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Old 19th March 2009, 06:22 PM   #1
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Default Newbee want's to learn about tube amps, etc...

I have taken a recent interest in tube amps. A friend of mine recently lost his father and while cleaning out his house he found an old Scott Stereomaster 299B amp. knowing I was into speaker building, he subsequently gave it to me. I have not even plugged it in (neither did he) I don't know if it works or not. It appears complete with all tubes in place. It is pretty and clean and without any pitting or discoloration anywhere. I have heard that you should do some inspection and testing on these vintage amps prior to use when they are found like this. We have no idea when it was used last. It appears he was the original owner and as my friend understands this amp went into storage when his father "upgraded" to solid state years ago.

I want to learn all I can about tube amps now that I own one. Can anybody suggest a comprehensive yet easy for the beginner book that I can get started with. I am interested in things like biasing the tubes and other terms tossed around on the forums.

So, finally.....this amp looks great! Perfect in fact. Should I just plug it in and try it out or something other than this.

Thanks again to all!
Sincerely,
Jeff Miller
Lawton, OK
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Old 19th March 2009, 07:24 PM   #2
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Default Do you know how long it has been storred?

There are things that deteriorate with age like aluminum electrolytic capacitors, Those round cans that are either silver or have black paper sleeves on them. They become leaky and leak electricity to the metal chassis. This can be dangerous, ie lethal, if they are very leaky. It needs to be brought up slowly with a variable transformer (variac) when you first turn it on. Make sure all the tubes test good. Replace bad ones before turning it on. Make sure there is some load on both output channels like a speaker connected to each channel output jack, Leaky caps will let you know with a lot of hum. Make sure there is a good fuse (not one overrated) in the fuse holder. If something is very wrong the fuse will blow. Just make sure it is the right (correctly rated) fuse and not a 10A one. I wouldn't touch the metal chassis at first while it is on until you know no caps are leaking! Ray Hughes
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Old 19th March 2009, 08:29 PM   #3
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Default Your symbol

Your motorcycle...is that the new CBR1000RR?
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Old 19th March 2009, 08:31 PM   #4
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You can also wire a lightbulb into one leg of an extension cord and do your initial power-up with that setup if you cannot get your hands on a variac. Search the forum for this trick, start with a 40W bulb or less

If the unit has not been powered for decades, you may need to allow the electrolytic caps "reform" which is also accomplished by slowly increading the voltage with a variac or other means. Otherwise they may go "pop" and spew nasty goo inside the amp during initial turn-on.

A good beginner tube book is Bruce Rosenblit's Beginner's guide to tube audio design

http://www.amazon.com/Beginners-Guid.../dp/1882580133

Another book is Morgan Jone's "Valve amplifiers"-this one is a bit more technical/advanced, and is sort of the DIY tube bible.
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Old 19th March 2009, 11:05 PM   #5
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Default That pic is A KAWASAKI ZX10R..

couldn't find a pic of a CBR1100RR. I rode a Kawa, just need to update the pic. Ray
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Old 19th March 2009, 11:40 PM   #6
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Default FIRST! Get a schematic or HOWARD W. SAMS fact sheet

Sometimes there are a few ebay sellers that sell these. I don't think they are made anymore like most things done well in the USA. This is a popular SCOTT unit and maybe someone here or either on AA (the rubber room)( AUDIO ASYLUM) might be able to copy it and email it to you. If I had it I would. The best book about into tube electronics is the THE RADIO AMATEUR'S HANDBOOK by the ARRL (Amateur Radio Relay League). But don;t get a new copy. Look for one about 1959. These are published yearly. The beginning chapter on tubes will familiarize you with diode, triode, pentode, tetrode and basic resistors, capacitors, inductors, and transformers. The rest o f the book is HAM oriented most of which can be ignored but it has a very good tube manual in the rear and a good introduction on chassis building. The best chapter is on power supplys. The next best book is RADIO ENGINEERING BY F.E. TERMAN. It has the best chapter and discussion on Class A amps I have ever read. And it's old too. The first edition is around 1939, the second around 45 or during the war.

The new book that have been mentioned are good but VALVE AMPLIFIERS by Morgan Jones is typically British. You know the British. They mount their meters upside down and ground the positive side of the battery. Like their subway trains. To open a door, you have to open a window, stick your hand out the window and open the door from the outside.

Then you need a good tube manual; the GE ESSENTIAL CHARACTERISTICS MANUAL is the best and can be had from ANTIQUE ELECTRONIC SUPPLY in Tempe, AZ. I wouldn;t invest too heavily in tube manuals because most of this stuff is on the webb; FRANK'S ELECTRON TUBE PAGES has most every tube ever in existence and their GE< TUNGSOL< SYLVANIA< MAZDA< PHILLIPS or RCA right there for you. The German pages of this seem to load faster for me.

