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Old 19th May 2011, 10:36 PM   #401
jprco is offline jprco  Canada
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Rudi, I would check again to make sure that none of heat sink mounted transistors have shorted to it. As I mentioned earlier, the MJE's I was using both shorted to the heat sink.
You know what damage can occur if you power up under such a condition!
Good luck finding the problem,
Jean
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Old 20th May 2011, 02:50 PM   #402
AndrewT is offline AndrewT  Scotland
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use a bulb tester at every intermediate stage of construction. It allows safe and damage free power up. Then (while the bulb is glowing and mains power still plugged in) measure where the excessive current is escaping.
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regards Andrew T.
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Old 20th May 2011, 03:04 PM   #403
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Location: Hamburg / Germany
They call me "Mr. Bulb", Andrew:

Click the image to open in full size.

Bild: bulk00398x8.jpg - abload.de

I use a High Voltage Halogen lamp, 40W.

I think, that the problem I am having, is home-made.
I bought a couple of Toshiba KSC5171 and KSA1930 from an ebay-seller (Hongkong) and used them as VAS (KSC5171) and drivers.
I measured the Hfe of a KSC5171 yesterday and my DMM showed a value of 65.
I wonder, if they are counterfeits.

I have already begun to replace them by BD139 and MJE and will power on again - of course with assistance of the bulb tester.

Best regards - Rudi_Ratlos
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Old 20th May 2011, 03:38 PM   #404
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Dear DX Blame friends,

I really recommend you something like this:

Click the image to open in full size.

BULB tester

Price: 5
Function: delimits the output of your transformer to approx. the Watts value of the lamp
Howto: insert the lamp in serial with one of the main's wires of the transformer
Benefit: prevents your precious transformer (and yourself) from "suffering" a short on your AMP PCB

Best regards - Rudi_Ratlos
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Old 21st May 2011, 02:40 PM   #405
boring is offline boring  Singapore
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Any more boards available? I need:

2X amp boards
2X PSU
2X speaker protector

Thanks!
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Old 21st May 2011, 08:24 PM   #406
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Sorry, there are no PCBs left.

Best regards - Rudi_Ratlos
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Old 2nd January 2012, 03:29 PM   #407
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Location: Switzerland and Mississippi
Hi Rudi, am putting finishing touches on DX ST amp and am using only one transformer. Is it better to run one power supply board for both amp boards or to run two power supply boards, and just conneting the AC inputs of transformers to both power supply boards. Will this make any difference. Appre iate again your effort in making the boards.

Best, John
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Old 3rd January 2012, 06:53 AM   #408
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Hello John,

there are 2 ways to do the setup.
First way: 1 transformer and 1 PSU, feeding the power to both of the AMP PCBs, and the second way: 2 transformers and 2 PSUs, each one feeding one AMP PCB.

The first way is more economic, saves space and is - in case the transformer and the reservoir capacitors are big enough - in most cases adequate.

I use the second way - I call it dual-mono setup -, if I feel that the AMP is "worth it".
In this case the power consumption of one channel does not affect the power consumption of the other channel.

According to my ears the DX BlameES with 2 big SANKEN output-transistors was worth a dual-mono setup.
I do not know the DX BlameST, so: it simply depends on your ears and on your feeling.

Best regards - Rudi
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Old 9th January 2012, 12:40 PM   #409
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Thanks Rudi, I set it up with one transformer and seems to be working nicely on the bias. I had trouble on one channel and fooled around with the trim pot and found that it was broken, replaced it and they both channels bias nicely now. I have 100 R in place of the fuse and adjusted for 10 mv, or should this be 4.7 -6 mvolt as you put in the builders manual. Once I know this then I will cut out the resistors and put in fuses and speakers and try it out.

Cheers, John
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Old 9th January 2012, 12:43 PM   #410
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Join Date: Dec 2009
Location: Switzerland and Mississippi
I believe I saw that Carlos adjusted for 10 v with 100 R and 4.7 with 47r over fuses on you tube but not sure which is correct or if it matters too much. However I want to make sure it does not go up in smoke b y too much and am only self taught in these things. thanks again, John
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