Great pulls from the recycling scrapheap

[Tubetec]

Todays find was a Thurlby Thandar instruments EL302 bench psu ,
30V@2A ,single rail , linear regulated ,UK made , its not as nice as the two HP units I have already ,but its still a real workhorse .
The cal cert is only a few months out of date and a basic test with a DMM seems to show everything is working as it should .
It has a Logitech badge and ident code.

TTi EL302.JPG (24.63 KiB) Viewed 10725 times

[mediatechnology]

Maybe we should change the thread title to "Great Pulls."

I got a similar B&K Instruments supply a few years back that a friend found at a recycler.

[Tubetec]

Im not sure how to change thread titles ,
'Great pulls from the recycling scrapheap' would add context ,
One things for sure , the amount of good usable equipment available from this source isnt likely to come to an end anytime soon .

[mediatechnology]

I got an email the other day from a recycling firm looking to pick stuff up and inquired about them selling stuff from the "heap."

Never heard back but should probably pay them a visit.

I edited your first post to change the thread title since the hits keep on comin'.
I think you can do that as well.

[Tubetec]

Id been thinking about using a 110V Hitachi angle grinder I picked up recently ,
As luck would have it today there was a pair of the yellow worksite isolation transformers down at the recycle ,
0.75 kvA and a 3.3kvA units ,
As I was on foot I decided against hauling away the larger unit which weighed around 30lbs , instead I took the smaller 750W ,
It looked like it took a fall as there was some damage to the case around the 110v output socket , other than that it needed a new mains cable and plug on the 240V side and a handful of nuts, bolts and washers to put it all back together .
I spent an hour or so working on it , adding a piece of tough plastic over the damaged area .
The job was a good one , it works perfectly , not only have I saved myself around 85 euros on the price of a new transformer , but also the resources and human effort that goes into making it . Its another win/win for me and the planet .
Uptil now I had been using a 500vA autoformer as a bench 110V supply , but it was a bit of a pig of a thing with a noisey buzz , it also generated quite a lot of heat when energised but left idle .

[mediatechnology]

Great find!

The "0.75 Kva" label bothers me.

"v" and "a" were people and should be uppercase "V" and "A."

[Tubetec]

I copied what the label said without thinking ,
the mistake seems to be common enough online .

They recommend derating by 33% for continious use , the usual benchtop 110v autoformers typically derate by 50% .

I was wondering , would disconnecting the secondary centre tap from ground be of any use in a benchtop situation , obviously the equipment PE/chassis must still make a connection to mains earth for safety reasons .

[mediatechnology]

It is a common mistake.
I sometimes capitalize "S" for seconds which should be lower case.

JR had a big thing about "bus" and "buss."
I think "buss" came from Bussman.

The grounded center tap is not something we see often in the US on 110/120 branch circuits.
It is similar to the Equitech isolation transformers and keeping it grounded, for "balanced power" might actually be quieter than floating it.
https://equitech.com/

US 220/240V circuits do have a neutral center tap which is then bonded to earth ground.
On residential service it is bonded at the service entrance.

[Tubetec]

I read up a bit about isolation transformer safety ,
some guys in the trade fit fuses inside the housing on both secondary wires , as the primary thermal cut-out isnt always fast enough acting to prevent damage under certain fault conditions .

I was down the yard again this afternoon just before they shut for the weekend , I found a Stihl battery powered lawn mower , I was able to grab the battery and charger , which work perfectly , really I should have taken the mower too as in all likelyhood its only a minor fault and parts are readily available if the need arrises , I'll be going back down first thing Monday morning , hoping its still there .
Its a 500 euro machine new with very light usage by the looks .
People have more money than sense these days........

[Tubetec]

I went down and grabbed the Stihl mower , its a model RMA 339 , 625 euros new ,including the battery and charger
Somehow the mechanical interlock had gotten out of alignment , after a quick dismantle and re-assembly its working again , there was no broken parts

I dont have a lawn in my new place so I had to test it out on a nearby grassed area , it does what its supposed to do ,
Its good for 300 square meters on a single charge ,
Manufacture code dates it to 30/2020 ,
its in good general condition apart from a few abrasions and scuffs in the lower plastic cutting deck ,
I spent a bit of time giving it a good clean as there was some accumulations of grass and pollen inside the motor housing ,
I added a couple of wide cable ties as one of the cable retainers was broken .

I already have at least two interested buyers , both friends of mine

I know you mentioned how much you love the weekly mow Wayne ,
I miss being groundskeeper at my old place a lot ,
Sadly not a patch of green underfoot in my new place , its concrete jungle all the way .




Just a few more thoughts on the iso transformer ,
It would be nice to add a few extra bells and whistles specifically for the test bench,
A bypassable series lightbulb limiter , abillity to lift the secondary centre tap ground reference, proper fusing of the secondaries , a set of multimeter probe test points , and maybe incorporating a short loop in the cable to get the current clamp meter in there .