I am so proud of the work you do on this integrated Scott amp. If it was mind I would get it working for the rest of my life. 74 years old now . What a clean job.
I could watch you work for hours. I love your attention to detail. When doing a job like this one that attention is what can and often does mean the difference between a successful repair and one that might possibly temporarily fix something but still might mean trouble somewhere down the road. A complete understanding of how something should work is paramount but it will only get you so far if you get sloppy or lazy anywhere in the repair. I would feel comfortable bringing apiece of work to you just because it appears to me that you care not just about making the repairs but making the repairs also look like they could have come from the OEM. Detailed oriented work if you will. Good tech's are worth their weight in gold to me. I have quite a bit of audio equipment but nothing that could really be called vintage except for some speakers, but I am considering a purchase of a vintage receiver or amplifier in the very near future and will be looking for someone who has the same approach to doing a job right as it appears you do.
I have a later version 299D i restored last year sounds fantastic . I used 716 orange drops for the coupling capacitors and replaced all electrolytic caps with sprague atoms mounted under the chassis and left original caps in place for original look . . Man it sounds fantastic
Love to know what the owner thought, wonder if all the caps and various new components improved the sound. Talk about icing on the cake if it sounds better then ever. Thanks for this, very entertaining 👍
I have a The Fisher X202B that is similar to the Scott. My thinking is that the magic is in those 7591a tubes! The McIntosh MC225 uses the 7591 tubes as well. Great to keep these beautiful sounding machines running. I’ve heard nothing better and I have experienced a lot of equipment.
Another great video on tube amps! I have really enjoyed your videos and have learned a lot from them. Keep up the great work. I would love to build a tube amp myself and have really benifited from your videos so thanks. Tony (W0ALA)
Great video and well explained but very surprised you didn't change out all of the electrolytic cans. They are already very old and are probably leaky. The extra cost would give you and your customer a higher degree of confidence that the unit will not crash and burn any time soon. Did you check the ESR of the sections or at least check the AC ripple?
At 30:30, when you talk about the possibility of having too much negative voltage available from the bias supply because of having replaced the selenium rectifier with a modern silicon diode bridge, you explained the effect of this circuit change backwards and incorrectly. Having too high a negative bias means that the output tubes would be throttled back too much, running somewhat "cold", almost as if there is a "governor" on them, and with not enough plate current going through them, which would tend to make for higher output distortion, and might also cause the B+ voltage on the filter caps to be a little too high, since they're not being loaded down by what should normally be a higher amount of current draw from the output tubes. Having higher-than-normal B+ voltage might mean that the old electrolytic caps in the unit could be stressed from the increase voltage. I've worked on a few of these same units myself, and I found it is especially important to make sure that pins 4 and 5 on the preamp tubes, and socket contacts 4 and 5 for those same tubes, are clean and tight and making a reliable electrical connection r, because if any one of those total of *eight* pin to socket connections don't make a reliable, consistent electrical connection, the heaters of all four preamp tubes will go dark and the unit won't play. if the unit is left turned on, with B+ going to the preamp tubes but the filaments not heating up, the useful lives of those tubes will also be shortened.
I can do very basic diag but my forte is automotive tech at a chrysler store, love tube gear because of the superior sound keep posting, have watched for hours on end thanks
I am constantly amazed at the condition I find 50-year-old plus amps in. Original tubes are, of course, always in sockets and are usually in pretty good shape. More often then not, the power supply caps have problems and they are frequently soldered to the chassis and, of course soldered to the circuit. A time-consuming task! I have caps that are designed like tubes in that they can easily be put into a octal socket. Seems to me that parts that are prone to fail should have temporary connections like tubes do. Have you ever put in sockets for these tube-like power supply caps?
Great tutorial video and now ready to start on my 299d! Question: What are your thoughts about replacing the other 2 Electrolytic Cans as a precautionary measure ?
I am working on a Scott 299b and replacing the rectifier. I have black and white wires, can you tell me which goes to positive? I see your black wire went to positive and Bluet to negative. Also does it matter which way the orange wires go? Finally, did you install a resistor after the rectifier as I've read people recommend that. Thank you
Just inherited one of these from my grandfather, just slowly powered it on with a variac and she seems stable. What's a good test, line level tape in? Do you know if this runs 8 ohm speakers or 4? Thanks
Hi Mark, I realize this is 3 years old. You made mention of changing a resistor on the bias circuit after replacing the selenium rectifier. But, you never said which one or the value you used. I have just completed essentially the same resto on an LK-72-B (299D) and am at the point of verifying voltages. Thanks.
