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scott 299A question(s)...

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Posted on November 25, 2014 at 12:39:43
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 I have the later EL84 model with the tubes aligned along the back edge. I picked up a sams for the amp, however it shows the earlier model with the tubes along the middle perpendicular to the back. I also got a user manual that I was to use for setting bias, etc. The question is that the earlier model has 2-330 ohm 10 watt in parallel resistors into the first cap, my amp did not originally have ANY resistor coming into the first cap, so I installed one 330 10 watt, which is what I have seen in a number of pics online, is that correct? Also, the user manual is for the earlier version which has a different biasing technique, any suggestions on how I should bias this? thanks!

 

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RE: scott 299A question(s)..., posted on November 25, 2014 at 14:16:04
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Randy
you don't want just a single 330ohm there because your B+ will be too low under dynamic conditions.330 ohms from rectifier to first cap is way too high..If your had no resistor(s) there,someone could have taken it out or that's a slightly different model.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: scott 299A question(s)..., posted on November 25, 2014 at 15:34:03
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 yes, Michael, that is what I was wondering, there was no 330 ohm resistor and I thought it was just one in the set according to some of the pics I have seen. So you are saying that there is indeed TWO 330 10 watt resistors in parallel in the 299A that has the output tubes running parallel to the back panel, correct? The schematic that you linked, that is same one I have from my sams folder that shows the output tubes running perpendicular to the back, the earliest version. That is what I was hoping someone who has or has worked on this later (299A?) version of the amp could tell. I should note that the B+ is low on this relative to the schematic, as you have noted. However, I am not sure if I have the correct schematic for the later version Scott... thanks!

 

RE: scott 299A question(s)..., posted on November 25, 2014 at 15:49:30
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 If the output tubes run left to right or side to side, you have a 299B.
The outputs in the 299A run front to back.
The 299A has two 330 ohm 10 watt resistors in parallel but don't forget that two equal value resistors in parallel is half of the value of each resistor so that's around 165 ohms.
I'm sure that was done to get twice the wattage, or 20 watts.
If your 299 has white ceramic resistors standing up above the top side of the chassis near the rectifier tube and xfmr, I'd guess that one or more are the dropping resistors after the rectifier tube so see where the wires from those standup resistors go.
Check out the bottom view pic in this closed auction.

 

RE: scott 299A question(s)..., posted on November 25, 2014 at 18:45:25
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, Dave, my Scott is not that one, which is an EARLY 299B, as the schematic for the 299B has a different arrangement of the tubes and an 80 ohm resistor, more power in that set. My 299 late version has the same gold panel and bullet-head lights of the early version, from what I have found out the later version uses a 160 ohm 20 watt resistor, wow it is so hard to keep up with all the Scott variations!

 

RE: scott 299A question(s)..., posted on November 25, 2014 at 19:47:06
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 That's what I'm saying.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: scott 299A question(s)..., posted on November 25, 2014 at 19:51:48
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Dave
My Leak ST-50 has those standup resistors as well and I need a 100 ohm 10 watt..I tossed the old one out thinking I could get a replacement of the same style but I need one just to fill the hole in the center where the old one went...Who sells those? I would even buy a used one.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: scott 299A question(s)..., posted on November 25, 2014 at 20:21:54
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 Mikey,

I was going to say that you'd probably find a chassis mount 100 ohm 10 or 20 watt radial ceramic at the same place that still had a volume control for a Mac C-22 but I had to edit that first comment in this post after I did a better search.

There's a 110 Ohm 25 watt and a couple other radial chassis mount ceramics in the attached link.

There's no dimensions so your guess is as good as mine if the diameter of a 10-20 and 25 watt are the same and it's the length that makes the wattage difference or not.

Snatch some of those up before their gone. Good "hole fillers" for broken ones even if they aren't the right values. You could even do a series or parallel resistor under the chassis with the new one to use it.

You may need to go to "home" on the web page I linked, click on resistors, and scroll through to see the other radials.

 

You are the best my friend., posted on November 25, 2014 at 23:32:39
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 You have no idea how long I've looked for those.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

150 or 180 ohms, posted on November 26, 2014 at 08:21:44
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 that is what I can get at 20 watts, which would you suggest? thanks!

 

RE: 150 or 180 ohms, posted on November 26, 2014 at 10:56:26
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 Don't forget that you can use two 330 Ohm 10 watt in parallel to make a 165 ohm 20 watter.

Mouser Electronics has a selection of 330 ohm 10 watt.
That's the way Scott did it for a while and the parts list for the 299A calls out two 330 ohm 10 watt. R119-120 or R209-210 depending on the schematic and that's what's in my 299A.

I don't know what your skill set is but having done a 299A myself with some basic knowledge, lots of thinking things out and consulting the Internet, it wasn't easy because things like having the B+ voltages be high or vary due to different current draw of the 7189's wasn't second nature to me and that threw me off for a while.

Like it isn't bad enough for the reasonably experienced to see high B+ due to the higher line voltages today compared to the schematic voltages that were taken at 117 volts in.

 

RE: 150 or 180 ohms, posted on November 26, 2014 at 11:33:31
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, Dave, luckily local Arcade had 330 10 watts in stock, just put them in and am going to fire this back up and check the rails. I had to replace the terminal strip for those large resistors, it broke as I was removing the wires and resistors, wow, those 10 watters really baked the strip and the connecting wires insulation!

 

RE: 150 or 180 ohms, posted on November 26, 2014 at 13:30:32
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 "wow, those 10 watters really baked the strip and
the connecting wires insulation!"

