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Unusual diodes on 62 Princeton reissue

Discussion in 'Shock Brother's DIY Amps' started by Uncle Daddy, Apr 15, 2021.

  1. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    I've been looking over some pics of the Chris Stapleton 62 reissue and noticed a diode on each of the 6v6 sockets, running from pin 3 to 7. Any ideas what they do?

    diode cs.JPG

    Interesting how there's no twisted heater wires.
    cs.jpg
     
    fidopunk likes this.
  2. DavidP

    DavidP Friend of Leo's

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    They provide fault protection if the amp is run with no speaker load.
     
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  3. TwoBear

    TwoBear Tele-Holic

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    I see it’s tube rectified, Are they not a fail-safe in case the rectifier goes? I also see a fuse available outside, seems to be for the Mains, as usual, And then there also seems to be a fuse on the heaters the green wires, and also a fuse on the yellow, which should be the rectifier?

    Is this a copy of the black face Princeton that came out with white knobs originally? I think it was volume, tone and maybe speed and intensity for trem? if so that was an absolute Lil killer! I played in a band with a singer songwriter sort of John Hiatt type of guy who played one with the Tele, while I played my silverface Princeton. I had always gotten compliments about my tone, But his was easily way nicer sounding than mine
     
    Last edited: Apr 15, 2021
  4. XTRXTR

    XTRXTR TDPRI Member

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    I'm guessing there is no twisted wires because they rectify the heaters.
     
  5. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    Those fail safe diodes are normally fitted on the rectifier socket. These are on the power tubes.
    Yes, it's a Custom Shop replica of a 62 Princeton.
     
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  6. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    They shunt the OT to ground?
     
  7. danlad

    danlad Tele-Meister

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    They look to be flyback diodes to protect the output section from high voltage spikes from the output transformer. Never seen them referenced to ground through the heater winding though.
     
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  8. NSB_Chris

    NSB_Chris Tele-Meister

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    I don't see that they are rectifying the heaters. One heater tap of the secondary goes straight to a chassis ground lug, and the other goes through the fuse, pilot and then to one side of the socket heater connections. The other socket heater connections (pin 9 of the preamp tubes and pin 7 of the power tubes) are all chained and landed to another chassis lug. Looks to be true to the original except rather than grounding one socket heater connection right at the socket like I think the original did, they collected them and grounded at one point. The 6V6 plate diodes are connected to the most convenient ground connection point which is the grounded heater pin.
     
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  9. lathoto

    lathoto Tele-Meister

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    Enjoy that amp. One of the best amps Fender has released in a long time and probably the best reissue ever!
     
  10. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    The cap on the trem jack socket- is that to prevent switch pop?
     
  11. Urshurak776

    Urshurak776 Tele-Afflicted

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    Wow. If fuses pop you have to break out the soldering iron?
     
  12. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    Just came across this-

    OUTPUT SPIKE PROTECTION
    This modification involves taking three 1N4007 silicon diodes in series with the banded end connecting to pin three of your output tubes and the other end to ground. You use one on each side of a push-pull output. So for example, on a 100 watt Marshall the two tubes on the left, either pin three of either one of those tubes can connect to this diode to ground. And on the other side either pin three can connect to the other set of diodes to ground, as the tubes on either side are in parallel.
    We use 1N4007 silicon power diodes which are effective in suppressing spikes at certain frequencies. These will not necessarily prevent spiking on all amps! There is a fast recovery or high speed diode which will suppress higher frequency arcing however these diodes have a very distinct disadvantage as they alter the tone of the amp! They make the amp sound muddy as they bleed off high frequencies from the output transformer! Trainwreck does not use these kinds of diodes because of their effect on the tone.
    While the Trainwreck method does not eliminate spiking in every amp, it does not effect the tone at all. Every other method which will totally eliminate spiking will have a negative effect on the tone of your amp.
    Another point to remember concerning spiking is that hot biased amps tend to generate more high voltage spiking than properly biased amps.

    https://ampgarage.com/forum/viewtopic.php?t=30328
     
  13. danlad

    danlad Tele-Meister

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    Makes sense now! I had assumed a centre tapped heater winding.
     
  14. robrob

    robrob Poster Extraordinaire Ad Free Member

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    When people tell you that you must twist your heater wires tightly and use 1% 100 ohm resistors for the artificial ground to keep the voltage equal refer them to a chassis pic of this reissue amp. Have them glance at the heater wiring of the very high gain Soldano SLO too.
     
  15. Uncle Daddy

    Uncle Daddy Tele-Afflicted

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    Isn't that a centre tap to the transformer bolt?

    What do you make of this diode and resistor?

    diode2.JPG
     
  16. schmee

    schmee Doctor of Teleocity

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    The heaters are just single wires like some old Fender amps, the other side grounding through the chassis... right? There are no second set of wires to twist.

    Looks damn nice for a modern Fender. They ought to do more like this if they want to be a cut above the rest like they used to be.
     
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