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  1. Ylli

    Guitar Level To RCA Line Level Preamp

    The two 10K resistors provide 1/2 Vcc to BOTH opamps. A2 is not used as a buffer for that voltage - do not short the capacitor on the output of A2. Yes, the output of A2 is 9.1% of the input signal, and it's signal is fed to the inverting input of the 1458. The phase is such that it follows...
  2. Ylli

    Guitar Level To RCA Line Level Preamp

    Looks like A2 may be 'bootstrapping' the input impedance of the 1458, and that bootstrapping may have a variation over frequency. In which case you do NOT want to bypass that 10K with a capacitor.
  3. Ylli

    Need help with sourcing a resistor for a Peavey XR800F Plus

    The first one (without a visible designation) doesn't look too good either.
  4. Ylli

    Need help with sourcing a resistor for a Peavey XR800F Plus

    When you post excerpts from the parts list, it would help if you would let us know what resistor you are talking about. In this case it could be R130, R140, R230, R240, R270, or R273. The 0.22 ohm resistors you mentioned could be some or all of these: This appears to be a Class H...
  5. Ylli

    Newbie needs help determining correct voltage for this circuit

    At 240VAC input, the voltage across those 630V caps will be near 680 volts.
  6. Ylli

    Newbie needs help determining correct voltage for this circuit

    120 VAC only!. With 240VAC input, the voltage across the capacitors exceed that 630V rating .
  7. Ylli

    Comedy Thread

    Unexpected quenches were always exciting.. :)
  8. Ylli

    Comedy Thread

    Very reasonable description DP. I spent 5 years in CT hardware engineering and 33 years doing MRI hardware engineering (Analog/RF).
  9. Ylli

    Comedy Thread

    NO!! A Cat scan is NOT a type of magnetic resonance imaging. A CAT SCAN - Computer Aided Tomography uses X-rays to create a 3D image of tissue density . An MRI Magnetic Resonance Imaging uses a magnetic field and radio frequencies to image tissue chemistry. Totally different imaging procedures.
  10. Ylli

    Comedy Thread

  11. Ylli

    Op Amp Circuit Gain Does not Match LTSpice Simulation

    Danadak, recheck your schematic. You have the feedback resistor connected to the op-amp output, it should be connected to the top of the inductor.
  12. Ylli

    Gale 3090 Subwoofer repairable? Burning smell on circuit board - speaker is fine ( I think )

    From a bit of research, it looks like this is the same as a Sven HA-675. R331 and R332 are part of the filtering for the+/-12 volts that is used on the input board. Let's start by unplugging the cable from the amp board (the one that goes to the input board). Using your meter's ohm's range...
  13. Ylli

    Series Resistor in Place of Line Distribution Transformer

    Let's look at some numbers. The AMC+60 can deliver 60 Watts into a 4 ohm load connected to the 4 ohm output port. It is also spec'd to deliver 70 Vrms into a minimum impedance of 83 ohms. Let's put a 75 ohm resistor in series with an 8 ohm speaker and see how much power the amp will be...
  14. Ylli

    Series Resistor in Place of Line Distribution Transformer

    NO. It cannot. Using a series resistor will introduce more attenuation than you would get from a long cable run connected to the 4 ohm output port. If you want to use the 70V or the 100V ports, then get yourself an appropriate transformer.
  15. Ylli

    Series Resistor in Place of Line Distribution Transformer

    That amplifier has a 4 ohm output - why not just use that. It will efficiently drive a 4 ohm, 8 ohm or even a 16 ohm speaker.
  16. Ylli

    Scratching My Head w/ Crown CDi 4000

    Something I should have mentioned earlier: You are working on the AC line side of a SMPS. This circuitry is not isolated from the AC line and there are lethal voltages present. Even the V_BULKRTN node can have a voltage on it as long as the unit is plugged in even if it is switched off. Use...
  17. Ylli

    Scratching My Head w/ Crown CDi 4000

    U16, a LM393 dual comparator, has open collector outputs (pin 1 & 7). They can only pull down, not supply any current. It will pull down and disable the +15V_CTRL line if it detects the AC line is too low (U16B) or V_KSTART is too low (U16A). If U16 is not in the circuit, this fault detection...
  18. Ylli

    Scratching My Head w/ Crown CDi 4000

    Try lifting one end of D27 (or remove it if it is SM) and see if TP31 goes to +32 volts. If that does not allow TP31 to come up, then it almost has to be a bad U16, and you will have to lift pin 8 (or totally remove it - the unit should actually operate with U16 removed).
  19. Ylli

    Scratching My Head w/ Crown CDi 4000

    7 ohms is a problem. There is no path for V_KSTART through the transformer as long as D26/D27 are not defective. And 7 Ω is way too low even if you are forward biasing the Zeners. The only place I can see that might cause this is a defective U16 or a shorted C61. I understand changing a SM...
  20. Ylli

    Scratching My Head w/ Crown CDi 4000

    The V_KSTART (TP31) is used directly by one op-amp - U16. If that amp has a VCC/Gnd short it would also pull TP31 to 0 V. If C196 were shorted, I would expect to see 0.6 volts at TP31 (drop across D27).
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