Hi all,
I've got a problem with a Nava that was built from someone else.
The hi-hats and the ride and crash are slowly rising to full volume when first triggered by the sequencer.
When they reach full volume they respond normally.
The only thing these sounds share is that they're samples triggered from an eprom and that they have identical trigger circuits and very similar analog paths from the eprom to the output.
Hi-hats are reaching full volume faster than the ride and crash but their behavior is similar.
Schematics are here for all the sounds:
https://www.dsl-man.de/display/DSO/Nava+TR-909+Clone?preview=/17236005/17301561/Nava_v1.0l_Schematics.pdf#NavaTR-909Clone-Schematics:A circuit explanation is here:
http://www.network-909.de/hihatand.htmSo far the only clue I've got is that when I try to measure voltage (essentially putting a very big resistor parallel to the resistor which goes to gnd (say r491 on the hi-hat circuit) the sound completely stops.
Things I've tried:
Replaced the NAND chips and the 4013 ff.
Replaced the 100pF capacitor.
Replaced the actual EPROM on one of these sounds (don't know why just did it in case it did something)
Replaced IC51 (M5218) and C132
Checked q70 on the crash circuit in case it's a fake or malfunctioning..swapped it with the handclap one; clap works fine so q70 is good.
Also replaced the shift register responsible for propagating the trigger pulse from the MCU to the corresponding circuits..
Still nothing..
I'm unsure on how to proceed..
Any ideas would be much appreciated as this is troubling me for quite some time.