Good luck! Ray
P>S> I recuperating from a almost deadly motorcycle accident due to an idiot on a cell phone who wouldn't pay attention to their driving.
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Old 20th March 2009, 12:35 AM   #7
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Default Reply to replys

Thanks again for the info, I will start searching Amazon.com for copies of those old books, unless anybody out there has a better idea of where to get 'hold of them. Anyone out there have some copies they want to sell I would be interested.

Sorry about the accident! I just started to ride again after a 10 year vacation from it (had an accident that was the other persons fault too).

The reason you could't find a pick is because it is a 1000RR not 1100RR. It is what I bought recently, the pic looks like mine, thats why I asked. But now after looking at it longer I realize the tank is yellow too. CBR1000RR tank is black.....but what does that have to do with Tubes.....

Well I powered it up with a bulb in series and it works just fine...perfectly. One of the7189's is really glowing bright, not only at the top, but on (and through) the side. Looks like a blowtorch heating up a large oval area from the inside of the "metal shield" for a lack of better words. it is the one when looking from the front, is fartherest to the left.

It sounds "scratchy" when some, but not all, the knobs are turned. I understand that there is a product that can be used to clean the mechanism behind the knob. The potentiometer? I think.

Anybody have a suggestion of whats going on with that one 7189?

Otherwise it sounds great when you find a sweet spot on the loudness control that does not scratch.

Not much bass at higher levels. Gets muddy fast above 3-4 on the loudness control. Is that to be expected on a 20wpc amp?

The 7189's (x4) also appear to be Telefunken. Those are good right? I cant tell what brand the 6BL8's (x2) are. Also the 12ax7's (x4) are covered with a metal shield of sorts, dont know what kind those are either.

The previous owner took a Marks-a-lot pen and wrote on the chasis the number for each tube! Other than that there is a small "bend-back" on the right front/lower faceplate corner,
2-3mm that I can probably bend back to un-noticable. Other than that I really looks perfect, I mean perfect. Not a scratch, pit, rust-spot, or other discoloration anywhere on it!

Sounds really good with an old Kenny G and Steven Curtis Chapman cd played throgh a 20 year old Onkyo CD player I have. The speakers are a pair of recently built "recession buster" pair from Madisound.

I'll have to say the treble sounds better through this Scott than my Parasound 850II.

Comments, advice, chastizements....

Sincerely,
Jeff M.
Lawton, OK
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Old 20th March 2009, 12:45 AM   #8
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Default Schematics/owners manual

Oh yeah,
I bought a copy (Xerox) of the original owners manual and schematics on ebay for 7.00, It arrived before the amp did!
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Old 20th March 2009, 01:08 AM   #9
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Default Here's a 1958 ARRL handbook on ebay

http://cgi.ebay.com/ARRL-RADIO-AMATE...arms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A1| 294%3A50
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Old 20th March 2009, 02:08 AM   #10
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Quote:
Well I powered it up with a bulb in series and it works just fine...perfectly. One of the7189's is really glowing bright, not only at the top, but on (and through) the side. Looks like a blowtorch heating up a large oval area from the inside of the "metal shield" for a lack of better words. it is the one when looking from the front, is fartherest to the left.

Jeff,

That tube is passing excessive current. The anode (plate) is dissipating way too much power, which causes overheating and the red color you observe. Since its mate in a PP pair appears to be OK, the most likely cause of the problem is a "leaky" coupling capacitor between splitter and "final". Unfortunately that tube may have been destroyed.

There's only one option in current production 7189 equivalents, the Russian 6П14П-ЕВ (6p14p-ev), AKA EL84M. Jim McShane is THE man for tubes and other stuff needed to get the amp into tip-top shape. JMO, Flea Bay can be worse than Dodge City, before Wyatt Earp rode into town.

20 WPC is quite optimistic. 15 WPC is about right, real world.

Replacing the PSU filter caps., coupling caps., and out of spec. Carbon composition resistors is a matter of routine, when dealing with a unit more than 40 years old. Some of the bass issues you are having might be caused by insufficient PSU energy storage, due to 'lytic aging. Electrolytic capacitors literally dry out over time. Also, replacing the Selenium rectifier in the combined bias/heater negative supply with modern Silicon parts is

A nice online resource for rookies is NEETS, which is US Navy training material.

Yet another text you might try to dredge up is the 1st or 2nd edition of Basic Electronics for Scientists by James Brophy. Brophy's work is good for getting an understanding of both tubed and SS circuitry.MANDATORY. The OEM stuff is a ticking toxic time bomb.
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