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24th Jan 2021, 3:01 pm | #1 |
Triode
Join Date: Apr 2009
Location: Bicester, Oxfordshire, UK
Posts: 37
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Thermal paste / compound recommendations for H.O.T.
Hello,
Any suggestions for thermal paste / compound suitable for use with a mica washer on a horizontal line output transistor, please? These days it seems that the majority of available thermal pastes are targeted at low-voltage applications (mainly PC CPU / GPU) and these pastes contain metal. I have found that pastes do not even have a breakdown voltage parameter mentioned in their specifications, so I can't be sure if they will be safe to use for TV repair. Cheers Robin |
24th Jan 2021, 3:34 pm | #2 |
Octode
Join Date: Dec 2018
Location: Llandeilo, West Wales, UK.
Posts: 1,092
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Re: Thermal paste / compound recommendations for H.O.T.
Servisol or Dow Corning?
From Farnell, CPC, RS etc.
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24th Jan 2021, 5:46 pm | #3 |
Octode
Join Date: Dec 2008
Location: Wincanton, Somerset, UK.
Posts: 1,757
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Re: Thermal paste / compound recommendations for H.O.T.
Any silicone-based "white" compound should be fine. Don't use too much. It should not flow out more than a tiny sliver, if that.
John |
24th Jan 2021, 6:42 pm | #4 |
Heptode
Join Date: Dec 2003
Location: South Yorkshire, UK.
Posts: 900
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Re: Thermal paste / compound recommendations for H.O.T.
Not sure of your application but are thermal pad an option as they have better electrical and thermal properties than the old silicon grease
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24th Jan 2021, 8:07 pm | #5 | |
Triode
Join Date: Apr 2009
Location: Bicester, Oxfordshire, UK
Posts: 37
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Re: Thermal paste / compound recommendations for H.O.T.
Thank you for your replies.
Quote:
I did wonder about using a "modern" thermal pad instead of the mica washer and thermal grease, but I have no idea whether that would be a good option for such a high voltage & high frequency application. Has anyone else used thermal pads instead of the original mica washer for CRT H.O.T. TV repair? Also, whilst on the subject. The 2SD1398 transistor is in TO-3P package and when I removed the bad transistor I found that there were two mica washers between the transistor and heatsink. Is this acceptable practice? I'd be concerned that the thermal conduction would be badly impaired by using two mica washers? |
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24th Jan 2021, 8:14 pm | #6 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,953
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Re: Thermal paste / compound recommendations for H.O.T.
Could the two micas be an attempt to control stray-capacitance between the transistor and the heatsink?
Or to handle the peak voltage more reliably? I remember using two micas to reduce collector-to-earth capacitance in an 80M HF transmitter which featured an AUY10 Germanium TO3 transistor as the RF power-amplifier. |