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Valve Amp Trouble - PLEASE help

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Hi, my carlsbro amp head arrived this morning, but it doesn't seem to be working. The 4 valves were packed seperately inside the case, so i 'installed' them, and took it over to my freinds house, where my cab was.

The ohm rating of my cab is 8 ohms, and the closest setting on the amp was 7.75, so i used that. The mains settings on the amp are 110, 225 and 250, so i used 250. When i switched it on, the pilot light lit up which was encouraging, but...

When i played the amp made strange noises, a kind of rattling, appartently my friend could see the valves blinking.

Has anybody got any idea what's wrong with it? please help me if you can, im very sad. :(

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I would run it 225v and check the valves are all seated right....is the amp new or s/h and how was it delivered? valves dont like to be treated rough....unlike me.

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update: the amp had been working all along, it turned out that the lead we used to connect the head to the cab was faulty. When playing a little, i noticed a slight ring (which turned out the be somthing loose in the cab), so we tried running it on 225V - After a while playing it smoked and made some horrible noises (not Good).

I think im going to leave the amp a while, to let it cool down, and then try it again on 250V. Fingers crossed getting it working again wont envolve me paying 20,000 pounds to get it fixed.

shit.

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for the mains try 225

as for the ohms part, i dont think your amp should have a setting of 7.75 ohms, the only ones i have EVER seen are 4, 8 or 16 (there are a few others, all moltiples of these though)

and ignoring that, you would indeed be fine using 7.75/8ohms

(having a quick peek at the carlsbro page, all the amps seem to have 1x16ohm and 2x8ohm outputs)

as said above, i would check all the valves are seated correctly and installed the right way

and valves should definately not be blinking... the light given out should be steady

if you dont really know what you are doing with regards to the valves, get the amp to someone who does know what they are doing, and hope that you havent accidentally put them in the wrong way and damaged something

which amp is it? the 50 top?

David

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Hi there. The ohm setting was actually 7.5 and not 7.75. The valves were actually glowing steadily - they must have been heating up or somthing. It is the 50 top, it sounded excellent until it blew up.

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i would be extremely doubtful if thatl work on 250.

its odd how it has both 225 and 250, isnt uk voltage 230v these days? and used to be 240v?

youl of blown something, a valve perhaps, or maybe a resistor that was protecting the valves. open it up, check all the resistors, if ones black thatl be the problem.

make sure everythigns off when you do this, and dont probe around with a dmm if you dont knwo what your doing, those filter caps ( the big ones) store a lot of voltage which will fry you.

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i would be extremely doubtful if thatl work on 250.

its odd how it has both 225 and 250' date=' isnt uk voltage 230v these days? and used to be 240v?

youl of blown something, a valve perhaps, or maybe a resistor that was protecting the valves. open it up, check all the resistors, if ones black thatl be the problem.

make sure everythigns off when you do this, and dont probe around with a dmm if you dont knwo what your doing, those filter caps ( the big ones) store a lot of voltage which will fry you.[/quote']

I think it was working fine on 250, before we messed around with the vaultage setting. I had a look at it earlier, something seems to have frazzled, perhaps to the extent that it completely disappeared. I have no idea what though, so i took it into rnb earlier. Not a good situation, but hey, what can you do?

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according to the carlsbro site, the 50 top has 1x16 and 2x18 ohm outputs, no mentions of 7.5...

if you dont really know what you are doing (putting in the valves, or opening it up) then i would definately take it to a tech

there are lethal voltages inside guitar amps, and even if the amp is switched off capacitors still hold these charges, so if you dont know what you are doing, keep away from them

David

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I think it was working fine on 250' date=' before we messed around with the vaultage setting. I had a look at it earlier, something seems to have frazzled, perhaps to the extent that it completely disappeared. I have no idea what though, so i took it into rnb earlier. Not a good situation, but hey, what can you do?[/quote']

Too low a voltage is never going to cause electronic components to fry......is it?

Amps and other band related electronic equipment are normally built to deal with two voltages...110 for the states and 220-240 for the UK and Europe...

It is more likely that the damage was caused by wrong impedance setting...the load will have been seriously fucked up by using a duff lead.....

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Too low a voltage is never going to cause electronic components to fry......is it?

