Electronics service manual exchange: schematics,datasheets,diagrams,repairs,schema,service manuals,eeprom bins,pcb as well as service mode entry, make to model and chassis correspondence and more. GEM MK-20M ELECTRIC ORGAN.
GEM
Now known as GeneralMusic, GEM sold quite an impressive array of combo organs,among other keyboard instruments. They also marketed consoleorgans under the Galanti name (GeneralMusic's current chairman isMatteo Galanti - perhaps the founder?). GEM stands for 'GalantiElectro Musical'. GeneralMusic bought out Elka in the early1990's (I got most of this company info from MitaTechs). I've never seen a Galanti, but did hear from an owner of one whodescribed it as 'bright blue and really sick sounding'.
| Model P | Jumbo | Jumbo 61 | Mini |
| Mini-Deluxe | Gemini | Caravan | Dakota |
| Europa | Intercontinental | S49 | S61 |
| Rodeo 37 | Joker 61 | Riviera | Challenger |
| Imperial |
The first fewmodels listed here all appear to have virtually the same features,which are almost identical to those of the Vox Jaguar. Unlike theJaguar, however, many(most? all?) of these have only a single 'footage'available, unlike the Jaguar, which provides different mixtures of 16',8' and 4' at various parts of the keyboard (see 'Jaguar' in the Vox section). The Bass Chords feature, however, does seem to operate on the Gem'sexactly like it does on the Jaguar, adding polyphonic treble voices tothe keys in the bass section, with the lowest key pressed sounding abass note in as well. This is a rather unusual feature for comboorgans, which leads me to suspect that the Gem's are somehow related tothe Jaguar. Other than the fact that they're both Italian (likeabout 3/4 of all combo organs!) I don't know what that relationshipis. The Jumbo, Mini, Mini-Deluxe and Gemini all seem to beespecially close cousins, sharing the above traits, plus the straight,furniture-style legs, and a built-in amp with speaker ontop.
Model-P
A Jaguar with reverse-color (i.e., normal) keys? Well, notquite, but they do seem to share many common traits. This has gotto be the most common Gem around. For a long time, I didn't evenknow what the model name was (neither did anyone else!). But I'vesince seen 2 or three nameplates, all with with 'P' shown as the modelname. |
Controls:
- Knobs: On/Off, Bass Volume and Vibrato Speed.
- Tabs: Vibrato, Bass Chords,Flutes, Reeds, Strings, Horns
Here's a sample ofthe sound: Gem Organ.wav Not a bad soundinglittle organ, really.
Also see SandroOliva's GEM web page for some nice pictures of his Model P
And here's a neatadvertising flyer I picked up on eBay. I don't know what dateit's from:
The Model P also appearedunder the 'Briscoe' name. Never heard of them, but it'sobviously a GEM with a different nameplate:
Apart from the 'Briscoe'nameplate, and the ID badge, it's identical to the GEM Model P, stand andeverything. The ID badge, (which is a bit fuzzy in the picture), placesBriscoe Music in Vancouver, BC, and proclaims the model name to be'CHORD', no kidding, just 'CHORD' (those crazy Canadians!). I guess they didn'tfeel like trying to top 'Model P' (which wouldn't have taken mucheffort, anyway).
