Convert old Carlsberg Sidewinder to JCM800/JTM...

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vmaxvmax
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Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by vmaxvmax »

I have an old Carlsbro Sidewinder 60 watt EL34 combo. Had it from new. Bought it in preference to a Silver Jubilee JCM 800 - oh why? The ignorance of youth... It was about the same price. It had more knobs.

The preamp sounds dreadful - always did - but I am thinking of converting the amp to a Marshall clone - JCM800 or JTM... Schematic attached. I have also added a document from an engineer who did some work on another one and uploaded his record.

It all works properly and I did replace all the electrolytics a couple of years ago.

It is easy to use the power amp as it is because the power amp and preamp are separated; the power amp on its own chassis and the preamp on a board above it. There is a send/return arrangement. The transformers are good quality and are very heavy (Drakes if I remember properly).

What do you reckon? - Keep the PA without change and build a preamp on turret board, or do you think the PA needs modifying too? I see that the circuit is not that different to a Marshall 50 watt PA.

Any ideas or suggestions are welcome!
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vmaxvmax
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by vmaxvmax »

Help, what do you reckon?

Is it efficient to use the existing preamp board and re-route, replace and disconnect audio paths. I.e., take the output for first triode via changed pot to the second triode changing caps and resistors along the way etc, etc... Bypassing irrelevant component paths.

Or start with a new preamp board? :roll:

Any ideas?
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Bieworm
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by Bieworm »

IMHO always more efficient using a clean slate. Less confusion. Will always look nicer in the end
...but there are always mad max fans that love making machines out of scrap. Maybe even petrol powered ;)
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by zaphod_phil »

Bieworm wrote:
Tue 06/23/20 8:56 am
...but there are always mad max fans that love making machines out of scrap. Maybe even petrol powered ;)
Diesel is better! :lol:
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by Bieworm »

zaphod_phil wrote:
Tue 06/23/20 12:43 pm
Bieworm wrote:
Tue 06/23/20 8:56 am
...but there are always mad max fans that love making machines out of scrap. Maybe even petrol powered ;)
Diesel is better! :lol:
Methane!!! Let's help mother nature a hand 😁😁
Or them 80's solar panels...
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crgfrench
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by crgfrench »

Such a cool project and great documentation. Maybe keep the PA and just build the new preamp turretboard first. That would be my approach. Good luck with it!
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vmaxvmax
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by vmaxvmax »

Thank you for the replies! :D

I hadn't thought of petrol or diesel for power as, here in France, we are moving toward electrical power...

You think new board for the preamp rather than mess up the existing PCB..? It would be cleaner but more expensive...

Yes, I did think I would keep the PA - It is very similar to a standard Marshall 50 watt (JCM800 etc).

The transformers are definitely good ones if weight is anything to judge them by! They make the combo a think of wonder for anyone trying to lift it! :twisted:

I did build a JCM800 preamp in a (largish) pedal with a SMPS and that sounds pretty good straight into the effects return, so the PA does sound OK and it goes loud.

Even the voltages are in the ball park - and for JCM800 voltages seem to be somewhat variable anyway!

I can't quite work out why the preamp is so awful - maybe the diodes - though when disconnected it seems the preamp can't handle the increased power without choking and farting out.

I can't even push the preamp hard via the 'clean' channel as that can't handle even a booster pedal with out farting.

The PA overdrives nicely though :wink:

Nowhere near as forgiving or versatile as my 18 watter - which loves being pushed hard at the from end.

As an aside - the original speaker is a Celestion Sidewinder which allegedly can handle 150 watts with an efficiency of 103 db at one watt. I have to say, the speaker cone is very stiff and I don't much care for the sound (sounds like a blanket over the combo) - I currently have an old early '70's G12H in the combo which sounds much better - though it still doesn't make ups for the crap sound of the preamp.

I do now wish I had gone for the Silver Jubilee at the time as it now seems much more enduring! I think the Carlsberg now can occasionally be found for as little as £150!

The transformers are definitely good ones if weight is anything to judge them by! They make the combo a think of wonder for anyone trying to lift it!
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by Bieworm »

vmaxvmax wrote:
Wed 06/24/20 4:57 am
Thank you for the replies! :D

I hadn't thought of petrol or diesel for power as, here in France, we are moving toward electrical power...

