21.6V across the resistor explains why it's burning.
0.7V across the Zener indicates it's back to front, i.e. forward biased, check it's direction again.
J309 may now be damaged but fix the Zener & resistor first.
Buy yourself a plug board. A couple of £ from Maplin and many others. Ideal while your learning and continues to be useful long afterwards.
Save that expensive Veroboard for proved circuits.
0.7V across the Zener indicates it's back to front, i.e. forward biased, check it's direction again.
J309 may now be damaged but fix the Zener & resistor first.
Buy yourself a plug board. A couple of £ from Maplin and many others. Ideal while your learning and continues to be useful long afterwards.
Save that expensive Veroboard for proved circuits.
AndrewT said:
Morning Andrew
Thanks for checking those figures
I'm not trying to challenge your advice, but when I measured the voltage across the Zener, before I cut the tracks and added a couple of links as per Audio1st diagram, I took a reading of 36v from this side of the Zener. Should the anode or cathode be connected to the drain pin of the J309?
Zener Data Sheet
http://www.datasheetcatalog.org/datasheets/105/105630_DS.pdf
I have some spare parts to swap out the faulty components and will have a go at this tonight
Hi,
what power of Zener is that?
A 400mW glass packaged Zener will do the job better and cheaper. Rapid sell them for 2p each.
A 24V 400mW Zener requires at least 0.8mA (5%) to operate properly and better to have at least 1.7mA (10%) to operate well.
A 1.3W device asks for too much current to get around the knee in the I vs V curve.
what power of Zener is that?
A 400mW glass packaged Zener will do the job better and cheaper. Rapid sell them for 2p each.
A 24V 400mW Zener requires at least 0.8mA (5%) to operate properly and better to have at least 1.7mA (10%) to operate well.
A 1.3W device asks for too much current to get around the knee in the I vs V curve.
I go over this sort of circuit with the meter, checking that each connection, of each component is connected to what it should be, and perhaps more importantly, that it is not connected to anything that it shouldn't be.
That can be a long and laborious job, but usually results in the circuit working first time.
Like Barry, my suspicion was that there was a short somewhere. Barry pointed pointed out one possibility, but there may be another one or two!
That can be a long and laborious job, but usually results in the circuit working first time.
Like Barry, my suspicion was that there was a short somewhere. Barry pointed pointed out one possibility, but there may be another one or two!
AndrewT said:
Hi Andrew
I’ve built a LM317 regulated supply, but this is my first project by following a schematic, and first with discrete components.
I have really appreciated all the help so far and I have learnt a lot from this exercise as I’m sure others will have too.
A large number of users on this forum may be quite technical but will have had little experience in electronics. Most wouldn’t even try to have a go if it wasn’t for the likes you, Audio1st and Nick to name but a few.
