Cannot power on Blackstar ID:CORE BEAM

[Hammerstein]

Hello there!

My amplifier seems to have given up very suddenly and without no obvious reason: I simply cannot power it on. I used the amp earlier today without any kind of problem. I turned it off afterwards, and returned a couple of hours later, unable to start the amplifier.

It is a Blackstar ID:Core Beam, bought about one year ago.

Nothing happens when I turn the power switch, no lights, no sound or any sign of life at all. All external connections have been checked. However, the green lamp of the power supply is alight just like usual.

Any suggestions would be greatly appreciated! Has anyone else experienced something similar with this model, or any amplifier in general? I am myself a newbie when it comes to troubleshooting and repairing amps, but would love to learn as muc has I can about it. What should I look for when I open up the amplifier?

[Mick Bailey]

Welcome to the forum.

Do you have any means of checking the power supply output? The first think you need to know that this is working correctly.

[guitardad]

Check the power supply. Should have 16V DC center pin positive.

The BlackStar power supplies are similar to power supply bricks used for laptops.

https://www.amazon.com/E-TOP-Netbook...=16vdc+adapter

You want 16VDC 3.5Amp (or 4A) output, center pin Positive 2.5mm plug

[Hammerstein]

Welcome to the forum.

Do you have any means of checking the power supply output? The first think you need to know that this is working correctly.

I suppose you mean with the use of a multimeter, or a similar instrument?

[Mick Bailey]

A multimeter will check the presence of an output voltage, but sometimes this can collapse under load. I recently has a bad keyboard PSU that measured correctly on its own but had a faulty solder joint where the output cable connected to the PCB. This dropped the voltage right down when the keyboard was switched on. The only true test is to load the PSU. I have the convenience of a resistive dummy load that I use to verify PSUs.

Anyhow, I would check the PSU voltage then plug it in and check the voltage at the Amp's DC socket with the amp turned on to see if it held up. These are pretty complex amps - more computer than amp oriented. Check for the presence of any internal fuses and check they're not blown.

[Hammerstein]

Back again: There doesn't seem to be any fault within the PSU, I took it to my local music shop and checked the output voltage.

I will open up the amplifier as soon as possible and look for the internal fuses. Hopefully, it will provide something of value.

[Hammerstein]

I am giving this another shot. I have some time on my hands this summer and have recently bought a multi meter.

I have opened up the amplifier and there seems to be no blown fuses. What should I look for next?

[Mick Bailey]

Take a look at the DC socket and check the voltage is present inside the amp. Also, make sure the solder connections (presumably to a PCB) are good. A broken solder joint is commonplace on DC sockets.

[Hammerstein]

Sounds like a plan. First I have to do a fair share of reading about measuring voltage in a safe way. Any tips (or good resources) on measuring voltage? Safety considerations basically.

[Mick Bailey]

There's a safety consideration for yourself and another for the circuit you're working on. As this amp is powered from an isolated DC low-voltage power supply then there's a much lower risk of shock than if it was directly mains-powered. You always have to be sure that despite this there's no internal circuit that steps the voltage up again and a clue to this is often if there's a tube in there it can be powered from an inverter circuit that generates a high enough voltage to give you a nasty shock (200v-300v).

You need good insulated probes with sharp tips that won't slip. When probing a circuit you have to make sure you don't short out any components - that could give you more problems than you started with. I always 'anchor' my negative probe while I use the positive probe. That is, I look where my negative probe is placed and ensure it's firmly located with a comfortable but sure grip before using the positive one. I'm not then looking at two probes at once and this reduces the chance of slipping. When lots of measurements are needed with reference to ground I'll often use a clip lead to a convenient grounding point - then I only need to look at one probe. Keep your meter close to where you're working so you don't have to move your head to take a reading.

Know how your meter operates and how it scales. Some meters auto-range, some have fixed ranges. When measuring voltages set your meter to the appropriate range and establish whether it's DC or AC you want to measure. If you don't know what voltage to expect, set the range to the highest and then drop it a range at a time until you get a reading. Be sure to know what your meter displays if it's over-range (where the voltage you're reading is higher than the range selected).

Another safety tip for your circuit is not to attempt a voltage measurement with your meter set to a current range (A or mA) as this will short out the circuit under test. Especially important of you've been measuring current before you put your meter away. It's a good idea to always return your meter to voltage testing - with many meters this involves relocating one of the probe plugs.

[kanks]

There is vey little safety concerns with this amp unless your working on the power brick as it's purely a modelling amp. I've fixed a few by reflowing the dsp. It's a bga so takes special tools and a bit of practice. That being said its already broken.

[KellyGrant]

I have the same issue. If I wiggle the power cord on the back of the amp I see some life, so it's likely a solder connection. Can't get the back connector off!!

[g1]

Can't get the back connector off!!

Which? Remove the screw on the DC jack and the nut on the 1/4 inch jack, flip the board over. If the orange wires don't leave enough room, de-solder them from the switch.