I Have an older valve amplifier. I have replaced all components and valves. Recently one channel will be loud and distorted whilst the other is thin and weak. Always the same channel.
Plugging and unplugging the RCA leads will induce the problem and, after a while, correct it. removing and replacing the input and PI valves will also correct the problem. Its not the speakers nor i believe the OT. It "feels" like it is something to do with the input earth's.
I have on oscilloscope on its way but in the mean time, this is driving me insane.
Help
Plugging and unplugging the RCA leads will induce the problem and, after a while, correct it. removing and replacing the input and PI valves will also correct the problem. Its not the speakers nor i believe the OT. It "feels" like it is something to do with the input earth's.
I have on oscilloscope on its way but in the mean time, this is driving me insane.
Help
http://www.oocities.org/stereo20/dwnloads/stereo20.gif
Hope this helps. my CRO was delivered today, hope this will help me to find the problem, I dont mind spending some money if it helps find the problem. it is ******* me off
Grid leak resistors replaced(my second thought) its something like that.
Take one of the output valves from the loud side (when IT happens) and it makes no difference,
feed back circuit also came to mind
If i new what it was I wouldnt take up your time, I am baffled
Hope this helps. my CRO was delivered today, hope this will help me to find the problem, I dont mind spending some money if it helps find the problem. it is ******* me off
Grid leak resistors replaced(my second thought) its something like that.
Take one of the output valves from the loud side (when IT happens) and it makes no difference,
feed back circuit also came to mind
If i new what it was I wouldnt take up your time, I am baffled
OK, Leak Stereo 20. Two suggestions:
1. gently tap with an insulator (piece of wood?) around the circuit while it is working to see if you can make it happen - the fault may be near where you were tapping.
2. monitor the voltage across C12; it will vary a little as your mains varies. See what happens to this voltage when the fault occurs.
Look out for other symptoms: red valves, hum, whistles etc. The PSU and grounding are the only connections between channels so these is the only ways one channel can affect the other. Could the fault be in the source or preamp?
1. gently tap with an insulator (piece of wood?) around the circuit while it is working to see if you can make it happen - the fault may be near where you were tapping.
2. monitor the voltage across C12; it will vary a little as your mains varies. See what happens to this voltage when the fault occurs.
Look out for other symptoms: red valves, hum, whistles etc. The PSU and grounding are the only connections between channels so these is the only ways one channel can affect the other. Could the fault be in the source or preamp?
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Leak Super 50 and probably your Stereo 20 use a pair of 3.3M resistors in the phase splitter which are almost always bad. Leak, Avantic Beam Echo and EMI all used variants of these circuits with large grid resistors in the LTP phase splitter. EMI used low noise cracked carbon resistors which all need to be replaced IMLE - pretty much true for the various types of resistors used in Leak amps as well.
Sockets, resistors, and capacitors should all be replaced in a Leak amp this old. (I've done a few and learned this the very hard way.)
Sockets, resistors, and capacitors should all be replaced in a Leak amp this old. (I've done a few and learned this the very hard way.)
Man, you are true, but in any case, sometimes components are bad although new. Here, some time ago, some 100K R´s was measured 267K without being use never before. And, some "low ESR caps" was exploded in the drawer also without use.
Check all voltage on electrodes lamps! Must correspond to the datasheet.
Then Check all of the capacitors C3, C4 and C6 - perhaps in them problems!!!!
Or better yet, start with the output of lamps - set the input of each of them sinus 1000 Hz, when all is well - connected to the input of lamps V2, etc.
Then Check all of the capacitors C3, C4 and C6 - perhaps in them problems!!!!
Or better yet, start with the output of lamps - set the input of each of them sinus 1000 Hz, when all is well - connected to the input of lamps V2, etc.
NO! Voltage at tube electrodes varies according to designer goal. It is not necessary that they MUST be the datasheet voltages, in such papers, the manufacturer offers ONE possible value combinations in order to show device performance.
OK, just to help clarify things:
- a datasheet usually describes a component, such as a valve/tube or resistor
- a circuit diagram/schematic, which may appear in a user manual or service manual, shows how the components are used in a particular amp
To fault trace an amp you need the circuit diagram. To design an amp you need the datasheet. If you need to fault trace without a circuit diagram then a datasheet will help, but could mislead too.
- a datasheet usually describes a component, such as a valve/tube or resistor
- a circuit diagram/schematic, which may appear in a user manual or service manual, shows how the components are used in a particular amp
To fault trace an amp you need the circuit diagram. To design an amp you need the datasheet. If you need to fault trace without a circuit diagram then a datasheet will help, but could mislead too.
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