Amps and other band related electronic equipment are normally built to deal with two voltages...110 for the states and 220-240 for the UK and Europe...

It is more likely that the damage was caused by wrong impedance setting...the load will have been seriously fucked up by using a duff lead.....

what exactly is an impedance setting? resistance? If so, im quite sure that 7.5 is the right one. I wouldn't have thought that a broken lead, that connected the head to the cab, would damage the head?

The guy in rnb tried explaining something to me about flooding the amp with too much current or something. He said that if i had used the 110 setting, the head would be as good as scrap. i really do hope its not overwhelmingly broken, for obvious reasons, not a very good day on the whole.

hot.

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what exactly is an impedance setting? resistance? If so' date=' im quite sure that 7.5 is the right one. I wouldn't have thought that a broken lead, that connected the head to the cab, would damage the head?

[/quote']

Come on now....think about this.....what are you setting the impedance for? the resistance of the cab.....broken lead....zero resistance....damaged components.

Oh and if the amp is fitted with the correct fuses then surely introducing too much in the way of voltage would blow the fuse not the amp....isnt that what fuses are for?

I don't want to worry you but r&b have a very poor track record for repairing my amps....and related equipment

Laney lc30 valve combo.....4 attempts the repair was eventually done out-with the shop.

Laney 150 bass head....4 attempts....the first twice they returned it to me saying they could find no fault, and the amp failed after 30 seconds of me testing it.

Samson guitar radio..2 attempts, returned to me on both occasions claiming it was ok.. took a refund and bought one from Bruce Millers.

I would go as far as saying the in-store staff don't have a fucking clue....good luck.

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I have had similar experiences to Graeme C with R n' B. They refuse to reveal the identity of their amp tech and will not allow you speak to him/her directly, which is very encouraging. I use them for revalve/rebiasing but only because it's slightly more convenient.

I went to a small TV repair shop in Inverbervie called "gerry K". It was recommended to me by Real Shocks. The guy takes a long time, but he gets the job done eventually and doesn't cost a bomb.

Nice to hear someone else has been introduced to the "wonders" of valve amplification.

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what exactly is an impedance setting? resistance? If so' date=' im quite sure that 7.5 is the right one. I wouldn't have thought that a broken lead, that connected the head to the cab, would damage the head?

The guy in rnb tried explaining something to me about flooding the amp with too much current or something. He said that if i had used the 110 setting, the head would be as good as scrap. i really do hope its not overwhelmingly broken, for obvious reasons, not a very good day on the whole.

hot.[/quote']

the impedance setting is making sure the heads output is the same impedance as the speakers in the cab, measured in ohms

this lets the maximum power transfer between the head and the speakers, use a different impedance and you wont get the full volume of the amp coming through. it is possible to use different impedance cabs with an amp, but i wouldnt recommend it

if you dont connect anything to the output, you are very likely to blow the output transformer of the head. so by playing without a cab plugged in, or by using a cable that has shorted you risk blowing the head

its something to do with the amp creating lots of current at the output, but having nowhere for it to go and building up in the transformer, and boom, no more transformer. that would be the flooding the ampwith too much current thing they mentioned (bear in mind i dont know if this is technically correct, but i am pretty sure this is how it work, or a simplified version at least)

unfortunately replacing the output transformer and any related components it has taken down with it is a costly process...

running the amp with a lower voltage than recommended shouldnt damage it, but i would try and have it running on the right voltage

a lot of modern amps do have the ability of running on both US and UK power supplys, there is usually a switch somewhere to select which it runs on though, as if it is set to runon us voltage, and you plug it into the uk mains, boom

David

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using the wrong impedence means that the full power is not outputed to the cab.

i.e some of it is outputed, and some is reflected back into the amp (bad).

having said this iv ran my amp at the wrong impedence just tos ee what it soudned liek and it didint blow up....

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using the wrong impedence means that the full power is not outputed to the cab.

i.e some of it is outputed' date=' and some is reflected back into the amp (bad).

having said this iv ran my amp at the wrong impedence just tos ee what it soudned liek and it didint blow up....[/quote']

it can be done safely, i just cant remember whether it is safe to run a higher impedance cab than the amps output, or a lower impedance cab...

one os safe to do to your amp, though as said above the full sound of your amp wont be heard

David

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