(Thanks to Lorne for thepictures)
Jumbo
| Similar to the 'Model-P' above, with a red topand black bottom, but has reverse-colored keys, so its' even more likea Jaguar, plus the obligatory built-in amp and speakers, and screw-onlegs. The top has a metal panel on the front, like a Jaguar, that says'Jumbo Gem' on the left, and has numbers (1-29) above all the naturalkeys, and a '+' above all the accidentals, and says 'Transistor' on theright. The nameplate for this guy says 'Model J'. (The Jumbo is the one at the back - thanks to Kirk for thispicture and the ones below) |
Controls:
- Tabs: Vibrato(Red), Bass Chords(White),Horns(Yellow), Strings(Blue), Reeds(Green), Flutes(Purple)
- Knob: Volume/Power
| Tabs - looks almost exactly likethe Mini and one of the Gemini's | The Jumbo and Gemini packed andready to go. The Jumbo looks like a slimmed-down FarfisaCompact, doesn't it? |
And here we see a slightly different version ofthe Jumbo. Aside from the 'normal' color keys, and somewhat smaller speaker grille, it has an additional knob, for Vibrato Speed (thanks to Izzy for the pictures, and Frank for identifying the extra knob) |
Jumbo 61
This appears to be much more than just a 61-key version of the'Jumbo' (above). The panel above the keyboard reads: 'Jumbo 61 GEMR6'. Here's a short description from the owner of the one pictured:: '...very good sounds and a really fast vibrato, it has only8 tones but if you combine it it sounds as good as an Hammond' He says his was built in 1974. Then this impression, submitted by a visitor from Finland: 'A friend of mine owns one, but it'smanufactured in Sweden under the brand Viggen Jumbo 61. It doesn'tsound anything like a Hammond, but you can get some weird eerie soundswhen combining percussion & straight voices and adding a slowvibrato' |
Controls:
- Knobs: Bass Volume, Balance, Vibrato Speed
- Rhythm: Volume, Tempo, Start/Stop, Automatic, Swing, BossaNova, Tango, March, Blues, Waltz
- Bass Voice Tabs: Bass On/Off, Bass Flutes, Bass Strings
- Treble Voice Tabs: Horns, Strings, Cornets, Flutes
- Vibrato: On/Off
- Percussion Voices: Flutes, Strings
- Knobs: Percussion Volume, Percussion Time
Mini
Three, count-em, three whole octaves of combo organbliss! Built-in amp and speaker! Multi-colored voice tabs,and lovely red tolex! Here's a short owner's impression: 'This organ looks really cool because of the slim body andit has chrome legs. The best sound from it has to be the green tabwhich is reeds, sounds like the Farfisa.' NEW(Photo courtesy of Sandro Oliva. See his GEM web page for more on the Mini as well as some excellent pictures of his Model P) |
Controls:
- Knob: On/Off Volume
- Tabs: Vibrato, Bass Chords, Horns, Strings, Reeds, Flutes
Mini-Deluxe
| I guess 'Deluxe' means wood-grain(rather than that nasty old red tolex!) Otherwise, it looks verymuch like the Mini (above) and the Gemini (below).. |
Controls:(I'mnot certain of these - I'm assuming they're the same as the Mini,Gemini and Jumbo)
- Knobs: On/Off Volume, Vibrato speed
- Tabs: Vibrato, Bass Chords, Horns, Strings, Reeds, Flutes
Gemini
| Looks like just another version of the Mini andMini-Deluxe(above). Same 37 keys, same 6 tabs and two knobs, samebuilt-in amp and speaker. This one was available with Redtop/Black bottom, all Red, and Grey top/Dark Grey bottom (like the oneshown). The oscillators on this organ have only one divider, sothere are really only two octaves of each note available. When'Bass Chords' is switched off, the lowest octave plays 'bass' notes,and is monophonic. The bass notes are lower, but are an octavehigher than that found on most combo organs. When 'Bass Chords' is on, the bass octave, in addition to bass notes, alsoplays the same notes as the next octave up (middle octave) |
Gem Mk 10m Manual Online
Controls:
- Knobs: On/Off Volume, Vibrato speed
- Tabs: Vibrato, Bass Chords, Horns, Strings, Reeds, Flutes
| The picture on the left is the same as above forthe Jumbo. The Gemini is at the front. This 'Gemini' seems to be a cross between the Gemini shown above, and the 'Mini'. Same name and similar black/grey color scheme as the other Gemini, but no Vibrato speed control, and the tabs areidentical to the Mini (and the Jumbo) |
Caravan
I'mgoing to assume that this is a GEM, even though there's no brand namedesignation anywhere to be found. My original description for itwas limited to 'with a veneer top'. I don't even remember where Igot that from, but there's that veneer top, so this must be it! Also, in Peter Forrest's 'A-Z...', he describes a Gem Caravan as'Portable single manual (49-note) budget organ withamp/speaker)'. Not to mention that the controls are virtuallyidentical (in function, if not appearance) to the 'Jumbo' and 'Model P'(above).
