Apex A-class PSU problem

[andresolomko]

HI! Anyone who build it actually. I do have a problem.
I build only upper part i.e. positive. I am feeding a circuit from bridge rectifier
from 24v transformer via diode bridge. So I have 37 v (about) on input.
As soon as I have no load, it gives me 25, 6 -26 v (I tried with different transformers) With load attached I have a drop in half.
Also with load on collector of BC640, which is linked to NPN output device I have 0v, i . e. it's locked Without load it shows about 10v.
I got a few cases when it was running properly, by changing transistors, but after a while
it gives a smoke, and BD640 and 22R are dead.
I couldn't obtain BD241/2 so I was using MJE29/30T (more powerful)
now I tried with TIP31/32C with the same result
My guess is the problem on this cascade BD640-NPN output. Can't think of anything else.
Schematics are suggesting BD241/2. I can get those in a few days, but only
C version. Will it work?

Anyone please help!

 

[Project16]

What is the pcb you use?

 

[andresolomko]

I am using this one what was on original thread I am not sure how to upload image hereView attachment apex psu mirrored.pdf

 

[Project16]

The problem can then come pinout of bf245 because according to the manufacturer there different pinout.

 

[andresolomko]

Thanx a lot, that's interesting. I am not sure which one I have. But what should be correct voltages on BF245? Can you enlight. Would it work at all with wrong pinout?

 

[andresolomko]

I have no idea what 245 I have there is no markings on packages, only "made in china"
(no doubt) and BF245C/107 on a device itself

 

[AndrewT]

The problem can then come pinout of bf245 because according to the manufacturer there different pinout.

I got bf244 and bf245 a while back.
My test results were all over the place.
Until I realised (after asking here) that I had assumed wrongly that the devices had the pin out shown on the wrong manufacturer's datasheet.

Fortunately very few were damaged, due to DS symmetry.

markings:
f D331 BF 244A
f B444 BF 244B
f B516 BF 245C

And codes in the obverse dimple. (I'm not stating them here in case a Faker copies them).

 

[andresolomko]

Thank you for a kind replies. Here is a Bf245 what I use: http://docs-europe.electrocomponents.com/webdocs/002f/0900766b8002f1a2.pdf
It's made by some "DS" company, but datasheet supplied is from Philips.
If I can believe this doc, it's all correct on pcb, or did I miiss something?
To make things even more confusing, here is one example: Transistor Fet - Bf 245 - Bf 256 - Bf245 - Bf256 - R$ 10,00 no MercadoLivre If you look at this datasheet gate and drain and sourse have changed positions. Even pinout is definitely from Philips.

 

[andresolomko]

i.e. pinout on my bf245c looks like that DSG looking from pin side from top

 

[andresolomko]

Actually i tried it with 2ks170. There is a huge voltage drop. no more then 5v I can get and
then it drops to 4 with load
I am just thinking if I am using BF245C instead of A, can it be a problem? Anyone with experience? Pls help?

 

[andresolomko]

I found today fairchaild-made NOS 245A. Pinout is sure right. Installed it. Device works fine, regulates etc. as soon as you have load attached it drops to 9v max. Even LED make such a problem.
Anyone can reply? Did you actually build it with this layout?
I have seen so many reports of successful building. Problem is around BC640C what I am using and TIP31. Sometimes device works for a short while properly, but then you have a BC burned. I burned 2 pieces today

 

[andresolomko]

Ok, my problem was introduced by a bad diode. Easy fix, hard to guess.
Just one question: I installed BD440 instead of BC640. Seems to be working, but is there any potential danger?