Catalinbread CB30  [traced]

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mmolteratx
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Post by mmolteratx »

Got this in last week but I didn't have any desoldering bread up until today. So here it is. I'm not entirely sure about the 470p coupling cap and the 47p cap in the tonestack. They're those little blue ceramics with the codes 471 and 47 stamped on them, respectively. They seem odd to me. Anyways, on to pics.

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Post by atreidesheir »

They're those little blue ceramics with the codes 471 and 47 stamped on them, respectively.
I believe you have AC capacitors there.
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Post by atreidesheir »

HIgh voltage. maybe
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Post by mmolteratx »

They're rated at 1kV. I just took a look at the English Channel schem and the 470p/47p caps make sense. What about the 470k/330p combo from drain to gate on Q1? Localized feedback of some sort?

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Post by mcaviel »

:hmmm: i wonder why he put two 100nf and 220nf as electrolytics.

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Post by RnFR »

mmolteratx wrote:They're rated at 1kV. I just took a look at the English Channel schem and the 470p/47p caps make sense. What about the 470k/330p combo from drain to gate on Q1? Localized feedback of some sort?
that's what it looks like. possibly to quell oscillation? although, I would think that the 470K would reduce the feedback immensely.
mcaviel wrote::hmmm: i wonder why he put two 100nf and 220nf as electrolytics.
$$$. at least they look like they are the "audio grade" low leakage/ESR variety.

the soldering does look a bit dodgy. it seems as though many of the joints were deeply cut into with a flush cutter. not good practice. a better way would be to cut the leads first, then solder. that way you don't put any risk to the joint. right, Dirk? :wink:
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mmolteratx
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Post by mmolteratx »

RnFR wrote:
mmolteratx wrote:They're rated at 1kV. I just took a look at the English Channel schem and the 470p/47p caps make sense. What about the 470k/330p combo from drain to gate on Q1? Localized feedback of some sort?
that's what it looks like. possibly to quell oscillation? although, I would think that the 470K would reduce the feedback immensely.
mcaviel wrote::hmmm: i wonder why he put two 100nf and 220nf as electrolytics.
$$$. at least they look like they are the "audio grade" low leakage/ESR variety.
Most likely it's for mojo. I've seen a few posts from Nic talking about using different types of capacitors for different positions.
the soldering does look a bit dodgy. it seems as though many of the joints were deeply cut into with a flush cutter. not good practice. a better way would be to cut the leads first, then solder. that way you don't put any risk to the joint. right, Dirk? :wink:
Yea, a couple joints seem to be held together by small drops that didn't make it all the way through as well. I'll be touching up a couple before I put it back in the enclosure. The 1/2W carbon comp in the feedback path is odd. And there's an electro positioned backwards from the way the silkscreen indicates. A couple caps aren't flush with the board. A number of "problems" I've never seen before in a Catalinbread build.

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Post by bajaman »

yes - that input coupling electro is the wrong way around on the schematic!! :wink:
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Post by bajaman »

AND that 220n electro looks like it is reversed as well - possibly on purpose :scratch: :hmmm:
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Post by mmolteratx »

The input cap and 220n electro from source to gate on Q4 are as they're placed and as the silkscreen shows on the board. The 100n before Q5 is the one that's placed in the opposite direction of the silkscreen and is drawn as it appears. It is odd for sure.

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Post by mmolteratx »

Here's the 100n input cap:
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Here's the 220n cap from Source to Gate of Q4 (marked Q3 on the silkscreen):
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And here's the 100n cap that has the "wrong" orientation when looking at the silkscreen:
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Post by mmolteratx »

Anyone want anymore pics? I'm about to box this back up.

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Post by ShortScaleMike »

Unverified - corrections and build reports welcome as always.

Yes I am not proud of C7

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Post by roseblood11 »

ShortScaleMike wrote:Yes I am not proud of C7
Why not use one more column? 21 holes fit in a Hammond 1590B...

Can someone please measure the current draw at 18V? I´d like to build a version with integrated voltage doubler based on the ICL7660S and with a JFET-Treble Booster in front of the CB-30. I guess that the ICL7660S should work with both circuits, at least if the bypass LED's run at 9V only.

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Post by roseblood11 »

Is the schematic really correct? At least the 680nF film cap in parallel with the 22µF power filtering cap doesn´t make any sense to me. I often use 100nF ceramic there to improve the filtering at higher frequencies, but why use a much more expensive and larger film cap there? :hmmm:

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Post by mmolteratx »

roseblood11 wrote: Can someone please measure the current draw at 18V? I´d like to build a version with integrated voltage doubler based on the ICL7660S and with a JFET-Treble Booster in front of the CB-30. I guess that the ICL7660S should work with both circuits, at least if the bypass LED's run at 9V only.
I gotta find my 18V supply but I should be able to measure it sometime this weekend.
roseblood11 wrote:Is the schematic really correct? At least the 680nF film cap in parallel with the 22µF power filtering cap doesn´t make any sense to me. I often use 100nF ceramic there to improve the filtering at higher frequencies, but why use a much more expensive and larger film cap there? :hmmm:
I've traced it twiced and came up with the same thing both times. The power filtering is a little :scratch: to me as well but it's definitely a 680nF cap in parallel with the 22uF. It's a large Panasonic film with the code 684 printed on the side and a Nichicon FG electro with 22uF printed on the side.

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Post by ShortScaleMike »

Thanks for the corrections and advice guys, I think I've fixed the area around the output of the section mu amp stage and also the C7 crapness, as always, input welcome.

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Post by roseblood11 »

The layout shows a direct connection from "Gain 2" to "Bass 2". :hmmm:

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Post by roseblood11 »

= missing trace cut at g12

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Post by ShortScaleMike »

Good spot! sorry about that.
cb30_092.gif

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