affected by the potentiometers, if I turn up the volume, it goes up as well as the tone pot affects the way it sounds (from bassy to treble ).

jesven · Post by **jesven** » 29 Oct 2015, 23:58

Actualy the led turns on when it Touch the negative track of the led can this be a ground issue.? Need help

DrNomis · Post by **DrNomis** » 30 Oct 2015, 00:27

Using your multimeter set to read volts,check the voltages in the power supply, on the output pins of the LM7815, and LM7915 3-Terminal regulators you should read +15V and -15V respectively, if not you might have a blown regulator or a short-circuit somewhere, starting with the first post in this thread, read through them till you come to a list of voltages I posted, compare them with what you read in your build, the list of voltages I posted was to help other members troubleshoot their builds....hope that helps.....

By the way, it's normal for the tube to glow a dull orange and get a bit warm (the dull orange glow comes from the tube's heater)...

jesven · Post by **jesven** » 30 Oct 2015, 07:56

Thanks Dr nomis, i didn't checked all the voltages yet, but the 7815 didn't gave me the correct numbers so I did what should be done, I took it out and soldered a new one, still no sound, but when i touched the 7815 I could hear some radio signals lol, now I have a tube radio

then I realized 1N4007 diodes looked weird , like blown ones so I changed them too, then I plugged the pedal and the 7815 got really hot, as well as the capacitor that spilled some juices before , then I saw the problem ( I pray heavens this solves everything) there was a little short-circuit between the 1n4007 diodes , it blew up the capacitor and also the 7815 then, when I remove the short-circuit, the pedal behaved as before I changed the 7815, no sound when turning it on, not even radio, so I'm guessing that happened before, I'll try replacing those caps at the Ac in as well as the 7815 and the 1N4007 , hope that solves the problem .

Maybe im wrong but when I heard radio I realized that control board is not the problem ass I could turn volume up and down , tone , but not drive, maybe because tl082 is not receiving the correct voltages or maybe that has nothing to do with the drive , who knows.

jesven · Post by **jesven** » 04 Nov 2015, 17:32

Well I could take some pics, as you can se, I can't say my work is neat , but I tried my best to make this pedal, i can't make it work all I have is radio and that's all I have, can't measure pinouts anymore cuz I broke my multimeter, but 7815 and 7915 didn't marked 15v and -15v measuring AC, they marked those numbers measuring DC may be that's the fault, I changed both ,also I changed every electrolitic cap and diode, and still working the same, radio and that's all. I broke A500k pot trying to take a good pic but I re attached it with some solder now is controlling the volume of the radio as it has to. Hope poct could help to identify the fault, sorry for the mess, (old flux could look as some kind of short-circuit or bridge , if a better picture is needed, please let me know)

Cheers ...

bajaman · Post by **bajaman** » 04 Nov 2015, 20:04

On your fifth picture it looks like the 120p capacitor and the 33n capacitor have been placed incorrectly. The 120p capacitor should be connected across the drive or gain pot and the 33n should be connected at the bottom of the board next to the 10k input resistor. i may be wrong but it looks like you have these reversed in your picture

Please get yourself another multimeter and measure the DC voltages on the 7812 and 7912 regulator IC s - you should see 12v DC on pin 3 of each of them (of course it should be a -12v DC on the 7912

). Just set the meter to DC NOT AC voltage scale and connect the other probe to ground.
Once you have confirmed that you have the correct DC voltages on the output of both regulators we can then help you get this pedal working

cheers
bajaman

jesven · Post by **jesven** » 04 Nov 2015, 20:54

Thanks Mr. Bajaman yo the best, I soldered everything as shown in the layout below (the one in the page 1 of this post) tracks are little bit different on the pcb (also posted on page 1) the black thing is the 33n and the blue one next to it is 120p, I have to change or move them .?. The voltage regulators ics measures 15v DC and -15v DC , I'm using a 15 v Ac/1.1A power supply, is it wrong .?

