To lose all the voltage across R5,
Either the resistor is faulty,
the tube is in conduction and drawing enough current to drop the voltage.
Or a short?
So if you put the meter on DC volts and put one lead on each side of the resistor we should read the voltage drop that "should" give an idea of current.
Or pull V2 and see if the voltage comes up.
Regards
M. Gregg
Either the resistor is faulty,
the tube is in conduction and drawing enough current to drop the voltage.
Or a short?
So if you put the meter on DC volts and put one lead on each side of the resistor we should read the voltage drop that "should" give an idea of current.
Or pull V2 and see if the voltage comes up.
Regards
M. Gregg
So it looks like the tube or something is drawing current?
The problem at this point is we don't know how much its supposed to drop.
Regards
M. Gregg
I think that, when he worked this a few hours ago, I checked it, I found around 60volts after R5...Does it help ?
Yes,
If you have the tube out and its still low voltage, then it sounds like a short!
Turn it off and discharge the power supply.
Check from each side of the R5 to ground using resistance.
Or from the anode connection of V2 to ground with resistance.
Regards
M. Gregg
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The only other thing,
Is the oscillator is not getting pulses on the grid!
However with the tube out there is nothing to load the R5 resistor?????
Regards
M. Gregg
Is the oscillator is not getting pulses on the grid!
However with the tube out there is nothing to load the R5 resistor?????
Regards
M. Gregg
No, it's OK !!
I tested again : Without the 12AX7, the HT line is a little higher : 177v, and after R2 I have 170v ! And then 170v at the pin 6 of the (missing) tube...
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So :
The V2 tube is a ECC81 Mullard, I got this tuner with his genuine tubes.
You know, first I tested without the tube, and I found the same voltage drop.
I tested it again, just now, and I found no more voltage drop.
Just now, I have put the tube in place, and no more voltage drop.... WITH the tube in place ! Just like when it was working...
And if I power my amp, just to test it.... Yes, the tuner works !!! There's NOTHING to understand in this tuner !!! 🙁
The V2 tube is a ECC81 Mullard, I got this tuner with his genuine tubes.
You know, first I tested without the tube, and I found the same voltage drop.
I tested it again, just now, and I found no more voltage drop.
Just now, I have put the tube in place, and no more voltage drop.... WITH the tube in place ! Just like when it was working...
And if I power my amp, just to test it.... Yes, the tuner works !!! There's NOTHING to understand in this tuner !!! 🙁
Look very carefully at the valve base connections,
Make sure there are no bad connections,
Also that the connections are well apart from each other.
Regards
M. Gregg
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If you have a voltage drop with the tube out of the base,
Then there is a short!
Bend the tube base connections away from each other!
Regards
M. Gregg
Then there is a short!
Bend the tube base connections away from each other!
Regards
M. Gregg
Also check,
Around the IFT and make sure there are no fine wires or solder bridges.
If you look at the drawing,
If the tube is not in the circuit what can draw current?
There is nothing else that can unless there is a short.
If R5 is good. then to get a voltage drop across the resistor current must flow through it. The valve is the only path to Gnd unless something is shorting.
There is a capacitor connected from R5 to ground C12 I think. Its the only other possible path if there is not a short!
Regards
M. Gregg
Around the IFT and make sure there are no fine wires or solder bridges.
If you look at the drawing,
If the tube is not in the circuit what can draw current?
There is nothing else that can unless there is a short.
If R5 is good. then to get a voltage drop across the resistor current must flow through it. The valve is the only path to Gnd unless something is shorting.
There is a capacitor connected from R5 to ground C12 I think. Its the only other possible path if there is not a short!
Regards
M. Gregg
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Yes, perhaps this is the key !
I used this morning a K2 bomb (something to clean contacts) on the valves pins. I think you're right, I have to check very carefully the dry joints on the valve base, and the connectors inside for the tube pins.
After R5, I have now 73v. I think I'll re-solder all the joints of the base...
Does it sound you logical, coherent, this kind of problem just because a bad contact on a pin of V2 ? And Thank you very much for your help !!! 🙂
I used this morning a K2 bomb (something to clean contacts) on the valves pins. I think you're right, I have to check very carefully the dry joints on the valve base, and the connectors inside for the tube pins.
After R5, I have now 73v. I think I'll re-solder all the joints of the base...
Does it sound you logical, coherent, this kind of problem just because a bad contact on a pin of V2 ? And Thank you very much for your help !!! 🙂
Yes try this,
Also if that does not work the capacitor C12 is a possible connection to Gnd!