Yes but had one 20 watt 160-165 ohm been in there the same thing would probably have happened because the heat would have been the same.

It would probably be a good idea to leave a bit of air flow space in between the two 10 watters and not have them touching each other along their entire length.

That terminal strip and associated wiring insulation in my 299A isn't all that bad.

I suppose it could depend on the use the unit saw and what kind of current draw conditions that resistor saw.



 

RE: 150 or 180 ohms, posted on November 26, 2014 at 16:30:31
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 yes, don't know the history of it, other than there was NO resistor in that space, just a bare wire connecting to the cap and the little 5 watter, amazing what some idiots will do! Luckily, the Scott survived the butcher job, and is singing away today, wonder how long it will take to break in with the new caps and PS rebuild? BTW, how is the phono stage in it? Also, what do you use for cables, those RCA jacks in the back are so close together I can't easily get my cables connected to the inputs!

 

RE: 150 or 180 ohms, posted on November 26, 2014 at 18:04:40
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 I'm not the one to ask about cap break in. That's one of those issues of never ending debate that I don't and won't deal with. If a cap doesn't sound good in 5-10 minutes it goes away in favor of a cap that sounds good to me more or less right away.

I have zero patience to wait hours in the hopes that something will sound better, except for speakers that have mechanical components to loosen up. You need to use your own mindset/beliefs and sonic taste.

As for new PS lytics, my own feeling is that they are what they are after 5 minutes.

After recapping a few pieces and not being happy with the results and having to go through a lengthy trial and error process with different caps here and there to restore the sound I liked I'm now in favor of not replacing caps with "better ones" just for the heck of it.
The exception are the PS/bias lytics, cathode bypass lytics and output coupling caps because those could cause some expensive problems if they fail.
Those Sprague Bumblebee caps with the color stripes are suspect due to some manufacturing problems so I might replace those depending on where they are used.

As far as I know the phono section in these Scotts are pretty well regarded and I have no complaints with mine.

My phono cable has Vampire RCA connectors that fit fine and I make other cables with Canare RCA's and a couple of different cable types depending on the use.

I was ready to live with the 299A and sell off the "better stuff" until I got a good deal on a Sherwood S5000 early version and I like that better in a few ways. But had I never heard the Sherwood, the 299A would have been OK.

 

RE: 150 or 180 ohms, posted on November 26, 2014 at 21:30:24
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 Dave, the Vampire entry-level RCA connectors will work on the Scott phono inputs? The Vampires look a little big, but they are good, yes? What kind of wire do you use with them to make up the cables? Thanks!

 

RE: 150 or 180 ohms, posted on November 26, 2014 at 22:33:35
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 The Vampire 557 entry level male RCA's look like the ones I have. They fit the Scott, Sherwood and Mac C-22 just fine and I've never had a problem with them.
I also use the Canare F9's. They just make it without touching each other in the scott.

For phono with a cartridge that needs to see a low capacitance, like a total of 200pf for the best response curve, I use a 17 pf per ft very flexible coax that I got when I worked for an audio company but you won't find that on the market as it was made for them only.

I also have belden 9259 coax that's 17.3 pf per foot but it's not as felxible and If I remember correctly I had to buy a whole spool.

For a cartridge like some of the Shures that like around 400 pF, I prefer the Vampire wire that is now, as far as I can tell, only sold on E-Bay by a company in Gainsville Florida. It's CCR or CCR OFC and an E-bay search should bring that vendor up. They have premade cables too and I don't see why they wouldn't be good for high level interconnects as well even at around 60-70 pf per foot.

I personally seem to like the bare copper coaxs. Either stranded center conductor or solid wire center conductor.

Some people like the Mogami mic wire but using two center conductors and a braid around them means special attention to what end the braid is grouned at because it's just a shield and not a signal conductor. I believe the grouned end would be at the preamp to dump any hash/RFI the braid picked up.

Kind of funny that I don't go for the "cap breakin" thing but I'm fussy about how different wire sounds. Silver interconnects and litz speaker cable drives me nuts every time.

Having grown up with mono tube equipment then stereo, using lamp zip cord for speaker cable and never hearing about breakin or wondering what caps were in anything was glorious and so was the sound that I'm now used to and like so I'm more a best bang for the buck guy rather than "high end" that I could never listen too for very long.

 

RE: 150 or 180 ohms, posted on November 27, 2014 at 08:27:08
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, Dave, your post is very informative! I too am a "bang for the buck" kinda guy, that is in part because I no longer have a job that is making money, and am back in school to get a job, or start up a new business doing electronics repair, so I am adding to my knowledge base by working on and learning from all the experts out here! I am currently using a Denon DL301 MkII cartridge, a LOMC, not sure that that will work directly into the Scott (or Sherwood when I get that one working...) but having the phono stage is a good option. And it is good to know that there are good quality plugs that will fit on those closely-spaced input jacks, thanks so much!

 

RE: 150 or 180 ohms, posted on November 27, 2014 at 09:32:43
DaveV
Audiophile

Posts: 513
Location: SC
Joined: December 26, 2009
 I think I found the Asylum around 2001 and reading about things people liked and didn't like was interesting and certainly food for thought.
Some of the suggestions I found to be things I liked and others weren't.
Having been around "high end audio" for many of my working years only reinforced my belief that I'm a late 50's to mid 60's tube equipment and speaker person.
If someone asks what I like or use I'll tell them but all that remains an opinion based on the way I like to hear music reproduced and how the combinations react in my system.
There's lots of wrong ways but only one right way. To have a system that draws you into the music and makes your feet tap.
Finding that combo is the hard part that can take you down many dead end paths.

 

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