Boss DM-3 - No delay sound

[Dinosass.Jr]

Hello fellas,

New to the forum but always reading and learning here.
I bought a BOSS DM-3 that powers up and passes signal but there is no delay effect when switched on.
Making tests i found signal til C16, but nothing after that.
Could it be the MN3205 or MN 3102?
I tried to adjust the trimpots but no signal too.
I am grateful for all the help.
Thanks in advance!

[j_flanders]

Could it be the MN3205 or MN 3102?
I tried to adjust the trimpots but no signal too.

RT1 provides bias for the signal going into the bbd chip (mn3205).
There's a (very) small range where it will work.
Slightly above or slightly below the ideal setting you get a very distorted output from the bbd, and just a tiny bit further either way you'll have no output at all.
When turning that trimpot it's best to probe/monitor right at the output of the bbd.

RT2 is the trimpot that removes clock noise from the bbd output.
When set just right, the amplitude of the clock signals, which are out of phase, will be equal and thus when summed they will cancel out.
That 10k Ohm trimpot provides a way to make them equal.
This is more of a fine tuning trimpot and it will not kill the output of the bbd chip, no matter how you set it.

MN3102 provides:
1) the clock signal to the bbd (the 'ticks' it provides, makes the bbd step through its stages, causing the delay)
No ticks is no delay is no output. Check the frequency with your DMM if it has such a setting. Put the rate knob on the pedal at max delay time, otherwise the clock frequency will probably be outside the range of your DMM. It will be around 10kHz with the rate knob at max and around 100kHz with the rate pot at minimum.

2) the correct power to the bbd chip. Check the voltage it supplies to the bbd chip (mn3205) with your DMM

[Dinosass.Jr]

Thank you for all the information J!

I tried to adjust the bias and clock trimpots with a probe on the output of MN3205 but doesnt worked. Also i tried to replace some caps but nothing.
I'll try to replace the mn3102.

Edit: I replaced the MN3102 but no effect. The chip is working cause i've tested in a BOSS CE-3

Thank you again!

PS: Sorry for the bad english!

Edit 02: I found to problem!! Was a solder joint trought R56 and D4. I think the last owner tried to fix something and made that.

Thank a million times for your help!!!

[j_flanders]

Edit 02: I found to problem!! Was a solder joint trought R56 and D4. I think the last owner tried to fix something and made that.

Great, well spotted.