Regards
M. Gregg
Let us know how it goes!🙂
Make sure the power supply is dead before you work on it.
Regards
M. Gregg
Make sure the power supply is dead before you work on it.
Regards
M. Gregg
Thank you for all !! I'll begin with the contacts of the valve base.
You know, the RF part in this tuner is not large, is deep, and with a few layers, stairs in the components disposition. So, to solder or desolder the small capacitor at the bottom of the stage, capacitor soldered with the small wire of a transformer, when I nearly can't see where I solder... It's a fun game !!!
I'll check all that, this evening or to-morrow.. And if it works after putting it in his case, it's won !!! I'll tell you the results of all that. Thank you very much again !!!
You know, the RF part in this tuner is not large, is deep, and with a few layers, stairs in the components disposition. So, to solder or desolder the small capacitor at the bottom of the stage, capacitor soldered with the small wire of a transformer, when I nearly can't see where I solder... It's a fun game !!!
I'll check all that, this evening or to-morrow.. And if it works after putting it in his case, it's won !!! I'll tell you the results of all that. Thank you very much again !!!
Hello M. Gregg !
So :
- I checked all the contact of the 12AU7 base, it looked ok.
- I re-soldered all what I could in the RF section, without moving the components. From time to time, I stopped to power on the tuner to listen it, it worked again.
- I could finish to put it in his case, I did all the manipulation in a "normal way", without excessive care, and no problem ! 🙂
- I could power it on, let it get his working temperature, and listen it on
, with only a T soft antenna...
I LOVE this little tuner !!! A soft, pleasant, natural restitution. Perhaps it's not the most accurate, sharp, but it's PLEASURE, and it's by far the most important. And I was surprised by the numbers of stations I could hear in good condition and stereo, with a so primitive antenna ! I live near Spain, I could receive more than 45 stations, french and spanish ; some better than others, of course, but with a very good average signal.
For what I could check, it doesn't seem to be in need of an alignment.
I have a few questions :
The original power cable isn't grounded, I changed it with the french standard. Is it a good idea to use a grounded cable, to connect the case to earth ? Do you think it can be interesting for a question of noise reduction ? I have also the impression that, sometime when I use the tuning button, it tickles a little...
Do you think I'll get a sound quality improvement if I replace the 3 capacitors, at the output of the stereo decoder, with good quality film capacitors (MKS, or MKP) ? I'm not in a "collector way" with this tuner, I would like it to be the best it can, without changing his schema or adding components, of course.
But, like this, with the few components I changed (some resistors, a few capacitors in the IF and on the decoder board), I'm really surprised with its sound quality and natural !! A british restaurant isn't the best place to go, but you really know how to design Hifi gears ! 😉 (and how to play rugby, too, I agree...
)
Thank you for all M. Gregg ! (And I apologize for my several and sure english mistakes...)
So :
- I checked all the contact of the 12AU7 base, it looked ok.
- I re-soldered all what I could in the RF section, without moving the components. From time to time, I stopped to power on the tuner to listen it, it worked again.
- I could finish to put it in his case, I did all the manipulation in a "normal way", without excessive care, and no problem ! 🙂
- I could power it on, let it get his working temperature, and listen it on
, with only a T soft antenna... I LOVE this little tuner !!! A soft, pleasant, natural restitution. Perhaps it's not the most accurate, sharp, but it's PLEASURE, and it's by far the most important. And I was surprised by the numbers of stations I could hear in good condition and stereo, with a so primitive antenna ! I live near Spain, I could receive more than 45 stations, french and spanish ; some better than others, of course, but with a very good average signal.
For what I could check, it doesn't seem to be in need of an alignment.
I have a few questions :
The original power cable isn't grounded, I changed it with the french standard. Is it a good idea to use a grounded cable, to connect the case to earth ? Do you think it can be interesting for a question of noise reduction ? I have also the impression that, sometime when I use the tuning button, it tickles a little...
Do you think I'll get a sound quality improvement if I replace the 3 capacitors, at the output of the stereo decoder, with good quality film capacitors (MKS, or MKP) ? I'm not in a "collector way" with this tuner, I would like it to be the best it can, without changing his schema or adding components, of course.
But, like this, with the few components I changed (some resistors, a few capacitors in the IF and on the decoder board), I'm really surprised with its sound quality and natural !! A british restaurant isn't the best place to go, but you really know how to design Hifi gears ! 😉 (and how to play rugby, too, I agree...
)Thank you for all M. Gregg !
(And I apologize for my several and sure english mistakes...)
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