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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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21st Jan 2020, 8:18 pm | #1 |
Diode
Join Date: Jan 2020
Location: Apeldoorn, Gelderland, The Netherlands
Posts: 3
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Mains setting meter CT160
Hi, I'm new on this Forum.
I have the following Problem. I have a AVO CT160, which is in my possession for a long time. Never really used it but the problem is the meter reading when switching it on. The reading for the mains, (~ Circuit Selector) stays in the middle of the scale. I bought this CT160 from a friend, but probably the meter has been changed. I've read different threads about this meter and it seems that serials nr. above 4000 (mine has 4466-N-62) have a different resistance. After measuring the movement coil is 3200 Ohms. Too much I think. Can anybody give me a simple solution so the reading will be Full Scale. The Shunt resistor is 10K and there is no swamp resistor inside the meter. See attached picture. Any help is welcome. I want to sell this CT160 but first I want to repair it, if possible. |
27th Jan 2020, 11:32 am | #2 |
Octode
Join Date: May 2009
Location: Linkoping, Sweden
Posts: 1,465
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Re: Mains setting meter CT160
You should use the service manual and go through the checks there before you do anything else.
/Martin
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Martin, Sweden |
27th Jan 2020, 11:43 am | #3 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
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Re: Mains setting meter CT160
Given that the meter has an fsd of 30uA without the 10k shunt and 39.75uA with the 10k shunt, your reading of 12.4uA at 40% of fsd looks fine to me.
12.4 X 100/40 = 31. The resistance reading of 3200R (spec 3250R) looks good too. The fault is probably elsewhere.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
27th Jan 2020, 7:22 pm | #4 |
Octode
Join Date: Oct 2007
Location: Exeter, Devon, UK.
Posts: 1,554
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Re: Mains setting meter CT160
CT160 set mains.
I have found the two resistors R3+R4 = 1.32M 1% tend to go high, so check the value of those, as they set the calibration of the whole instrument. wme_bill |
6th Feb 2020, 1:44 pm | #5 |
Triode
Join Date: Jan 2020
Location: London, UK.
Posts: 41
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Re: Mains setting meter CT160
If my eyes don't deceive me, that meter seems to be set for a mains voltage of 215v?
isn't Netherland nominal 230v with probably 5% variability on top of that? couldn't the higher voltage damage it, or at least throw it off calibration? |
6th Feb 2020, 2:52 pm | #6 |
Diode
Join Date: Jan 2020
Location: Apeldoorn, Gelderland, The Netherlands
Posts: 3
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Re: Mains setting meter CT160
Hi all.
I found the problem of this. In the lead of the 2 tubes there is a jumper which was not connector. Zo the qurrent was'nt enough to provide full scale of the meter. Thanks for thinking with me. Roel |
6th Feb 2020, 6:53 pm | #7 |
Octode
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,782
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Re: Mains setting meter CT160
Glad you've found the problem. It's a very good and useful tester. There are a couple of modifications outlined in several posts on this forum which are designed to protect the "unobtainable" components of this tester. Please PM me if you can't find the details.
John |