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Thread: Silvertone 1484 Copy - 7 Pin Mini Phase Inverter?

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    Silvertone 1484 Copy - 7 Pin Mini Phase Inverter?

    Hey everybody,

    Long time since I last posted here, but I'm starting a new project and I'm wondering if anyone has suggestions for me here on an issue I'm considering. I'm planning on building a copy of a Silvertone 1484 out of a Bogen CHB-100 PA amp. Err, maybe a 1485 since this is also a 4 output tube model. Either way, I'm planning to drop the (useless) reverb and just concentrate on the important stuff from the 1484. I'm thinking though, since the Bogen uses a 6c4 tube as a phase inverter, which is a 7 pin mini single triode, is there a dual triode I can drop into that 7 pin mini socket to get similar setup as the 6cg7 in the Silvertone circuit?

    I've been looking over the data for a tube called a 5964 and it seems like it might work, but I'm wondering if anyone has any suggestions or advice? Ideally I would really like to keep the 7pin mini size if possible, just for its weirdness factor and for the chance to try something new.

    Here are the relevant links for more info:

    Silvertone 1484 schematic: http://www.webphix.com/schematic%20h...ertone1484.pdf
    Bogen CHB-100 schematic: http://www.webphix.com/schematic%20h...gen_chb100.pdf
    6CG7 datasheet: http://www.mif.pg.gda.pl/homepages/f...093/6/6CG7.pdf
    5964 datasheet: http://www.mif.pg.gda.pl/homepages/f...137/5/5964.pdf

    Thanks!

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    Member RWood's Avatar
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    Might I suggest using the 7-pin socket for a pentode input tube (like a 6AU6) and then use one 9 -pin for a second channel input, the other 9-pin for the phase inverter?
    That's what I plan on doing with a CHB-35 (same amp as yours but two fewer 7868s)


    RWood

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    Old Timer olddawg's Avatar
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    Why not completely gut the thing except for the chassis and transformers, replace all of the tube sockets with new ceramics for the correct tubes, and use a turret/eyelet board. In the long run you will spend less money, time, and grief. Shortcut the shortcut. New sockets are inexpensive. All of the old stuff is unreliable and you will be chasing ghosts.

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    Supporting Member loudthud's Avatar
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    The 5964 should work but will need to be re-biased for best performance. Hope you can find a reliable source that is reasonably priced.

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    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
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    thanks for the responses guys!

    I appreciate the feedback. I know exactly what you're saying with the "chasing ghosts" comment, I've done similar re-builds on other amps in the past and it's difficult (if not impossible) to get them to be reliable in some cases. For this project, I'm only planning on using it at home/for recording for now so I'm not too worried about the unreliability factor in the near future. I'm planning on just using it as a testing pad to try new ideas until I get to something I like, at which case I'll probably draw the circuit out and then gut and re-build from scratch. I'm contemplating all the options I have based on what you guys have posted. Once I get it done I'll let you guys know how it turned out!

    thanks again

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    It's been some years, I see. I'm interested in satisfactory application of 5964's...

    I just bought some cheap by odd NOS tubes, 8 x 5964 medium-mu 7-pin twin triodes (common cathode), intended for long-life computer service (no OS obsolescence!, 6J6-similar?), and 5 x 7060 (9-pin medium mu triode+power pentode, 12-15 V filament, more of an RF/IF tube than audio).

    I haven't compared the 7060 pinout to more common triode-pentodes yet, but I don't care about pin compatibility...the common cathode pinout of the 5964 is a little restrictive, but not impossibly.

    Thanks

    Murray

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