Paradise Builders

maybe there is something else to do but sit at the puter
 

Attachments

  • slå rødder.jpg
    slå rødder.jpg
    30.1 KB · Views: 527
Member
Joined 2005
Paid Member
Working on another couple Paradise boards, one is working fine but the other is stuck at 15V at the output.....

Boards are working fine now, and the error was quite interesting.

A lesser-known fact is that bipolar transistors work both ways (collector and emitter reversed). the current gain is low, but if the circuit does not depend so much on this, at first glance it looks fine.

In this case, Q15 and Q16 were inserted the wrong way. They are the "bottom" transistors of the current mirror used in the current source for the input stage, and since this is a stacked current source , and the transistors were still doing something, it was not immediately obvious. Instead, there was some offset, which I thought was caused by mismatch in the transistors. But it was a mismatch between the upper and lower current mirror, caused by the reverse mounting. The servo could not correct this amount of mismatch - an indication how weak it actually is. Once the transistors were mounted correctly, everything worked fine.

Many thanks Ricardo for the numbered drawing, I used it extensively in this case!
 
I'm sorry - I'm one of these "color by numbers" guys. I don't really understand what happens and I need simple instructions :D.

You write the J310 is not ideal. I assume Rgs is R108 (3k3R) in my board? So what I have today is a J109 (came with the GB) and 3k3R. Please be certain you do not mistake the J109 for something else, we caused some confusion earlier in this thread because of this ;). Anyways, I take it from your answer that this is "not possible".

So you suggest SK170. I will have to replace the 3K3R with something around 360R? Does it matter if SK170 BL or GR?

Thanks for you patience.
Sven
 
Last edited:
I'm sorry - I'm one of these "color by numbers" guys. I don't really understand what happens and I need simple instructions :D.

You write the J310 is not ideal. I assume Rgs is R108 (3k3R) in my board? So what I have today is a J109 (came with the GB) and 3k3R. Please be certain you do not mistake the J109 for something else, we caused some confusion earlier in this thread because of this ;). Anyways, I take it from your answer that this is "not possible".

So you suggest SK170. I will have to replace the 3K3R with something around 360R? Does it matter if SK170 BL or GR?

Thanks for you patience.
Sven

IMO the best choice is the J113 (using a 1K Rgs resistor). But all resistors needing a 2K or less Rgs are good. The J109 is currently the worst one simulated :)
 

Attachments

  • Jfet's for 1mA current source.PNG
    Jfet's for 1mA current source.PNG
    68.3 KB · Views: 442
I'm sorry - I'm one of these "color by numbers" guys. I don't really understand what happens and I need simple instructions :D.

You write the J310 is not ideal. I assume Rgs is R108 (3k3R) in my board? So what I have today is a J109 (came with the GB) and 3k3R. Please be certain you do not mistake the J109 for something else, we caused some confusion earlier in this thread because of this ;). Anyways, I take it from your answer that this is "not possible".

So you suggest SK170. I will have to replace the 3K3R with something around 360R? Does it matter if SK170 BL or GR?

Thanks for you patience.
Sven

And, trying to un-confuse this a bit more, to be more clear. The 'impossible' means that it is impossible to have a 1mA current source (in this application) using the J109 and the 1mA was the design parameter for this current source.

On the other hand, the power supply will happily function using the J109 and 3k3, but; the supplied current will be between 600 and 750mA (not the design goal) and it will not be a CCS (not the design goal). Especially the last (it not being a CCS) hurts the performance of the PSU (but slightly).
 
Member
Joined 2005
Paid Member
Thanks for the hint - too bad my R1 boards never oscillated.... Yes, it would be interesting to compare sonic signatures. Also, I was thinking about putting the "Calvin buffer" into my paradise R3.

With so many Paradise stages out there, we should be able to come up with a "Paradise Fest" :D
 
I only have one channel of Paradise so far, but I have just shy of half of the "Calvin buffer" done [right hand schematic in #52]. I posted a picture in Calvin's buffer thread. It is scary looking, but small enough to fit in some empty space on the Paradise pcb. Now I just need to muster the courage to tackle the lower half and the output Zobel, a few more wires to interface with the world are also still missing.