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Station X 2nd May 2019 1:30 pm

Re: Elizabethan LZ-29
250VAC will be fine as a starting point. I didn't know what ranges your meter has.

Sideband 2nd May 2019 4:06 pm

Re: Elizabethan LZ-29 the risk of sounding patronising....we have already said that the resistor will run hot and the reasons for it. We have already said to leave it running for at least 20 minutes, possibly even longer to burn off any grease/oil that may have got on to the resistor. Then you ask if you should leave it running......YES!!! If everything is working, chances are that there isn't a problem. You haven't answered the question of whether you have the circuit or service manual. Have you changed any other components (capacitors for instance)? You also haven't said why you changed the rectifier in the first place. We try to help but there is only so much possible with limited information from you......

Dorian27 2nd May 2019 6:09 pm

Re: Elizabethan LZ-29
Yes I did change RECTIFIER as I thought it was faulty but know put original back a day ago and all seems to run well apart from smoke on resistor .My volt meter reads 200v AC and750v AC so I took readings on resistor on750 and results are there are 3pins two segments first segment reads 200ohm and volts accros it is 110v and second segment at 1.5k reads 230v if I set meter to 200v AC I get 200ohm 11.0 and 1.5k at23v I have not squared any of these as I not sure which is correct if I measure straight across I get 132 v AC maybe you can let me known if this makes any sense to you many thanks

Station X 2nd May 2019 6:40 pm

Re: Elizabethan LZ-29
I'll rephrase that.

Meter on 750VAC range:-

Volts across 200R resistor 110VAC.
Volts across 1.5k resistor 230VAC.

Meter on 200VAC range:-

Volts across 200R resistor 11VAC.
Volts across 1.5k resistor 23VAC.

What I'm unsure of is which set of readings to use:-

Volts across 200R resistor 110VAC. 60.5 Watts
Volts across 1.5k resistor 230VAC. 35.2 Watts

Volts across 200R resistor 11VAC. 0.605 Watts
Volts across 1.5k resistor 23VAC. 0.353 Watts

Volts across both resistors 1.7k 132VAC. 10.25 Watts.

Do the readings have decimal points or leading zeroes?

Boater Sam 2nd May 2019 6:53 pm

Re: Elizabethan LZ-29
That makes the total dissipation less than a watt.
So this resistor must dissipate more when the motors are running, I reckon there is no fault.

Station X 2nd May 2019 6:56 pm

Re: Elizabethan LZ-29
Good point. The motor needs to be running when taking readings.

Dorian27 2nd May 2019 9:29 pm

Re: Elizabethan LZ-29
I did have motor on play when doing the readings on the 200v AC reading there was a decimal point but can't remember where I can do them again at week end if needed and thanks again

Station X 2nd May 2019 9:56 pm

Re: Elizabethan LZ-29
I'd bank on the 200VAC range readings being correct, in which case the power being dissipated is less than a watt, which is low for a wirewound resistor of that size.

If the 750VAC range readings are correct then the power being dissipated is nearly 100 watts which looks impossible.

I'd leave it running for a while and only get worried if the paint starts burning off the resistors.

Dorian27 4th May 2019 4:53 pm

Re: Elizabethan LZ-29
Hi thanks to you all for your valuable help . I left it on and the smoke has gone and all seems well. Thanks again for everything.

Boater Sam 4th May 2019 4:56 pm

Re: Elizabethan LZ-29
You're welcome, glad to help.

60 oldjohn 5th May 2019 3:49 pm

Re: Rectifier

Originally Posted by 60 oldjohn (Post 1140519)

Originally Posted by Dorian27 (Post 1140363)
fired up and sounded great for about fifteen mins then the big green mains dropper resistor started smoking so I turned it off.

Might it just be years of damp and dust burning off ? More measurement need to be taken to be sure.


Sound like I was right, They say there is a first for everything!


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