Dan N I did and still have the LK-72. Basically, I replaced all the caps in the PS and all of the coupling caps. I found a few resistors that were out of tolerance and replaced those, as well. Of course, as referenced, the selenium rectifier bridge was replaced with a modern one. So, bias voltage automatically increases. This was my question to Mark about the value of the resistors in the bias circuit.
The D version of the 299 series uses 1847 incandescent bulbs, powered from the 6.3VAC filament winding, not neons like previous versions, which ran off the high voltage supply. I like the neons better, but that's my personal preference. The incandescents are easier to change though.
Hi Blueglow, I have a 299d but the Right Channel plays alot louder then the left channel. After about half hour of playing it would then drop low to the left channel volume . Any suggests as what might be the issue? Thanks much.
Having those wires running over the can capacitor bracket mounted underneath is a recipe for disaster. Recapping an amp like this with modern components should last many many years. I can see many years of heating/cooling and different conditions taking their toll on the insulation and eventually shorting out. Sorry, forget the looks I'd put that bracket on top of the chassis where it belongs
another thing I just noticed, moving that capacitor bracket underneath as you did gets the bare wires very close to the amp bottom plate. They are flimsy at best and this could also lead to problems... move it up top and avoid any of these problems. Cheers.
Never seen anyone mount the chassis clamp for a cap on the bottom??? Looks MICKEY MOUSE, not to mention your concerns. Great video otherwise but as they say, one ahhh crap kills a hundred at-a-boys.. :)
At 28:30, using a Dremel tool wire brush to clean those Jacks is an absolute No-No! Certain to leave scratches in the adjacent aluminum chassis and it'll take the silk screening right off as well if you slip and get too close to it. Use a powered pencil eraser! The old style large AC powered ones with induction motor and a long quarter inch diameter rubber eraser rod, as used by draftsman in the old days, are the best way to go, but a modern miniature battery powered eraser from an art store or available online will work if you find one where the motor has enough torque and you can get some semi- abrasive eraser Nubs to fit it. Pink eraser nubs or rods designed for removing pencil are okay if the corrosion or pitting isn't too bad, but gray erasers designed for removing ink are much better if the jacks are heavily tarnished, corroded, or pitted. I should mention here that several of the battery-powered pencil erasers we found come with really soft vinyl erasers that are of little use for any kind of metal polishing, and you might have to try obtaining different erasers from different sources, but they're very handy little tools once you figure out how to get him set up right. Anyway, I am surprised that you don't know these tricks. Haven't you ever cleaned relay contacts with an eraser shaped into a wedge or chisel tip? certainly, every old-time ham radio operator, or anybody who worked with radios an Electronics in the military, knows about these techniques.
Never seen anyone mount the chassis clamp for a cap on the bottom??? Looks MICKEY MOUSE, not to mention your concerns. Great video otherwise but as they say, one ahhh crap kills a hundred at-a-boys.. :)
All kidding aside.. great that you took the time to go through this amp, there is a wealth of valuable information. Please invest in a small tripod. The camera bouncing all over the place is seriously distracting. The addition of a steady image would make this a super video. Thanks!
![[LIVE] : ONE ลุมพินี 82 วันนี้!! คู่เอก | ยอดไอคิว vs อับดัลลาห์](http://i.ytimg.com/vi/hSsyTl_9bqs/mqdefault.jpg)
I am so proud of the work you do on this integrated Scott amp. If it was mind I would get it working for the rest of my life. 74 years old now . What a clean job.
I could watch you work for hours. I love your attention to detail. When doing a job like this one that attention is what can and often does mean the difference between a successful repair and one that might possibly temporarily fix something but still might mean trouble somewhere down the road. A complete understanding of how something should work is paramount but it will only get you so far if you get sloppy or lazy anywhere in the repair. I would feel comfortable bringing apiece of work to you just because it appears to me that you care not just about making the repairs but making the repairs also look like they could have come from the OEM. Detailed oriented work if you will. Good tech's are worth their weight in gold to me. I have quite a bit of audio equipment but nothing that could really be called vintage except for some speakers, but I am considering a purchase of a vintage receiver or amplifier in the very near future and will be looking for someone who has the same approach to doing a job right as it appears you do.
Nice job! It's a pleasure to look over your shoulder while you work. Thank you for sharing
I have a later version 299D i restored last year sounds fantastic . I used 716 orange drops for the coupling capacitors and replaced all electrolytic caps with sprague atoms mounted under the chassis and left original caps in place for original look . . Man it sounds fantastic
I loved the restoration easy to understand great job.
