Reset your TR707 or TR727 to factory settings.. here is the buttons combination to give your drum machine a fresh new start and to check leds and screen, buttons.
Keep pressed CLEAR and INSTRUMENT/GUIDE and switch on the legendary (yes, legendary) drum machine.
All the lights will turn on, then step leds will blink one by one.
After the light show, press ENTER/CARTRIDGE to proceed with the screen test.
Press the buttons and see the relevant dots show up on the screen.
How to use the TR707 or TR727 to output midi notes, and use it as a midi controller to play other midi modules, samplers (bear in mind its defaut midi channel is 10):
STOP the pattern/track if it is playing.
Enter TRACK PLAY mode.
Holding SHIFT press INSTRUMENT/GUIDE and MIDI CHANNEL.
This procedure will mute the instrument’s internal sounds but will allow you to control external gear using the TR707 or TR727.
To revert back to default, using the internal sounds but NOT transmitting midi notes, and if you have a TR707/727 that is silent, just use the same keypresses again.
Common troubles with these machines:
PSU jack fail, power transistor 78M05 (can be substituted with 78S05), power supply section electrolytic caps.
Dim screen=check the power supply section.
Try different psu transformers too: Roland’s own are recommended, etc
These are machines that heal themselves.. put them aside for a while or leave them turned on for some time and they will fix themselves.