Rocktron

[Valvehead]

Check the output voltages on pin 3 regulators 7815/ 7915/ 7805/ 7905
If no proper voltages, it is best to replace the appropriate regulator with the new.

If there is still no corresponding voltage, most probably a defective some of the tantalum 10uF or the ceramic is 0.1uF in filtering.
It is unlikely that some of the ic peripherals are defective.

I have nothing coming out of those 4 regs. just some mV . So the problem should be before those in the circuit ?

[The Dude]

What voltage is feeding the regulators? What AC voltage do you measure at the power in jack when connected. If power in is good, but nothing at regulator inputs, something is likely open. If your power is low even at the AC input, something is drawing excessive current. Does the wallwart get hot? It could be that a regulator is shorted input to ground (or something else, cap, diode, etc.).

[vintagekiki]

I have nothing coming out of those 4 regs. just some mV . So the problem should be before those in the circuit ?

4 pin DIN Power JA1.

Check that pins 3/4 (JA1) has a connection to PCB gnd (no chassic gnd).
If there is no connection check FC1 conductive capacitor .022uF

Check fuse 3A slow blow, power switch SW1.
Is there an add wire between W3 and W4, which provides power between connectors from JA1, power switch SW1 to *W4 PCB contact. The detail is located at C13 (100uF) near U23 (LM317T)

If they are correct, they would have the voltage between the contact *W4 (PCB) and PCB gnd. This is the voltage coming from the 4 pin DIN Power JA1 connector.
All voltages are measured in relation to PCB gnd (no chassic gnd)
The connection between PCB gnd and chassic gnd is over R28 (10 Ohm) and C27 (.01uF)

[Valvehead]

What voltage is feeding the regulators? What AC voltage do you measure at the power in jack when connected. If power in is good, but nothing at regulator inputs, something is likely open. If your power is low even at the AC input, something is drawing excessive current. Does the wallwart get hot? It could be that a regulator is shorted input to ground (or something else, cap, diode, etc.).

the wall wart is 8.5 vac --tested.

when unit is on ...nothing at the jack .01 vac...power switch tests good...wall wart isnt hot .

[Valvehead]

4 pin DIN Power JA1.

Check that pins 3/4 (JA1) has a connection to PCB gnd (no chassic gnd).
If there is no connection check FC1 conductive capacitor .022uF

Check fuse 3A slow blow, power switch SW1.
Is there an add wire between W3 and W4, which provides power between connectors from JA1, power switch SW1 to *W4 PCB contact. The detail is located at C13 (100uF) near U23 (LM317T)

If they are correct, they would have the voltage between the contact *W4 (PCB) and PCB gnd. This is the voltage coming from the 4 pin DIN Power JA1 connector.
All voltages are measured in relation to PCB gnd (no chassic gnd)
The connection between PCB gnd and chassic gnd is over R28 (10 Ohm) and C27 (.01uF)

pin 3/4 are not grounded to chassis

fuse good

w3 to w4--ok

. 02 vac fro W4 to chassis ground

r28 / c27 test ok--they are getting to ground

[Enzo]

Go right to the pins of the power jack. Does your 8vAC remain when power switch is on, or does it disappear to zero?

[Valvehead]

pretty much zero Enzo .....power switch on

[Enzo]

So you do get 8v at those pins with power switch off? I am trying to be clear that the voltage is present until the switch is turned on, or not present AT THE PINS ever.

Your adaptor makes 8vAC, but unplug from the wall and measure resistance between the active pins. An open transformer winding can still APPEAR to make 8vAC but any load makes that collapse. Just as a guitar amp can make noise when a cord is plugged in with no guitar.

[Valvehead]

So you do get 8v at those pins with power switch off? I am trying to be clear that the voltage is present until the switch is turned on, or not present AT THE PINS ever.

Your adaptor makes 8vAC, but unplug from the wall and measure resistance between the active pins. An open transformer winding can still APPEAR to make 8vAC but any load makes that collapse. Just as a guitar amp can make noise when a cord is plugged in with no guitar.

i get no AC at the pins at the in jack of the preamp---switch on or off.

not present at the pins ever . in the amp


wall wart un plugged from the amp---has 8.5vac.....and 1.8Meg ohms at the active pins---un plugged from the wall---2.0 M ohms

[Enzo]

It sounds like your adaptor is open. Do you have a AC adaptor of some sort that produces about 9v that we could somehow cobble into this circuit for tests?

If you get 2 meg between pins 2 and 3/4 of the adaptor, then it is open.

[vintagekiki]

pin 3/4 are not grounded to chassis
Is there a connection between pin 3/4 and PCB ground?

fuse good

w3 to w4--ok

. 02 vac fro W4 to chassis ground

r28 / c27 test ok--they are getting to ground

It is assumed that the Rocktron AC adapter and his connecting cable is correct and adapter it has the prescribed AC voltage on its DIN connector.

Question

How much ac voltage is between pin 3/4 and pin 2 DIN Power JA1 measured when

a. when Power switch SW1 is OFF.
b. when Power switch SW1 is ON.

a. If there is no ac voltage when Power switch SW1 is OFF, defective is Rocktron AC adapter, connecting cable between AC adapter and DIN Power JA1 or conductive capacitor FC2

b. If the AC adapter for Rocktron is correct, its DIN connector produces the prescribed ac voltage, and when Power switch SW1 ON does not have ac voltage, check

- fuse (3A slow blow), fuse holder F1, connection between fuse holder F1 and PCB.
- power switch SW1
- conductive capacitor FC3
- Diodes D5, D10, D11 or some of the capacitors in the circuit U21, U22, U25.
- voltage multiplier D6-D9 or some of the capacitors in the circuit U23
- voltage multiplier D1-D4 or some of the capacitors in the circuit molex tube PCB (CM3 pin 8)
- voltage multiplier D1-D4 or some of the capacitors (C2, C3) in the circuit U19, U20

[Valvehead]

It sounds like your adaptor is open. Do you have a AC adaptor of some sort that produces about 9v that we could somehow cobble into this circuit for tests?

If you get 2 meg between pins 2 and 3/4 of the adaptor, then it is open.

i think you got it--hooked in that 9v / 250ma wart---it powers right up....looks like i shorted the new one.Ill order another

thanks for your time boys !!!!!

[vintagekiki]

The user manual is a miracle

Power requirements = 9VAC/ 3.4A

https://www.manualslib.com/manual/670710/Rocktron-Voodu-Valve.html?page=107