Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on July 24, 2022, 02:08:39 pm
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Where would i put the B+ fuse in this layout? Also what is the 150k resistor to ground doing?
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Imho, the fuse should go in one of the transformer winding arms. The fuse type and rating can be determined by either testing, or design.
The use of a zener in each winding arm is a concern. In general, the zener needs to have a lot of design margin with respect to peak current/dissipation and to conductive cooling. One could presume that the zeners are included to fit better with the output stage valves, but it could also be to include a voltage margin on the first filter capacitor - that all gets a bit dicey depending on mains voltage variation, and the exact power transformer being used.
It sounds like you may be trying to clone someone else's schematic - which is fraught with risk unless you intimately know all the parts being used and the application and measurements that have been made.
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- i didnt intend to use those extra 2 diodes.
- what is the 150k doing?
- i understand the risks and have decided to proceed with caution
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150k resistor is to bleed the filter caps after power is switched off. i usually don't go this low in value
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Use 220k bleeding R, 3 watt
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Some Marshall’s put the 1/2 amp slow blow fuse right after the the rectifier; before the fist filter.
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Always a reference to look at >>>
http://www.valvewizard.co.uk/fuses.html
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And of course https://dalmura.com.au/static/Valve%20amp%20fusing.pdf