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Type: Posts; User: neazoi

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    Closed: Re: Active HF phase shifter?

    I do not mind tuning for this application. But having to change the capacitor for each band is undesirable. Also having to tune both the phase AND the amplitude is undesirable, as it will be too...
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    Closed: Re: Active HF phase shifter?

    Thanks very much for the interesting simulation and ideas!
    I think I will stick to the RC circuit and try to correct any amplitude difference on later stages by ACG amplifiers or by a level...
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    Closed: bfq162 pnp comlementary?

    I need to find a pnp complementary for the bfq162 which is to be used in a class-C HF amplifier.
    Is there anyone complementary in the same package?
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    Closed: Re: Active HF phase shifter?

    What does it mean FvM? That with the values shown it won't have amplitude variations? Wave I understood that right?
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    Closed: Re: Active HF phase shifter?

    You mean replacing the resistor with an inductor and the capavitor with a variable one?

    How about leaving the resistor as it is and replacing the capacitor with a variable one? This won't degrade...
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    Closed: Re: HP 54520A Blown Fuse Problem

    Ok, but I have replaced these caps with other used ones I had and it still blows the problem. So I do not think this is the fault. But thanks for the hint.
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    Closed: Re: Active HF phase shifter?

    Thanks. I will give it a try. I thought the potentiometer and capacitor values were calculated for the required phase shift. Ok it is nice to hear that it can work with other values too.
    It will be...
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    Closed: Re: HP 54520A Blown Fuse Problem

    Well, I desoldered Q3 completely. I also desoldered R12. I also changed C22 and C23 with other used ones I had.
    The PSU still blows the fuse. So thankfully I hope it is something in the HV side and...
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    Closed: Active HF phase shifter?

    This circuit comes from a national semiconductor application note (AN-32).

    Is it suitable for HF usage (1-30MHz)?
    If not as it is, what components values should I change? (I will use a J310...
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    Closed: Re: HP 54520A Blown Fuse Problem

    There is no R13 and R14 in my circuit, instead the line is connected directly to c3. So I think I am going to desolder the q3 as Brian suggested. Maybe disconnect R12 too.
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    Closed: Re: HP 54520A Blown Fuse Problem

    What is the crowbar?
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    Closed: Re: HP 54520A Blown Fuse Problem

    I think I am going to check the mkp caps and the big electrolytics first. First in circuit then desolder them and check their capacitance and resistance with a multimeter. But is would be wiser to...
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    Closed: Re: HP 54520A Blown Fuse Problem

    Always amazingly helpful! :)
    I also suspected the primary side of the PSU. Something overheated, a faulty component that fails after heated, a leaky capacitor, things like this. Problems related to...
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    Closed: Re: HP 54520A Blown Fuse Problem

    I have verified that the main PSU is the problem. I connected the PSU to the mains but disconnected all the output cables from the PSU that power the oscilloscope. The mains fuse still burned out...
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    Closed: BAT41 cheap diode alternatives

    Hi, I am looking for BAT41 cheap diode alternatives for my charge pumps in this circuit.
    I have put there the 1n5711 and 1n5712. Bur all of these diodes cost about 10 Euros per 100 pieces.
    I need...
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    Closed: Re: HP 54520A Blown Fuse Problem

    Yes, correct. The scope works and measures ok until the fuse blows after a minute or so (variable). I noticed that in the SMPSU and in the CRT PSU there are two separate fuses, which are not blown....
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    Closed: Re: HP 54520A Blown Fuse Problem

    Yes the fuse if of the right size (4A)
    The line voltage is set correctly.
    I have the service manual but this does not even have schematics!

    As said, the scope works ok for a minute or so then...
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    Closed: Re: HP54520A problem, first hints

    Brian, I bypassed the RFI filter module shown in this thread. Again after a minute or so, the fuse (I have added in the bypass circuit) blown away. So it is not the RFI filter.

    What else could...
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    Closed: HP 54520A Blown Fuse Problem

    Hi I continue the problem from this older thread
    https://www.edaboard.com/showthread.php?381937-HP54520A-problem-first-hints
    Please read this thread first.

    Now I have removed the mains RFI...
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    Closed: Re: Replacing resistors in small MCU circuit

    1. Thanks I will do this 1k and try it.
    2. I have even tried it without any filter in the past just direct pin output to the scart sound in. It worked but the sound was loud as you said and it was...
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    Closed: Re: Replacing resistors in small MCU circuit

    No if 1.5k is critical for the operation I won't change it, it doesn't worth it.
    How about the other points?
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    Closed: Re: Replacing resistors in small MCU circuit

    Here it is
    154192
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    Closed: Replacing resistors in small MCU circuit

    Hi in this circuit http://qrp.gr/cb2/hardware/schematic_simple.gif I wonder if:

    1. Can I replace R1 with 1K? Will it matter in the RS-232 port signals?
    2. Can I replace R6 with 1k? It is just...
  24. Closed: How does single signal reception work in this transceiver?

    Hi I have designed this transceiver which is capable of upper sideband (USB) detection whereas keeping the LSB in AM mode and attenuated. So sort of single signal reception.
    This works like a charm,...
  25. Closed: Re: Grid leak VS Diode detection in regen set, advantages disadvantages

    Here are some changes I did on the third circuit to hopefully operate on a low voltage.

    1. Instead of using a variometer for L2/L3, use static coils and connect a shunt variable capacitor in order...
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