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 Another build conundrum 
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Post Re: Another build conundrum
When you spoke before about FETs failing, I thought not only me then :)

I don't ground my radios, there are enough loops through the coax and DC supplies, but I do ground everything on the work bench.
I made sure that the bit of the soldering iron has a low impedance to the mains earth, and that the scope, SA etc ground terminals are connected to each other and the mains earth. Everything metal is grounded, and I have bare metal I touch before touching part of a circuit. I also have a couple of crocodile clips on leads to clip onto the chassis of whatever I have on the bench.

I hardly think that is the problem with a 4148, but it is worth going through it all one day.

Hope you get some adjustment soon :)

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Sat Feb 02, 2019 11:52 am
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 Another build conundrum 
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Cheers Steve. I think you use the precision gold iron, so how have you ensured a good tip grounding?

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Sat Feb 02, 2019 12:04 pm
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 Another build conundrum 
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Post Re: Another build conundrum
G4YVM wrote:
Cheers Steve. I think you use the precision gold iron, so how have you ensured a good tip grounding?


I made an extension for the iron lead, so now I have a socket under the front edge of the bench that the iron plugs into, I hate the lead coming from the back of the bench and dragging everything all the time.
When I did that I took a wire out that is connected to the metal on the iron.

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Sat Feb 02, 2019 12:22 pm
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 Another build conundrum 
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Post Re: Another build conundrum
Sangoma wrote:
G4YVM wrote:
Cheers Steve. I think you use the precision gold iron, so how have you ensured a good tip grounding?

When I did that I took a wire out that is connected to the metal on the iron.


Do you mean you removed an internal wire from somewhere or you added an earth lead?

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Sat Feb 02, 2019 12:26 pm
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 Another build conundrum 
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Post Re: Another build conundrum
G4YVM wrote:
Sangoma wrote:
G4YVM wrote:
Cheers Steve. I think you use the precision gold iron, so how have you ensured a good tip grounding?

When I did that I took a wire out that is connected to the metal on the iron.


Do you mean you removed an internal wire from somewhere or you added an earth lead?


I added an earth lead from the extension I made

The iron and controller are still standard

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Sat Feb 02, 2019 12:32 pm
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 Another build conundrum 
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Post Re: Another build conundrum
Thanks

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Sat Feb 02, 2019 12:39 pm
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 Another build conundrum 
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Post Re: Another build conundrum
So was it faulty diodes then?
And I did mean goosed as in faulty - a Zenner can go short circuit as well as open circuit.
As for the Soldering Iron, I use a precision Gold and it is ESD safe out of the box.


Sat Feb 02, 2019 1:25 pm
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 Another build conundrum 
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sri senior moment pressed da wrong key


Last edited by G0AYD on Sat Feb 02, 2019 1:44 pm, edited 1 time in total.



Sat Feb 02, 2019 1:39 pm
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 Another build conundrum 
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Post Re: Another build conundrum
i still got your old pu2..
and old boat anchor (PSU)
you want em back?


Sat Feb 02, 2019 1:42 pm
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 Another build conundrum 
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Post Re: Another build conundrum
What's a pu2

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Sat Feb 02, 2019 1:53 pm
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 Another build conundrum 
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Post Re: Another build conundrum
M0XXQ wrote:
So was it faulty diodes then?
And I did mean goosed as in faulty - a Zenner can go short circuit as well as open circuit.
As for the Soldering Iron, I use a precision Gold and it is ESD safe out of the box.



Thanks.ks.for the info

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Sat Feb 02, 2019 1:54 pm
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 Another build conundrum 
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Post Re: Another build conundrum
M0XXQ...yes duff diodes. All three had come low impedance wires...

However, if I could return your attention to the circuit. Ahem...

I have replaced the diodes but I still cannot get any real bias current. I get about 25 milliamps quiescent which I can drive up to around 50mA key down with the bias pot fully opened. It ought to be 200mA. I also get no RF out with my sig gen connected.

On the circuit Tr 101B a 107 is the driver and Tr102 an IRF510 is the PA.

I get the following voltages for these: (supply is 13v)

Tr101B BS170. D. 10.72v
G. 5.29v
S. 2.43v


Tr 102 IRF510. D. 13V
G. 0.63V
S. 2.47V


I think this figures are right. At point B on the circuit I get zero volts...far from right. I suspect the zener but destroyed it trying to get it out for testing...its not suspect anymore, its a known gonner. I'll replace the zener tomorrow and see if that puts the volts back at B.

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Sun Feb 03, 2019 11:03 pm
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 Another build conundrum 
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Post Re: Another build conundrum
Dave, heading to Amsterdam now - will look at the schematic during my stopover at Schiphol.


Mon Feb 04, 2019 4:20 am
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 Another build conundrum 
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Post Re: Another build conundrum
G4YVM wrote:
M0XXQ...yes duff diodes. All three had come low impedance wires...

However, if I could return your attention to the circuit. Ahem...

I have replaced the diodes but I still cannot get any real bias current. I get about 25 milliamps quiescent which I can drive up to around 50mA key down with the bias pot fully opened. It ought to be 200mA. I also get no RF out with my sig gen connected.

On the circuit Tr 101B a 107 is the driver and Tr102 an IRF510 is the PA.

I get the following voltages for these: (supply is 13v)

Tr101B BS170. D. 10.72v
G. 5.29v
S. 2.43v


Tr 102 IRF510. D. 13V
G. 0.63V
S. 2.47V


I think this figures are right. At point B on the circuit I get zero volts...far from right. I suspect the zener but destroyed it trying to get it out for testing...its not suspect anymore, its a known gonner. I'll replace the zener tomorrow and see if that puts the volts back at B.



The .63V is what I would expect at the top of the diodes. not 5V1

If you are going to get bitten by the building bug, do you have a scope?

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Mon Feb 04, 2019 5:10 am
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 Another build conundrum 
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Post Re: Another build conundrum
Steve, I do yes.

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Mon Feb 04, 2019 8:14 am
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