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F3 and F4 Clone PCB Reissue group buy, also F5 PCBs

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tms0425

Member
Joined 2006
Re: Current Limiting thermistor

rickmcinnis said:
Dear Peter or whoever has an opinion,

Are you using this in your amps?

Mr Pass suggests a CL60 thermistor to be placed in the primary of the power transformer.

I have know nothing about thermistors, other than what they do, so what is a CL60 thermistor?

Do you recommend these be used and if so would you recommend a part number, please.

Thanks,
Click to expand...
For the F4 and F5 I used one CL60 in each primary winding and another from chassis ground to power supply ground, all per what was published in Nelson's service manuals. The Digikey number for what I used is KC006L-ND and they seem to work as expected with my toroids. No blown fuses and no hum or noises from ground loops.

Tom
 
Peter Daniel

Peter Daniel

Member
Joined 2002
audiosector.com
Paid Member
Yesterday I installed Caddocks MK132 in place of Mills feedback resistors. I used 4 x 150R per board, which gives slightly more gain. The sound seems to be less forward and maybe a bit better bass, but nothing really major.
 

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rickmcinnis

Member
Joined 2006
MK132's for feedback

Dear Peter,

Thanks for the link for the thermistors.

Do you think there will be a heating problem with the substitution of 1.5 watt rated resistors versus Mr. Pass's specification of 6 watts?

How do the 75 ohms resistors affect gain?

I am in the process of collecting parts and always take an interest in what you are doing!

Thanks,

Rick McInnis
 
A

adn6244

Member
Joined 2008
Diomedian said:
It has previously been noted that the lead spacing of the resistors was 0.2", and that Peter recommended Vishay CFM-50 or Caddock MK132 resistors, both of which have 0.2" lead spacing. The Dales you use there are CFM-55s (or their military equivalent).

-j
Click to expand...

I have a stupid question to ask here.

I went around searching for cmf50 and noticed that most of the stock mouser has is only 1/4W or 0.25W whereas MK132 smallest is 0.75W.

appreciate advice what is the minimum requirement as the range is quite big from 0.25W to 0.75W.

Thanks again
:smash:
 
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