The T1 is an organ/synth split. The organ can be placed across entire keyboard or the "bass" can be selected which gives a couple different decay modes and basic filter controls. See the video T1/C which I haven't played. Sounds like the filter is a bit more interesting perhaps. But the T1 non/c I worked on has a typical diode/resistor/capacitor keying card in back, a TMS3614 divider board next to it, a shielded HBF4727 divider board in front behind keys, and many transistor arrays (48; 4/note) in between on the left side. The TOS board and oscillator is in the middle and under the keys are some boards related to the synthesizer/bass function.
The tantalum capacitors in the rear card (keyer) were dropping out every few minutes on the one I serviced recently. When one fails it WILL kill the whole keyboard. Also a C was missing and bad diodes were found OPEN on the same board but it didn't correlate to that C, the lower one. I reseated it's card too though so perhaps it was just typical card connection issue. Clean all those for sure. Mostly fairly reliable chips in these I believe. Had a few board cracks up top also that had to be soldered together. 16' was on all the time prior to fixing that. ALSO one of the TDA0470's apparently was leaking. Isolate by probing with scope on the diodes near the top on many of the boards which are in series with a resistor to the output. If all gate signals are normal (measured on the traces coming fromt he rear board on the mother board..use a long probe. They should go from somewhat positive to some volts negative when the corresponding key is pressed). and you still have, with tabs selected and all but percussion turned down, lingering sustained note(s) then it is one of the 48 transistor array cards no doubt. Probably the array chip since the other stuff is pretty reliable.
The T2 schematics online have almost all the stuff the T1 has but more of it. So you can get by with T2 schematics I believe to operate on a T1. BEWARE however that a few changes exist. First of all the P-499 board is the P-499B on T2. They rout the second pin from the front of the rear connector on that board (purple wire) to the P-514 board via the interconnect board..whatever it is called. The diagram SHOWS a wire going straight from Pin 9 of the 4023 chip A2, to the buss wire. This isnt' the case though. It goes instead to a 4011 on back rear of P-514 and then out again to the next door brown wire which goes up to the second bass buss wire. Naturally, the first one I work on had no second octave. The reason? The chip that didn't show up in the schematic until I looked at the P-514 and traced the wires finally to there through the sad little tight bundles. lol. Isn't that somethin'? Amazing how many of those 'random' times I just happen to fall into the hole of poor documentation isn't it? Well hopefully someone else won't have to now. Many tantalum caps blow out on the keyer board also. Replace them all with regular 1uF 50V units. Tantalum no longer necessary as tolerences are adequate usually I believe.
Lots of discrete parts but some oddball ones. Ask if you need a specific part. I'd like to find a source for the odd slider caps. And the space age knobs.
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