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  1. dorke

    Low Hum Coming From SONY ICF-C218 Clock Radio Speaker? Can It Simply Be Fixed?

    Harald, The hum can be 60Hz(USA ) as well if the rectifier is half-wave. This isn't the case here since the rectifier is full-wave. It will be 60Hz if the hum is coming from the transformer duke duke explained. montecarlo, can you identify the frequency of the hum in any way? may be even audio...
  2. dorke

    Generate 70MHz signal with 5 voltage levels

    Welcome to EP, 1. First question to answer is what modulation scheme are you after? 2. A DAC(Digital to Analog Converter )would probably be your choice.
  3. dorke

    Serial communication problem.

    Yes you did !
  4. dorke

    Kenwood TS 830S

    Thanks Dave, From the SM : V1,the driver Pentode is 12BY7A . So still, HT of 350V looks o.k.(a bit high). Please check all DC voltages on V1 with a DVM ,including the heater(ACV!) per the SM :
  5. dorke

    Difference between phase register and pdc register

    Basically the difference is related to single PWM signal vs. multi-signal PWM. The PDC stands for Pwm Duty Cycle register. It is setting the Duty cycle of any kind(single or more) of PWM output. In the case of Multi-signal outputs PWM applications, the PAHSEx register determines the phase...
  6. dorke

    Kenwood TS 830S

    Swatde kharp. I haven't ever used this SSB/CW HAM radio. Something seems to be wrong with your description: Where did you get the idea that HT of the 12AY7 (dual Triode audio)should be 850Volts? 350V sounds o.k(even a bit high). Did you check the output in CW mode? What are you using to...
  7. dorke

    Serial communication problem.

    I wouldn't use that circuit as it is. First thing is to protect the B-E junction of the Transistor from large negative voltage at "Mark" (Up to -25V theoretically) using a reverse diode. Second thing is to eliminate the "transmitter part". BTW, the transistor can be 2N2222,2N3904 etc. Here...
  8. dorke

    Serial communication problem.

    There is a cheaper solution in your case. What you actually need is "2 receiver only",you don't need Transmitters at all. That means you don't need the DC-DC +/- converter , thus no caps. You can use the MC1489A IC (vcc=5v) that costs 0.7$(1PCS) on Digikey and Mouser. It is an old 80's...
  9. dorke

    Serial communication problem.

    Interesting. I add problems with cheap stuff bought from Ebay/china as well. Learned my lesson,the hard way , and avoid buying ICs from china any more. :(
  10. dorke

    Serial communication problem.

    Looks like you have found the problem,it is the +4V DC shift that the MAX chip (probably,make sure there is nothing else causing that)introduces on the RX lines. That voltage shouldn't be present. This shifts the signal level to faulty value of about 0V (fig 4) Have you tried same scoping...
  11. dorke

    Serial communication problem.

    Some differences are: 1. MAX3232 doesn't have internal pull-ups on transmitters TTL inputs(like you mentioned), thus it's unused inputs have to be tied to VCC or GND. while MAX232 is internally terminated and can be left open. 2. MAX3232 has ESD protection while MAX232 doesn't have it (which...
  12. dorke

    Serial communication problem.

    Hop, No doubt about it, the RS232 is an obsolete thing. I have used it in so many ways,practically have used most of the functionality of the DB25 pins... that was in the mid 80's to mid 90's. Nowadays, the way to go is with USB. Except cases like this one here: HellasTechn has to meet the...
  13. dorke

    Serial communication problem.

    The Max232 and Max3232 are not the same! Which one are you using?
  14. dorke

    Anyone know what this is?

    Armando, Please take care,this equipment can kill you! I hope you know what you are doing!
  15. dorke

    Serial communication problem.

    Bob, You shouldn't be ,not at all! The DB-25 connector is indeed a "design by committee" 'it is a design of the early 60's and held for 40+ years. There was a great need for "supporting signals" to the basic Tx,Rx,GND signals It was designed that way for simplicity and with a global look at...
  16. dorke

    Serial communication problem.

    There should be no problem with your basic design, there is no "collision" and thus no need for buffers etc. You have one transmitter feeding 2 receivers and that should basically work (see drawing). Although it is not strictly according to the RS232 standard. There are some issues with your...
  17. dorke

    Resistors, Capacitors, Zener diodes... Why the funny values?

    Adam, 1. Voltage references which are "powers of 2"like 1.024 and 4.096 may be very useful in many applications like A/D and D/A conversions,they are not "strange" at all. 2. The voltage values of the zener diodes are about the same as the E series. 3. Why do you think 5.6v zener is...
  18. dorke

    Resistors, Capacitors, Zener diodes... Why the funny values?

    A few notes: 1. "you cant start with 0!" that is true in the "theory" of the E series, but a zero ohm resistor is available and very useful in many situations. 2. The 1-2-5 series is also used in currencies denominations, like the Euro ,USD and many other decimal currencies . The main issue...
  19. dorke

    What's an easy way to supply power to a breadboard without using batteries?

    Welcome to EP. What kind of power connection does your motor have? Can you post a photo? A "direct connection" should be used,preferably fused. If your motor actually needs 5A your power supply should be conveniently able to supply that. Use one with higher rating ,say 6-7.5A .
  20. dorke

    Help with modification of radio Sony ICF-SW35

    Well, Even in the case that you are exactly tuned to a FM stereo broadcast, a receiver (don't know about this specific one)may be actually delivering Mono Audio ! That may happen if the station received is far and it's signal is weak, the station's audio may have a lot of noise in stereo and...
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