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Old 23rd July 2007, 07:39 PM   #2581
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Default Prepare one screw in each heatsink to be your provisory ground


Solder one wire to each screw...or attach it tight, and run those wires to your central ground... star ground.. or the name you prefer.

Of course you will be able to ground your heatsinks if you are using insulators to your transistors...because not using them...each heatsink will be opposite in voltage.... one will have the positive supply and other the negative supply...Booooom!

regards,

Carlos
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Old 23rd July 2007, 08:32 PM   #2582
Nordic is offline Nordic  South Africa
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DAMNNNNNNNNN!!!!!!!!!!!!

I just thought it was ok, after takeing out the 47uf cap next to the 220 one.. it stopped crackleing, and I eventualy after an hour or so, hooked up some music... well it played nicely and then thud... blew both fuses... speaker is still ok though.

I was wondering... can I use those output transistors from Bora's amp in the DX?

I can get geniuine ones of that, if at an extravagant price...
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Old 23rd July 2007, 09:02 PM   #2583
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Default The unit i have made was using the Dx amplifier output


Not exactly the same as Bora design.

I think the transistors you are using are enougth.

But of course, if those problems you had are not enougth and you want more problems....... than... serve yourself.

Those drivers are crazy to oscilate...they are terrible!

regards,

Carlos
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Old 23rd July 2007, 09:05 PM   #2584
Nordic is offline Nordic  South Africa
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OK, that is why I ask, but I can only get more fake toshibas... in 2sc5200..

I see some genuine ones on e-pray
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Old 23rd July 2007, 10:29 PM   #2585
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Default Re: The unit i have made was using the Dx amplifier output

Quote:
Originally posted by destroyer X

Not exactly the same as Bora design.

I think the transistors you are using are enougth.

But of course, if those problems you had are not enougth and you want more problems....... than... serve yourself.

Those drivers are crazy to oscilate...they are terrible!

regards,

Carlos
Hello Carlos

Those drivers who are crazy to oscilate, is it the bd139 and bd140 ?

Thank

Gaetan
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Old 24th July 2007, 02:43 AM   #2586
kvholio is offline kvholio  Netherlands
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Perhaps Carlos meant the drivers used in Bora's schematic, mje 15030/15031.
I've tried them as drivers in the DX, causing it to oscillate
well below clipping-level.

2sc3281/2sa1302 probably works fine for outputs, i haven't tried them.
2sc3421 works fine in the VAS, they can withstand higher voltages than bd139

Best regards,

Klaas
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Old 24th July 2007, 03:20 AM   #2587
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Hello Klass

I was think about bd139 and bd140 because I did read in the Dx thread they can do more oscillate compared to tip41 and tip42 .

Thank

Gaetan
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Old 24th July 2007, 07:25 AM   #2588
Nordic is offline Nordic  South Africa
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I was asking about swapping the output pair.... I thought those other ones would oscillate... but I ordered some genuine Toshibas now, will just have to wait till it gets here... will get a few extra pairs of the fakes, just to make sure it is not something else, before I stick the nice ones in there...
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Old 24th July 2007, 08:24 AM   #2589
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Hi Nordic,

Unless it is something like you causing the amplifier to fail with a slipping meter probe, I would scrap that amplifier pcb and start afresh. Not worth the risk to outputs and LS.

Cheers ....... Graham.
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Old 24th July 2007, 08:25 AM   #2590
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Default Yes.... i was talking about MJEs.... those ones are terrible


I have used for some monthes till i decide to not use them anymore...say.... those MJE15030 and 15031

The plastic ones, from Toshiba, the ones i have suggested to the high power unit,... are better, they have not too much gain....they are units not addicted to oscilations...even beeing able to work in very high frequencies.

BD139 is worst than TIP41 related oscilations....more addicted to...but better in audio, as it is able to work into higher frequencies... TIP41 and TIP42 selection was to avoid risk of oscilation...to make the amplifier more safe, more reliable...but off course have losses in sonics because of that...but less risk to receive complains back too.

Graham had many 2SC5200 fakes.... he discover that using a capacitor from base to colector made his units work fine...he used into his 200 Watts amplifier.... of course if underpowered fakes were your case.... it will burn to tell you they are fake.

Some fakes are only the units considered "junk" into the factory.... political and technical decisions were made:

For instance.... Dc gain lower than 80, than junk!

Those non accepted could be "deviated" from the trash box destiny .... and than entering the market with lower price...some of them can be original Toshibas that did not have passed into the quality control rules only...do not meaning exactly they are entirelly bad transistors..... TIP35 can be an option to replacement, at least to 8 ohms uses.... but also there are many fakes of TIP35... also 15004 and so on!

There are moments that i use the original parts the schematic indicates....more because the designer saying that his schematic was not followed exactly...reason why sounded not so good...in those moments i install the original to check and confirm...as i already know they do not make differences, if original or not..have to respect the linearity into the frequency, the current, the voltage, the gain, and obbeying that..if number 0o211 or o0122 do not mind... change nothing into audio..but sometimes i use the standard original schematic parts...there are "millions" of possible substitutes that will sound absolutelly the same!

I use to work with standard transistors....good and reliable...BC556, 547, 546,557...... BD139/140.... 2SC5200 and 2SA1943.... Sanken 2SC2922 and 2SA1216 (or other number, do not remember)...and those high voltage plastic ones i suggested to turbo version... 2SC4427 i think and it's complementary.

Why?..... to finish with that conversation designers use to say that transistors "sounds"..... this way, i will not turn crazy searching for hundreds of transistors...i use something standard to compare all amplifiers.... the best one with BD139 will be the best...as it is linear to the voltage i use...always 37 Volts...this allows me to compare two units...as they are using same transistors and same voltage...

If you do not reduce variables... parameters of judgment, amplifier designers will be saying...

-" sounded not good because..."

- You have not used my board
- You have not used my supply
- You have not used my capacitor
- You have not used the correct supply voltage

So.... the construction is always the same type...parts always the same...voltage the same and speaker the same....this way..compared "Elecktronix with Sounhisterix" the best will be the best...no conversations about parts.... those thing are stories to put babies to sleep....Myths!

I have made too much amplifiers and replaced too much transistors to believe in those things...negative!

regards,

Carlos
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