PSU heater voltage at 1.3V?

[MrKettle]

It's going to be tomorrow at least before I can get to it to test again. I have a spare regulator so I may wire that one up again and test the voltage at the input to it before the regulator is connected to check there isn't a case of GIGO going on.

[MrKettle]

And the verdict is that the rectifier is also dead and it isn't coming out without taking the circuit track with it, so an email has gone in to request replacement internals for the PSU.

[pre65]

Can you not solder a new bridge to the legs of the old one ?

[Richard]

Hi, that's a pain they can be difficult. I'm with Philip and think you have little to lose just cutting through the old bridge and then removing the legs from the pcb one by one. Then make up the daughter board bridge with 1N5822 or similar schottkies. You will then have long legs to feed through to remake any damaged track connection.

http://www.world-designs.co.uk/forum...ead.php?t=4158

UF4007 would be fine for the HT or high voltage schottkies if you have deep pockets.

The 78S05 probably failed first time then connecting the LM1084 the wrong way may have taken out the rectifier. If you use Pre3 and Phono3 from it the heater load is 1.5A so the 2A rated 78S05 would be working pretty hard. The LM1084 is much better rated at 5A.

If you do get the later pcb re-consider how the instructions show to connect the regulator. It is shown connected from below with short wires soldered on top after both are in place, so removing the pcb after would be difficult, typical manufacturer method that You could clip the leads I suppose to get it out again but short wires as originally done are better for diy imho.

[MrKettle]

Given the hamfistedness of the soldering I may take this opportunity to change over. Does anyone have a circuit diagram for the later PSU3?

[bob orbell]

Hi Mk, if you are running PRE3 & PHONO3 then you do need the CD, if you are running WAD2,s then you will need the same components as you already have, the circuits are the same but with some different resistor values, what are you running? BOB

[Richard]

Here's both for anyone finding themselves in a similar situation or wanting to rebuild theirs instead of modding the early one.

The "arrangement 2" referred to earlier was built on the first PCB using a bridge made of schottkies in place of BR1 and a LM1084 5V reg (still with the 2 diodes ground lift) in place of 78S05 (change the reg pinout wires over).

The later PCB changes are,
1) provision for fitting bridge package or separate diodes for the heater (I would definitely fit shottkies there rather than the bridge package)
2) pinout positions and order changed for LM1084 ADJ
3) provision for 2 resistors to set regulator voltage instead of the 2 diodes
4) double sided re-worked track layout

I'm sure Matthew will be able to supply the board and parts needed

[MrKettle]

The swap over has been done now with the Schottky diodes and with the regulator attached via wires. Initial signs in the very short amount of Radio 3 that I had time to check were that it was working as expected (with no relay chatter from the Pre3) once I realised that I may have had the wiring colour scheme for the heaters reversed originally, but there will be a fuller check in due course.