Psu 3 testing

[justin brown]

Hello all,
I've finally finished building my psu and phono 3s XL.
So now I'm testing. Voltages are within spec, apart from the heater terminal pins on the pcb. The spec is between 5.9-6.7. Mine read 7.
The led also blows after about half a second.
I have checked all of the joints and wiring, the position of the components, and it looks fine, but obviously there is too much voltage passing through somewhere.

Any suggestions?

Thanks,

Justin.

[John Caswell]

Hi Justin,
Look carefully at the wiring/components around the LT1084 regulator. Are they around the right way is the insulation between regulator and case there or correct.
With everything correct the voltage out of the regulator should be very close to 6.3 Vdc.

John

[justin brown]

Thanks for your input John. I checked everything you said...
Wandering around on my lunch today, I started to think...
I'd only had the mm on 600Vdc! A replacement LED (of the correct voltage, from Matthew) and I am away! Very happy to have done this. My phono is built, but I have a little bit of tidying up to do... I wonder if I'll be playing records tomorrow?

[John Caswell]

Hi Justin,
An easy error.
I know people don't like standard DMMs but the autoranging ones can be a pain as you often do not notice they have changed ranges.
It is very good practice to use a standard one and set it to what you think is the required range and then it soon shows if it has been overranged.

John

[justin brown]

Hi John,
It isn't an auto ranging mm! I think it boils down to what you said about before (engaging brain first-having to make a decision as to what to do/how to use it/what the setting should be).
Up to that point, the range I had needed to use WAS the 600Vdc setting... I suppose I slipped into a mode of not thinking about what I was testing for.
I have been in regular contact with Matthew Snell since I started testing, and he has been extremely kind and patient. He did ask if I knew how to use a mm (in a way which was supportive and encouraging, not patronising)...and it just got me thinking (whilst I was at work) about logical reasons. It then occurred to me that the reading that I needed was a real number, not an integer. Then it clicked! When I got home I tested it and that was it.
I completed the phono stage itself today, and only ran a couple of checks on it. They were both fine, the LED worked, and the valves were glowing. So, I set it up..I have been without vinyl replay for about 6 weeks, so I was Verging on desperate for a listen... Unfortunately there wasn't any music. I've had a break for a couple of hours, but I am now running some continuity tests as I type this, and think I may have found (the first) fault... So, we shall see...

Justin