S.E.X. > 2A3 Monoblock OPT

[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 ken@dangerfields.ca
- 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

 

[Ken]

There's a Canadian Tire just up the road from me  and I did see that meter.  I thought that it only being able to read down to 400R could be a problem.

 

[Paul Birkeland]

Those are ranges on the meter.  The 400 ohm setting will have three leading digits, a decimal point, then one more digit.  If you're trying to measure a 0.01 ohm resistor (which is extremely difficult to measure anyway), then you'll get a 000.0 on the meter, but it can certainly measure below 400 ohms.

 

[Paul Joppa]

For the parts order, add four small resistors for grid stoppers; we've often used 220 ohms but anything from 100 to 500 ohms is good. Carbon or metal film are acceptable; carbon composition is better in theory but tends to be fragile unless you get a premium part.

Also don't forget the 3K power resistors should be rated 20 watts, not 10 as in the parts list. Inexpensive metal-oxide ones are fine, but seem to be out of stock in many places; Ohmite wirewound are good, available, and not too costly:

https://www.mouser.com/ProductDetail/Ohmite/B20J3K0E?qs=%2F%252B4YgdRx4NhlrL7xcy2z3g%3D%3D

 

[Paul Birkeland]

I would add to PJ's recommendation not to use the chassis mount type resistors (with the gold heatsinks).  They will only dissipate their rated power if they are mounted to the side of a battleship, and derating them can be tricky.

 

[Ken]

@PaulJ:  I will order the grid stoppers as you said.  I did already find the Ohmite 3K 20W resistor at Mouser.

@PaulB:  that meter I linked at Mouser is less expensive and since they're both likely made in China anyway, would it do the job?  I'm already ordering from Mouser anyway.

 

[Ken]

@PaulJ:  what W rating for the grid stopper resistors?

 

[Paul Birkeland]

Grid stoppers handle no current (well, nearly no current), but it's nice to have a reasonably stout part with long leads, so a 1/4W part is a nice idea.

 

[Ken]

There are these three resistors on the original parts list.  What voltage rating should I order?  Mouser offers Vishay/Dale in 200, 250, 300, 350 V

249K 1/4W metal film
681 1/4W metal film
182 1/4W metal film

 

[Paul Birkeland]

Those all need to be rated for at least 10V.

 

[Ken]

Paul, they're rated between 200-350V