How fast a 2520 can be destroyed ?

[vertiges]

this little missing wire cost me a lot of money !!!


Just for clarify... I have to apply 1V 20Hz at the RED/ BROWN wire of the transformer with one resistor of 1k (1W) of load at the output ? Then reduce the 20 Hz turn down to less than 10mV ?

How much time ? :shock:

Can I do this without a scope ? :?:

So what you're telling Keith is :

this distortion can't be heard as a "normal" distortion, but there is definitely a degradation of the signal ? :roll: You mean, my 312 preamp will sound like a beh*ringer ?

eD

 

[peter purpose]

So just to get this straight....
The fact that there was no ground reference on the input, coupled with a 68R termination of the output transformer secondary and built by a French Canadian on stipboard, caused the drawing of large amounts of current, thus rendering the 2520 bolloxed?

 

[nielsk]

The gain control pot should be 25K reverse log, and the rgain resistor should be 200 ohms and should go between the cap on the other side of the pot and ground. Your 20K pot will work, it will just reduce the total range of gain control

 

[SSLtech]

Peter, the termination was SIX ohms, not sixty-eight...

The lack of a DC voltage reference caused the 2520's formidable output current drive to be brought to bear upon an unsuspecting transformer...

Yes.

eD, you don't need a scope to demag... a scope is a good tool for hunting and finding distortion, but it won't help you fix it... it just helps you to see WHEN it's fixed. -Of course I have access to a few distortion analysers here, so I'm spoiled rotten....

Personally I am always wary of DC-coupled transformer connections, and would NEVER connect one up without measuring the DC offset first, but of course I learned this a long time ago the way so many others did... by making the mistake.

Anyhow... it could be worse. -It could be a Porsche alloy V8 motor that you built, and you could have left a loose nut in, to tap-dance on a piston crown and bugger up the entire block... now THAT costs a lot of money!!! -(ask me, and I'll send you pictures!)

Transformer: I'd just take it to a twenty-pound (weight, not cost!) 2"-tape bulk eraser, switch it on and slowly bring it into the field, leave it there for an hour or so and then slowly take it out of the field. You'll be fine. -The dead 2520 will need a funeral, unless of course it's not potted, in which case it can be repaired... -I don't know the Petey-Purpose-like 2520s intimately... -I'd like to, however! :grin:

25K versus 20K... only about a dB's worth difference I suspect. On a log scale, the resistance has to accellerate dramatically for every dB's worth of change, so as long as it's reverse log, don't fret too much.

The effect on the signal would very likely be to 'bend' the signal towards one pole or the other. There would be no sharp steps like clipping, so no 'fizz'. There'd be no crossover distortion to speak of, so no 'crunch'... it's hard to hear, but it won't sound like a behringer... it just won't sound 'right'.

Anyway, you can pass signal and it doesn't irreversibly hurt anything to use a transformer with a magnetised core... it just sounds a bit funny.. perhaps 'vague' compared to a clean, punchy API in good health.

Keith

 

[vertiges]

[quote author="peter purpose"]So just to get this straight....
The fact that there was no ground reference on the input, coupled with a 68R termination of the output transformer secondary and built by a French Canadian on stipboard, caused the drawing of large amounts of current, thus rendering the 2520 bolloxed?
[/quote]

Yes Peter you've got that right !!!

Excepted that I'm not Canadian but Belgian... :green:
(It's good to have a mother in Europe when evilBay sellers don't want to ship to North America. Keith knows what I'm talking about)

Pfff... according to me, those 2520 burn to quickly !!!! :evil:

eD)))

 

[peter purpose]

[quote author="vertiges"]
Pfff... according to me, those 2520 burn to quickly !!!! :evil:

eD)))[/quote]

I design that in so that I can sell more of them to noobie Belgians.

 

[vertiges]

[quote author="SSLtech"]Peter, the termination was SIX ohms, not sixty-eight...
[/quote]

It's was 68 Ohm actually. It was the shunt resistor of an attenuator circuit that was not supposed to be there anymore. :evil:

[quote author="SSLtech"]
eD, you don't need a scope to demag... a scope is a good tool for hunting and finding distortion, but it won't help you fix it... it just helps you to see WHEN it's fixed. -Of course I have access to a few distortion analysers here, so I'm spoiled rotten....
[/quote]

Ok.

[quote author="SSLtech"]
Personally I am always wary of DC-coupled transformer connections, and would NEVER connect one up without measuring the DC offset first, but of course I learned this a long time ago the way so many others did... by making the mistake.
[/quote]

Now I KNOW !!! :grin:

[quote author="SSLtech"]
Anyhow... it could be worse. -It could be a Porsche alloy V8 motor that you built, and you could have left a loose nut in, to tap-dance on a piston crown and bugger up the entire block... now THAT costs a lot of money!!! -(ask me, and I'll send you pictures!)
[/quote]

I own a V8 too... But it's a Ford, not a Porsche... :wink:
Hopfully, I'm not playing with its engine !