Theone shown here was found by Brad at MelbourneMusic Once again, I won't even attempt to compete with hiscolorful description, which I lifted and edited (only slightly!) fromhis eBay auction:
'Fromthe country that brought you Farfisa, Elka and Eko, comes yet anothercheesy comestible....The Caravan! This refugee entrant in theMiss Beautiful Organ contest really does outcheese many of the othercheesemakers. Four octaves of sheer bliss.....not only a Vibrato On/Offrocker tab, but a Speed control as well!! Add to this a stunning arrayof user accessible controls.....rocker tabs for Brass, Strings, Reedsand Flutes....you can even use them all together!! WOWWEE!!!! And youthought that modern synths had versatility. There's also a Bass toLower keyboard tab for those great walking Bass lines. On the righthand side of the keyboard are a line output and a headphone output.Unbelievably,it also has a small monitor amp and speaker built in,assuring the user of superb sound reproduction - as only a 5' speakercan do. So what does it sound like? Very similar to theTeisco/Rheem or Eko/Howard organs....CHEESY!!!!!!!'
Whatcould I possibly add to that! I guess I could methodicallylist the controls, in my usual boring fashion:
Controls
Knobs: Vibrato Speed, On/Off Volume
Tabs: Vibrato, Bass Chords, Brass, Strings,Reeds, Flutes
Dakota
From Peter Forrest's'A-Z':
Two-manual combo organ with bass pedals, reverb, tremolo andvibrato. Circa 1971-?
Original price: £365
Europa
From Peter Forrest's'A-Z':
Portable single-manual (37-note) ultra-budget organ withamp/speaker. Circa 1971-?
Vibrato, tape recorder input and output socket
Original price: £62.50 , 1974 price: £79
Intercontinental
From Peter Forrest's'A-Z':
Two-manual(upper 61-note C-C, lower 49-note C-C) combo organ. Mid 1970's
A large and heavy instrument, particularly deep front-to-back, with reverse-colour keys on the bottom 17-notes of thelower keyboard, 17-sliders, and no fewer than 51 chunky rocker switches.
Piano, clavichord and spinet sounds as well
17-note pedalboard
1974 price: £675
S49/Sprinter 49
| Neat looking organ with fourvoices and three presets (Piano, Harpsichord and 'Synthy-Wah'?),Vibrato and Sustain (nice touch, Gem!), plus built-in amp andspeakers. This otherwise attractive package is marred by thepresence of a 'Magic Chord'/Rhythm/Accompaniment feature, which I can'teven bring myself to document. But the pictures are pretty nice,so you can figure it out for yourself. |
(Thanksto Frank G. for the great pictures!)
S61/Sprinter 61
| Looks like the big brother to the Sprinter 49(above). More keys, and apparently morefunctions. Plus, that 'MagicChord'Rhythm/Accompaniment section (ooooh!), and an internalamp/speaker. It also comes in black, like the S49. (Thanks to Larry for the photos) |
Rodeo 37
| Only 37 keys, 5 voices, and that dreaded rhythmunit, but a ewL portable little guy, eh? Nice colors onthose tabs, too! |
Controls:
- Voice Tabs: Flute, Brass, Reed, String, Wah (wah is avoice, not an effect!)
- Vibrato: On/Off
- Rhythm Tabs: Latin, Rock, Swing, and two more unknown (butwho cares?)
- Knobs: Volume, Drum Volume, Tempo
Joker 61
Thanks to Carlosfor these pictures of the Joker 61. I have no more information onit at this time.
Riviera
| Well, it doesnt 'say' GEM anywhere on this guy, but it's clearly from the same stable. (Thanks to David and Paul for supplying these pictures.) |
Controls:
There are also two jacks to the right of the keyboard. I don't know what they do (one is probably for headphones) |
Challenger
Now we're getting somewhere! Multiple footages in multiplevoices, drawbars, tremolo, bass sustain, and percussion! And lookat that collection of creamy colors! Enough to forgive the excessof wood-grain laminate, I suppose. If I'm interpreting the'Legato' tab correctly, it even has multiple-triggeringpercussion! Hey, Hammond - get a clue! (well, I'm probably about45 years too late with THAT advice.)
NEWNormally, the bass section is restricted to just that - no switch to extend thetreble section downward. But apparently when a set of bass pedals isplugged in, the bass keyboard section is automatically switched to do just that- neat! (thanks to A.W. for that tidbit).
It also has a separate Bass outputjack, which can be handy. I think they must have taken the'Tremolo Upper' tab from the Imperial (below), since there's really no'upper' manual.
