Hammond X77 Owners Corner

[music-man]

i took a look at the schematics and i think what i'm going to do is just take the parts list for the power supply, pinpoint all the rectifier diodes and transistors and start replacing. hopefully that have the right stuff at radioshack.

[indianajo]

You can test diodes and transistors with a DVM. .6v forwards, infinity backwards (at 2 v test voltage). transistor the base is the center of two diodes, per the meter. See Thomas Floyd Electronic Devices the Electron Flow Version 2nd Ed or another trade school or community college text. I like the non-autoranging Craftsman dVM for diode & rectifier checking.
Radio Shack sells rejects, or very near. I used to buy **** from them but there is a serious reason they went bankrupt, IMHO. Good Riddance. Not much better quality at Sterling Electronics or Electrotex in the seventies, but at least the absolute rejects were marked down in special bins. I told you about the **** short life e-caps I bought there. The Mullard tubes from Sterling were okay, also the motorola transistors. The good stuff may have been behind the counter but the counter guy didn't have time to talk to onsey twosey buyers, they had a line of serious customers all the time.
Transistors and diodes, you go by the package size, and polarity in transistors (npn/pnp). MJ15015/16 should cover most organ TO3 packages (metal diamonds) TIP31/32C should cover most TO220 packages (little plastic squares with a metal tab opposite the leads) . MPSA56/06 should cover most signal packages like TO92. Watch pinout on TO92 or little metal cans old ones are EBC newer are BCE. Diodes, 1n4003 should cover most organ rectifiers up to 1 amp, but the big packages 10 mm diameter ones for 3 amps MJR802 works. Zener diodes, there are 60 different voltages, I keep about 7 types and nothing smaller than 1.3 watt. You can stack up several zeners to get any voltage you need, fine tune with .6 v 1n4003 (forwards, not backwards) to suit.
The priveldge of buying first quality parts from newark, mouser, digikey or allied I find to be a real time saver. Worth the $8 freight and the $25 minimum buy. You do have to learn how to use the selector table, instead of talking. Newark has a chatroom for newbies.

[bnelson218]

To bnelson218,
I'm quite impressed with your modification of the X77. How did you sense the velocity for midi on the upper manual? I assume an additional contact must be added since the Hammond ones hit all at the same time - roughly.[/QUOTE]

Actually, I spent quite a bit of time trying to figure out how to make it work. Typically, MFGs use two contacts, like you said, one that closes slightly before or after the other, or in an SPDT configuration, but there's no way to achieve this in the Hammond. And adding a lever switch or leaf switch (like the old Mass-Rowe string bass systems used) under the key is out because there's only 5mm of space beneath a key when depressed. I discarded the Harp Sustain, Brush & Cymbal, and Percussion electronics, which gave me 3 sets of open contacts on the UM, so sending Note-On/Note-Off data was no problem, but how to do the velocity? Then I came across Force Sensing Resistive strips, or FSRs. I buy mine at Digi-Key. Long story short, they sense the force applied and turn it into a resistance output. These, in addition to an Arduino/Mega processor, and some cool code written by a friend of mine in Dublin, and I now have velocity sensitive MIDI.

The pictures are of the MIDI encoder board and an FSR pad, although these are not used in the organ. I chose the FSR strips which are 21" or 22"in length, so 2 are needed to run the length of the keyboard. They're mounted on a 1/8" think felt and positioned so that the front mounting bolt of the key channel strikes them. I get a perfect weight response from the FSR and the strips do not hinder the key action at all.

[bnelson218]

I would never buy parts at Radio Shack. When they first opened their doors they were a good place to shop, especially since they hired geeks like me, giving them a sales staff that knew the difference between an electrolytic capacitor and an audio-taper potentiometer. Actually, I was glad to see them close their doors.
NTE electronics (http://www.nteinc.com/) is a great place to get transistors. They can cross-reference probably 90% of the transistors out there, and I've had good luck crossing the Hammond transistors, and Thomas also. To buy the NTE item, I then go to Parts Express (partsexpres.com). It might sound odd, but I've also had great luck buying parts off Ebay. I'd venture to say that 85% of my X77-B project has come from there. The prices are reasonable and typically you're buying in quantity. I'm dealing mostly with Asian sellers, so the shipping time is longer but also usually free. Just a thought...

[indianajo]

Very creative, use of a rubber pad. Can the computer analog input tell one note from other? My 8 year old TV is beginning to turn itself off when I push the lower volume button, and the DVD player started doing random things when a control was pushed at one year of age. I've been thinking of Honeywell Hall effect sensors and magnets to sense the second contact digitally. They would work great on the white keys, lots of room, but I havn't dissassembled the H100 to figure out the black key mechanism yet. When I bought four sample sensors last month, I stupidly bought the latching ones anyway. The stock on the straight digital output ones is in the UK, $25 line item charge to get them flown in and through customs. Or an analog output Hall effect sensor, you could use quad comparator IC's and a pot per key to set the trigger level.

