Author Topic: Recovering ST1 with 4kVA Dunlite - looking for schematic  (Read 1199 times)


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Recovering ST1 with 4kVA Dunlite - looking for schematic
« on: July 21, 2021, 01:11:26 PM »
I finally understand the Lister bug, what amazing engineering.

I've been rebuilding an ST1 I got that hand't been looked after and after more than six months of pottering away at it in spare time, I have it thundering away (no muffler yet  :o ).
I've managed to overcome most of the issues I've faced thus far. I'd appreciate some help from the knowledge here though. I've read every relevant post and looked everywhere I can for an electrical schematic for the dunlite alternator and control box with no luck. I will say though that I learned a lot about all things lister reading loads of posts here. So thanks for all the great knowledge thus far.

Serial #: 5455 ST1 26 (I gather the 26 means 26 years after 1950, thus 1976).
Its coupled with a Dunlite 4kVA alternator and a "Dunlite Control" box. Attached are some photos of the name plates and inside the control box.
There are no electronics and any sort on the alternator it self that i can see. I've closely looked at the brushes and can not see anything there. As far as i can tell, its all in the box.

The alternator

Alternator name plate

Control box name plate

Inside the control box

Does anyone have a schematic for the alternator and control box?

AC output voltage is low (165-170v) at 50hz when no load. Used a resistive load (kettle) and the voltage rises once loaded to low 220s. I can't figure out how to adjust the voltage output at all.

I have figured out that big power resister with the adjustable tap seems to control the contractor cut in threshold. I'm getting 7-20ish volts DC across it (jumping around wildly).

I have managed to get the voltage higher by winding up the governor and accepting 60hz at which point I get about 200v when unloaded and it pulls on up to 235-245 when pulling 2-3.5kw.
So I sort of have it working but its not ideal to have it running at 60hz. Would really like to find out how to adjust the voltage.

The things I have done to the ST1 it self are as follows if you are interested. Otherwise stop reading here :-)

When I got it was in a pretty sad state. It had been undercover but the more I opened things up the more issues I found and honestly I am realising now that it really needs a complete once over.
What I've done so far is:
.040 rebore, new piston and rings
New valves, new springs, regrind seats and new seals (original guides remain as engine shop said they were in spec), new tappet arm bushes, new oil feed line tees etc
New gaskets and orings from the bore up including head and base gaskets. New injector pump element, new injector nozzle.
New cam shaft oil seal. New air filter, fuel filter....the fuel filter was terrible! OMG. Upstream and down!
I adjusted shims for correct compression ratio, have adjusted valves initially and after bed in. Ring end gap etc
Big end didn't "seem" to bad (very rough push pull test).
Checked and cleaned oil pump. Cleaned sump and mesh screens.

Checked the bearings and brushes in the alternator.
Reattached terminal blocks and reterminated all wires properly on alternator

I haven't pulled the bottom end, nor taken the flywheel off and I am pretty certain I am going to have to as the fan/flywheel shroud that the alternator attaches to is loose and vibrates a little when I run it and I think the bolts are behind the flywheel.

However, I have it running now. Starts very easily now after redoing the injector and pump.
What a satisfying feeling cranking it over and it thumping to life  ;D

I've eyed a CS 3/1 at a friends place. Thats my next one to try to get a hold of.

Thanks for all the great info on this site. Lots of super generous people!
« Last Edit: July 22, 2021, 12:10:25 AM by OzWildman »


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Re: Recovering ST1 with 4kVA Dunlite - looking for schematic
« Reply #1 on: August 09, 2021, 12:35:13 PM »

Shot in the dark here....

What kind of regulation system? Maybe transformer based as I think that's an inductor/toroid in the pic.

Where are you getting the excitation DC voltage from? How much?
If brushed, it's coming from "somewhere" and feeds the slip rings via brushes. Possibly that transformer in the pic.

Since you are getting some AC, it seems you have enough residual magnetism to start things rolling, meaning you are creating enough AC for rectification to happen (implying not enough field current upstream).

While I'm not sure this is the problem, you can verify this scenario by field flashing; connect a 12V battery, correct polarity to the brushes. Do you get 240?

Are both slip rings and brushes in good nick, springs are ok and free to move?
If ok, then trace back from the brush to the source of DC and see what's going on there.

You can measure the DC voltage at the brushes; disconnect the wires to the brushes and feed the brushes your own (variable)DC, a bit higher from another source( battery/ps?)  and see if you get your 240VAC at 50Hz. Again, a 12V battery should suffice.

If brushless, are the rotating diodes good? Is the excitation stator winding ok? Field flash here also?

Again, what kind of regulation system?
Regardless, be careful....