Farnell type C1 power supply

[drgius]

Hello everyone,

does anyone have any service manual for the FARNELL C1 Power supply?

I brought this power supply home, to sit beside me on my workbench, because it used to be my grandfathers (never seen him using it tho). When plugged in power supply has constant CI (current limiting) light on. I have opened case and couldn't find anything obvious.

before starting this new thread I tried to search for any info that is already posted and found this thread https://www.eevblog.com/forum/repair/farnell-c1-bench-power-supply/ , unfortunately the link provided to collection-achivist is not working for some reason and I sent pm to the SgtTech but his last activity was in 2020 

any help is greatly appreciated!

I have uploaded few more pictures that shows boards inside
https://imgur.com/a/cOYSL7h

[bob91343]

Many of these power supplies have a protection diode across the output.  I bought one at a swap meet for $2 and sure enough, replacing the shorted diode fixed it.

[FIXITNOW2003]

I have fixed some TTi PL320's with shorted diodes across the output

[drgius]

thanks for your inputs Fixitnow2003 and Bob91343, I will try to probe inside and basically check every single diode to see if it's blown or not 

edit:
I was testing diodes with my fluke 115 and I thought they were fine because meter indicates around 0.6v drop , but not I have the benefit of the doubt. Can someone talk me through how to test Zener diodes with DMM? Google suggested me few websites and they all basically says that DMM in resistance mode should read relatively low resistance on forward bias and in Megaohms in reverse bias. I am now checking Zeners made by hughes HS2051 and getting both ways.... Is this an indication of a bad Zener diode? if I go to diode mode it shows 0.6v forward bias and around 1.3v reverse bias.

I have attached few pictures to show what I mean.
   

[BrokenYugo]

To properly test a zener you really need it out of circuit and you need some current limited source of voltage higher than the zener voltage (a DMM is good for like 3 volts). You also need to know what the zener voltage is supposed to be.

It was suggested you check one diode, they told you where it was, across the output, follow the output + and - back until you find a power diode between the two. It sounds like it may be functional otherwise, hence the suggestions to check the output diode which is often damaged by user error.