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Scott 299C and 7591 tubes [message #10013] Sun, 18 November 2007 10:08 Go to next message
theo is currently offline  theo
Messages: 5
Registered: May 2009
Esquire
Hi Everyone,

First time posting. A little background to my question: I picked up a Scott 299C a couple of years ago without really knowing what I was doing. I heard they were a good amp to try out that tube sound for not too much $, so I figured why not, I've been curious for a long time. The amp played well, but with quite a bit of hum and crackle on one side. Some "expert" told me to change out the original 7591 tubes with new ones and that would solve the problem. So I got some brand new (Russian I think) 7591s and put them in, then fired up the amp. After about a minute there's a really BIG POP and the amp goes dead - no sound at all! This freaked me out so much I immediately unplugged it, wondering what kind of god-awful damage I unwittingly inflicted. I just couldn't deal with it and put the poor thing away for probably a year and half and just went back to this Yamaha solid-state amp that I have. The Yamaha is big and loud, but not amazing. Anyway, to make a long story longer, eventually I decided to take the Scott somewhere that knows this stuff and find out what the problem was. I looked on the web and called around for someone/place local (I'm in the SF bay area). So there's just not a lot nearby except for some guitar amp guys (I wasn't sure if they would really know how to treat this old hi-fi stuff and didn't want to make another mistake). Since it seemed this was going to be more of a process than I thought and since it had been so long since I last tried it, I decided to clean the pins and reseat the original tubes (about all I know how to do), then try the old Scott once more before just taking it SOMEWHERE. I hooked up my JBL Century 100s (more vintage!) and pulled the power knob, expecting nothing, or for it to blow up! Now I have no idea how or why, but the Scott powered up and worked! Not only worked, it sounded great! I mean so bizarre I can't even believe it myself. I've been using it now for about 3 months and it sounds amazing. The hum/crackle problem is not there now. The sound really does live up to what others have said. Hopefully I'll never have to go back to solid-state again. Here's the question: Should I just never mess with the tubes in this amp again? Was it that it just didn't like those Russian tubes, or... ?

I'm very curious how long I expect this old (not sure how old) totally original amp to play well if I just leave it alone.

Any insight much appreciated!

theo

Re: Scott 299C and 7591 tubes [message #10015 is a reply to message #10013] Mon, 19 November 2007 09:20 Go to previous messageGo to next message
real_one is currently offline  real_one
Messages: 55
Registered: May 2009
Baron
Check to make sure you didn't blow a capacitor. If so, replace it. If not, enjoy!

Re: Scott 299C and 7591 tubes [message #10016 is a reply to message #10013] Mon, 19 November 2007 16:30 Go to previous messageGo to next message
Forty2wo is currently offline  Forty2wo
Messages: 163
Registered: May 2009
Master
The crackle and pop may just be dirty sockets. The act of removing and replacing the tubes cleans them to a degree. If you plan to use it on a regular basis I would consider replacing the electrolytic caps and maybe upgrading the bias supply…John

Re: Scott 299C and 7591 tubes [message #10035 is a reply to message #10013] Sun, 16 December 2007 07:19 Go to previous messageGo to next message
SteveBrown is currently offline  SteveBrown
Messages: 330
Registered: May 2009
Grand Master
I have heard that new manufactured tubes may have slightly smaller pins than the original. That, combined with old, dirty and worn sockets, may be all that's wrong. I assume when you got the loud POP, it wasn't a Bang (cap going out), nor did you smell smoke. Right? If so, I'd bet it's just the pins. By the way, check your tube plates and make sure they're not red or glowing. Personally, I'd get an old amp like that checked out. As I recall, this amp used DC from the front end filament supply to also provide fixed bias on the outputs. Good chance you need to replace the low voltage rectifier and the power supply caps. A good tech can tell you for sure. In the mean time, don't leave it unattended while running...


