Channel strip mute issue

[pb]

hi all,

i have a TAC Scorpion II, 30-4-8-2 Configuration.

i am part way through re-capping the channels, 25 completed so far.

everything is working on the desk, with one exception.

on one of the channel input (S1101) boards, the mute led is behaving strangely,

the channel passes audio fine,
eq works,
sends fine,
buss sends fine,

the AFL engages,
AFL led works,
AFL signal is good,

engage mute,
mute works,
mute led is so faint as to not be lit. 

then engaging AFL,
takes out both the led's,
to very faint.

i have already re-capped this channel,
the issue was there both before & after the re-capping,
i have also swapped the three transistors with new ones, just to see if that could solve it.

i have measured R65 and it is fine.

i also re-floated a heap of random solder joints on this board.

can anyone help me figure this out, or at least suggest a way i can pin it down.

best

pb

 

[moamps]

If CR10 lit correctly when S20 is pushed and mute is not engaged, then CR5 is faulty.

 

[pb]

hi moamps,

thank you for your reply, i did wonder this myself.

i have had a meter on both legs of CR5 and it shows very little resistance, (0.05)ohm, this is the same as CR10, i guessed if it was damaged it wouldn't pass anything, like a blown bulb?

should i just try dropping in a replacement led?

 

[moamps]

... i guessed if it was damaged it wouldn't pass anything, like a blown bulb?

Sometimes LEDs behave erratically  because of overload or mechanical damage.

should i just try dropping in a replacement led?

Yes.

 

[pb]

moamps,

thanks so much for your replys,

i switched CR5 with a random red led i had kicking around, and it works.

i am not sure it is the exact same spec as the original one, as when mute is engaged, its glowing fine,

mute & pfl together, also both glowing fine,

but there is a very slight drop in brightness, compared to each engaged seperately,

its actually more noticable on the yellow PFL led,

i guess i need to find the correct replacement led now.

thanks again, very grateful, can plod on with the remaining 18 channels now