Dan Echo R10 repeats mod issue

[AROLB]

hello there, have recently got into building/light mods and just joined the board. many thanks in advance everyone. posting on a couple of sites to try to resolve this, hope it's ok!

just got a real old dan echo in the post today and proceeded to do the R10 jumper mod on it to push the repeat amounts to infinite. everything was working fine pre mod, repeating to a modest amount.

after taking out the resistor and replacing with a jumper, it now only does a single repeat, and couldn't reverse the outcome by putting back the previous resistor. any ideas? wondered if i did something to the circuit around it when doing the mod.

for your reference here's the pcb at the current state







thanks a lot!
rai

[ElectricDruid]

Welcome!

I'm guessing that R10 is some resistor in the feedback path that limits the maximum feedback level. In which case, replacing it with a jumper would increase the feedback level, which is what the mod is supposed to do.

If it didn't work, I'd guess that the jumper didn't make a good connection. Those solder joints look a bit "blobby" to me. I'd clean that solder off with the solder sucker and re-do them and see if that gets it going.

[bluebunny]

^^ What Tom said.  There's a distinct "ball" instead of a "cone" at one end of that R10 jumper.  Reflow! 

[Ice-9]

Check out the top side of the PCB R10 solder pads, it looks as if the top pad may be damaged. It's hard to see from these pictures but it looks like the top solder pad has gone. If that is the case you will need to find out what it connects to and solder directly.  Looking at the same pad on the bottom of the PCB it dowsn't look like it has a trace from it and this is partly why i suspect the top pad is the one that is meant to connect to somewhere. I will have a look to see if I can find a better picture online or a schematic.

EDIT - Checked out the schematic and R10 connects directly from the centre of the feedback pot to the negative side of C24, The side of R10 that connects to C24 looks like it could be a bad solder joint/short.  I would clean up the solder pads and connect either R10 or a link directly to the repeat pot and C24 pads.

[AROLB]

hello electricdruid - bluebunny - ice9

thanks for taking the time to look at these and providing the great observations!! it is correct that the jumper allows it to feedback to infinity.

ice9 u've absolutely nailed it, the centre of the feedback pot was no longer making a connection due to my clumsy solder work. earlier i put in a jumper direct from there to C24, and now its totally working again and with added infinite repeats  

all your support has been really appreciated. can't wait to build and mod more! cheers

[Ice-9]

Great to hear you have it sorted.