Blackstar series one 100 problem

[shane]

20240808_214309.jpg

Anyone know the values of the burned out components on this picture L6,R28,R27,D14,D13 ?
Blackstar series one 100w head. I could do with knowing what they do in the circuit too. I assume they are part of the fx send and return circuit since they are right next the to the loop Jack's, they're obviously connected to that cracked TL072 too.
Blackstar will not supply a schematic unless you are an authorised repair centre. So if anyone has one I'd be super grateful for a copy.

I don't like these amps but repair is for a guy I know, otherwise I'd probably have said no!

Hope you guys can help
Cheers
Shane

[LOUDthud]

Need more info.

Does the amp pass a signal ?

Has the Effects Loop ever been used ? With what equipment ?

Did the amp just fail while in use with no connections to the Effects Loop ?

Any difference when a patch cord is connected from Send to Return ?

Any chance a speaker cord from another amp was connected to the Return jack ?

[shane]

Thanks for replying, the amp blows the mains fuse pretty much as soon as its turned on. That's how it came to me, so I cant answer any of those questions, sorry.
The guy bought it in that condition for a very cheap price.
I have no history of how it's been used. I suspect there must be some possible issue with the low voltage supply to have caused that.
Without a schematic I'm in the dark really.
I'm thinking if I could at least replace the damaged stuff, I'd at least have a chance to see if it works.

[LOUDthud]

It takes quite a jolt to split an IC in half, probably a serious fault with the power supply for the IC. If you just replace the blown components, chances are they will just blow up again the next time power is applied. You should be using a Variac or at least a light bulb limiter. The inductor looks like just a ferrite bead with a wire run through it, it might have some smoke damage, but is probably ok. Does this amp have a Switch Mode Power Supply ?

[Stevem]

I will see if I can grab a schematic from them thru the music store I work for, but it's now Friday morning here and it may take to mid next week for me to hear back from them.

Mean time I see IC chips burn up all the time when the circuit they are used in is allowed to get over worked due to poor design or power supply issues.

That IC may run on both a positive and negative D.C. Supply and the regulator transistor for either might be bad, so unpower that IC by removing it or cutting open its power supply trace and see if your power rail(s) to it is still working .

You might try and find a schematic for there smaller club 40 watt amp and check out its effect section since it might be the same if not very close enough to give you a idea as to what going on.

[shane]

Hi guys. Thanks for the replies.
Loudthud, don't think it has a switched mode supply, and yes I do use a lightbulb limiter so I'll power it up with that once I've replaced the damaged parts.

SteveM, I'd really appreciate a schematic if you can get one thank you.

I'll check the supply at the appropriate pins on the chip, I'm sure it's gonna be + and- 12v or so.
Without the schematic it's gonna be fun tracing it back to the power supply.
I have a schematic for one of the ht stage 100, which I'd guess would have a similar loop but may not be much help finding the PS components as the main boards are very different.
Once again cheers guys

[Stevem]

I found a schematic for the club HT 40 here.
It’s effects loop section might give some help to you.