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  1. Jon Snell

    Need help replacing pot for a mpa40bt

    Choose the one you require from this list...
  2. Jon Snell

    I need help in recording a tube amp.

    It is using Line Out as I read it. No need to fuss with loading.
  3. Jon Snell

    I need help in recording a tube amp.

    Just use a high wattage resistor, say 10Wastt, between 4 and 10 Ohms instead of a loudspeaker. You can tap your loudspeaker across the resistor and insert a 2.2Watt vehicle marker lamp bulb in series with the speaker. This will protect the amplifier by supplying a load and attenuate the...
  4. Jon Snell

    Drake 1202-304/4 power transformer for a 1985 JCM 800 50 watt

    The original transformer had these colours for the primary windings. Common - Blue 110v - black 120v - brown 200v - red 220v - orange 240v - yellow Have you got mains going in? Have you any continuity between the primary windings? This will give you an idea of what is what...
  5. Jon Snell

    Issue with schematic and layout not matching concerning fuses

    A 4BA nut runner is what I use, close to 7mm. or I think this may fit they are known by different names. You could just use a pait of pliers.
  6. Jon Snell

    Issue with schematic and layout not matching concerning fuses

    Move your live wires as shown.
  7. Jon Snell

    Issue with schematic and layout not matching concerning fuses

    I would think another explanation for the wrong fuse shown is the mains fuse is within the Shurta IEC connector? If it is, the wiring shown is correct.
  8. Jon Snell

    Issue with schematic and layout not matching concerning fuses

    The mains, 240v comes in from your IEC power connector, Grn/Yel bonded to the chassis using a crimp tab, NOT solder tab! to one mounting bolt of the mains transformer. The Scn tag of the transformer connects to the chassis also. Blue goes to one side of the mains switch. Brown goes to the fuse...
  9. Jon Snell

    Issue with schematic and layout not matching concerning fuses

    A 2A fuse will be for 110volt and 1A for 240v. The addition of the 315mA fuse is probably a good idea, it helps to protect the power supply when the output valves fail.
  10. Jon Snell

    Early 70s Fender Pro Reverb Rice Crispies and High Idle Noise Floor?

    I would check the preamp and driver valves first if the anode load resistors are know to be good. Don't forget, just because it is new and shiny, doesn't mean it is perfect.
  11. Jon Snell

    BF/SF amps, Where does Z come from?

    Point Z is a test point that unfortunately is not included in the service information. My guess is it is a point to measure the AC signal on the anode of the second 7025. Point Y is another test point.
  12. Jon Snell

    how to read the color codes on Mica Capacitors

    Your photo is upside down, take note f the arrow for direction of reading. Should read Brown, Black, Orange and the value is in pF.
  13. Jon Snell

    Electrolytic Cap Shopping

    In the UK, (I have no idea where you are), I use RS or Farnell as wholesalers and CPC as trade suppliers. Not had any issues yet.
  14. Jon Snell

    Can constant fans make speakers too dry and brittle and cause damage?

    No worse than keepimg your gear in a Ford Transit van, like we used to in the 70s. They never suffered from high humidity. Standing water may damage the cabinets but as you have stated, it only got their feet wet so no harm done.
  15. Jon Snell

    Headphone jack on a Carvin X60

    I am not aware of any X60 with a Phones output. Slave out on the early ones yes. Is it original I wonder and yes, valve amplifiers must have a load of some kind to avoid dangerous voltage spikes killing the output valves and transformer.
  16. Jon Snell

    Why we always tell you to make some space on your cathode bypass caps...

    Is this lessons on how to burn your house down?
  17. Jon Snell

    Warped speaker frame - any way to fix/salvage?

    A picture or few of the damage would help! Don't forget the seller has a duty to make good your costs.
  18. Jon Snell

    Reissue Fender-type amps that are reliable?

    I make my own turret boards from my own drawings. An early amplifier I made 9 years ago, came in for service last week and upon removing the covers, it looked like it had been made yesterday and all it required was a new set of output valves. Other repairs that have badly damaged boards, I make...
  19. Jon Snell

    Solder Question

    I have a roll of this and use it for sealing UHF and VHF Aluminium cases to make them RF tight. Good for soldering dirty materials but destroys your soldering iron bit if you don't clean the bit thoroughly! Close melting point to the 40/60 listed...
  20. Jon Snell

    Solder Question

    40 60 is not listed with any of the wholesalers I purchase from. Maybe you meant 60 40.
  21. Jon Snell

    Pre-amp tube in circuit simulator

    The best way to explore this circuit is to build it because you will get an accurate result straight away, instead of calculations that don't mean much, as a valve is a valve and as such each valve varies wildly in specifications, making calculations practically worthless in my experience...
  22. Jon Snell

    AC30/6 (Weber 6V30) Brilliant Channel Fuzzy Noise

    That sounds like too much gain or your input signal is too high for the two stage pre amp. Note the anode of V1a is connected directly to the control grid of V2 via a 500pF and 100pF capacitor, (some call the 100pF a 'bright' capacitor). I would scope the anode of V2b and see what is happening...
  23. Jon Snell

    what do you understand when someone says all the coupling caps ?

    Correct, Coupling capacitors are as you suggest.The 33k is a resistor. The Decoupling capacitors are circled in white Hope that helps.
  24. Jon Snell

    Possibly may need a new amp class.

    Class A. Think of A = always; That means 'always conducting'.
  25. Jon Snell

    Princeton Reverb Tube ring

    If it is not a valve causing this common issue, check for ceramic capacitors that have gone microphonic. Tap each component gently with a biro or plastic rod to check if it rings. Edit: More info added.