Scope Guru

[peter purpose]

Tell me Guru...what can be told of this?

Your servant.

 

[gyraf]

Upper (NPN-) side of output push-pull stage basis-emitter shorted?

 

[peter purpose]

Hi Jakob,
No, that doesn't seem to be the problem.
Any further clues?

peter

 

[BradAvenson]

So is the scope broke, or is this the circuit you are testing?

 

[peter purpose]

Brad, it's the circuit I'm testing.

Jakob, there is continuity between emitters, but with 2x 5R6 resistors in there. Should these be increased in value?

peter

 

[BradAvenson]

Did it bias up properly DC wise?

 

[peter purpose]

Brad, I'm assuming that means 'is the right voltage being applied'? If so....yes. They draw + & - 18V straight from the pins.

peter

 

[gyraf]

It seems that it's your positive-going half wave that is missing.

1 - How is the output DC offset? Is it because it runs into the +18?
2 - How does base signal wave form on upper (NPN) transistor look?
3 - What is this circuit?

 

[peter purpose]

Hi Jakob,

"It seems that it's your positive-going half wave that is missing."

Where can you buy one of these?

1 - How is the output DC offset? Is it because it runs into the +18?

Well, there's -6.36V at the output...!!!!

2 - How does base signal wave form on upper (NPN) transistor look?

The same..!!

3 - What is this circuit?

The 'ahem' pp op amp.

peter

 

[gyraf]

Whoever drives the base of the upper transistor is probably gone?

 

[peter purpose]

Thanks Jakob

 

[peter purpose]

That's what it was.
Jakob....You're some man for one man..!!
Thank you very much indeed.

peter

 

[BradAvenson]

[quote author="peter purpose"]Brad, I'm assuming that means 'is the right voltage being applied'? If so....yes. They draw + & - 18V straight from the pins.[/quote]

Well, in my vagueness what I meant to ask is what the DC volatages looked like with no signal. The thinking is that the output is suppost to be near the 1/2 supply voltage. When it is not it will clip a bit prematurely and very asymmetrically.

Either way, it looks like you have figured it out.

 

[chrissugar]

Hey Kubi

Don't tell me that you memorised all the waveforms from the entire wavetable of the XT like me. Welcome to the club! :green: :green: :green:

chrissugar

 

[Steve Jones]

Oh God, don't remind me - I have a Waldorf Wave (the big one with the flip up front) and a PPG Wave 2.3, and a Microwave 1 all in the workshop at the moment.... Ouch.

 

[chrissugar]

Yeah Peter, sorry but I can't resist. I know NewYorkDave would use a picture of Nadine but I have to show my favourite rack. :grin:
It is a shame to have these but not a single Waldorf mug. :sad:

Hey Kubi, some more wavetables to memorise. :green: :green: :green:

chrissugar

 

[Guest]

Do I win if I went to work in Waldorf once?
(not the company - the village outside hiedelberg)