Nice amp and great restoration!
Love to know what the owner thought, wonder if all the caps and various new components improved the sound. Talk about icing on the cake if it sounds better then ever. Thanks for this, very entertaining 👍
I have a The Fisher X202B that is similar to the Scott. My thinking is that the magic is in those 7591a tubes! The McIntosh MC225 uses the 7591 tubes as well.
Great to keep these beautiful sounding machines running. I’ve heard nothing better and I have experienced a lot of equipment.
Great job i just love watching your videos always learn something new thanks for posting
Another great video on tube amps! I have really enjoyed your videos and have learned a lot from them. Keep up the great work. I would love to build a tube amp myself and have really benifited from your videos so thanks.
Tony (W0ALA)
great video, just getting my lab established. learn so much from you Mark. Great job man.
You can add the sound back now. They stopped copyright striking these.
Great video and well explained but very surprised you didn't change out all of the electrolytic cans. They are already very old and are probably leaky. The extra cost would give you and your customer a higher degree of confidence that the unit will not crash and burn any time soon. Did you check the ESR of the sections or at least check the AC ripple?
Always test ESR, always...
My thoughts exactly.
At 30:30, when you talk about the possibility of having too much negative voltage available from the bias supply because of having replaced the selenium rectifier with a modern silicon diode bridge, you explained the effect of this circuit change backwards and incorrectly. Having too high a negative bias means that the output tubes would be throttled back too much, running somewhat "cold", almost as if there is a "governor" on them, and with not enough plate current going through them, which would tend to make for higher output distortion, and might also cause the B+ voltage on the filter caps to be a little too high, since they're not being loaded down by what should normally be a higher amount of current draw from the output tubes. Having higher-than-normal B+ voltage might mean that the old electrolytic caps in the unit could be stressed from the increase voltage.
I've worked on a few of these same units myself, and I found it is especially important to make sure that pins 4 and 5 on the preamp tubes, and socket contacts 4 and 5 for those same tubes, are clean and tight and making a reliable electrical connection r, because if any one of those total of *eight* pin to socket connections don't make a reliable, consistent electrical connection, the heaters of all four preamp tubes will go dark and the unit won't play. if the unit is left turned on, with B+ going to the preamp tubes but the filaments not heating up, the useful lives of those tubes will also be shortened.
Thank you for very informative documentary.
Nice job, very clean condition amp, I really enjoy the true class-A sound of my tube amp and I only use during the winter.
Thanks for the video, very impressive. Good.
I can do very basic diag but my forte is automotive tech at a chrysler store, love tube gear because of the superior sound keep posting, have watched for hours on end thanks
That is a nice amp. I used to repair them in the 70s. I would like to find one in that condition to fully restore.
great job i really enjoy my fisher kx 200
I would like to see you build a point to point headphone amp. Love your videos, keep them comming.
I am constantly amazed at the condition I find 50-year-old plus amps in. Original tubes are, of course, always in sockets and are usually in pretty good shape. More often then not, the power supply caps have problems and they are frequently soldered to the chassis and, of course soldered to the circuit. A time-consuming task! I have caps that are designed like tubes in that they can easily be put into a octal socket. Seems to me that parts that are prone to fail should have temporary connections like tubes do. Have you ever put in sockets for these tube-like power supply caps?
Great tutorial video and now ready to start on my 299d!
Question: What are your thoughts about replacing the other 2 Electrolytic Cans as a precautionary measure ?
I am working on a Scott 299b and replacing the rectifier. I have black and white wires, can you tell me which goes to positive? I see your black wire went to positive and Bluet to negative. Also does it matter which way the orange wires go? Finally, did you install a resistor after the rectifier as I've read people recommend that. Thank you
How do clean tube sockets?
Thanks, Eddie
3k3 from cathode to ground in a fixed bias amp?
Just inherited one of these from my grandfather, just slowly powered it on with a variac and she seems stable. What's a good test, line level tape in? Do you know if this runs 8 ohm speakers or 4? Thanks
Hi Mark,
I realize this is 3 years old. You made mention of changing a resistor on the bias circuit after replacing the selenium rectifier. But, you never said which one or the value you used. I have just completed essentially the same resto on an LK-72-B (299D) and am at the point of verifying voltages. Thanks.
Dan N I did and still have the LK-72. Basically, I replaced all the caps in the PS and all of the coupling caps. I found a few resistors that were out of tolerance and replaced those, as well. Of course, as referenced, the selenium rectifier bridge was replaced with a modern one. So, bias voltage automatically increases. This was my question to Mark about the value of the resistors in the bias circuit.
