My amps were nowhere near 93mA and as mentioned in the instructions your amp may be different... so there doesn't seem to be an ideal value and I think it will vary according to the IRF510's fitted in

#help #magicsmoke #troubleshooting

To all, After some testing - I measured R5 with the amp powered off as I turned the trim pit and then tried the bias adjustment procedure again (QCX+ Practice Mode on) - I have come to the conclusion

#help #magicsmoke #troubleshooting

Charles Let's assume that everything with visible damage needs replacement. Designers sometimes do what you did, so we don't have to, to create a design. You obviously took it beyond its limits. After

#help #magicsmoke #troubleshooting

Greetings all, In going to adjust the bias for the 40m 50W PA that I've built, I began with R5 turned all the way down as per the instructions. Putting the QXC+, which was outputting 4.24W into a QRP

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Roy I just tried my new sucker and am pleased for the cost. Ordered it from Ali Express for USD3.47 cheers de Barry

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Brilliant! Just bought mine from eBay as Amazon insisted on trying to prime me. I've got 2 WW2 HROs to recap and restore shortly, this will be just the job. 73s Ted 2E0THH

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Excellent job! I'm pickin' up one of those things right away

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Well I got the BS-170s out without permanently destroying the PCB! 🤣 Just used my $19 vacuum solder iron from Amazon! Just need to find socket pins for plugging in the new BS-170s! Roy WA0YMH

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Uh, Guys The input capacitance of 3 BS170's in parallel is 120 pf, max. The input capacitance of the IRFZ44 is 1900 pf average. That much cap looks like a 10 ohm resistor at 40 meters. You may be able

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For components like that I usually start by cutting the leads off close to the package, removing the leads one at a time, and then desoldering the holes with braid, bulb, or pump. 73, Willie N1JBJ

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I have a bit of an history destroying transistors on my QCX+ (after several sets I realised that the coax between my ATU and the TRX was intermittently faulty :-o ) and replacing them with the right t

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Pin sockets carved from a machined IC socket? 73, Willie N1JBJ

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Mike, The driver has to charge & discharge that capacitor every time the output level changes, it needs a much higher current capability or the gate won't keep up with the RF signal, i.e very poor 'hi

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Okay, I don't know if there's any way to edit my original post or not but I am not looking for a substitution for the transistors. I'm looking for a different way of mounting them so that I don't even

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Nope -- didn't notice -- amplifier design not my forte' but the IRFZ44N was listed an equivalent. "close enough for government" maybe. So what is the impact of the capacitance difference? Mike W9MDB

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However have you looked at the input capacitance presented to the drive system? 1n8F vs max 40pF Regards Nick M0HGU

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The IRFZ44N looks like overkill and just takes a little more drive voltage. https://www.componentsinfo.com/irfz44n-pinout-equivalent/ https://pdf1.alldatasheet.com/datasheet-pdf/view/17807/PHILIPS/IRF

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Check this post from sometime back regarding these transistors. https://groups.io/g/QRPLabs/topic/72086057 Ron

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Sorry I forgot to include the fact that I updated the firmware before I even started testing it. So yes it's always been running with version 1.03.

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Interesting idea. If this is a solution that would be amazing. Does this fix it, when everything quits?

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