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Old 20th February 2009, 04:25 PM   #241
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Hi Richard,
Yes both zeners face the same way. I think my problem is I didn't have any J309 and I have used a different N-Fet. I will have to order some..I managed to get all the transistors from Maplins.
It looks as if your centre pin on the J309 goes to the 1k resistor?
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Old 20th February 2009, 05:13 PM   #242
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Quote:
Originally posted by audio1st
Hi Richard,
Yes both zeners face the same way. I think my problem is I didn't have any J309 and I have used a different N-Fet. I will have to order some..I managed to get all the transistors from Maplins.
It looks as if your centre pin on the J309 goes to the 1k resistor?

Yes my 1k resistor goes to the centre pin (source) of the J309
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Old 20th February 2009, 05:23 PM   #243
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I think the 1k should go to Gate and the 130r goes to Source.
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Old 20th February 2009, 06:29 PM   #244
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Got it sorted, V- so far, forgot to connect the reservoir cap. Stable now..
25v transformer, with 27v Zener ends up with -25vDC after all the regulation.

26.5v across Zener.
11v across Fet
0.8v across R2.
FET connections, G to 1k, D to Zener and S to 130r...
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Old 20th February 2009, 06:55 PM   #245
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Quote:
Originally posted by audio1st
Got it sorted, V- so far, forgot to connect the reservoir cap. Stable now..
25v transformer, with 27v Zener ends up with -25vDC after all the regulation.

26.5v across Zener.
11v across Fet
0.8v across R2.
FET connections, G to 1k, D to Zener and S to 130r...

Audio1st! Its a marathon not a sprint

So is the schematic wrong, or am I misreading it?

Well done BTW
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Old 20th February 2009, 07:12 PM   #246
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Hi Richard,

Schematic is right, I have used a different Fet, opposite pin out to the J309, makes no difference as long as you follow the correct G,D,S connections.
You may have damaged your J309, but you might as well swap the 130r and the 1k with each other and see if it helps?. My zeners are 1.3W from Maplin. Have you installed a new Zener yet?
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Old 20th February 2009, 08:03 PM   #247
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Quote:
Originally posted by audio1st
Hi Richard,

Schematic is right, I have used a different Fet, opposite pin out to the J309, makes no difference as long as you follow the correct G,D,S connections.
You may have damaged your J309, but you might as well swap the 130r and the 1k with each other and see if it helps?. My zeners are 1.3W from Maplin. Have you installed a new Zener yet?
I'm just about to
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Old 20th February 2009, 10:01 PM   #248
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I have replaced the Zener, J309 and R2 resistor

For the purpose of this test I have kept R2 (130R) connected to the Gate, Drain is connected to Zener and Source to 1K.

Click the image to open in full size.

Here are the readings...

Across R2 (130R) =34.8v
Across Zener=27v

Gate (Connected to R2)=34.8v
Source (Connected to 1K) =33.1v
Drain (Connected to Zener) =27v

Output 24.9v

The light bulb illuminates for a second and goes out immediately. Before the component swap the filament in the bulb would flicker dimly whilst the on button remained pressed

If some of these readings are too high I will swap the 1K and R2 resistors around.
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Old 20th February 2009, 10:52 PM   #249
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Hi Richard,
Your R2 wont last long with 35 volts across it..

Swap them over and see what you get, if no better you must have still got a short somewhere.?
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Old 21st February 2009, 08:35 AM   #250
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I have swapped the two resistors around so the R2 is 1k and the resistor before it is 130R

The voltages are now...

Across R2 (1K) =34.5v
Across Zener (27v) =28.1v

Gate=34.3v
Source=33.3v
Drain=28.3v

Output 25.8v

The output voltages have increased and the voltage is still to high across R2.

I will check again for shorts
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