Controls:
Bass Voices: Subbass 16',Diapason 16', Gedeckt 8', Bourdon 8', Octave 4', Sustain
Effects(red): Reverb,Vibrato, Vibrato Full, Vib. Delay, Bass Drum Bass, Brushes
Knobs: Volume-Bass On/Off,Speed Trem-Vibr., Perc. Volume, Perc Time.
Treble Voices:
16' (black): Bourdon, Cello, Diapason
8' (white): String, Oboe, French Horn, Trumpet,Flute, Clarinet
4' (green): Flute, Octave, Salicet
2-2/3' (purple): Quint, Cimbel
2' (blue): Flute, FifteenthPercussion:
Effects (black): Perc. Coupler, Tremolo Upper, Legato
Voices (white): 16', 8', 4', 2-2/3', 2'Drawbars: 16', 8', 4', 2-2'3,2' (and one more I can't make out)
And now a nice collage of the controls:
Imperial
Imperial I:
| And here we have theImperial. Big brother to the Challenger, and a formidable lookingbeast, indeed!. It has the same voice tabs for the upper manualas the Challenger, but the Bass section is lacking a couple (Gedekt 8',Octave 4'), and the drawbars are missing. But it makes up for itwith several Sustain voices, as well as a nice selecton ofmulti-footage tabs for the lower manual, which is MUCH better than theFarfisa VIP's and Compact Duo. Hey, Farfisa - get a clue!(onlyabout 35 years late with that advice). The one pictured here I'm going to dub'Imperial I'. See the closely related 'Imperial II' below |
Controls:
Bass Tabs: SubBass 16',Diapason 16', Bourdon 8', Tibia 8', Sustain
Lower Tabs: Vibrato Off/On,Reverb Off/On
8' (white): Tibia, Reed, Horn, Salicional, Dulciana
4' (green): Flute, Clarion, Octave
2' (blue): Flautino, PiccoloUpper Tabs:
16' (black): Bourdon, Cello, Diapason
8' (white): String, Oboe, French Horn, Trumpet,Flute, Clarinet
4' (green): Flute, Octave, Salicet
2-2/3' (purple): Quint, Cimbel
2' (blue): Flute, FifteenthPercusson Tabs:
Off 1/Effect 2/Coupler 3, Tremolo Upper,Legato, Perc 16', Perc 8', Perc 4', Perc 2-2/3', Perc 2'Left of upper keyboard:
Red tabs: Bass Drum Bass Off/On, Brushes BassOff/On, Bass Drum Great Off/On, Vib Delay Off/On
Knobs: Vibrato Speed, Vibrato Depth,Volume-Bass Off/On, Balance Lower/UpperRight of upper keyboard: Per.Time, Perc. Volume
Right of lower keyboard:
Reverb Volume(knob)
Sustain: Short/Long, String 8', Celesta 8', Carillon 8', Cembalo 8', Vibraharp 8'
| Note the 'G'-shaped stand - sameas on the Model P | A collage of the controls |
ImperialII:
In typical GEM fashion, there wereat least two versions of the Imperial. The 'Imperial I',described above, and this one, which I'm going to call the'Imperial II'. It differs in the following ways:
|
Controls:
Bass Tabs: SubBass 16',Diapason 16', Bourdon 8', Tibia 8', Sustain
Lower Tabs: Vibrato Off/On,Vibrato Delay
8' (white):Tibia, Reed, Horn, Salicional, Dulciana
4' (green): Flute, Clarion, Octave
2' (blue): Flautino, PiccoloUpper Tabs:
16' (black): Bourdon, Cello, Diapason
8' (white): String, Oboe, French Horn, Trumpet,Flute, Clarinet
4' (green): Flute, Octave, Salicet
2-2/3' (purple): Quint, Cimbel
2' (blue): Flute, FifteenthPercusson Tabs:
Off 1/Effect 2/Coupler 3, Tremolo, Legato, Perc 16', Perc 8', Perc 4', Perc 2-2/3', Perc 2'Black Drawbars: Ped. Vol,Vibr. Speed, Vibr. Vol., Perc. Time, Perc. Vol., Reverb, Balance
White Drawbars: 16', 8', 4',2-2/3', 2'
Right of lower keyboard:
Sustain: Short/Long, String 8',Celesta 8', Carillon 8', Cembalo 8', Vibraharp 8'
Ibought the one pictured here, and can now expound upon it at greaterlength:
Musicstand: It came with a plexiglass music stand that says'Imperial' on it. I'll try to get a picture up soon. I haveno idea how it survived, since it must be removed to close the lid, andthere's no proper place to store it. Alas, the legs didn't fareas well, and have gone on to Combo Organ Leg Heaven.
