Questions about Baumans 1731 and 25twenty boards

[Category 5]

I am sourcing parts for my op-amps.

I have two BOM sheets...one for the 1731 and one for the 25twenty. Which version of the board is the 25twenty list for?

Also, are there any of Bauman's boards assembled that I can see some pics of? What about parts layout PDFs? The print is small, especially on the 25twentys, and a bit scary!

So Mouser has the following transistors. Will these do for the Melcor?

They don't have BC550C, but they have BC550 (whole name) and BC550BTA. Which should I get? ...or should I hold out for some 550C if someone come across them?

For Q1 and Q2 (BC414C) I am going to use a matched pair of BC550 (so far I think I'll get the plain BC550 from Mouser)

For Q3 and Q4 I am going to get a pair of BC560C from mouser (non matched right?)

For Q5 and Q6 the BC550 again

For Q7 and Q8 Mouser has BD139 and BD140. Any need to match these? they are the most expensive.

For all the capacitors C1-C3 and CD1 and CD2 can I just use the Panasonic ceramics? They are nice and small.

All that's left is the resistors and the diodes. These should be straightforward enough. Anyone know of any small resistors?


For the 25twenty (I think I'll do the 1731s first) I was planning to also substitute the BC550 for the BC414C parts. Is R7 3k or 5k? And are ceramics okay for the caps? Also, what's with J1? I don't see the note.

Thanks!
Shane

 

[pmroz]

I am sourcing parts for my op-amps.

I have two BOM sheets...one for the 1731 and one for the 25twenty. Which version of the board is the 25twenty list for?
mine says 2520BC

Also, are there any of Bauman's boards assembled that I can see some pics of? What about parts layout PDFs? The print is small, especially on the 25twentys, and a bit scary!
pics on Fabio's site, api thread, etc.

So Mouser has the following transistors. Will these do for the Melcor?

They don't have BC550C, but they have BC550 (whole name) and BC550BTA. Which should I get? ...or should I hold out for some 550C if someone come across them?
BC550C = Msr 512-BC550C or 512-BC550CTA (tape, cheaper)
BC560C = same deal

For Q1 and Q2 (BC414C) I am going to use a matched pair of BC550 (so far I think I'll get the plain BC550 from Mouser)
For Q3 and Q4 I am going to get a pair of BC560C from mouser (non matched right?)
For Q5 and Q6 the BC550 again

Those are the replacements Fabio gave me as well.

For Q7 and Q8 Mouser has BD139 and BD140. Any need to match these? they are the most expensive.
For BD139/BD140 you can sub BD135/BD136, Mouser or Digi

Input transistor pair are the only ones i'm sure need matching. Others too maybe, just don't know yet... someone else jump in....

All that's left is the resistors and the diodes. These should be straightforward enough. Anyone know of any small resistors?
Phoenix .25/.40w/.50 1% metal film (Digi cat page 1011) are smaller than Yageo from Mouser. I bought Yageo first, and a few Phoenix... then re-ordered Phoenix for opamps... the Yageo are just too big there.
For other brands compare the size specs... after buying resistors twice i don't want you to have to.

For the 25twenty (I think I'll do the 1731s first) .... are ceramics okay for the caps?
Si (yes), NPO or COG ceramic

There's another post around here with some discussion of opamp part values...
http://www.groupdiy.com/index.php?topic=4796&highlight=2%2A5%2A2%2A0

... good reading for Melcor opamp stuff...

 

[robomatique]

Another question about the transistors.

I know that BC550 can normally be substituted with BC549, 548, 547 as well as BC560 can be substituded with BC559, 558, 557.

It is quite easy to find BC559C and BC549C , would these be ok or what is the difference between them and the 550, 560 (the pinout are the same)?

Thanks

Robert

 

[clintrubber]

It is quite easy to find BC559C and BC549C , would these be ok or what is the difference between them and the 550, 560 (the pinout are the same)?

As I always understood it the 550 & 560 are slightly lower noise - or perhaps better put: they have a lower max noise spec value (as much as 1 dB...).
Some other datasheet also mentioned a higher max collector emitter voltage for the 550 when compared to the 549.

So you can't go wrong with the 550 i.s.o. 549 etc, but if you can't find 550 etc I doubt you will notice much/any difference in practice.

Bye,

Peter

 

[pmroz]

They don't have BC550C, but they have BC550 (whole name) and BC550BTA. Which should I get? ...or should I hold out for some 550C if someone come across them?
BC550C = Msr 512-BC550C or 512-BC550CTA (tape, cheaper)
BC560C = same deal

Hey robomatique, go to Mouser and paste these #s...

