Hi,
When building a new x0xb0x, the vco seemed normal. Now that the x0x is completed, the VCO is unstable. When I caliber TM4, impossible to stay on 65.4 Hz over 10 seconds. The VCO oscillates constantly 65.4 Hz, 65.5 Hz, 6.6 Hz and others. It is even sensitive to body heat, if I move away from the x0x hertz subside! I changed the thermistors but no difference ...
I also noticed that if I blow hot air on the thermistors hertz increases, while it makes no sense I think they should drop.
It's been several days looking where is the bug.
Unstable VCO
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- antto
- Posts: 1636
- Joined: Thu Apr 15, 2010 3:21 pm
Re: Unstable VCO
i think the point of those thermistors is to compensate for changes in temperature (be it due to room temperature and/or temperature inside the x0x)
..and keep the VCO more or less at the same tuning
if you blow hot air at the components - you will surely hear how it changes
same goes if you heat the elements (be it while soldering or by holding them with your hands)
leave it to relax with the surrounding temperature for a while, and then see if the tuning varies significantly again
..and keep the VCO more or less at the same tuning
if you blow hot air at the components - you will surely hear how it changes
same goes if you heat the elements (be it while soldering or by holding them with your hands)
leave it to relax with the surrounding temperature for a while, and then see if the tuning varies significantly again
- diplowave
- Posts: 103
- Joined: Wed Aug 21, 2013 9:49 am
Re: Unstable VCO
I just have several x0xb0x at home, i compared and others have their more stable VCO.
And especially in contact with the heat, hertz decrease.
While on my last x0xb0x in contact with the heat, the vco does the opposite, it increases in hertz. I think it is abnormal.
And especially in contact with the heat, hertz decrease.
While on my last x0xb0x in contact with the heat, the vco does the opposite, it increases in hertz. I think it is abnormal.
- diplowave
- Posts: 103
- Joined: Wed Aug 21, 2013 9:49 am
Re: Unstable VCO
I was afraid that the thermistors are not good, i thought they were maybe CTN.
I desoldered one, i tested it, is PTC.
But there's a problem somewhere because the VCO has its measures in hertz changing abnormally too easily.
I desoldered one, i tested it, is PTC.
But there's a problem somewhere because the VCO has its measures in hertz changing abnormally too easily.
- diplowave
- Posts: 103
- Joined: Wed Aug 21, 2013 9:49 am
Re: Unstable VCO
Problem solved :
Oxidation on 2sc1583 legs.
And electrolytic capacitors poor quality. (I bought the complete kit to someone else)
Oxidation on 2sc1583 legs.
And electrolytic capacitors poor quality. (I bought the complete kit to someone else)
Please be positive and constructive with your questions and comments.