No power to Crack

[Stanshall]

Hi there, noob here. I've just finished my first build and unfortunately get no power to the Crack when I switch it on. I've checked all connections, really took my time with it, and I don't see any mistakes. No power to the LEDs nor tubes. All my resistance checks came out correct.

Besides resoldering every connection, is there a way I could analyse where the issue might be?

Any help would be much appreciated.

 

[Paul Birkeland]

Did you install the fuse?  (It goes in the little clip, not the square tube in the power entry module)

You can measure AC voltage between L and N on the IEC power entry module to be sure you're seeing line voltage.

-PB

 

[Stanshall]

Thanks, Paul.

The fuse is definitely installed correctly.

To measure line voltage, do you mean connect it to the mains and measure on the reverse of the IEC power entry module?

I am using a 240v transformer, by the way. I wonder whether there's anything different I needed to do with my wiring?

 

[Paul Birkeland]

To measure line voltage, do you mean connect it to the mains and measure on the reverse of the IEC power entry module?

Yes.

 

[Stanshall]

Ok, I got approx 240v from the lower neutral pin and a flickering/not a lot from the upper neutral pin.

Would this suggest that my switch soldering needs redoing, in the first instance?

 

[Paul Birkeland]

Ok, I got approx 240v from the lower neutral pin and a flickering/not a lot from the upper neutral pin.

Look at page 15 in the manual - the pins are very clearly labeled with white letters.  You want to measure the AC voltage between "L" and "N".  We have not gotten to the power switch yet.

 

[Stanshall]

My apologies.

I get a zero reading between L and N.

 

[Paul Birkeland]

I get a zero reading between L and N.

This indicates improper fuse installation, or a blown fuse.

You can remove the fuse, set your digital volt meter to beep for continuity, then test the fuse.  (Our fuses can be a little tough to visually inspect)

 

[Stanshall]

I'm getting a flickering reading of 0.5-0.7 for the fuse which seems to suggest it's not blown.

As you can probably tell, I'm an absolute beginner, so I may have misinterpreted that reading.

I'll pick up another fuse tomorrow, though, will give it a try.

Is it worth my testing the voltage without a fuse, as a separate check?

 

[Grainger49]

Hmmm,

If you have a good fuse then post pictures of the IEC module and the wiring to the power supply. 

I'm thinking something is open (what is often called a short).  The voltage is not getting there because of some attachment, or a misplaced wire.

 

[Stanshall]

Thanks very much. It's bedtime over this side of the world but I'll get on the case tomorrow.

I appreciate the patience and support!

 

[Doc B]

Looking at the logic of the circuit, the other place where the current can be stopped going through the transformer primary is the power switch. If it was heat damaged during soldering it could cause this problem. With the amp unplugged from the mains socket, test the resistance across the terminals of the power switch with it thrown to the on position and see if you get the correct very low ohm reading. If it reads high/open when switched to on, the switch probably needs to be replaced.

Sometimes the terminals themselves will wiggle a bit in the switch body if this is the case.

And for those who may be new, in fact an open circuit is the exact opposite of a short circuit. An open means a connection that should be there isn't. A short means a connection that shouldn't be there is.

 

[Stanshall]

Obviously, I couldn't sleep thinking about it.

I've just checked the resistance across the switch and I get a 0.1-0.3 ohm reading, which seems to be ok.

I'll post pics tomorrow. First time solderer, what I think is my best/cleanest work may well be a disaster area.

Thanks again fellas.

 

[Paul Birkeland]

There's a very real chance that you also aren't quite measuring the AC voltage correctly.  You can measure the AC voltage between the outer two holes in your power cord while it's plugged in.  You should see 220V-240V at this point. 

If you don't, then consult the manual for your meter to be 100% sure that you are performing the measurement correctly.

-PB

 

[Stanshall]

Quick update on this one. I've tested the IEC power entry module and I got a reading of around 240v, which is a start.

I've attached some photos below of my wiring/soldering of the IEC. Any help, as ever, is much appreciated.

Cheers.

 

[Paul Birkeland]

With the power switch on, what kind of AC voltage do you see between terminals 1 and 2 on the power transformer?

 

[Stanshall]

I've got a reading of 236v.

 

[Paul Birkeland]

OK, that's good! How how about power transformer terminals 4 and 5?  How about 9 and 10?

 

[Stanshall]

4&5 give a reading of only 5v.

9&10 give a very erratic reading, jumping around.

Unbelievably, I've just seen that B7L and B8L have not been soldered. I've read through the manual several times though and can't see when I was supposed to have soldered these. The bottom of page 18 says attach but do not solder these points.

Have I gone wrong somewhere?

 

[Paul Birkeland]

Unbelievably, I've just seen that B7L and B8L have not been soldered. I've read through the manual several times though and can't see when I was supposed to have soldered these. The bottom of page 18 says attach but do not solder these points.

The tube socket pins are not differentiated by lug height (sometimes the only octal sockets we can get only have one hole per socket pin connection).

At this point, you should have glowing tubes? 

The erratic reading at 9 & 10 should be stable - if your meter has multiple ranges, try going down one (since you can measure the ~230V going into the amp, and that pair of transformer terminals should be ~160).  Do you get the same erratic reading at power transformer terminals 6 and 7?