Circuit Overview:
I was mistaken re: this being a divide down machine. My apologies. The PE-1000 (which I finally got one in here..number 770098 which I guess is the 98th one made in '77, has 60 keys that each have their own oscillator. It's a rather different one using an scr device it appears and timing capacitor(s) so that it reaches a threshold then discharches the caps it appears to produce a sawtooth type waveform which is largely why these sounds so awesome it appears. Then there is a quad op amp that a section of is used to buffer this event for each of four notes. THe VCF's are a transistor/fet circuit that is not the Korg 35 module but has similarities it appears. I can get near self-oscillation on this one by adjusting the 10K pots on that board. There is a glide function that requires a switch and the native pedal has a toe switch it appears on the end of the CC pedal 10K resistor that subs in the for the panel's lpf control. Anyway it has the Reed, Pipes and Brass preset that can have the attack paraphonically (2 part... there is one trigger for the high and one for the low half of the keyboard. ) adjusted along with the manual button that goes all to knobs. Here you can select the wave type with square and two pulse widths, the native 'saw' and a chorused saw that interjects a 1 second ish lfo into the cards in some pattern of odd notes probabaly. I see the LFO but didn't check phases. Anyway quite a machine, along the lines of the RMI Electra-piano with a cool high/lowpass filter each with resonance and an over filter it appears that is simple to take the edge off as needed. The 'expand' I'm not quite sure what it does. It seems to envelope the highs out longer...?
Service Tips:
Use of a headphone amp recommended in tracking whether the oscillations are happening on each scr. Beware again that glide needs a pedal. Also note that on the one I worked on the increasing of the attack envelope with heavy lfo will cause the note to sound like it's coming in on a random pitch :-). Various oddities that might be confusing on this one. I had someone spill on the one I did and take out a transistor by rust and a couple diodes leaked causing extended play when keys aren't being hit. Get the diagrams and figure out where everything is first! Fortunately they at least NUMBER the connections on the boards and in the diagrams. I had to label some in the schematic to figure out where everything is by tracing with a continutity checker to make sure I had the right potentiometer etc.
Myran Rivand donated this bit of information from his restoration:
I just finished referbishing my PE-1000. Mine had died 30 years ago because a cat desided to mark it. At that time
I had removed the pcb's and cleaned them well, but it still had problems. I worked in industrial electronics and
did printed circuit design and board assembly, so I new how to take care of the boards. At that time I did not
have any schematics, so I just left it as is.
While looking on line for info on the PE-1000, I found the schematics and started to repair the keyboard. The
keyboard switches were good, and most of the circuits worked. Some of the oscillators would not tune properly.
I replaced the tuning capacitors on the affected oscillators, and it tuned fine. I had to replace some capacitors
in the envelope circuits and some of the transistors. I had also had to change some of the SCR's in the oscillators.
The instrument select pushbutton switches were good. Some of the instrument sounds were lower than others, and
I found that the input and output capacitors in the LP preamp were bad. I change the ones on the HP preamp also. Now
all the sounds ( instruments ) are at the same volume, and have the proper tone ( timbre ).
The oscillator circuit is made up with the 324 amp and the timing cap's, resistors, and the SCR.
The block diagram structure for the audio path;
- Oscillator to Gate to VCA to Instrument select to Filter to Output amp.
Most of the components are still available. I found replacements for the transistors and the SCR. I did not look up
the IC amps used for the HP / LP pre's, or the IC's on the filter / control pcb, as mine worked fine. I can look
them up if needed.
I thought I would share what I did and found repairing my PE-1000. Mine is a K4 version with the wood vaneer.
(and regarding tuning he adds)
I found some of the original capacitors, on my PE-1000, to be sensitive if moved. The capacitors were glued to the
SCR's. When replacing some of the SCR's, I had to unglue the cap's, and noticed that some of the cap's became
intermittent. Also some were damaged from the original cause, cat pee. I replaced the bad capacitors with, ' YX
polyester film capacitors '. These a physically smaller, but work well. I have not noticed any drift in the
oscillators. These cap's do not have some of the values as the original cap's, but using the chart on the schematic
you can get values close to what is required.There are holes on the cirucit board for 2 capacitors per oscillator,
so you can combine 2 values to get the value required. I had to change some values so the tuning resistor was not
to close to it's limit at either end. This means that I had enough adjustment to tune properly.
The serial number on my PE-1000 is; 770007. -Myran
Parts: