It was suggested to replace the 10R therm with a 4R7, 7.5A for those biasing above 1A.
Since that point the PS has been modified to use a parallel pair of the 10R parts. A note/pdf was added to the first post
This is the new P/S board not yet shipping from the store???
Could the original boards be modified for more bias? With additional Thermistors?
For this dunce would it be better to wait for new boards and discard V0 R2 for higher bias and dual mono? Hoping store will allow multiple sale for dual?
I am way out of my depth here and hoping to learn something when others chip in to correct me...
However, I was thinking more of the first current limiter that is prior to transformer and not the two (or four) that provide the R in the CRC filter... my concern was if the capacitance of the first C (in the CRC), is increased dramatically then this first current limiter may get hot (and it's resistance drop), well before the inrush current is down to an acceptable level. The rational would suggest that a current limiter of similar cold resistance but larger capacity (thermal mass or rating in joules), might be needed.
However, I was thinking more of the first current limiter that is prior to transformer and not the two (or four) that provide the R in the CRC filter... my concern was if the capacitance of the first C (in the CRC), is increased dramatically then this first current limiter may get hot (and it's resistance drop), well before the inrush current is down to an acceptable level. The rational would suggest that a current limiter of similar cold resistance but larger capacity (thermal mass or rating in joules), might be needed.
New patch of the F5m kits already sold out? I added notify me when available but no notifications so far. I really do not wanna miss this. It would be my first amp. I really need this to test my preamps. 😆
Newly built or repaired audio equipment should never be immediately connected to an audio system.
This could damage the other system components if there is a problem with it.
Check the circuit operation thoroughly with a DVM and scope, do a burn-in, and then recheck.
Then (and only then) connect to a "junk" system for further, "live" testing, but not yet to a "good" system.
Otherwise, your "good" system may become your "junk" system.
This could damage the other system components if there is a problem with it.
Check the circuit operation thoroughly with a DVM and scope, do a burn-in, and then recheck.
Then (and only then) connect to a "junk" system for further, "live" testing, but not yet to a "good" system.
Otherwise, your "good" system may become your "junk" system.
@BeardyWan
The thermistor ahead of the transformer has been shown on prior drawings with a "CL60 type" reference.
FW amps use a 300va transformer with 60,000uF per rail I believe (120,000uF total). The same basic CRC supply with a 400va xfmr is commonly used, often with additional capacitance. I'm building out a dual mono version with 75,000 and will go with the CL30 that NP references in the beefier PS shown in the F5 Turbo article.
The thermistor ahead of the transformer has been shown on prior drawings with a "CL60 type" reference.
FW amps use a 300va transformer with 60,000uF per rail I believe (120,000uF total). The same basic CRC supply with a 400va xfmr is commonly used, often with additional capacitance. I'm building out a dual mono version with 75,000 and will go with the CL30 that NP references in the beefier PS shown in the F5 Turbo article.
@Holzarbeiter : For dual mono (i.e., one transformer and one PS board per channel), I would go with two of the original PS boards.
Based on googling it seems the green thermistor is a discontinued Microtherm SCK108, where the 108 stands for 10ohms and 8A, with a tolerance of 20%.
Is this an acceptable replacement?
https://au.mouser.com/ProductDetail/EPCOS-TDK/B57464S0100M000?qs=E/3ZYvLbbh/jlrFYxPDfQA==
Unless there's some other spec I haven't accounted for?
Is this an acceptable replacement?
https://au.mouser.com/ProductDetail/EPCOS-TDK/B57464S0100M000?qs=E/3ZYvLbbh/jlrFYxPDfQA==
Unless there's some other spec I haven't accounted for?
Replacing the provided therm with the 4R7 7.5A version as suggested would be my choice in that position.
Just reading between the lines here but I'm assuming that the modification allowing 2 parallel pieces of the original spec may well be because, like so many parts, a very large supply is on hand. Happy to be corrected if I'm wrong on this. Cheers
Do you mean the original offering for F5M is sold out? NP has shipped revised kits to store but afaik not been listed.
There was a confusing update on the webpage from 22nd April 2024 - This kit contains the updated version of the power supply board. So I was thinking that already new patch was sold out.
Part of the webpage was accidentally released.
The first batch has been sold and Mr. Pass has sent on a revised batch to the store which we are all waiting for.
When announced soon you will be able to order. I have this info only from watching the thread.
You won't miss out as you have signed up to be notified.
I have not started my F5M build from the initial kit offering as real life has gotten in the way. I have also not been intensely following this thread recently. With that being the case, am I better off ordering the new essential kit with the updated power supply board and using that for the build? If so, has the updated thermistors value been determined. I already have the higher value 5 ohm resistance EPCOS B57236S0479M000 but gather a higher value is being suggested. I apologize if I am asking an already answered question.
That is the Question not answered yet.
I will be doing both just to find out.
It depends on the store providing multiple sales to one member if Dual Mono. I've been on and off trying to decide myself. Sort of have to as we committed to the first kits anyway and won't play music stashed away.
This is not a big deal - mostly we wanted to accommodate those who want to run higher bias.
hello I check the availability of the essential kit for the FM5 almost every day, and still nothing, any idea of when it will become available again?
A few moon's ago I asked if there was something between an ACA and a full-blown First Watt clone to suit my modest English dwelling. The answers were a bit too technical for me to understand/implement, but no longer, my sweet sounding F5m sits hot (and a little smelly - or is that the dog...) currently playing Nick Drake. So to all of you sitting on unbuilt first batch kits, just build and listen.