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Scott 222B rebuild

Brycecb750

Brycecb750

Active Member
hello everyone
Fun weekend project, I don't know if I've seen a cleaner Scott! Replaced all the electrolytics, all coupling caps are K40y's, put .0022 in place of .0018. I left the .02 ceramic discs in the cathode bypass. Gold mepco resistors in the phono amps. All the original telefunken tubes tested strong.
One strange thing was, the circuit for the 6bl8's looked like it was for a 6u8 or 7199, but the tubes were correct 6bl8's. It was working but there was only 8 or 9 volts on the plates and still sounded decent, just not much output volume. So I changed it to stock and it came alive! Could it have been factory weird incorrectly?? Maybe that's why it's in such good shape, it just wasn't used much due to it sounded poorly.
Anyhow, it sounds awesome!! Throwing it on my klipschorns tomorrow for some burn in!
 

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Nice work ! The 222-B is a great amp ! I also have a 222-B I rebuilt a few years ago. Mine came with all the original tubes, all Telefunken
except the 6BL8's which are marked 'Made in France'. I also added 10 ohm cathode resistors on the EL84's, makes it easy to measure
current and also acts as a fuse to protect the output transformers if anything goes wrong. To keep things running cool......I run mine on a
'bucking transformer' which outputs exactly 115 VAC.
 
That's great enjoy your new amp, I've been thinking of getting a Scott again myself but have two fishers and
one Eico so another amp in the house may be two much plus is there a big enough sound difference between
them all?
 
Congrats, beautiful and professional work. You'll enjoy the sound of your Scott for years to come... It looks pristine.

Patrice
 
mikey99 said:
Can you provide more details on the re-wiring you did on the 6BL8's ?
Click to expand...
I changed to plate resistors to 100k's, they were 220k's. Also removed a 330K going from b+ voltage to the cathode of the pentode. It worked before doing this, but just sounded bad and the amp didn't have much output volume.
 
tube-a-lou said:
That's great enjoy your new amp, I've been thinking of getting a Scott again myself but have two fishers and
one Eico so another amp in the house may be two much plus is there a big enough sound difference between
them all?
Click to expand...
I had a fisher x101d I fixed up a while ago, I did a bunch of stuff to it like this 222b, but it always had a vagueness to it, that was very pleasing and sweetness, but I just like the sound of the scott's better, but there were aspects of the fisher I miss, I let a friend use it with his heresys and he loves it. I never had much Eico stuff other than a AF4, would love to hear a Hf81 or something like that someday. I have a fixed up 299C that's really nice, but I like a 222C maybe the most, and a 200 has been nice to listen to.
 
mikey99 said:
Nice work ! The 222-B is a great amp ! I also have a 222-B I rebuilt a few years ago. Mine came with all the original tubes, all Telefunken
except the 6BL8's which are marked 'Made in France'. I also added 10 ohm cathode resistors on the EL84's, makes it easy to measure
current and also acts as a fuse to protect the output transformers if anything goes wrong. To keep things running cool......I run mine on a
'bucking transformer' which outputs exactly 115 VAC.
Click to expand...
The high B+ is always a pain in these, I replaced the 33 ohm resistor after the recto with two 20 watt 50 ohm resistors, a little overkill, but its what I had on hand and I don't mind the extra power handling, those are the gold block resistors in the back. got the mail voltage down to a few volts over what the schematic calls for. I wouldn't mind having some 10 ohm resistors in there for added protection, thats a cool idea!
On my 299c, I put two UF4007 before the 5AR4, just to make it easy on it, have you ever tried that? It sounds great but I wish I had a switch to hear if its a noticeable difference in the sound.
 
Brycecb750 said:
I had a fisher x101d I fixed up a while ago, I did a bunch of stuff to it like this 222b, but it always had a vagueness to it, that was very pleasing and sweetness, but I just like the sound of the scott's better, but there were aspects of the fisher I miss, I let a friend use it with his heresys and he loves it. I never had much Eico stuff other than a AF4, would love to hear a Hf81 or something like that someday. I have a fixed up 299C that's really nice, but I like a 222C maybe the most, and a 200 has been nice to listen to.
Click to expand...