(A weird noise can be heard if I touch the 3 or 4 pin of the tube, like a drain noise, radio can be heard if I touch the resistor on the upper right corner on the control board)
Thanks .

bajaman · Post by **bajaman** » 04 Nov 2015, 22:44

Are you sure that black capacitor is 33n ? It certainly looks like a 120p silver mica type from your picture!
The blue capacitor next to it should be 47p
The two orangey brown capacitors near the gain control should be 10n and 120p (left to right) - the second one certainly does not look like a 120p !
Please confirm what is written on the sides of these capacitors.
You say that the blue capacitor is 120p - that is not the correct place for it - there should be a 47p in that space and the 120p should be across the gain control.
cheers
bajaman

jesven · Post by **jesven** » 04 Nov 2015, 23:19

Ye, sorry its 47 p , from left to right I have a 104 cap(1uf) just upon this one a 473cap(can't remember its value) then the orangies at the top right a 103 and next to it a 121 (from left to right ) then at the lower part the 333 (33p) and next to it the blue one marked as 470. And that's it with the caps , also on the main board I have a 104 next to the ground wire and on the tube board a 473 .

I forgot to mention the polarized ones, both are 22uf 16 v (those in the control board)

jesven · Post by **jesven** » 04 Nov 2015, 23:55

You made me think about the black cap so I changed with other one marked as 0.033N , still working the same

bajaman · Post by **bajaman** » 05 Nov 2015, 04:43

104 is 100n or .1uf
473 is 47n or .047uf
333 is 33n or .033uf
470 is 47p
121 is 120p
103 is 10n or .01uf

These are all correct then

The numbering system for capacitors is: the first two numbers are the value followed by the 3rd number which is the number of zeroes in picofarads.
Therefore 473 is 47 followed by 3 zeroes or 47000pf
It is more common to refer to it as .047uf in the USA or 47nf in Europe

A microfarad (uf) is 1000000 picofarads (pf) or 1000 nanofarads (nf)
470 is therefore 47pf because the 3rd number signifies that there are NO zeroes after the first two numbers.
Hope this explains things for you.

Having established that you have the correct parts fitted and the correct voltages on the output pins of the two regulators, you will need access to a signal generator and oscilloscope to trace the signal path. It would be a good idea to visit a friendly local technician at this stage - he should be able to find what is wrong with it fairly quickly.
If you still want to try and get it working you will need to measure the DC voltages on pins 1 and 7 of the dual opamp TL082 next and let us know they are. They should be close to 0 volts DC if that part of the circuit is working correctly. Pins 8 and 4 of the TL082 should be +12v and -12v DC respectively. Good luck - stay with it - we will get it working for you yet!
cheers
bajaman

bajaman · Post by **bajaman** » 05 Nov 2015, 04:55

You say that the blue capacitor on the tube board is 473 (.047uf) but it is completely different to the 473 capacitor on the control board under the tone control. Are you SURE that it is 473 and not 470 ? ( it looks like the blue capacitor on the control board under the opamp end.

jesven · Post by **jesven** » 05 Nov 2015, 05:10

Ye those are 473 but they came from different stores , the little one is ceramic multi-layer and the green one is a plastic one .
How can I measure the dual opamp pinout .? Just like the voltage regulators.? Or there's another method.?

I noticed that pedal affects the guitar tone, it sounds like bassy when pedal is bypassed that doesn't happen without the pedal, is it normal.?

bajaman · Post by **bajaman** » 05 Nov 2015, 08:33

Ok
You have the right capacitors

If the pedal sounds bassy when bypassed then i think you must have a solder bridge or short near the input connection on the control pcb. Have a good look at this section - the 10k resistor, the 33k resistor, the 1M resistor and the 47pf capacitor. One of these is shorted somewhere - use your multimeter on the ohms x 1 scale and check these four components and their traces on the pcb - you may find it a good idea to scrape between all these components and tracks with a craft knife if you have not got a multimeter that reads ohms.
Keep going
bajaman

jesven · Post by **jesven** » 06 Nov 2015, 06:09

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

jesven · Post by **jesven** » 06 Nov 2015, 07:55

Also I measured the ic voltages those are :

8=0.0v. 7= 0.0v. 6=0.0v. 5=15.11v

1=14.52v. 2=14.52v. 3=-15.01v. 4=-15.01v.

Whats wrong with this .?

DrNomis · Post by **DrNomis** » 06 Nov 2015, 08:14

jesven wrote: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.

DrNomis · Post by **DrNomis** » 06 Nov 2015, 08:43

jesven wrote:Also I measured the ic voltages those are :

8=0.0v. 7= 0.0v. 6=0.0v. 5=15.11v

1=14.52v. 2=14.52v. 3=-15.01v. 4=-15.01v.

Whats wrong with this .?

Looks like the Op-Amp IC might be damaged, have a look at the list of voltages I have posted above this post, those voltages are from my fully working build and are what you should be measuring in your build.....

BAJA Real Tube Drive pedal project [documentation]