[bnelson218]

Very creative, use of a rubber pad. Can the computer analog input tell one note from other?

No, the FSRs do not distinguish between notes. That's what I'm using a set of contacts for in conjunction with a keyer system that uses 4066 quad switch ICs. And the FSRs sit on a felt pad, not rubber, and are struck by the front screw of the key channel (from the player's side) which is in the same position for both the white and black keys. The Arduino processor handles converting the resistance reading from the FSRs into velocity, and it also scans the onboard Mod and Pitch wheels, and the pedal sustain switch located on the expression pedal.

[indianajo]

Okay, thanks. I play up to 7 notes at a time and some of them are supposed to be louder than the others, not always the top one. So I'll soldier on with my digital velocity encoding experiment. Hall effect or LED-sensor interruptus, Thanks for the tip on the key channel mount screw. Maybe if I magnetize it? or if I glue a little magnet in the plastic part maybe I'll have a bit more vertical room for a sensor. Honeywell IC's are not as thick as real TO92 transistors, if I lay them on the back.

[music-man]

OK, i posted some time back about a problem that i was having with my bass pedal signal on my X77GT. At high volumes, the pedal notes make an unusual pulsating, almost vibrato like sound. the sound is more prominent with the lowest pedal draw-bar pulled out, and not so noticeable on the other pedal draw-bars (if at all). if you adjust the pedal level and cutoff settings on the pedal gate amplifier very low, it goes away, but your pedal tones are too silent to be heard above the keys.....any ideas what would cause such an anomaly? also, i noticed that there is a potentiometer on the underside of the pedal gate amp (only accessible when the amp is unbolted and flipped over). any ideas what this adjusts? possibly related to my problem? any input would be helpful.

[Guest]

I need help with my Leslie 77L speaker - where does that black wire from the Space/Tremelo Generator connect to?
The wire out of that plug on the power supply is about 6 inches long leading to a blade connector.
A very soft material that looks unused since 1968.

https://c2.staticflickr.com/2/1603/2...134ebccb_b.jpg

[Admin]

Is it a blade connector or a round pin that pulled out of a molex connector?

[Guest]

It is a blade connector for a screw or nut - at a right angle.
I thought at first it connected to the closest signal amp board, but that would be bad design with such a short wire.
Could it be for operating the Space/Tremelo Generator with it unplugged during testing?

[bnelson218]

X77-B Update

Finally got the new control panel back from the powder coating service. It looks great with the textured black finish. The bends are similar to the original panel, although I wanted a little more of a slant where the actual control overlays go for visibility purposes. Doing this on Disability income takes time, but luckily I was able to find the right machine shops--I got the Aluminum panel, laser cuts, bending, and powder coating all for under $100.00, so I'm pretty happy.

[GSDC1100]

Has anyone had any luck by-passing the X77L Leslie (for the X77), and routed the signals through a mixer? I am finishing up the X77 and have to work on the Leslie which as you know for this paring is junk. Even as a Newbie I can debate this with anyone and win. I have PM'd a number of X77 users and the common thread is "don't know what Hammond was thinking" The X77L is ugly, smells, hums, bulky, did I mention ugly, and I would really like to run the X77 with a neo-ventilator through a PA. The only place the Leslie belongs is in the barn under the picture of the dogs at the gambling table, and even that is an insult to this picture.

I have made an attempt to by-pass using the Echo output (should be the same as the main) and running the vibrato, non-vibrato, percussion and pedals through the mixer. The problem is that there is so much internal switching that different switching setting give all kind of problems. Sometimes 2 manuals are active, sometimes 1, sometimes none, sometimes reverb on pedal knocks out manuals, sometimes the same setting gives different results. I have counted at least 2 dozen settings trying to get a hold of this, and it is not making any sense.

Any one who has seen the block diagram on the first page of the service manual knows what a mess this is. I suppose I can spend the next few months trying to trace but the service manual is lacking as confirmed by those who have it.

Has anyone tried and succeeded at this. I just want to play.............

Thank all

[Admin]

I don't know what Hammond was thinking, but it certainly wasn't running an X77 or any other of their organs through PA systems. Like or not the X77L is an integral part of the X77.

That being said, you should have no problem taking the non-vibrato, percussion, and bass channels and running them into a mixer provided that you realize that anything to do with vibrato isn't going to work. That means keeping the manual, pedal, percussion, celeste, chorus, and reverb vibrato tabs in the up position.

[GSDC1100]

I agree that it should be a fairly easy connect, but it is not consistent. I therefore have to conclude that I have some further electronic problems within the X77, and not just switching issues. I know that by-passing a Leslie for a neo-ventilator is just wrong, but having shown the X77L to a seasoned Hammond friend reinforced my attitude that it is a mess. This pairing and the block diagram in the service manual showing the signal routing confirms this was a bad idea, in any world. I wish I had found an easier TWG when I thought about getting back into keyboards. Thank you for your input.