Mains setting meter CT160 - UK Vintage Radio Repair and Restoration Discussion Forum

Commerwel · 21st Jan 2020, 8:18 pm

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.

Dekatron · 27th Jan 2020, 11:32 am

You should use the service manual and go through the checks there before you do anything else.

/Martin

Station X · 27th Jan 2020, 11:43 am

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.

WME_bill · 27th Jan 2020, 7:22 pm

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

golexica · 6th Feb 2020, 1:44 pm

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?

Commerwel · 6th Feb 2020, 2:52 pm

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

John_BS · 6th Feb 2020, 6:53 pm

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

21st Jan 2020, 8:18 pm	#1
Commerwel Diode Join Date: Jan 2020 Location: Apeldoorn, Gelderland, The Netherlands Posts: 3	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. Attached Thumbnails

27th Jan 2020, 11:32 am	#2
Dekatron Octode Join Date: May 2009 Location: Linkoping, Sweden Posts: 1,465	Re: Mains setting meter CT160 You should use the service manual and go through the checks there before you do anything else. /Martin __________________ Martin, Sweden

27th Jan 2020, 11:43 am	#3
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,288	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. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

27th Jan 2020, 7:22 pm	#4
WME_bill Octode Join Date: Oct 2007 Location: Exeter, Devon, UK. Posts: 1,554	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
golexica Triode Join Date: Jan 2020 Location: London, UK. Posts: 41	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
Commerwel Diode Join Date: Jan 2020 Location: Apeldoorn, Gelderland, The Netherlands Posts: 3	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
John_BS Octode Join Date: Dec 2008 Location: Wincanton, Somerset, UK. Posts: 1,780	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