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

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#602
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
 
#603
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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#605
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
 
#616
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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