Rockster Lives!

Express, Liverpool, Rocket, Dirty Little Monster, etc.

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Beerman
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Rockster Lives!

Post by Beerman » Wed Feb 02, 2011 12:50 am

Don't suppose anyone has built an Octal Rocket according to the Schematic posted in http://ampgarage.com/forum/viewtopic.ph ... er&start=0 this thread?

I'm working from schematic and layout at the following link. http://imgur.com/a/MSXkd

I'd love to see a picture of how the pots are wired.... I'm not convinced I've got mine right...

Picture here: [IMG:1024:768]http://i.imgur.com/ImXtm.jpg[/img]

I'm also hunting down another fault.... it keeps blowing fuses on start up.

An few build photos here: http://imgur.com/a/B1Bm9

Would appreciate any feedback from more experienced eyes.
Last edited by Beerman on Sat Mar 05, 2011 10:57 pm, edited 1 time in total.
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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Wed Feb 02, 2011 1:03 am

http://imgur.com/a/MSXkd

I can help you if you have questions rjguitar is out of town for awhile.

Mark

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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Wed Feb 02, 2011 1:06 am

Here are shot of rj's amp I could only find one good one of the pot wiring.

Later you can shorten a lot of your wiring from the tube sockets if you wish.

Mark
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Beerman
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Re: Rockster Lives!

Post by Beerman » Wed Feb 02, 2011 1:20 am

Thanks Mark.

Firstly...
[IMG:524:1052]http://i.imgur.com/mFSN7.jpg[/img]
Note the circled 5K...

[IMG:986:710]http://i.imgur.com/K0DwZ.jpg[/img]
Which doesn't appear here...

Where does it go?
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Beerman
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Re: Rockster Lives!

Post by Beerman » Wed Feb 02, 2011 1:53 am

Gotcha... you were a step ahead of me.

So it actually looks like this?
[IMG:408:728]http://i.imgur.com/8EoQ2.jpg[/img]

Thanks.

Still got to sort out the short (or other error) in the power supply... it keeps blowing the mains fuse on start up.

Don't suppose there is anything obviously wrong there that I'm just not seeing?

Will come back with any more questions when I'm past that issue.
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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Wed Feb 02, 2011 1:57 am

I do not use that 5k resistor just wire the wiper (middle) of the bass pot to the wiper of the 25kL mid pot.
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Beerman
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Re: Rockster Lives!

Post by Beerman » Wed Feb 02, 2011 2:25 am

So it should look like this then? (From the inside)

[IMG:640:400]http://i.imgur.com/uDLfe.jpg[/img]

I note also that RJ has his Cut control wired opposite to me.
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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Wed Feb 02, 2011 3:05 am

Here is how I see it. There are two ways he has drawn this but I think this is less confusing.

Mark
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RJ Guitars
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Re: Rockster Lives!

Post by RJ Guitars » Wed Feb 02, 2011 3:11 am

Beerman - Welcome to the Rockster world... I was supposed to be over on the other side of the world this week but those plans are on hold for now. Mark knows these things better than i do so maybe he can help us sort this out...

The schematic you have is using a mid control borrowed from another circuit... it's not what i ended up using on my build though. I would have to look at that build to see if I still have it the way it is in Mark's photo.

For future reference keep in mind that going back to the old Matt Taylor Rocket Schematic is a good way to sort out the preamp on the Rockster. I think it is most useful to go back to the original Rocket schematic and see what the mid control was doing there.

There is no pot on the original Rocket amp, just a 10K to ground off of the Bass control.

Then if we simply replace that 10K resistor with a 25K pot, then we have created a mid control. I'm not sure if this is a conventional mid control, but it will work.

I added a 5K resistor to the tail of the mid pot so that it wouldn't bottom out when it went to zero resistance.

Also, I have a 250K pot for the bass control on a lot of old schematics, I think it's always best to use a 1 Meg for that.

After we are sure my drawings are right, I'll make the "fixed" schematic rev available to anyone who wants it... next we can go after the layout.

rj
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RJ Guitars
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Re: Rockster Lives!

Post by RJ Guitars » Wed Feb 02, 2011 3:18 am

Beerman wrote:... I note also that RJ has his Cut control wired opposite to me.
that's an interesting part of the Rocket amps... I think the cut control works backwards.

Unless mine is a pre "fix" photo -- more knob=more cut

Let me know if that agrees with what you find.

rj

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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Wed Feb 02, 2011 4:18 am

More knob brighter the tone.

My Dizzy 30 works the opposite more knob deeper tone.

Beerman
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Re: Rockster Lives!

Post by Beerman » Wed Feb 02, 2011 4:31 am

Thanks again Mark - and RJ now too...

I'm back onto my power supply issue - it looks like I have an intermittent short on the HT (300-0-300) and the 5v winding.

With side loading on the leads it kept on blowing fuses. Have untwisted, and 'relaxed' all the leads, and now it works.

Guess I'll take it off and have a look to see what goes on...
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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Wed Feb 02, 2011 5:08 am

Hmm not sure what you have going there.

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M Fowler
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Re: Rockster Lives!

Post by M Fowler » Wed Feb 02, 2011 5:09 am

Another way to wire the tone controls
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Beerman
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Re: Rockster Lives!

Post by Beerman » Wed Feb 02, 2011 5:47 am

RJ Guitars wrote:Beerman - Welcome to the Rockster world...

After we are sure my drawings are right, I'll make the "fixed" schematic rev available to anyone who wants it... next we can go after the layout.

rj
Thanks RJ.

I'm Graham in Melbourne - I bought most of these parts from you just before Christmas last year.

The PT is the Edcor EM0726-240. I've got the end bells off, and everything looks fine, no bad smells. The Primary winding leads feel solid, as do the 6.3, and the HT, but the 5V leads feel different - like they are not attached quite as well.

I've already cut the leads - so I imagine that any warranty Edcor may have offered is gone...

Will investigate further and let you know what I find.
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