The ebay generator restoration thread

The ebay generator restoration thread

Author
Discussion

Blue32

Original Poster:

438 posts

168 months

Saturday 18th October 2014
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I gave the battery tray a couple of coats of satin black paint and attached to the frame.


Battery charging circuit built, its based on a LM350K voltage regulator. The output of the regulator has been set to 13.8v so it will bring the battery up to the correct voltage without over charging.


I connected the charging circuit to the battery cable which feeds the starter motor, the output from the charger is the red wire behind solenoid.


All finished


cold thursday

341 posts

127 months

Saturday 18th October 2014
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Excellent work going on here.
Thanks for sharing this. I have been following the thread for some time.
Respect to you thumbup

Edited by cold thursday on Saturday 18th October 22:06

paul.deitch

2,086 posts

256 months

Monday 20th October 2014
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Morningside said:
Ah, the good old 555.
OT - The guy that designed the 555 died not long ago.

ruggedscotty

5,606 posts

208 months

Monday 20th October 2014
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excellent thread. Nice pictures and detailed write ups....good on you sir

MatrixXXx

653 posts

151 months

Tuesday 21st October 2014
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Be careful your battery doesn't block your air flow into the alternator windings.

williredale

2,866 posts

151 months

Tuesday 21st October 2014
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Cracking thread. Bookmarked!

hornetrider

63,161 posts

204 months

Tuesday 21st October 2014
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williredale said:
Cracking thread. Bookmarked!
Fascinating thread, love it.

grahamr88

421 posts

172 months

Thursday 30th October 2014
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Since we have an in-house generator expert, I may as well try to get some help here!

I recently bought a secondhand 2.2 kVA generator, with a Honda GX140 engine. Sold to me as fully working, but I think I know why it was cheap now.

The voltage output seems to be all over the place. At idle, with no load, the engine surges a lot, and the voltage seems to vary hugely accordingly.

When I stick a load on there, such as a 2 kW fan heater, the voltage settles down to about 220 V, and remains fairly stable.

With the fan heater on a lower setting however (1 kW maybe?), the voltage output soars, going well over 300 V at times (and maybe higher, I switched off the power output fairly quickly at this point!) I think this is what killed my battery charger and tyre warmer the other day.

I don't know quite how the voltage regulation works in this generator, I've had a bit of a look inside the alternator, and it has a 10 µF capacitor but not a lot else. The capacitor seems ok when checked with a multimeter - the resistance starts low (ish) and quickly increases to infinity.

Is the voltage output controlled entirely by the mechanical governor? This is certainly moving a lot, especially with no load, but I've not checked the internal parts of it.

Any ideas as to what the issue might be? I'd like to fix this rather than give up and buy another, but don't want to spend too much money chasing dead ends.



Edited by grahamr88 on Friday 31st October 11:29

hidetheelephants

23,772 posts

192 months

Thursday 30th October 2014
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With the passive uncontrolled ones the capacitor is critical, and not expensive to replace; as they can start to go off without going short circuit it's a low cost option to just replace it to see if it helps. The speed/voltage instability may also be the governor mechanism, so have it apart, or at least clean and lubricate the bits(AKA blast any grot off with squirty oil).

grahamr88

421 posts

172 months

Friday 31st October 2014
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Thanks, I'll pick up a new capacitor this weekend and see if it helps. Got to be worth a try! The governor mechanism moves freely enough, the spring seems fairly weak though, I wonder if that's part of the problem.

UPDATE: I went to get a new capacitor earlier, and the place offered to test the old one. It had a capacitance of 9.5 µF, so within the tolerance, and they were confident that it wasn't the problem.
They did suggest that I give the contacts a good clean up to ensure that it's connecting properly, which I did, and now when I test it with a 1 kW load, the voltage is around 280 V (+/- 10 V), so slightly better, but still not good. May be totally unrelated to cleaning the contacts of course!

I forgot to mention before that this also has a 110 V output, which I measured at around 140 V without any load, and I unfortunately don't have any 110 V tools I can connect to it. So whatever the problem is, it seems to be affecting both outputs, unless the 110 will droop down to where it should be under load.

Edited by grahamr88 on Friday 31st October 11:37

hidetheelephants

23,772 posts

192 months

Friday 31st October 2014
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The spring may well be the culprit then.

