Blackstar HT Stage Amp Input Stage question

[industrialarts]

Hi

I am working on a Blackstar amp and the inductor at the very input is bad. Could someone explain exactly what it does? I mean I know it's there to filter but really how effective is it considering that there is 12 to 20 feet of cable in front of it?

Also, this is not exactly how the amp is configured. There is a 0.1u cap across the input side of the inductor and the each side of the output has a capacitor in-line. Hope that makes sense.

In repairing the amp I am considering leaving the inductor out since finding a replacement would be difficult.

Thanks for any insight

 

[Newmarket]

Schematic ? Model no ?

 

[industrialarts]

I'm a nidiot - forgot to attach schematic. It's an HT-5R mkII but doesn't match the schematics I found. It is more like the Stage 60-100 but the difference is that (reagarding this schemo attached). C500 is .1uf and is in front of L1 and C501 is not a three legged cap (?) and does not attach to the shield.

Thanks

 

[CJ]

i am working on a blackstar ht venue mk 2 as we speak,

guess what the problem is,

zero ohms across the input jack, this one has an inductor ,

pulled a smd cap it is ok, so i am guessing indutor also,

they are used to filter out hi freq noise like digital effects crap and other gremlins,

i was looking all over for a schemo with the same front end yesterday and this shows up, thank you and good luck!

oh, and ditch the inductor.

 

[industrialarts]

That's wild. I had 100 ohms to ground on the tip and it was caused by inductor as well. Just like you, lifted the cap thinking it had to be it. Mine stumped me for a bit since the schemo didn't match and there was faint signal all over the ground.

Got it working by jumpering the inductor pads, works fine so I mark this one fixed.

 

[CJ]

Good to know!

Yeah this one has IC numbers that do not match any schematics.