Please Help !!! fixing a Tone Bone Plexitube Distortion Pedal

[eschertron]

i'm so relieved to hear that. so i hope this should be quite an easy repair. that was my initial thought but then my mind started going for worst case scenarios. :-)
Thanks Bill

My worst-case scenarios always involve me being impatient. So my advice is take it slow. And practice on some broken thing before you approach the pedal - as advised before.

[Iddo]

hi,
some progress made - i've replaced the capactior and the diode. the shop gave me a 1N4007 instedat of a 1n4001 and just like nosaj said it should work.
i was so thriled that it did turn on but it sounds like this - (the changes in volume is because i'm turning the pedal's level knob while recording)
https://we.tl/t-gUqUmUh9rS
then i took out the 4007 and replaced it with the original 4001 and it turned on but still sounds like some power tool :-)
where should i go from here ?

[Enzo]

1N4001 and 1N4007 are electrically the same other than high voltage rating. If one sounds different, it is because one is defective.

[nosaj]

hi,
some progress made - i've replaced the capactior and the diode. the shop gave me a 1N4007 instedat of a 1n4001 and just like nosaj said it should work.
i was so thriled that it did turn on but it sounds like this - (the changes in volume is because i'm turning the pedal's level knob while recording)
https://we.tl/t-gUqUmUh9rS
then i took out the 4007 and replaced it with the original 4001 and it turned on but still sounds like some power tool :-)
where should i go from here ?

To say this could be a very involved repair is an understatement. We do not have a schematic that correlates to your board, so there will be guesses here.
Based on your info provided and the schematic I found I am thinking you replaced C6 on the schematic I have. If that has any similarity to your board then it's very possible U4 is out (I'm not real sure if Voltage regulators handle reverse polarity or not).

The only things I can think of to see if anything can be narrowed down is to pull the tube and see if it's still making noise, see if the switches changed removed the noise(with and with out the tube). Check the voltage at pins 1 and 6 on the tube socket.

Just understand we're working on for example here's an anology. Say we have a map of Florida from the 1950's and we're now in 2019. A lot of things can be very similar but also different.


nosaj

[Helmholtz]

hi,
some progress made - i've replaced the capactior and the diode. the shop gave me a 1N4007 instedat of a 1n4001 and just like nosaj said it should work.
i was so thriled that it did turn on but it sounds like this - (the changes in volume is because i'm turning the pedal's level knob while recording)
https://we.tl/t-gUqUmUh9rS
then i took out the 4007 and replaced it with the original 4001 and it turned on but still sounds like some power tool :-)
where should i go from here ?

Did you verify (by measuring inside the pedal) that the pedal actually gets full 15V from the powerbank? This is also to make sure that the powerbank still works properly and wasn't damaged by the wrong polarity connection.

If so the next step would be to verify the 12V after 7812 regulator which feeds the tube heater and then the +/- 6V opamp supply voltages.

Do we have a valid schematic from Radial?

[Iddo]

ok first thanks a lot about the help everybody !!!
Helmholtz - I am using a 15v stabilized transformer. the Mooer powerbank is fine.
1. now some question for nosaj you said to check the pins - and Helmholtz you said to check the voltage - but how can i check if the power is down - nosaj you said not to check when the circuit is on ?
2. are these voltage regulators - https://upload.wikimedia.org/wikiped..._regulator.jpg
and if so do you mean the one just to the right of the capacitor i replaced (labeled Q1 in my pedal) or the two below the fifth potentiometer from the right (labeled Q7 and Q8) ? or all of them.
3. what is U4 I can't find any U on the circuit ?

i also thought maybe I should reverse the capacitor maybe i put it wrong ?
Thanks.

[Iddo]

clean sound - bypass is working great - with and without a tube - but any distortion sounds horrible - taking the tube doesen't seem to solve anything. as far as i can tell the tube looks ok

[Helmholtz]

I am using a 15v stabilized transformer. the Mooer powerbank is fine.

What do you mean with stabilized transformer? A regulated DC power supply?

1. now some question for nosaj you said to check the pins - and Helmholtz you said to check the voltage - but how can i check if the power is down - nosaj you said not to check when the circuit is on ?

To check operating voltages, the circuit has to be powered.

The Uxs in the schematic of post #2 are designators of integrated circuits. The Qs mean transistors.

I suggest to start with measuring the heater voltage of the tube between pin #4 and #5. Should be 12VDC. Pin #4 and PIN #5 should each measure +/- 6VDC to circuit ground.

As already noticed, the reference numbers/labelling of components may differ from schematic to actual circuit board. And we are not sure if the schematic is valid.

[Iddo]

Hi Helmholtz - yes it's a regulated DC power supply.
regarding the IC's - as far as i can tell there are only two visible - maybe there's also one in the epoxy covered as well - anyway, one says -
O72D
JRC
H023B

and the other reads:
OP725
G #1711
3776788

i am getting approx 14.6V on the 7821 voltage regulator.

now the tube is a crecent so looking from the outside where the joints are made i am going clockwise counting from the hollow of the crecent - so between 4 and 5 there is 14.5V.

nosaj sorry for the question - only continuity is forbidden - now i get it.

how can i check the two IC's ?

[Iddo]

offtopic question

i hope it's ok with you i'd like to know in this schematic -
http://zappers.narod.ru/originalzapper.gif

where the lines cross but there's no dot that marks a connection neither a loop above that marks they are not crossed - like the line going from C1 down - is it connected with the line going down from leg 1 of the 555 ?

and also do you have a recommendation for some basic beginner's guide - book, videos whatever works ?

Thank you

[Jazz P Bass]

The 'old school' way of drawing a line that crosses but does not connect was to put a hump in the line.

The 'new' way is to simply draw the line directly across the other.

If there is not a 'dot', then there is no connection.

[Helmholtz]

i am getting approx 14.6V on the 7821 voltage regulator.

14.6V at the regulator output and more or less the same at tube heaters is close or the same as the power supply input voltage and means that the 12V regulator IC (7812) is defective.

[Iddo]

Thanks Jazz P Bass

[Iddo]

Helmholtz so, do you recommend trying to change the voltage regulator and see where to continue from there ?

[Helmholtz]

Helmholtz so, do you recommend trying to change the voltage regulator and see where to continue from there ?

It is probable that there is more damage than just the regulator IC. If you don't understand what you are doing, you might easily cause more damage.This might be a job for a professional technician with signal generator and scope.