The D version of the 299 series uses 1847 incandescent bulbs, powered from the 6.3VAC filament winding, not neons like previous versions, which ran off the high voltage supply. I like the neons better, but that's my personal preference. The incandescents are easier to change though.
You have a very old meter too, i used to had one of that in back in 1986
Adding the heatshrink really makes a difference.It really looks better and safer.Nice.
Too bad he didn't want to do a more in depth restoration.
Maybe the customer isn’t in love with these 7591 amps like some of us are or couldn’t afford more.
can i put cl-80 on my 99' transistor amp?thanks,love your work
another great video... Is it for sale? and do you ever sell your rebuilds?
Hi i should be interessed to knows where you have found the yellow 1µf PE condensator? Thanks
Nice!
Does the HH Scott 222c sound better then this amplifier
What are you using for your bench speakers? They sound good.
Just wonder if you have any USA vintage integrated tube amp for sale ? It would be nice if it stored by you. BTW I am very enjoy your videos ! .
Hi Blueglow, I have a 299d but the Right Channel plays alot louder then the left channel. After about half hour of playing it would then drop low to the left channel volume . Any suggests as what might be the issue? Thanks much.
Why didn’t you convert it to a three wire power cord?
what are those caps replacements called? original were paper capacitors right?
31:30 ... "The Ends" by Everlast. Great song from 1998-99.
What distortion meter are you using? thanks!
Having those wires running over the can capacitor bracket mounted underneath is a recipe for disaster. Recapping an amp like this with modern components should last many many years. I can see many years of heating/cooling and different conditions taking their toll on the insulation and eventually shorting out. Sorry, forget the looks I'd put that bracket on top of the chassis where it belongs
another thing I just noticed, moving that capacitor bracket underneath as you did gets the bare wires very close to the amp bottom plate. They are flimsy at best and this could also lead to problems... move it up top and avoid any of these problems. Cheers.
Never seen anyone mount the chassis clamp for a cap on the bottom??? Looks MICKEY MOUSE, not to mention your concerns. Great video otherwise but as they say, one ahhh crap kills a hundred at-a-boys.. :)
Any consideration to stuff the original cap to maintain retroness....
At 28:30, using a Dremel tool wire brush to clean those Jacks is an absolute No-No! Certain to leave scratches in the adjacent aluminum chassis and it'll take the silk screening right off as well if you slip and get too close to it. Use a powered pencil eraser! The old style large AC powered ones with induction motor and a long quarter inch diameter rubber eraser rod, as used by draftsman in the old days, are the best way to go, but a modern miniature battery powered eraser from an art store or available online will work if you find one where the motor has enough torque and you can get some semi- abrasive eraser Nubs to fit it. Pink eraser nubs or rods designed for removing pencil are okay if the corrosion or pitting isn't too bad, but gray erasers designed for removing ink are much better if the jacks are heavily tarnished, corroded, or pitted. I should mention here that several of the battery-powered pencil erasers we found come with really soft vinyl erasers that are of little use for any kind of metal polishing, and you might have to try obtaining different erasers from different sources, but they're very handy little tools once you figure out how to get him set up right.
Anyway, I am surprised that you don't know these tricks. Haven't you ever cleaned relay contacts with an eraser shaped into a wedge or chisel tip? certainly, every old-time ham radio operator, or anybody who worked with radios an Electronics in the military, knows about these techniques.
So negative….try to be more constructive with your comments this Guy is very skilled , but clearly not perfect as you “are”:-/
I think it would have looked better if the bracket was on the top side, and there would be less wire rub points as well.....but thats just me I guess.
Never seen anyone mount the chassis clamp for a cap on the bottom??? Looks MICKEY MOUSE, not to mention your concerns. Great video otherwise but as they say, one ahhh crap kills a hundred at-a-boys.. :)
what was that song/artist you were playing towards the end, at around 34:27 and i think the same at 41:23?
Ya, what song is that??
I would like to know what song is that as well
Same here, would love to know
I have replaced Selenium rectifiers with diode bridges .And all the voltages change ..you need to adjust the bias in most tubes to sound original.
Your microphone cartridge is loosen inside....sound is vibrating in a ugly way.
Good god hold the camera still... haha!!!
All kidding aside.. great that you took the time to go through this amp, there is a wealth of valuable information. Please invest in a small tripod. The camera bouncing all over the place is seriously distracting. The addition of a steady image would make this a super video. Thanks!