TTi - PL330 Bench Power Supply Repair

[node1e]

HI all,

I managed to pick up a Thurlby Thandar Instruments PL330 bench power supply for free knowing that it didn't work but figured I could crack it open and fix it.

I've got it open and found a burnt out resistor, it looks like a current sense shunt of some kind. It was open circuit and I've managed to remove it from the board but now are stuck as to what value to put back in there. Image below shows the resistor position, its on the control panel PCB with the 8-seg displays and voltage/current control pots.

Any help appreciated.



Thanks

[singapol]

You can write to TTI and ask for service manual? Like in this thread?

https://www.eevblog.com/forum/reviews/hello-(and-the-insides-of-a-tti-thurlby-thandar-pl330-power-supply)

[Andy Watson]

This thread has a link to the early version service manual:

https://www.eevblog.com/forum/buysellwanted/tti-pl310-psu-service-manual/

I have a copy of the later version, but the forum software won't allow me to attach it (too big ).

[PTR_1275]

I've got the full service manual at work, if you pm me your email address I can send it through to you.

The 1 ohm resistors on the regulator board normally burn out if there is a overload too. The transistors on the ones I've repaired have never gone bad.

[PTR_1275]

I just looked at your photo in more detail, the gold Aluminium resistor to the left of the red box is the current sense resistor. I can't remember what the one you've marked is but I'll see if I have a copy of the manual on my phone.

[voltsandjolts]

Not sure if this is the revision of manual you need...

[node1e]

Update:
With the manuals received and thanks to PTR_1275 I have been able to successfully replace the burnt out resistor with a 2K2 3W wire wound resistor and the PSU is now working and found a new home on my work bench.

Thanks for the all the help.

nodee

[PTR_1275]

Awesome to hear you've got it working and there wasn't anything else wrong with it.

I know the ones on my bench needed their voltages to be tweaked a little bit, did you do a cal check while you had it open?

[node1e]

That would of been a good idea! I'll get my meter out and have a check later today.

Thanks,
nodee