Re: Scott 299C and 7591 tubes [message #10040 is a reply to message #10035] Tue, 18 December 2007 10:42 Go to previous messageGo to next message
theo is currently offline  theo
Messages: 5
Registered: May 2009
Esquire
Hi Steve,

The amp has been running and sounding fantastic ever since I re-tried it a couple of months ago. From what I was told, everything in the amp is original, including the tubes. After my experience mentioned in the original post, I'm very leary of using anything but NOS tubes when the time comes. I just hope I can find some good ones before these need replacing. The amp sounds so sweet now that at this point I've pretty much adopted the mindset of "if it ain't broke don't fix it." It seems alot of people say the caps and such NEED to be replaced, but I'm afraid if I get someone to work on it, some of the original magic could be lost. Does anyone know how long this beauty might run without any work being done on it?

Theo

Re: Scott 299C and 7591 tubes [message #10041 is a reply to message #10040] Tue, 18 December 2007 10:49 Go to previous messageGo to next message
SteveBrown is currently offline  SteveBrown
Messages: 330
Registered: May 2009
Grand Master
Theo, could be it will run forever, you never know. I would check the temperature of the big can electrolytics (power down, wait a couple minutes and see if they're hot - don't grab the connections). They should not be hot, but depending on how close they are to tubes, they may be warm. If they're not near any tubes or other heat generating stuff, they should be cool. A tech could easily check the coupling caps for leaks, which is also a good idea. I'd agree that this i a really nice sounding amp, I've played with the similar 299D before giving it to my son. One of the things I really liked in this amp is the phono stage, so I hope that you're spinning some vinyl and taking advantage of that slice of magic, too. Best of luck!

Re: Scott 299C and 7591 tubes [message #10042 is a reply to message #10041] Tue, 18 December 2007 15:20 Go to previous messageGo to next message
theo is currently offline  theo
Messages: 5
Registered: May 2009
Esquire
Steve,

I checked the caps for heat as you suggested and they get a little warm, but I think that's just because they are close to the tubes. They definitely don't get hot.

You're so right about the phono on this amp. I couldn't believe my ears when I first played a record. The sound almost seems three-dimensional. I'd really like to get a better turntable (any suggestions for a nice, not too expensive turntable?), but even with this average Sony turntable I have, the sound is amazing.

I read an article in Rolling Stone (latest issue) about modern digital sound quality and basically the article ends saying that hi-fi, audiophile sound quality is over - a thing of the past. Amazing, with all this new technology, sound quality is actually getting worse! And people seem to be OK with that. Me, I'll stick with this 45-year old Scott if that's what it takes to get the real deal.

Theo

Re: Scott 299C and 7591 tubes [message #10043 is a reply to message #10042] Tue, 18 December 2007 15:39 Go to previous messageGo to next message
SteveBrown is currently offline  SteveBrown
Messages: 330
Registered: May 2009
Grand Master
Well, I think a great table is a similar vintage AR XA, which is the older of the AR line. This is a suspension table, similar in design to the Linn or Thorens kinds of tables. It does not work as well if you have bouncy floors, but given a good foundation, or shelf mount, it is a very nice table. I happen to have one sitting in a closet doing nothing ... Or, any of the Thorens tables are excellent. Most of the ARs and Thorens are going to be easy to get into (low $$). They're not as sexy looking as, say, a VPI Scout, but I've owned a Scout and I choose other tables for their sonics and eventually sold the Scout. It's hard to go wrong with the basic Thoren's design of a belt driven, suspended table and that's why you see so many others mimic it.

Re: Scott 299C and 7591 tubes [message #10044 is a reply to message #10043] Wed, 19 December 2007 02:32 Go to previous message
theo is currently offline  theo
Messages: 5
Registered: May 2009
Esquire
Steve, I'm sure the AR XA is very good (thank you for the offer) but I think I'd like to get into something a little less vintage I don't know much about Linn or Thorens. Any particular model I might want to check out?

Also, what do you think about linear tracking tables? I know they were quite popular for a while, but maybe not so much now. I've always wondered if those produce better sound on the inner tracks of a record. The increased distortion on those inners grooves has always bothered me, so if there was a table (perhaps linear) that would reduce this problem, I'd really be interested.

Thanks very much for all the info!

Theo

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