I have built the p06 RIAA preamplifier from Rod Elliot. I cannot get any sound from it. I can only hear a very vague musical signal when the preamp is turned full volume. I have used metal film caps in place of polysterene ones. Do you thing that this may be a problem? What is the diffrenec between MKT caps that have a cubical constructions and those that have the traditional look?
Can I use MKT capacitors for bupass reasons in place of ceramic ones?
Thank you
Can I use MKT capacitors for bupass reasons in place of ceramic ones?
Thank you
If you have bought pcb's from Rod you can always surf to his forum and get help there from him in person.
http://www.instantboard.com/users/rode/
http://www.instantboard.com/users/rode/
I am relatively new in electronics. I have constructed an AKSA 55W and the BOSOZ with no mistakes. I do not have mauch experience so maybe if you connect something wrong it does not blow up or smoke. It just misfunctions. I will let you know of my findings.
If someone knows anything about the caps questions I stated earlier I would like to see their comments.
Thanks again,
without smoke
George
If someone knows anything about the caps questions I stated earlier I would like to see their comments.
Thanks again,
without smoke
George
gchrist said:
If someone knows anything about the caps questions I stated earlier I would like to see their comments.
Thanks again,
without smoke
George
HI George
If they are made from the some material...the difference will be only cosmetic .
But in general the cubical construction gives them more resistance against humidity and the cleaning fluids used to clean the boards.
It depends...MKT are better in the audio band (but no so good as poplypropilene or polistyrene)...the ceramics are better for power supply bypassing in the VHF region (very high frequencies)
Regards
I may have found the problem. Some resistors from Digikey measure differently than what the colour stripes refer to. Instead of measuring 100K I only measure 80K. This happens with the resistors I used in the circuit but also on all of the spare resistors that were left over. The same happens with a 180K resistor.
I do not understand why this is happening. I will buy today new resistors and I will let you know.
Thanks
George
I do not understand why this is happening. I will buy today new resistors and I will let you know.
Thanks
George
In worst case the circuit should produce some sound even with the wrong component values or types [provided the error is not huge, ie: 100k replaced by 100 ohm ]
For 100k resistors : Have you tried measuring them without placing your fingers in contact with the measurement tips of your multimeter or the legs of the resistors?
Be aware that our body is conductive enough to thrash high-value resistor measurement and low-value capacitor measurement
Check if U1 is receiving and outputing any signal, without excess offset. Check same thing for U2
Also check if both U1 and U2 receive the right supply voltages
]For 100k resistors : Have you tried measuring them without placing your fingers in contact with the measurement tips of your multimeter or the legs of the resistors?
Be aware that our body is conductive enough to thrash high-value resistor measurement and low-value capacitor measurement
Check if U1 is receiving and outputing any signal, without excess offset. Check same thing for U2
Also check if both U1 and U2 receive the right supply voltages
gchrist said:
If the resistors that measure OK are lower value resistors ,is because then your fingers resistance in parallel have less influence.
Another possibility ...your mulltimeter can have more accuracy in certain ranges than in others.
But i agree with Eva...this difference in the resistors is no reason for your pre do not work.
Tube Dude was correct. I was wrong. When measuring the spare resistors I touched them with my fingers and that altered the final measurement result. All resistors are OK. On the underside I can see no errors. Everything looks very tidy on the bottom with no bridges between any tracks. The power supply (P05) is working fine and gives me +-15V Dc.
I have connected the - voltage from the ps to the - voltage point on the riaa pcb. The same with the + and ground points. I beleive that on the riaa pcb all the outer connection pins are GND pins and all the inner connection pins are signal pins. That is how I have connected my power and signal wires.
The ICs are ok, they get the correct voltage and have the correct orientation. I do not know where to start and what to measure. Hoe do I measure the input signal from my TT? One point from the voltometer goes to the hot rca inner connector. Where do I put the other point of the voltometer. Do I put it to the GND point of the RIAA pcb at the input location or the power GND on the riaa pcb on the other side of the pcb? I cannot measure the input signal and trace it afterwards on the pcb. I turn the scale on my voltometer to 200mV and I get a reading of 00.3! Is this 3mv or 0.3mV?
What is my ground reference point for measurements?
When I plug the TT signal to another input on my preamp (not thr riaa one) I get signal at the output of the preamplifier which is strong but without riia demodulation. When I pass the TT signal through the riaa module I get silence. You can faintly hear the music in the background.
Finally some resistors when measured on the riaa board give a different measurement from the spare ones that I measure off the board. Other just measure fine on or off the board. Is this ok?
I will look at the capacitors values this afternoon. Maybe a capacitor somewhere has a wrong value. WHo knows I may be lucky!
George
I have connected the - voltage from the ps to the - voltage point on the riaa pcb. The same with the + and ground points. I beleive that on the riaa pcb all the outer connection pins are GND pins and all the inner connection pins are signal pins. That is how I have connected my power and signal wires.
The ICs are ok, they get the correct voltage and have the correct orientation. I do not know where to start and what to measure. Hoe do I measure the input signal from my TT? One point from the voltometer goes to the hot rca inner connector. Where do I put the other point of the voltometer. Do I put it to the GND point of the RIAA pcb at the input location or the power GND on the riaa pcb on the other side of the pcb? I cannot measure the input signal and trace it afterwards on the pcb. I turn the scale on my voltometer to 200mV and I get a reading of 00.3! Is this 3mv or 0.3mV?
What is my ground reference point for measurements?
When I plug the TT signal to another input on my preamp (not thr riaa one) I get signal at the output of the preamplifier which is strong but without riia demodulation. When I pass the TT signal through the riaa module I get silence. You can faintly hear the music in the background.
Finally some resistors when measured on the riaa board give a different measurement from the spare ones that I measure off the board. Other just measure fine on or off the board. Is this ok?
I will look at the capacitors values this afternoon. Maybe a capacitor somewhere has a wrong value. WHo knows I may be lucky!
George
I think I have traced the problem with an active loudspeaker probing the pcb to see where the signal stops. It stops at the legs of capacitor c5 just before the output pin. This capacitor is used to block any DC from the output signal.
One leg has signal ok while the output leg of the capacitor does not. I changed the cap with another one but to no avail.
Should this cap be 1uF or some other value?
Can I bypass this cap?
Regards
George
One leg has signal ok while the output leg of the capacitor does not. I changed the cap with another one but to no avail.
Should this cap be 1uF or some other value?
Can I bypass this cap?
Regards
George
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