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  1. Lowerleftcoast

    Mongrel schematic, please review

    Fender's go to was/is 470R. Watch it... the 470k you mention is a common mistake. Since this amp design looks very tweed era, I might try it without. Sound wise the difference with/without is just noticeable. Maybe if you had the amps side by side and could switch between the two. Imo, they...
  2. Lowerleftcoast

    Mongrel schematic, please review

    Datasheet says it is good for 60uF. 40uF is enough for a design like this, imo. OMMV. A lot of old designs ran without screen resistors. Maybe it was the lower B+ that helped save it from having trouble. I look at the original design as a cost saving measure. Less parts and less labor. I change...
  3. Lowerleftcoast

    Mongrel schematic, please review

    Pros: they will work, more filtering. Cons: maybe the touch sensitivity will be less with the 22uF caps. More on power filtering: The power handling capability of the choke must be large enough to handle all of the current in this design. Typical Fender designs place the choke after the OT CT...
  4. Lowerleftcoast

    Ultra Clean Push-Pull EL84 design?

    One of my friends has a Carvin Vintage 16. He installed the Hasserl mods for clean. He uses it as a clean platform and it takes pedals well. Yep, it has a pair of EL84s in it. It has two gain stages before the PI. Besides the tone stack it is not much different than the Pro Jr with the mods I...
  5. Lowerleftcoast

    Ultra Clean Push-Pull EL84 design?

    Cathode biased does not equal *a lot of clean headroom*.
  6. Lowerleftcoast

    Fender 75 amp issues again and again.....

    It is an old test. When you use your meter to check for voltages, you will hear a *pop* when probing the plate. Generally you start with the power tubes and work back to V1. In gain stages the *pop* should get louder as you progress to V1 because of the gain stages amplifying the signal. On the...
  7. Lowerleftcoast

    Ultra Clean Push-Pull EL84 design?

    I would build a Pro Jr. Change the Phase inverter to Blackface ab763 standard values. Reduce the filter resistor to provide more voltage to V1. Change the coupling caps before the EL84s to .047uF. 1k screen resistors on the EL84s. Change the NFB more like a Bassman. Maybe put in a NFB trim pot...
  8. Lowerleftcoast

    Fender 75 amp issues again and again.....

    You could use the 1750M. You would just need an alternate way to supply power to the screens. From the symptoms, I was wondering if only half of the waveform is being amplified. Are both power tubes heaters glowing. Pop test on each power tube? (Pop test all the way to the input?) Maybe try a...
  9. Lowerleftcoast

    Red Knob Twin. External fuse blowing. Burnt resistors/diode on filament supply. 6L6 socket burns. Bad 6L6?

    There is a connection between pins 2 and 3 under normal circumstances. Both have a reference to ground through the CT connections to ground. The socket looks like it has a layer of burnt carbon. If it is cracked or cannot be cleaned well, it should be replaced. If there is a carbon trace...
  10. Lowerleftcoast

    Red Knob Twin. External fuse blowing. Burnt resistors/diode on filament supply. 6L6 socket burns. Bad 6L6?

    Most likely there was HT on the heater wiring because the resistors acted like a fuse. A short inside a tube can do that. Putting the tube in incorrectly can do that. A loose screw or whatnot rolling around inside the chassis can do that, etc. Replace those resistors with 1/2W. When they blow...
  11. Lowerleftcoast

    Crate Vintage Club 30

    Do you have a schematic and layout for the VC30? IDK if this is the correct schematic for your VC30: https://www.thetubestore.com/lib/thetubestore/schematics/Crate/Crate-VC3112-Poweramp-Schematic.pdf If the PCB has numbers near the spades they should match the schematic/layout numbers.
  12. Lowerleftcoast

    Boothill amps 5F2? Anyone build one?

    You can get away with those values, imo.
  13. Lowerleftcoast

    RobRob Deluxe Micro Build - Measured Voltages - Advice Needed

    I can't speak for the 12AU7. The 6V6, in cathode bias, seem to sound best when they are pushed. The 12AU7 is one of the easiest tubes to get a hold of. Not much of loss should it fry. I liked Rob's advice. If it is not red plating, run it past the 100% figure and see how long it can take it...
  14. Lowerleftcoast

    RobRob Deluxe Micro Build - Measured Voltages - Advice Needed

    Is the oblivion blocking distortion??? Did you follow Rob's design exactly with the 470k control grid stopper on V2? The coupling cap after the plate of V1b can be reduced to help quell distortion. (On a 6V6 Deluxe I have reduced that .022uF cap to .0033uF. YMMV on a micro but, I would reduce...
  15. Lowerleftcoast

    Bassman jumpered compression and headroom question

    I think I will recant my statement in the previous post: "Idk if it would be perceptible but, it should retain a few more highs plugging guitar into Normal 2 then jump from Normal 1 to Bright 1." On reflection, it probably retains more signal with plugging into 1 and jumping from 2 to the other...
  16. Lowerleftcoast

    Bassman jumpered compression and headroom question

    I am not so sure the jumping is responsible for the compression. I would think the tube rectifier and primary impedance of the output transformer would be most likely reasons. There may be a small increase in gain. The usual comments speak of a *thicker* type sound. Maybe a little more complex...
  17. Lowerleftcoast

    Tube sets vs mix and match - worth it?

    To confirm your experience, I tried the short bottle TAD 6L6. "Not all that great" is how I would describe them. IDK if all Tad short bottle 6L6 perform the same but the sample I had were disappointing. OMMV.
  18. Lowerleftcoast

    5F4 build issues

    Yep. It is in a safe range. Usually it is expressed as *% of maximum plate dissipation*. You just divide the plate dissipation by the rated wattage of the tube to get the percentage. Congrats on the Hammonator 5F4. Nice looking addition. Your patience and persistence has been a good learning...
  19. Lowerleftcoast

    Loose pickups workaround?

    Probably well positioned extra rubber tubing, or similar. Under or on the sides of the pickup?
  20. Lowerleftcoast

    Beach Boys - Apple Bottom Jeans (1964)

    Everybody get low...
  21. Lowerleftcoast

    Vintage Bass Cab - Modern Speaker - meh…

    The Kappa LF drivers do not deliver the high range that is needed for a bass guitar. The D130 sounds nice, has a high sensitivity rating something like 103dB/1M but the xmax is too small and it is only rated for *maybe* 100W (JBL says 30W but the designer says more). It would be easy for a bass...
  22. Lowerleftcoast

    Boothill amps 5F2? Anyone build one?

    Nice first build. Since you have some experience, read through this: https://www.tdpri.com/threads/just-for-grins-a-draft-optimized-5f1.1088759/ and read through the Rob Robinette sites involving the Champ-ish amps. Also have a look at the 5E2 schematic. It has a choke that could be...
  23. Lowerleftcoast

    Manzanita wood for guitar?

    I know huh! I joke that CBD is the only thing that isn't on the *to be banned* list. To be honest, I appreciate many of the steps taken to clean the environment around here. We have a long way to go for some of the economically challenged areas, but there is the will to clean up the mess that...
  24. Lowerleftcoast

    Custom 4 way switch wiring help

    Check my work... EDIT: I think the pots will still have an effect.
  25. Lowerleftcoast

    Presence control

    I assume you are wanting a presence control on an SE amp. I haven't tried a presence control on a SE amp. I have read it wouldn't be very useful. YMMV. Idk which JCM schematic you are referring to... what is important: there should not be VDC on the presence pot. The cap associated with the...




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