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May 16, 2022, 01:16:23 AM

Author Topic: S.E.X. > 2A3 Monoblock OPT  (Read 240 times)

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Offline Paul Birkeland

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #15 on: May 09, 2022, 05:13:06 AM »
The BeeGlow also sort of lacks proper biasing instructions, so you'd need to figure that out as well. 
Paul "PB" Birkeland

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Offline Ken

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #16 on: May 09, 2022, 08:11:01 AM »
My recollection of the designs is that the B-glow is more problematical than the Afterglow, which is probably what you had originally. I'm away from my primary computer this morning, but I'll be back later today. I'll check what manuals I may have and post again. What (if anything) is installed below the chassis plate?
Here's a photo of the underside.  Pretty rag tag - a sign of the mess I was in back then I guess.  It might be better to think in terms of stripping everything from the underside and starting from scratch, which I don't mind at all.
I'm almost positive that I was building the Afterglow variant and I would be completely happy to stick with that if it is less problematic and more easily doable than using 300B.

Offline Paul Joppa

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #17 on: May 09, 2022, 01:14:25 PM »
A few preliminary notes, now that I've checked my files:

* I have an original Afterglow manual. I can't locate a digital copy, but PM me and I'll scan the old manual and email you a copy.

* You are fortunate to have the deYoung power transformer - it was well made and gave the right voltages, but was only used for one year.

* The big cathode resistor (2500 ohms/10 watts) should be replaced with a 3000 ohm, 20+watt resistor. (There was an error in calculating the part value that was not caught at the time.)

* You'll have to use a more recent version of the C4S current source circuit board - we'll work something out.

* The inline fuse is a poor solution and does not allow proper safety grounding. The usual solution is to install an IEC inlet/fuse holder in the wood base.
Paul Joppa

Offline Ken

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #18 on: May 09, 2022, 01:46:51 PM »
Thank you Paul.  I appreciate this very much.  PM on its way.

Offline Natural Sound

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #19 on: May 09, 2022, 02:59:30 PM »
I may have an old pair of c4s boards that you can have if I can find them. You may need to adjust the resistor values since it was originally setup for a S.E.X. 2.0. The original design that consisted of 2 separate boards. Perfect for a pair of mono blocks. I'll start digging if you are interested.

Offline Ken

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #20 on: May 09, 2022, 03:02:42 PM »
@Natural Sound.  Thank you :)  I am completely dependent on Paul J's advice about this.  He did mention a "more recent" C4S but I don't know enough about it to know what that means.  Perhaps he will clarify if/when he sees your post.

Offline Paul Joppa

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #21 on: May 09, 2022, 06:52:38 PM »
@Natural Sound -- Are those the older, brown boards? Do you have the original LEDs? (They are in a different format than the current HLMPs.) That would be more authentic than using current production boards!

Alternatively I was thinking  of the v.4.4 green boards, using the trimpot for a cathode resistor and implementing the soft-start function.

The other missing piece is a power switch that fits the old chassis cutout.
Paul Joppa

Offline Ken

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #22 on: May 10, 2022, 06:13:45 AM »
@Paul Joppa:  Paul, I received your PM and replied (twice) with a notice that the Replies were successfully sent.  However,  those replies are not showing up in my Sent Items folder in Messages, so I don't know if you actually received them.  In case not:

- you can email the manual to [email protected]
- I hear your advice about trying to build the two amps as mirror images; have to reconsider that
- when I'm shopping for the other parts, if I can't find a power switch of suitable size and rating, I can always use a Dremel (or similar) to enlarge the cutout in the chassis
- I will wait to hear further from you about the C4S boards
- great news that the bases are still available; will save a lot of hassle for me.

Offline Paul Joppa

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #23 on: May 10, 2022, 07:08:45 AM »
My messages to you should be in your Inbox. Yours to me should be in your Sent Items.

In any case, yes, I got your messages. I'll send the manual scan this afternoon.
Paul Joppa

Offline Ken

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #24 on: May 10, 2022, 07:15:18 AM »
Thanks.  That's what I figured.  Yours to me are there in my Messages but my replies are not in Sent Items.  Anyway, you received them so all is well.

Offline Ken

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Re: S.E.X. > 2A3 Monoblock OPT
« Reply #25 on: May 13, 2022, 03:05:02 PM »
@Natural Sound:  Paul J advised that he's going to come up with some new C4S boards for the Afterglows so I won't need to take you up on your offer.  Thank you though.