Skytronic 650,682. 0-30V, 0-10A psu repair

[m3vuv]

Hi all,i just received a Skytronic 650,682. 0-30V, 0-10A linear bench psu, thats faulty,as soon as i turn on the output it reads 50+v and relays click,a resistor gets hot on a pcb as well,i noticed t looks like its been dropped,the v adj pot was smashed off of the pcb,would that cause it,also any idea where to find a schematic?,i am layed up in bed after having a foot operation so cant get to my bench for a few days,TIA.

[m3vuv]

this is a linear job with tap switching,it contains a big big torroid.

[orbanp]

I wonder if the Welleman PS3010 is the same PS.
It is a linear 30V 10A PS. elektrotanya has the manual for it with the schematics:
<https://elektrotanya.com/cgi-bin/download2.cgi?dk=pnped36co84x71rtmddne26w35466i3uv1c3ll6m8k6lbu7a&fid=1620&file=velleman_ps3010_3020_power_supply_um.pdf>

PS: for whatever reason the possibility to include a link has disappeared for me

Regards, Peter

[m3vuv]

the webb addy isnt working

[m3vuv]

found it,it looks newer than mne,one thing is mine looks to use tip3055 outputs not 2n3055,i am bed bound at moment from an operation tho so cant check yet,i imagime its the same or nearly schematic wise tho,im not sure mine has a fan also but not 100% sure,thanks anyway,at least it gives me a starting point

[m3vuv]

thats mine in the pic.

[m3vuv]

would the missing/disconnected v coarse pot cause 50+v output and relays to go nuts?.

[mikerj]

would the missing/disconnected v coarse pot cause 50+v output and relays to go nuts?.

It certainly could.  This pot may be providing the negative feedback to stabilise the output, if so then without it I would expect the output to rail.

[m3vuv]

hope tomorow i can get to my bench without incident and fix it,so frustrated beeing stuck in bed.

[m3vuv]

ive managed to get a look at mine,it does have a fan,i took apart the remains of the old v adj coarse pot  and the carbon track seems to measure about 10k end to end,if this is the correct schematic,what would that pot be labeled as? tia,i just want to check it should be 10k.tia.

[m3vuv]

Well,i managed to get this together today,this is what it does:with the unit switched on but output off. The  tap switching relays buz quite loudly,on switching on the output v coarse fully ccw reads 2.7v,wont zero,the buzz of the relays is still there but not too loud,if i wind the voltage up too about 8v suddenly the buzz gets about half as loud againe,it stays the same untill i get too about 11v then it doubles in loudness,It stays like that untill about 25v then the buzzing stops,its quiet until max which is just under 32v,any idea what to check?,the schematic i have posted corresponds to my unit at a glance.This was just testing on the psu outputs with a dmm,not running any load,TIA.