[quote author="SSLtech"]
Transformer: I'd just take it to a twenty-pound (weight, not cost!) 2"-tape bulk eraser, switch it on and slowly bring it into the field, leave it there for an hour or so and then slowly take it out of the field. You'll be fine. -The dead 2520 will need a funeral, unless of course it's not potted, in which case it can be repaired... -I don't know the Petey-Purpose-like 2520s intimately... -I'd like to, however! :grin:
[/quote]

Whay do you mean by "not potted" ? Do you mean ugly melted plastic everywhere ? :shock:

[quote author="SSLtech"]
25K versus 20K... only about a dB's worth difference I suspect. On a log scale, the resistance has to accellerate dramatically for every dB's worth of change, so as long as it's reverse log, don't fret too much.
[/quote]

You made it very clear ! :thumb:

[quote author="SSLtech"]
Anyway, you can pass signal and it doesn't irreversibly hurt anything to use a transformer with a magnetised core... it just sounds a bit funny.. perhaps 'vague' compared to a clean, punchy API in good health.
[/quote]

Ok... now I see...

eD)))

 

[vertiges]

[quote author="peter purpose"]

I design that in so that I can sell more of them to noobie Belgians.[/quote]

:shock: :shock: :shock: :shock: :shock:

rhhhhhaaaa now you confess !!!

:grin:

 

[SSLtech]

Ah, the ford V8 is probably an Iron Block, or even if not, it has some iron or steel sleeves... You could drop a hammer in there and start it up without bending anything very much...

-A Porsche thin-wall, all-aluminium block REALLY does throw in the towel when you so leave a single nut in there though!!! :twisted:

Keith

 

[vertiges]

[quote author="nielsk"]The gain control pot should be 25K reverse log, and the rgain resistor should be 200 ohms and should go between the cap on the other side of the pot and ground.[/quote]

This resistor sets the maximum gain of the 2520 right ? :roll:
If I put a 20 Ohm instead... (I don't intend to, but it's just a "If I-question")
is the 2520 gonna be cooked ?

Are you sure that resistor should be on the other side between the cap and the ground ???

eD

 

[AnalogPackrat]

[quote author="vertiges"][quote author="SSLtech"]Peter, the termination was SIX ohms, not sixty-eight...
[/quote]

It's was 68 Ohm actually. It was the shunt resistor of an attenuator circuit that was not supposed to be there anymore. :evil: [/quote]

But at DC, the DCR of the output transformer primary is what matters (transformers don't work at DC--that is the core does not couple DC from one winding to another). So about 6 ohms (or whatever the DCR of a 2503 winding is) is what you used to generate excessive sand-melting heat upon which you could have cooked a tiny Belgian waffle...

[quote author="SSLtech"]
Anyhow... it could be worse. -It could be a Porsche alloy V8 motor that you built, and you could have left a loose nut in, to tap-dance on a piston crown and bugger up the entire block... now THAT costs a lot of money!!! -(ask me, and I'll send you pictures!)
[/quote]

Ooh, nasty. I bet the sound was glorious, too! "What's that infernal pinging all about?"

A P

 

[peter purpose]

[quote author="SSLtech"]Peter, the termination was SIX ohms, not sixty-eight...

The lack of a DC voltage reference caused the 2520's formidable output current drive to be brought to bear upon an unsuspecting transformer...
Keith[/quote]

Roger roger

 

[peter purpose]

No 2520 funeral needed Ed, I'll send you another set of transistors. Break out the soldering iron and magnifying glass.

 

[peter purpose]

Forgot to mention Ed....
There is a word in the English language that begins with the letter F followed by U, then S and lastly E.
Real equipment savers... :thumb:

 

[SSLtech]

[quote author="peter purpose"]Forgot to mention Ed....
There is a word in the English language that begins with the letter F followed by U, then S and lastly E.
Real equipment savers... :thumb:[/quote]

... :?: ...

"Fudgesale"...?

:?

Keef

 

[peter purpose]

:green: :green:

 

[3nity]

Ed sorry, I supposed that almost everyone should know that pins 6-7-8 of the CM75101APC should be connected to ground!
I should have mention too that the schematic is for refence only!


But i corrected so no other will commit the same suicide!
http://www.twin-x.com/groupdiy/displayimage.php?album=lastup&cat=0&pos=0

Ed see your pm's!

 

[vertiges]

Peter,

Are talking about this ? :

I'm not sure the 600A will fit in a 1U rack... :green:

eD)))

 

[vertiges]

[quote author="3nity"]Ed sorry, I supposed that almost everyone should know that pins 6-7-8 of the CM75101APC should be connected to ground!
I should have mention too that the schematic is for refence only!
[/quote]

3nity, that's not your fault... :shock:

There are many schematics available : the MP12 (Sound Skulptor), the Eisen, the A12 (SCA), etc... And I'm just talking about API style... They all have the path to the ground. I should have been more focused, less tired, less ignorant, less impatient, less whatever... !!! :roll:

In fact, the real guilty one is Peter !!! :evil:
He sells very fragile 2520 ! You just overload them with a few millivolts and they smell like hell !!! :green:
What a scandal !!!

And those Cinemag output transformers... just a few amperes, and they turn to "fridge-magnets" ! That's not serious...
What a shame !

Don't worry 3nity !!! J'assume mon incompétence !!! :wink:

eD)))

EDIT : the missing path to ground was not the only mistake I did !!!

 

[vertiges]

Guys, I would like to say thank you for your time, for your help, for your precious advices !!! I'm learning so much...

Thanks a lot !!!! :thumb: :thumb: :thumb:

eD_the_2520_killer