djm800 channel weirdness

Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic

   i have 2 old djm800s here with the same kinds of issues. they're old and crusty, but still usable so i'd like to fix them up a bit.

when in test mode, on some channels, all of the eq pots show the same weird behaviour. as in, channel 2, the high pot, the leds only start about 1/3 the way up, and end 2/3 the way up. that's all that lights up with full travel on the pot. i'd normally think that's showing me that the pot is bad, but when it's exacltly the same on high, mid and low eqs on the same channels, it must be something else.

there's a bit of bleed visible between channels too. changing eq on channel 2 shows small changes in the led meter for channel 3 etc.

anyone seen behaviour a bit like this before and maybe got a pointer towards what i might be looking at?

thanks if you have any suggestions.

Author	Message Topic Search Topic Options Post Reply Create New Topic Printable Version Translate Topic
cravings Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 30 January 2007 Location: Ireland Status: Offline Points: 7441	Post Options Post Reply Quote cravings Report Post Thanks(0) Quote Reply Topic: djm800 channel weirdness Posted: 15 January 2018 at 12:06pm
	i have 2 old djm800s here with the same kinds of issues. they're old and crusty, but still usable so i'd like to fix them up a bit. when in test mode, on some channels, all of the eq pots show the same weird behaviour. as in, channel 2, the high pot, the leds only start about 1/3 the way up, and end 2/3 the way up. that's all that lights up with full travel on the pot. i'd normally think that's showing me that the pot is bad, but when it's exacltly the same on high, mid and low eqs on the same channels, it must be something else. there's a bit of bleed visible between channels too. changing eq on channel 2 shows small changes in the led meter for channel 3 etc. anyone seen behaviour a bit like this before and maybe got a pointer towards what i might be looking at? thanks if you have any suggestions.

kedwardsleisure Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4947	Post Options Post Reply Quote kedwardsleisure Report Post Thanks(0) Quote Reply Posted: 15 January 2018 at 5:54pm
	99% of weird problems on Pioneers are due to beer ingress, or possibly WKD. Or smoke fluid. Sometimes Ribena. Unlikely Guiness. If there's any sign of stickiness inside then I would suspect a rotted track or board via. If you want to go into it at a diagnostic level then you need the diagrams. The pots are multiplexed by analogue switches onto a common eq bus which eventually ends up at the A-D inputs on the main DSP chip. Most of the time spent with the diagrams and oscilloscope will lead you eventually to something that could've been spotted in 2 minutes with a small magnifying glass..a corroded track, rusty connector or faulty FPC.
	Kevin North Staffordshire