What would you do with this 1986 Carlsbro power amp... Use the trannies to build a JCM or similar clone?

[Francis Eckersley]

Hi,

I have this old, all original, Carlsbro Sidewinder combo. I've had from new 1986. Its works but the preamp is not the best sounding. I did gig it a lot in the first few years until I got sidetracked with my ADA MP1 rack system + Marshall 9100 + Marshall 4x12, and nowadays I use my own built Marshall 18 watt clone.

The power amp is on a separate board/chassis at the back of the combo whilst the preamp board is above it and accessed from the front. It works well with plenty of power and no noise issues - I currently use it at home as a slave power amp utilising it's effects return for my own built JCM 800 preamp pedal with 280 v smps...

Anyhow, I have been thinking for some time about ripping it up and building a new 50/60 watt amp using the existing transformers which, whilst looking somewhat old and plenty gigged, work as they should. I am toying with the idea of cloning a JCM 800 head...

I have attached some photos of the power amp 'bits' and a circuit diagram.

Rip the goodies out and start anew, modify the existing amp (modify the preamp etc) or bin the whole idea? Any views as to it being a worthwhile endeavour?

The trannies are:
Mains - Drake 789-70
Output - Drake 784-375
Choke - Drake 292-710

 

[StingRay85]

Thanks pretty awesome. Rebuild it into something more useful?

 

[dtier]

Looks like a nice transformer set but challenging to relocate to a traditional chassis. They would have to be layed down to get the high voltage terminals inside the box. Custom cutting a blank chassis, etc. I would mod or replace the preamp depending on how much room there is to work in there. But you have lots of options.

Dave

 

[BlueX]

If the preamp is the weak part, and it's on its own board, maybe you can build a new one and put into the amp. Could get you a nice, working amp.

I have a soft spot for old stuff so I would save as much as possible of the original, somewhere safe.

 

[Francis Eckersley]

If the preamp is the weak part, and it's on its own board, maybe you can build a new one and put into the amp. Could get you a nice, working amp.

I have a soft spot for old stuff so I would save as much a

Thank you all for your interest! There is not a whole lot of space in the preamp area as it was all on a fairly compact/narrow PCB. I might be able to build a traditional turret board preamp and somehow locate the preamp valve off to the side.

 

[Francis Eckersley]

Looks like a nice transformer set but challenging to relocate to a traditional chassis. They would have to be layed down to get the high voltage terminals inside the box. Custom cutting a blank chassis, etc. I would mod or replace the preamp depending on how much room there is to work in there. But you have lots of options.

Dave

Could I not orientate the trannies as they are and run the cables down their sides into the chassis? Might not look as expected but would that cause problems?

 

[dtier]

Mainly a shock hazard if not completely insulated. 400+ volts. They could also cause a hum as well when you face the amp with your guitar at close range. End bells would resolve the issues but I don't think they would clear the terminals.

 

[Techdeth]

Send it to Henric hermansom . We will put the greatest preamp with it. . Here’s he’s preamp with a Marshall power

 

[Francis Eckersley]

Mainly a shock hazard if not completely insulated. 400+ volts. They could also cause a hum as well when you face the amp with your guitar at close range. End bells would resolve the issues but I don't think they would clear the terminals.

Thank you - it does look like the easiest option is just to change the preamp… The combo weighs a ton and ditching it in favor of separate head to work with my other speaker cabinets did seem appealing. I’ll have to look at a new turret board and adjacent mounts for the preamp tubes. At the moment there are 4 preamp ecc83’s whilst a JCM 800 type preamp will only need two. The 5th ecc83 PI is on the power amp board. The problem is that the available space for the preamp is about 1 u width by about 80mm depth and just a little over a preamp valves height… But I could spread a new JCM 800 preamp circuit width wise with the board and valves side by side I suppose.

 

[Guitar-Rocker]

It looks like a great candidate for a Hiwatt

 

[Francis Eckersley]

It looks like a great candidate for a Hiwatt

Now there’s a thought… In what form?

 

[Matthews Guitars]

What's the most classic Hiwatt that fits the general specs? Go with that. I doubt I'll ever find one in my price range but I would love to check out a DR103.

 

[Francis Eckersley]

What's the most classic Hiwatt that fits the general specs? Go with that. I doubt I'll ever find one in my price range but I would love to check out a DR103.

My question as to in what form was more about wether or not to try to mount the trannies in a new chassis/head and how - given that their mounts are not really designed for conventional layout on traditional chassis.

 

[paul-e-mann]

Hi,

I have this old, all original, Carlsbro Sidewinder combo. I've had from new 1986. Its works but the preamp is not the best sounding. I did gig it a lot in the first few years until I got sidetracked with my ADA MP1 rack system + Marshall 9100 + Marshall 4x12, and nowadays I use my own built Marshall 18 watt clone.

The power amp is on a separate board/chassis at the back of the combo whilst the preamp board is above it and accessed from the front. It works well with plenty of power and no noise issues - I currently use it at home as a slave power amp utilising it's effects return for my own built JCM 800 preamp pedal with 280 v smps...

Anyhow, I have been thinking for some time about ripping it up and building a new 50/60 watt amp using the existing transformers which, whilst looking somewhat old and plenty gigged, work as they should. I am toying with the idea of cloning a JCM 800 head...

I have attached some photos of the power amp 'bits' and a circuit diagram.

Rip the goodies out and start anew, modify the existing amp (modify the preamp etc) or bin the whole idea? Any views as to it being a worthwhile endeavour?

The trannies are:
Mains - Drake 789-70
Output - Drake 784-375
Choke - Drake 292-710

View attachment 131683View attachment 131684View attachment 131686View attachment 131685View attachment 131687View attachment 131688

Recycle as much of the amp as possible, I think you could convert it to an 800 affordably.

 

[Francis Eckersley]

Recycle as much of the amp as possible, I think you could convert it to an 800 affordably.

Thank you. The more I think about it, the more I am inclined to put a JCM 800 preamp in there, make some slight mods to the PI and power amp and add a presence control to the existing negative feedback circuit. From what I see, the power amp needs very little modification. The voltage levels are not way off either - both for the PA and the supply for the preamp.

 

[StingRay85]

Just clean out the entire amp besides the PT OT and choke, and build in whatever you feel like. It's always nice if you can save the face plate, and use the exact same functions on it. 2203 style, Hiwatt style... There's always enough room if you're doing nothing too crazy.