I want to open my Bluesbreaker combo..

[Guest]

Okay, I've never looked inside. Now I want to open the bluesbreaker combo to take some pictures of the innards and look around if everything is original and so. (Just look no touch, so don't worry ...)

Is this right or have I forgotten something that I should do before?

1. Power up the amp and play a little.

2. Take the cable out of the wall and play until sound is gone. So that caps are drained at least a little bit.

3. Unplug all other cables.

4. Take a insulated screwdriver and take the backpanel off the cab.

5. Take some photos and take a look around a little ( without touching )

6. Put the backpanel in place and fasten it again.

 

[Rich_S]

Re: I want to open my Bluesbreaker combo..

Step 1 is counterproductive. Just let it sit unplugged for 10-20 minutes; power off, standby switch on "standby". Playing through it with no power might help drain the filter caps.

Before you open it up, make sure you know what the filter cap(s) look like, where it/they are, and then stay the hell away from it/them.

 

[Guest]

Re: I want to open my Bluesbreaker combo..

Those blue ones are caps right... then there are caps inside on the board itself as well. But don't worry I won't touch those. Now

Something that I always wondered about and could get an answer to now as well when I'm in on the subject is what parts are sticking out. (Bluesbreaker chassi is almost the same as the one on the picture)

Is the big metal box to the right the tranny?

Then what's the other smaller metal box?

and at last, are the blue caps on the outside dangerous if you touch them as well?

 

[Rich_S]

Re: I want to open my Bluesbreaker combo..

I thought you had a JTM45 reissue - that's a 20 Watter chassis in the picture, but for your purposes they're similar.

Yes, those blue cans are the filter caps - each one actually contains multiple capacitors. The outsides are OK - it's the terminals (which protrude through to the inside of the chassis that have the high voltage on them. If your amp has things that look like those, then you know what filter caps look like.

The big metal box is the power transformer, the smaller one with the paper wrap sticking out is the output transformer. On bigger amps, the OT might be completely enclosed, more like the PT. I think the JTM45 and other big Marshalls all have a choke - it would look like the transformers, but be smaller.

Keep in mind it's not just the filter caps you need to be wary of. The B+ voltage is connected from the caps to all the tube sockets. Just keep your fingers away from and exposed leads or terminals inside the amp.

Don't think for a minute that I want to discourage you. I think that every guitar player ought to know a bit about what's inside his amp, and I applaud your curiosity and willingness to take a look. Proceed cautiously, and the knowledge you gain will make you safer in the long run.

 

[Guest]

Re: I want to open my Bluesbreaker combo..

yeah, it's a JTM45/Bluesbreaker but as I wrote it's quite similar so I figured that picture should do.

No I didn't think that you tried to discourage me... not at all. I'm always extremly careful when doing something to things that has do do with electricity. So many thanks for all info, that's all

But anyway, if Step 1 is counterproductive. What is the BEST way to drain the caps? If I unplug it from the wall tonight and leave it unplugged overnight. Then I play my guitar through it for a while tomorrow it witout plugging it into the wallsocket or powering it on. Will the caps be discharged then? Completely discharged or just a little discharged?

And the final question... Is it at all theoretically possible to drain the caps completely so that you could work inside a amp without any risk of getting shocked? :smokin:

Thanks for all the info! Any more replies are VERY welcome :banana:

 

[the guy who invented fire]

Re: I want to open my Bluesbreaker combo..

you can not simply drain the caps...

I have gotten popped by caps that were in an amp that had been unplugged from the wall for days...those caps hold a change for a good bit of time.

 

[Rich_S]

Re: I want to open my Bluesbreaker combo..

Some amps have bleeder resistors across the caps that bleed the voltage away - these Marshalls do not. You can drain the caps' charge by hooking a large-value resistor across them with clip leads. Look on Randall Aiken's page - he might have a paper on it.