'67 Gemini II tune up/sweep out w/pix

Small combos like Mercury and Jet, Jess Oliver's fliptop Portaflex, the Gemini, Echotwin, B25, V4, VT22 up to the 300 watt SVT

'67 Gemini II tune up/sweep out w/pix

Postby firebirdjake on Thu Jul 15, 2010 10:43 pm

Time to whip out the cobwebs so the old girl can kick out the jams !

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Vacuming out the uglies.
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Ahh yes.....doing the Archie Bell & the Drells....
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Never saw a reverb lock in one of these before !
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They mean it, too- also helps to take the fuse holder tip out too for clearance when removing the chassis- it's a tight fit !

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Sweet sounding old Jensen- missing the bell though.
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and here are the obligatory gut shots, Baron :cheers:
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Note the mis- wired diodes at the end o' the chopstick !!!!!!!! :shock: (and the uuugly, wrong value resistor)
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Wild Bill, the Hickok assists in tube righteousness verification !
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"We're Getting Closer to Our Home......" :lol: (BTW- that's a Busch NA, no alcohol consumed while the amp's opened up)
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Getting a Nice Wave at 31.5 watts !
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...and this mangled one flat out at 42 :ROFLMAO:
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Left 'er sideways cause of the "F" der grille cloth.... :oops:
Edit coming momentarily, folks :thumbsup:
and here it be- Sorry, forgot to take an after pic post installation of a heavy duty 15' 3 prong power cord and removal of the good ol' Black Cat "death cap", not to mention correcting the mis wired diodes....plus the one that was working both ways ! Too many AC-DC riffs I guess :lol: . The amp sounds great, punchy and tight with a real nice growl when cranked ! This one breaks up MUCH higher in the "Vs" than my '65 Gemini I, it gets dirty around 9-10 o'clock where this one stays cleanly up to around 2-2:30 or so. Guess Flip Tops will be hearing from me for a handle and some appropriate grill cloth. Wonder what this would sound like with 4- 10"s :twisted:

So here she is, another cute little Ampeg that had a party with a couple newer Fenders on her shakedown cruise :laff:
Keep on tweakin', everybody!

:jam: Jake :mrgreen:
Sua cuique voluptas

"What's polarity mean?" Quoth the "sound man" at a gig 11-16- 2012

Don't die with the Music in You!
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Re: '67 Gemini II tune up/sweep out w/pix

Postby BL!AST on Fri Jul 16, 2010 3:02 pm

Jake, first off those are seriously cool tattoos on you or whomever. You should post a pic of the tube one! Nice job on the G15, I myself have also wondered what one would sound like with 4 10's. I "un"hardwired the speaker in my old Gemini and put in jacks to run the amp into other stuff. I'll tell you what, she was alot louder through a 4x12. Which makes my ponder the question how much speakers have to do with volume.
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Re: '67 Gemini II tune up/sweep out w/pix

Postby firebirdjake on Fri Jul 16, 2010 4:53 pm

BL!AST, speakers (barring a good servicing/overhaul) can make the biggest difference in volume you can get, either way ! IIRC a 3db difference in speaker efficiency (you usually see it listed as XXdb @ 1w /1meter) will represent a doubling of your apparent volume*. You can use this to your advantage by putting more efficient speakers in an amp that just doesn't quite "get it" or a less efficient spkr. setup in an amp you want to "warm up" or have breakup at a lower volume. I have known people who lost the "sweet spot" in their small gig/studio amp(s) by putting in a more efficient speaker- the difference can be astounding !

Those are the tattooed arms of Mr. J. Filamenthead, have to get him to upload a clearer shot- didn't do them myself, but they're cool ! He made another local artist SWEAT over getting them just right :lol: , 'twas before we met. Have to put up pix of the ones I did for his wife, after seeking approval :thumbsup:

BTW- the "Archie Bell & the Drells" line refers to their song 'The Tighten Up'. :ROFLMAO:

Having a Lovely Time.........Jake :mrgreen:

ps) happen to have a set of 25w @ Celestions kicking around- may have to run a jumper wire :twisted: :dunno: but that line may get me a :bich_slap: from the Baron :roll:

*if I mis quoted this, please correct me, going by my fallible memory on that :wink:

