S.E.X. > 2A3 Monoblock OPT

[Paul Birkeland]

The BeeGlow also sort of lacks proper biasing instructions, so you'd need to figure that out as well. 

[Ken]

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.

[Paul Joppa]

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.

[Ken]

Thank you Paul.  I appreciate this very much.  PM on its way.

[Natural Sound]

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.

[Ken]

@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.

[Paul Joppa]

@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.

[Ken]

@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.

[Paul Joppa]

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.

[Ken]

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.

[Ken]

@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.

[Ken]

I now have a parts order pretty much together.  Actually, there aren't that many items missing or lost.  I was able to find most things at Mouser Canada and a few from our esoteria at PartsConnexion here in Canada.  I need advice/input about a couple of things please:

- for the fused IEC receptacle would 5A or 6A rating be appropriate?
- tubes were missing and I have no idea what became of them.  Brent Jessee has a good selection of NOS 5965/6829/12AV7 at reasonable prices but I don't want to pay the price for NOS or premium 2A3 until I have the system up and running.  Any recommendation for decent quality, reasonably priced current production as a place holder for the time being?
- my multimeter also vanished in the haze.  Recommendations for a reasonable quality hobbyist model?

Thank you.

[Paul Birkeland]

No, don't use a 5A fuse. 1-2A is plenty.  Used 5965s on eBay are dirt cheap; just grab some of those!

If you have a Harbor Freight Tools near you, they have a meter that's around $25 that works really well.

[Ken]

Thanks Paul.  The 5965s are not a problem, it's the 2A3s that are expensive, even for current production.  Although I did see a couple of places selling Chinese Penta for about $45USD.  How long they might last would be a crap shoot I would imagine.

Harbour Freight is not in Canada.  Would this meter from Mouser suffice as a starter for building this kit (price is in CDN dollars):
https://www.mouser.ca/ProductDetail/Digilent/480-001?qs=s%2FdyVPQMB4xWAQ%252Byz%2FlJpg%3D%3D

[Paul Birkeland]

How about this?
https://www.canadiantire.ca/en/pdp/autoranging-digital-multimeter-0520052p.html#plp