Unintended but cheap NAD

[Kilby]

I seem to have got myself an early 70s Carlsbro 50 Top combo, with original Fane speaker apparently the amp is very much in the Marshall JTM style

This is a little embarrasing as I didn't intend to come home with an amp, I simply went to the local dump (as somebody stole our bin) as there it was just sitting there, in a cage.

So I brought the poor little stray home with me to see what state it was in.

I dunno what it sounds like yet as it needs some as theres only 1 EL34 in here and one of the valve sockets needs replaced as one of the pin grips (cant think of the proper phrase) pulled out along with the valve. Everything (apart from the mains lead) appears to be original and there is no rust, burns or anything unpleasant in evidence, only a replaced mains cable




More pics including some nudie shots here :
http://s211.photobucket.com/albums/bb155/cta-102/Carlsbro/?action=view&current=Carlsbro_boardWinCE.jpg

Unfortunitely I thought it would be a bit cheeky (plus the car boot wasn't big enough for both) to also grab the bass bin in the other cage (with a nice big Eminance 15" speaker)

Rob...

[gwEm]

pretty cool :)

[Brow]

I have 1 of those but in a head format.

Loud, fat clean amp that takes pedals very well.

Enjoy!

[Oli]

To me it looks like the mains transformer could be a Partridge. Not totally sure, but it looks like one to me- and a nice oversized one at that!

My local dump never has anything apart from broken TVs and rusted girls bikes, that amp looks in great condition :)

[Kilby]

Thanks folks, time will tell as I never seem to have the time to do anything I actually want to (an afternoon stranded in IKEA took the happiness out of my day)

I believe it is indeed a Partridge transformer as thats what they (apparently) where used originally and the yellow lacquer is still on the bolts to hold the all the nuts in place is still intact.

Though theres only a couple of serial numbers on the transformer (any hints regarding identifying it ?)

It's a heavy bugger too

[MrBump]

Very cool, and a lucky find, methinks.

Mark.

[hamfist]

Very cool Kilby !

That PT defo looks like a Partridge, but the OT is not - probably changed at some point, I'd guess.

I'd guess that the amp hasn't been powered up for many years.  In such situations I've read that     it is advised to slowly power up the amp using a variac to "re-form" the electrolytics.  At it's age it might be just as well to replace all the electrolytics anyway, to be safe. If you can do the job yourself, its not that expensive.

 BTW, you didn't mention any cost for the amp, or did you literally just pick it up free from the dump ?

[Fourth Feline]

Great find !  :)

I recall that ace guitarist Bill Nelson used a Carlsbro valve amp head in the heyday of 'Be-Bop Deluxe'.  If it's good enough for bill ...   8)

[bobthemerciful]

I had a Carlsbro 60 TC 'til recently. Was my first amp. The output tranny looked identical to that one, and hadn't been changed (stilll had paint on bolts too) so yours could well be the original one.

[Kilby]

Very cool Kilby !

That PT defo looks like a Partridge, but the OT is not - probably changed at some point, I'd guess.

I'd guess that the amp hasn't been powered up for many years.  In such situations I've read that     it is advised to slowly power up the amp using a variac to "re-form" the electrolytics.  At it's age it might be just as well to replace all the electrolytics anyway, to be safe. If you can do the job yourself, its not that expensive.

 BTW, you didn't mention any cost for the amp, or did you literally just pick it up free from the dump ?

Unfortunitely I don't have access to a variac (have to check to see if I can knock something together) so the caps may have to fend for themselves :(

No problem with changing the caps myself, the bigger difficulty will be the biasing of the valves as I the only valve work I have done has involved a set of intact valves in the 1st place so I am a bit nervous of wacking in a complete new set.

In reality I only picked it up as I needed a speaker for my ZVex Nanohead

The amp was indeed my favourite price point FREE, as several people will testify around here I am seldom on the receiving end of good fortune, so expect to see the the announcment of somebody with a valve embedded in their forehead  :roll:

[Transcend]

Thanks folks, time will tell as I never seem to have the time to do anything I actually want to (an afternoon stranded in IKEA took the happiness out of my day)

I bet that the afternoon consisted of 10 mins finding what you wanted then the rest of the time finding the checkout/exit???

I hate ikea with a passion but i gotta admit they have the layout designed so that you have to look at everything which usually makes people buy more, however with me it just frustrates me as i like to go somewhere get something then go.

Back onto the actual topic, that amp looks in really good nick looking forward to seeing if it all works correctly once you have the issues resolved.

The tip near my house is just full of broken cookers/fridges/freezers and nothing more.

[HTH AMPS]

ok, so if you're worried about plugging the amp in due to the caps drying out, check this out from Geofex (slightly altered by me for added clarity)...

(1) pull out all the tubes.

(2) locate the wire that goes from the rectifier diodes to the first power supply filter stage, and (temporarily) solder a 100K (2w-5w) resistor in series with the wire.  This resistor will limit the current that can flow into the caps (and the amount of voltage that is applied to them) to safe values that will cause the caps' insulating layer to re-form.

(3) clip your voltmeter across the resistor, turn it on (no tubes in it, remember) and watch the voltmeter.

(4) when the voltmeter reading drops to less than 20-30VDC, your caps are formed (the forming could take hours to days).

(5) remove the 100k (2w-5w) resistor, you're ready to go (though a bias check would be worthwhile).

I would personally just plug the amp in and listen out for any really bad snap/crackle/pop and/or smoke upon first powerup.  The amp looks in good nick and I'd be surprised if there was any need to reform the caps. 

There's plenty of space in the chassis for modding too - that would make a great Marshall 2203 (heh heh)

[dave_mc]

haha, nice job rob. :)

[hamfist]

ok, so if you're worried about plugging the amp in due to the caps drying out, check this out from Geofex (slightly altered by me for added clarity)...

(1) pull out all the tubes.

(2) locate the wire that goes from the rectifier diodes to the first power supply filter stage, and (temporarily) solder a 100K (2w-5w) resistor in series with the wire.  This resistor will limit the current that can flow into the caps (and the amount of voltage that is applied to them) to safe values that will cause the caps' insulating layer to re-form.

(3) clip your voltmeter across the resistor, turn it on (no tubes in it, remember) and watch the voltmeter.

(4) when the voltmeter reading drops to less than 20-30VDC, your caps are formed (the forming could take hours to days).

(5) remove the 100k (2w-5w) resistor, you're ready to go (though a bias check would be worthwhile).

I would personally just plug the amp in and listen out for any really bad snap/crackle/pop and/or smoke upon first powerup.  The amp looks in good nick and I'd be surprised if there was any need to reform the caps. 

There's plenty of space in the chassis for modding too - that would make a great Marshall 2203 (heh heh)

Great post HTH. Thanks for the info !