512-BC550CTA
512-BC560CTA

these are on tape, 100x $4.00...

that's as easy as it gets here

 

[Category 5]

The 560s are in stock, but those 550s are listed with an 11 week lead time (yikes). Why in the heck can't they just stock them, and order them when the supply gets low. They can't take up too much shelf space!

Shane

 

[PRR]

> BD139 and BD140. Any need to match these?

No.

 

[Category 5]

BTW, here is the circuit I am using to match.

http://www.notapplicable.co.uk/audiolab/905-matching-transistor.gif


Any problems with unsing only a single 9 volt for power? The sheet says 10-15v, but a 9 volt is so convenient.

Also, I breadboarded the pnp version of the circuit just for fun (since I don;t have the bc550s yet) and picked up a pack of RS pnps.

With a single 9 volt I get abour .505 - .575v on each. What's wierd is that I get about the same if I put the transistor in backwards. Does this make sense or did my circuit go wrong? I checked it and everything looks like the sheet specifies.

Shane

 

[Sleeper]

http://www.groupdiy.com/index.php?topic=4796
here's the pics and some helpful info.
Sleeper

 

[Category 5]

Thanks sleeper. I forgot that thread. the board on the left isn't one of the 4 designs Fabio sent me, so it must be new. The one on the right looks like his BC1 rev.


I built my transistor tester tonight, and I only have one npn lying around (a 3904). It tests .601 vbe. Man, the circuit sheet is right. If you just touch the transistor for a second the vbe starts to drop rapidly! The transistors definitely have to be temp. stable and you can't put them in the tester with your fingers or the reading will be WAY skewed. I think i will plug all of mine into my breadboard, and just connect the tester that way. Then I won't have to touch them.

PRR, will I need to put more voltage into the tester or is a 9v (actually measuring like 8.75) okay?

Also, someone mentioned testing vbe using a multitester set for diode. I put my npn in there and get .635 . I wonder (even though it tests different than with the 741 schem.) if that would be close enough for matching. When I touch it the reading drops just like when i use the 741 tester.

Shane

 

[Bauman]

BTW, here is the circuit I am using to match.

http://www.notapplicable.co.uk/audiolab/905-matching-transistor.gif

That's what I'm using Shane!
I pick up the couple with closest VBE and arounf 10% difference in hFE.

the board on the left isn't one of the 4 designs Fabio sent me, so it must be new. The one on the right looks like his BC1 rev.

That's right. One is A2520, my own layout, double layer. The partlist on my site is for that board.
It matches the other opamps parts, except for QCS1, RCS1 and RCS2 that are the current source parts, (Q10, and 2 resistors I cant recall, need to check).

BTW just found out that this PP2.52.0 schemo is wrong, while mounting:
http://www.thediypill.phx.com.br/forumfiles/schPP2520_R268.gif
Peter use the current source for this version... will update that tonight.

I have now several 2.5.2.0BC blocks stuffed with different configs to test, I think next week I will have a better view of which one works ok.




:guinness:
Fabio

 

[robomatique]

[quote author="pmroz"]

They don't have BC550C, but they have BC550 (whole name) and BC550BTA. Which should I get? ...or should I hold out for some 550C if someone come across them?
BC550C = Msr 512-BC550C or 512-BC550CTA (tape, cheaper)
BC560C = same deal

Hey robomatique, go to Mouser and paste these #s...

512-BC550CTA
512-BC560CTA

these are on tape, 100x $4.00...

that's as easy as it gets here [/quote]

Thanks, but I am in europe and here it is much easier to find 559, 549 etc. What is the difference between them?

And... when it comes to matching, both hfe and vbe? Or is hfe enough? or only vbe?

Always thankful for any help!!!

Robert

 

[pmroz]

Robomatique, sorry, didn't see your locale... maybe not so easy

Fabio, thanks for the transistor link... I'm excited to hear how your tests go.

Paul

 

[clintrubber]

Thanks, but I am in europe and here it is much easier to find 559, 549 etc. What is the difference between them?

Hi robomatique,

If I understood your question correctly then it has already been answered, have a look 10 posts up from here.

Bye,

Peter

 

[Category 5]

How do I test for hfe?

Shane

 

[robomatique]

[quote author="clintrubber"]

Thanks, but I am in europe and here it is much easier to find 559, 549 etc. What is the difference between them?

Hi robomatique,

If I understood your question correctly then it has already been answered, have a look 10 posts up from here.

Bye,

Peter[/quote]

Oups missed that, thanks Peter!