Your right about the x101D, I had one and decided to sell it, it didn't have enough ooph for me. Now I have a X202C
and a KX200 and they really have the power I need for my speakers (close to thirty watts) which I like.
 
Brycecb750 said:
I changed to plate resistors to 100k's, they were 220k's. Also removed a 330K going from b+ voltage to the cathode of the pentode. It worked before doing this, but just sounded bad and the amp didn't have much output volume.
Click to expand...

Interesting, I checked the original Scott schematic for the 222B, and it shows the 6BL8 with a 100K plate resistor (Pin 1 and 6).
The SAMs photofact for the 222B shows a 220K plate resistor, but has (100K) printed right next to that. So I suspect
SAMS identified that some 222B's used 220K wheras others used 100K. My 222B has a 220K plate resistor.
 
Last edited:
Brycecb750 said:
The high B+ is always a pain in these, I replaced the 33 ohm resistor after the recto with two 20 watt 50 ohm resistors, a little overkill, but its what I had on hand and I don't mind the extra power handling, those are the gold block resistors in the back. got the mail voltage down to a few volts over what the schematic calls for. I wouldn't mind having some 10 ohm resistors in there for added protection, thats a cool idea!
On my 299c, I put two UF4007 before the 5AR4, just to make it easy on it, have you ever tried that? It sounds great but I wish I had a switch to hear if its a noticeable difference in the sound.
Click to expand...
Placing the 4007's before the 5AR4 really only does one thing: In case the rectifier shorts, the 4007's take over as the main rectifiers BUT, the voltage that is rectified becomes higher due to the small 0.7-1v drop of the diodes. This extra voltage may overrun the voltage ratings of your caps, but It is cheap insurance to protect the main filter caps.
 
mikey99 said:
BTW, found an interesting discussion on this very topic of 100K vs 220K plate resistors over at audioasylum :
http://www.audioasylum.com/cgi/vt.mpl?f=vintage&m=236481&VT=C
Click to expand...
wow! That looks just like what I was seeing with this one, nice find!
It worked, just sounded poor and not much output. After going to the 100K's, the voltage was right on. I've been listing to it for a day or so, and it differently has a upper mid rage bite. Using it in my office powering some partsexpress Dayton ref speakers, it sounded good, but did have strong top end. After listen to it on my klipschorns and tannoy's, I just don't like this aggressive top end, might sound great with darker speakers. I'm wondering whats the deal with those .02 cathode bypass caps, one on the 12ax before the volume pot (I think on other scott's, this is not bypassed with any cap) and another one on the 6BL8 troide cathode. The amps has plenty of gain, more than some of my other scott's, I was thinking about trying a 25uf, but the low end sounds great, its just that top end, so maybe I'll try it without the .02 on that 12ax.
 
triode17 said:
Placing the 4007's before the 5AR4 really only does one thing: In case the rectifier shorts, the 4007's take over as the main rectifiers BUT, the voltage that is rectified becomes higher due to the small 0.7-1v drop of the diodes. This extra voltage may overrun the voltage ratings of your caps, but It is cheap insurance to protect the main filter caps.
Click to expand...
Ah, great point, I don't need higher voltage, maybe I'll just leave it alone for now.
 
Bryce - If you are curious, you could pull out the rectifier and tack two 4007's across the tube socket. Then, bring the AC voltage up slowly using a Variac and measure how much higher the voltage becomes.
 
triode17 said:
Bryce - If you are curious, you could pull out the rectifier and tack two 4007's across the tube socket. Then, bring the AC voltage up slowly using a Variac and measure how much higher the voltage becomes.
Click to expand...
I might try that just to see. I'm rebuilding this amp for a friend and I want it to be really reliable and trouble free, so my thought on the 4007's was to increase the life and reliability of the 5AR4.
 
So I did remove the .02 bypass cap on the cathode of the 12ax7 before the volume pot, its slight but the difference is nice! Took a little off the upper end harshness I was hearing. One other thing I don't like about this amp is the loudness switch. I do use loudness when listening sometimes at lower volume, and this one seems to boost top end too much. So, I might swap out the 100pf for a 47 like in other scotts that I like.
 
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