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 Ceramic Resistor
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 Return to top of page · Post #: 1 · Written at 3:09:43 PM on 8 August 2016.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

Hi Everyone,
I am after a 150 ohm 20 watt ceramic wire wound resistor.
Is't for the HT circuit for an AWA Valve Amp.
I have bought a Chinese version but would like to get something more original.

Thanks
Josh


 
 Return to top of page · Post #: 2 · Written at 9:59:45 AM on 13 August 2016.
Garyoz's avatar
 Location: Perth, WA
 Member since 19 November 2008
 Member #: 381
 Postcount: 240

 
 Return to top of page · Post #: 3 · Written at 1:27:54 PM on 15 August 2016.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

Thanks Gary, The one I got from China looks similar BUT if it doesnt survive and I cant get an original style,
I will look at getting a newer one higher power and putting it under the cover and leave the original in place to look right.

Josh


 
 Return to top of page · Post #: 4 · Written at 2:32:17 PM on 15 August 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6678

Not usually a good idea to cover a power resistor, especially a 20 watt one.

Why the need to cover it?


 
 Return to top of page · Post #: 5 · Written at 2:42:30 PM on 15 August 2016.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

I want to keep the top of the amp looking as original original as possible, usually not a huge worry but this AWA is serial number 2 and from what we can figure out a prototype.
The Chinese one should be ok but if not I would use a 50w aluminium covered one bolted to the chassis under the cover it should be ok temp wise


 
 Return to top of page · Post #: 6 · Written at 9:01:40 PM on 15 August 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5239

I have replaced a missing field coil with one of those RS Metal clad ones. In the case of the set there really was not a desirable amount of room however, if you can mount one of them on a side plate, out of harms way (use transistor conductive grease under it), that will assist in dissipating quite a bit of the heat.

Marc


 
 Return to top of page · Post #: 7 · Written at 12:48:13 PM on 16 August 2016.
Pa Man's Gravatar
 Location: Golden Grove, SA
 Member since 10 April 2015
 Member #: 1726
 Postcount: 149

That's the Idea Marc, the other thing is its not like it will be run for long periods, purely for demonstration.

Josh


 
 Return to top of page · Post #: 8 · Written at 9:09:19 PM on 16 August 2016.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5239

I think a lot like HMV changing the screen resistors in the 52 series from 2 x22K 1W Parallel to a 10K seem to forget that W = VIt.

Its that "t" that causes a lot of issues, as in the 10K resistor mentioned slowly failing as I squared R tells us that the current drawn exceeds one watt. We will blame the bean counters & it causes me to stock 10K 2 & 3 Watt just for them.

This is why these things fail, cost cutting seeing underrated inferior parts being used.

I would not dare use anything that would stop the thing being continuous rated (many sets weren't)

Marc


 
 Return to top of page · Post #: 9 · Written at 5:46:15 PM on 21 August 2016.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6678

.PA Man: I came across this website that may be of interest to you:

http://dalmura.com.au/projects/amplifier.php


 
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