You think new board for the preamp rather than mess up the existing PCB..? It would be cleaner but more expensive...

Yes, I did think I would keep the PA - It is very similar to a standard Marshall 50 watt (JCM800 etc).

The transformers are definitely good ones if weight is anything to judge them by! They make the combo a think of wonder for anyone trying to lift it! :twisted:

I did build a JCM800 preamp in a (largish) pedal with a SMPS and that sounds pretty good straight into the effects return, so the PA does sound OK and it goes loud.

Even the voltages are in the ball park - and for JCM800 voltages seem to be somewhat variable anyway!

I can't quite work out why the preamp is so awful - maybe the diodes - though when disconnected it seems the preamp can't handle the increased power without choking and farting out.

I can't even push the preamp hard via the 'clean' channel as that can't handle even a booster pedal with out farting.

The PA overdrives nicely though :wink:

Nowhere near as forgiving or versatile as my 18 watter - which loves being pushed hard at the from end.

As an aside - the original speaker is a Celestion Sidewinder which allegedly can handle 150 watts with an efficiency of 103 db at one watt. I have to say, the speaker cone is very stiff and I don't much care for the sound (sounds like a blanket over the combo) - I currently have an old early '70's G12H in the combo which sounds much better - though it still doesn't make ups for the crap sound of the preamp.

I do now wish I had gone for the Silver Jubilee at the time as it now seems much more enduring! I think the Carlsberg now can occasionally be found for as little as £150!

The transformers are definitely good ones if weight is anything to judge them by! They make the combo a think of wonder for anyone trying to lift it!
Some advice...

Don't order turretboard and turrets from tube town in germany. The turrets are really useless..unsolderable!!
On the other hand, the board and turrets from jukeboxrevival.nl (holland) are great!! And cheap. They have also got the best components such as NOS caps,....
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vmaxvmax
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by vmaxvmax »

Bieworm wrote:
Wed 06/24/20 5:26 am
vmaxvmax wrote:
Wed 06/24/20 4:57 am
Thank you for the replies! :D

I hadn't thought of petrol or diesel for power as, here in France, we are moving toward electrical power...

You think new board for the preamp rather than mess up the existing PCB..? It would be cleaner but more expensive...

Yes, I did think I would keep the PA - It is very similar to a standard Marshall 50 watt (JCM800 etc).

The transformers are definitely good ones if weight is anything to judge them by! They make the combo a think of wonder for anyone trying to lift it! :twisted:

I did build a JCM800 preamp in a (largish) pedal with a SMPS and that sounds pretty good straight into the effects return, so the PA does sound OK and it goes loud.

Even the voltages are in the ball park - and for JCM800 voltages seem to be somewhat variable anyway!

I can't quite work out why the preamp is so awful - maybe the diodes - though when disconnected it seems the preamp can't handle the increased power without choking and farting out.

I can't even push the preamp hard via the 'clean' channel as that can't handle even a booster pedal with out farting.

The PA overdrives nicely though :wink:

Nowhere near as forgiving or versatile as my 18 watter - which loves being pushed hard at the from end.

As an aside - the original speaker is a Celestion Sidewinder which allegedly can handle 150 watts with an efficiency of 103 db at one watt. I have to say, the speaker cone is very stiff and I don't much care for the sound (sounds like a blanket over the combo) - I currently have an old early '70's G12H in the combo which sounds much better - though it still doesn't make ups for the crap sound of the preamp.

I do now wish I had gone for the Silver Jubilee at the time as it now seems much more enduring! I think the Carlsberg now can occasionally be found for as little as £150!

The transformers are definitely good ones if weight is anything to judge them by! They make the combo a think of wonder for anyone trying to lift it!
Some advice...

Don't order turretboard and turrets from tube town in germany. The turrets are really useless..unsolderable!!
On the other hand, the board and turrets from jukeboxrevival.nl (holland) are great!! And cheap. They have also got the best components such as NOS caps,....
Cool, thank you for the advice as I had been looking at Tube-Town... I often use Banzai, not the fastest return but reliable.

I'll check out jukebox revival.nl
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Bieworm
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Re: Convert old Carlsberg Sidewinder to JCM800/JTM...

Post by Bieworm »

Banzai is way too expensive. I buy at tube town ( anything but the turrets), jukeboxrevival or tonefactory
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