igor sontec 1 channel random bypass on power up

[alexgg]

hi

I have an igor sontec which sometimes, not always, but mostly when cold, ie often if switched off short period or overnight  , starts up with 1 channel in apparent bypass.

it usually starts working after some warmup period, almost always after I take the lid off to fiddle with / examine it.

its really annoying, if I go look inside it will usually start working again + you think its fixed. it can start stop working just during use, if you are changing settings, I don't mean really shaking the unit, I thought maybe something loose ? kind of checked the molex connectors.

sometimes flicking the bypass switch on/off worked.

I thought maybe it was bypass switch, I resoldered this, + have now actually hardwired to circumvent any possibility of faulty switch.

once you get it working it usually stays working till you power down for a while.

recent mods were doa outputs added, + resistors changed to make it +/-6db. I think it did this before any mods.

is there anything potentially obvious to look at ?

 

[rob_gould]

I can't see the schematic on my phone, but if it is relay bypass, I'd start checking the relay which does the bypassing, and the components and solder joints around it.

 

[alexgg]

I can't see the schematic on my phone, but if it is relay bypass, I'd start checking the relay which does the bypassing, and the components and solder joints around it.

hi rob

yes its a bit worrying that the array of resistors that I changed for 6db gain/reductions are kind of just after the eq in switch

tbh im not too au fait with the electronics terms so cannot tell you if it is relay bypass or not

the filters themselves each have a resistor on them that I changed and directly from these it busses to the eq in switch.

I cannot tell if just one of these resistors dropping out would totally drop out all filters at once ?? as that is the behaviour, intermittent total bypass mainly on starting up cold.

all of these resistors look pretty bad, ie I had a hard time desoldering the originals and the pads seemed to come up easy but all on a side of the pcb where they are not connected , I just kind of flooded them through + they all pass continuity tests + don't seem loose. not sure what to look for on these as resoldering would be difficult now. they do seem to work fine though except when intermittent eq bypass occurs.

cannot remember if problem happened before changing these in.

I resoldered most else around the switch I think.