BTW- pictures from J.s workbench- he is FAR more knowledgeable and and well equipped than I......but I'm watching VERY closely and searching for a 'scope :)
Sua cuique voluptas

"What's polarity mean?" Quoth the "sound man" at a gig 11-16- 2012

Don't die with the Music in You!
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Re: '67 Gemini II tune up/sweep out w/pix

Postby Baron Von Machinenmann on Fri Jul 16, 2010 8:38 pm

Nice job Jake. 8) 8)


But you haven't lived until you've gigged with a Gemini stack!! :P :wink: :lol:


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Re: '67 Gemini II tune up/sweep out w/pix

Postby firebirdjake on Fri Jul 16, 2010 9:38 pm

.........just wait for the next post from this tube afflicted Linden chassis lover, you tone hound you !

:mrgreen: Jake :thumbsup:
Sua cuique voluptas

"What's polarity mean?" Quoth the "sound man" at a gig 11-16- 2012

Don't die with the Music in You!
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Re: '67 Gemini II tune up/sweep out w/pix

Postby PeterS on Tue Jul 20, 2010 1:46 pm

If I remember rightly, Gemini I is cathode biased and II is fixed bias... do they have similar transformers? In other words, can one be converted to the other by changing the biasing? I hear they are roughly 20 and 30 watts respectively... is that much difference possible due to just a change in bias or does this mean Gemini 2 also has higher B+?
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Re: '67 Gemini II tune up/sweep out w/pix

Postby firebirdjake on Tue Jul 20, 2010 6:24 pm

J. or someone will have to chime in here, but I'll try my best ! :D To the best of my knowledge, the difference is due to the I being Cathode biased (22w/rms) and the II being fixed bias (30w/rms) as you state. The transformers LOOK the same, but tonight I will take a closer look and check the schematics to check the voltages. The change in biasing results in a fairly dramatic difference in sound and when the amp begins to breakup, which is mentioned in a previous post in this thread- they both sound really sweet and do make a GREAT gigging pair with an A-B box to switch between differing levels of breakup at usable volumes. Will respond with B+ voltages after checking- I was wondering the same thing myself!

:mrgreen: Jake.

BTW-BL!AST- Even though the amp looks large enough for 4-10" speakers, I forgot that a goodly portion of the cabinet's grill cloth area at the top is vented for tube/chassis cooling and not dedicated to holding the speaker, so my idea of (maybe) swapping out the baffle board while replacing the grill cloth is just a pipe dream ! There is a divider betwixt the chassis and speaker compartments so there won't be an Ampeg Super- Duper- Reverb coming any time soon unless I find one a Semi crushed or such. Seemed like such an interesting idea, too :whistling:
Sua cuique voluptas

"What's polarity mean?" Quoth the "sound man" at a gig 11-16- 2012

Don't die with the Music in You!
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Re: '67 Gemini II tune up/sweep out w/pix

Postby Baron Von Machinenmann on Tue Jul 20, 2010 8:18 pm

firebirdjake wrote:J. or someone will have to chime in here, but I'll try my best ! :D To the best of my knowledge, the difference is due to the I being Cathode biased (22w/rms) and the II being fixed bias (30w/rms) as you state. The transformers LOOK the same, but tonight I will take a closer look and check the schematics to check the voltages. The change in biasing results in a fairly dramatic difference in sound and when the amp begins to breakup, which is mentioned in a previous post in this thread- they both sound really sweet and do make a GREAT gigging pair with an A-B box to switch between differing levels of breakup at usable volumes. Will respond with B+ voltages after checking- I was wondering the same thing myself!




G2 for rhythm, G1 for organically complex lead tones. Indeed, G1 is cathode bias hence the orgasmic ,er, organic crunch and the G2 is fixed. I seem to recall the iron is different and I'd bet the B+ is a tad higher. I'll have to report back. :wink:
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Re: '67 Gemini II tune up/sweep out w/pix

Postby PeterS on Tue Jul 20, 2010 8:31 pm

Looking at a few schemos I say with not much confidence, I think it might be 390 volts versus 430 volts.
Makes sense, I think 20 vs 30 watts is too large a difference to be due to the bias alone...
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