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Old 25th January 2013, 12:18 PM   #1251
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Quote:
Originally Posted by hesener View Post
sorry but thats impossible. is the input shorted, or connected to GND with a low ohmic resistor? Then, the emitter votlage is the voltage from the connection between transistor and 33Ohm resistor, to GND / simply put the black cable of the DMM to Ground, and use the red cable to check all 8 emitter voltages..... thanks a lot and sorry if I have not said clearly enough whats needed...
Yes it is realy impossible, but I took the Voltage like you sais Dmm Black to GND and the red one to emitter. And all trannies are right (327= 327 and 337=337. And all Pimpels look upwards to vplus TP.
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Old 25th January 2013, 12:47 PM   #1252
brianco is offline brianco  Ireland
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Originally Posted by Libby123 View Post
Yes it is realy impossible, but I took the Voltage like you sais Dmm Black to GND and the red one to emitter. And all trannies are right (327= 327 and 337=337. And all Pimpels look upwards to vplus TP.
You have not confirmed that the positive input is shorted to ground as requested by Hesener. Is it?
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Old 25th January 2013, 01:07 PM   #1253
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Originally Posted by brianco View Post
You have not confirmed that the positive input is shorted to ground as requested by Hesener. Is it?
Sorry, I think it is not. I will measure.
But how will it be? could the trimmer do this?
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Old 25th January 2013, 02:37 PM   #1254
hesener is offline hesener  Germany
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Quote:
Originally Posted by Libby123 View Post
Sorry, I think it is not. I will measure.
But how will it be? could the trimmer do this?
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Originally Posted by Libby123 View Post
Q29 / Q26 / Q25 / Q2 is always -3,8V
If this were true, the input voltage should be around -4.5V (the VBE of the PNPs and the 3.8V)

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Originally Posted by Libby123 View Post
....and Q32 / Q31 / Q30 / Q1 is -4,8V
If this were true, the input voltage should be around -4.1V (the VBE of the NPNs minus the 4.8V).

Now, both of above conditions could happen at the same time, but only at a input voltage of e.g. -4.3V or so. It takes an odd combination of issues for that to happen....

could you please check R1 and R1b (the 10k resistor and the input offset trimmer), if they are not short-circuited or causing a short to a negative voltage somehow?

and, can you please check the collector - emitter voltages of the PNPs? That should be around 13V.

And, just for completeness, please measure the voltage on both ends of R5 (82 Ohms) just to see if the current source is operating correctly....

No worries, we'll get there....
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Old 25th January 2013, 02:44 PM   #1255
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Originally Posted by hesener View Post
If this were true, the input voltage should be around -4.5V (the VBE of the PNPs and the 3.8V)



If this were true, the input voltage should be around -4.1V (the VBE of the NPNs minus the 4.8V).

Now, both of above conditions could happen at the same time, but only at a input voltage of e.g. -4.3V or so. It takes an odd combination of issues for that to happen....

could you please check R1 and R1b (the 10k resistor and the input offset trimmer), if they are not short-circuited or causing a short to a negative voltage somehow?

and, can you please check the collector - emitter voltages of the PNPs? That should be around 13V.

And, just for completeness, please measure the voltage on both ends of R5 (82 Ohms) just to see if the current source is operating correctly....

No worries, we'll get there....
IŽll do. But all at a time (I am still at work).

Sure we will get it.
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Old 25th January 2013, 08:33 PM   #1256
hesener is offline hesener  Germany
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Originally Posted by quan View Post
How do you implement input loading switch if you don't mind me asking?
Quan
Here you go.... Not fancy but does the job nicely. Resistors are Dale RN65 (10 / 100 / 220 / 470 / 1000 / 2200), the switch is from C&K with silver contacts.
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File Type: jpg input impedance.jpg (116.7 KB, 261 views)
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Old 25th January 2013, 08:54 PM   #1257
Marra is online now Marra  United Kingdom
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Neatly done I will copy that.Thanks.
Where does the grounding post connect to?

Last edited by Marra; 25th January 2013 at 08:57 PM.
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Old 26th January 2013, 12:24 AM   #1258
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Keith, stick a star ground point in your psu box. You'll connect the the middle of each Hacker cap board directly to this for the power earths. You'll run a chasis gnd to it as well from each box and there will also be your tonearm earth and potentially turntable chassis earth. Just make sure the tonearm earth is lifted with a 10 ohm resistor and small cap as per the schematic. Also make sure the gnd on each signal line doesn't get continuity with the amp chassis, keep them seperate.

Feel free to pop over and take a lot at mine this weekend if the snow clears.

http://farm9.staticflickr.com/8220/8...0d557534_h.jpg
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hoping to pick up some things.
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Old 26th January 2013, 06:42 AM   #1259
quan is offline quan  Australia
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Quote:
Originally Posted by hesener View Post
Here you go.... Not fancy but does the job nicely. Resistors are Dale RN65 (10 / 100 / 220 / 470 / 1000 / 2200), the switch is from C&K with silver contacts.
Ok thanks Alfred, like they say -" a picture worth a thousand words". Just need to source the rotary C&K switch. I am still getting hum from my R3 , it is playing beautifully just need to get rid of it as it is obscuring the details. I will post a picture and ask for some advice.
Quan
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Old 26th January 2013, 08:05 AM   #1260
Marra is online now Marra  United Kingdom
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Thanks Simon.I'm hoping to listen to mine this afternoon.
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