Blue32

Original Poster:

438 posts

168 months

Friday 31st October 2014
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The unstable engine speed sounds like it’s a problem with the carburettor, Honda have a check sheet for diagnosing running problems http://www.honda-engines-eu.com/web/eec-public-sit...

It's probably worth stripping the carb down and cleaning the jets, it's common for the small holes in the main jet (no5 in the diagram) to become clogged. The trick is to find some really fine wire (I used a strand from some mains flex) and push it through all the holes and jets in the carburettor. Contact cleaner (aerosol type) from Maplin can be used to flush through the tubes inside the carburettor. My post on the 20th Sept on the previous page shows the main jet and the innards of the carburettor

Most of the poor/ non running engines we have encountered have been cured by stripping down and cleaning the carburettor, it can take a couple of attempts to get it right.

grahamr88

421 posts

172 months

Friday 31st October 2014
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Thanks for the advice, that's a handy check sheet!

I've had the carb apart once, and ultrasonically cleaned the jets, but it's certainly possible that it's still partially blocked so I'll have another go tomorrow.

I've bought myself a better multimeter (this is definitely a false economy!) which can measure frequency, so I'll try to measure the engine speed with that to determine whether it's the engine or alternator at fault.

I measured the output frequency with it earlier, and it seemed to be about 120 Hz... I'll confirm tomorrow, but that came as a bit of a surprise, especially since the voltage seemed to be about correct at the time.

Blue32

Original Poster:

438 posts

168 months

Sunday 2nd November 2014
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grahamr88 said:
Thanks for the advice, that's a handy check sheet!

I've had the carb apart once, and ultrasonically cleaned the jets, but it's certainly possible that it's still partially blocked so I'll have another go tomorrow.

I've bought myself a better multimeter (this is definitely a false economy!) which can measure frequency, so I'll try to measure the engine speed with that to determine whether it's the engine or alternator at fault.

I measured the output frequency with it earlier, and it seemed to be about 120 Hz... I'll confirm tomorrow, but that came as a bit of a surprise, especially since the voltage seemed to be about correct at the time.
120Hz doesn't sound right, the engine would be running at 6k rpm for that! What's the frequency when a load is applied ?
The engine speed should be around 3600 rpm for 50Hz. I think the governor should be set to give 53Hz at no load.

It might be worth checking the multimeter against the mains (via a transforemr for safety) as mains will be spot in 50Hz(just to confirm the multimeter is working properly).

grahamr88

421 posts

172 months

Sunday 2nd November 2014
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Ok just had a quick play, it's giving some very strange numbers!

Mains: 230 V, 50 Hz (multimeter is ok)
Generator at idle: 210 - 280 V, 750 - 900 Hz (!) (engine surges constantly)
Generator with 1 kW load: 240 V, 156 Hz (engine steady)
Generator with 2 kW load: 210 V, 260 Hz (engine steady)


Couple of photos of the innards if that's any help


spikeyhead

17,224 posts

196 months

Sunday 2nd November 2014
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I'll take a guess that the multimeter is counting harmonics rather than the main waveform. To see the real frequency you'll need an oscilloscope.

hidetheelephants

23,772 posts

192 months

Sunday 2nd November 2014
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spikeyhead said:
I'll take a guess that the multimeter is counting harmonics rather than the main waveform. To see the real frequency you'll need an oscilloscope.
What he said, those frequencies are all over the place.

grahamr88

421 posts

172 months

Tuesday 4th November 2014
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That makes sense. I'll have a scrounge around at work to see if I can find an oscilloscope or data acquisition kit.

EggsBenedict

1,770 posts

173 months

Tuesday 4th November 2014
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grahamr88 said:
That makes sense. I'll have a scrounge around at work to see if I can find an oscilloscope or data acquisition kit.
Don't know how good these things are but worth a google for 'USB Oscilloscope'.

http://www.amazon.co.uk/gp/product/B00CIO7L12/ref=...


???

spikey78

701 posts

180 months

Tuesday 4th November 2014
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Hi, I wonder if you could help me with an old Honda genny I've got.. I think it's a gx240 engine, it all works fine but I wonder if there is supposed to be some kind of idle control? The problem is that when running off load it's fine-as soon as you start putting electrical load on the genny the idle drops way down and then off course the power output drops too.
I seem to remember that it should maintain the rpm? Whereas now I have to manually wind up the idle when it's under load..
Hope that makes some kind of sense!
Thanks