Voicetabs: Quite a varied pallette indeed. I've only begunto explore them, but most do provide their own distinct sound, and, asyou can see, there's a BUNCH of them!
Voicedrawbars: These are separate and independent voices from thetabs, and, as explained later, are not subject to some of the specialeffects that operate on the tab voices. The drawbars are not asflutelike as you might expect, and are not simply different ranks ofthe same voice (like a Hammond). The 16' and 8' drawbars arerelatively 'flutey', and are different ranks of the same voice. The 4', 2-2/3' and 2' drawbars are ranks of a different, brighter voice,not as flutelike.
Reverb:Actually built-in (not just a switch to control an external reverb, likea Compact Duo or G101), and sounds pretty good. The Reverbdrawbar performs both the On/Off and Volume functions.
Bass voices: Operates like the 'Bass Chords'feature of it's Gem brethren - adds a bass voice (four, actually) tothe regular lower-manual voices, which the bass keys alsoactuate. It's not possible to set it for bass-only unless youturn off all the lower-manual voices (which is a definite option, sinceit's a 2-keyboard instrument). I haven't compared it with any ofmy other organs yet, but the 16' Bass voices go REALLY low, possibly anoctave lower that most bass sections. It has a really good sound,and the Bass Sustain works well, and as expected. It may bepossible to separate the Bass voices by using the 'Bass Output' jack onthe back - I haven't tried that yet.
Sustain.: Mine is wacked out now (actually, it soundsjust like the sustain on my Farfisa Professional, which is also wackedout), so I can't say much about it yet.
Vibrato/Delay:
Vibrato On/Delay Off = RegularVibrato
Vibrato Off/Delay On = DelayedVibrato (vibrato kicks in about 1/2 sec. after keypress)
Vibrato On/Delay On = RegularVibrato.
So the Delay tab operates independently from the Vibrato tab,not in conjunction with it, as you might expect.
Legato/Tremolo/Effect-Coupler(1/2/3)Tab: Ok, this one is real weird, but I'll try to explain it.
Gem Mk 10m Manual Free
- Effect/Coupler 'Off 1', Legato 'On': Converts all Percussion tabs to regular voices - no attack/decay atall, so it effectively gives you 5 additional voice tabs, with anextra bonus - the Perc Vol. controls the volume of these new voices independently of the others, so it's sort of a 'master drawbar' forthe new voices.
- Effect/Coupler 'Effect 2', Legato 'Off': Converts all Voice tabs to Percussion voices. Drawbar voices areunaffected, so you could select your voices with the drawbars, andhave a pallette of TWENTY-ONE different Percussion voices!
- Effect/Coupler 'Effect 2', Legato 'On':Converts all Voice and Percussion tabs to 'reverse envelope'percussion - i.e., instead of sharp attack followed by decay, it'sa slow rise to full volume - time and starting volume controlled by the Perc Time and Perc Volume drawbars - you can get a 'tape-reverse' effect like this - VERY strange! Again, the Drawbar voices areunaffected by this and continue to function normally.
- Effect/Coupler 'Off 1', Tremolo 'On:': Seems to have no effect,
- Effect/Coupler 'Effect 2', Tremolo 'On:': Converts all Voice and Percussion tabs to an on/off 'Repeat' effect (as in 'Won't Get Fooled Again', but not as sharpan on/off envelope - more like a reverse sawtooth wave than a square wave. Repeat Speed is controlled by 'Vib Speed' - 'Vib Volume' has no effect. Vibrato still functions as normal, if selected, and the rate is sync'd with the repeat effect. Again, the Drawbarvoices are unaffected (but Vibrato does affect them normally inthis mode)
Gem Mk 10m Manual Pdf
TheEffect/Coupler tab in position 'Coupler 3' seems to have no effect atall, so that may not be working on mine.