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
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
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
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
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-Guide-Tube-Audio-Design/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.
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-Guide-Tube-Audio-Design/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.
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.
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.
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
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
Here's a 1958 ARRL handbook on ebay
http://cgi.ebay.com/ARRL-RADIO-AMAT...972413&_trksid=p3286.c0.m14&_trkparms=72:1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A1|294%3A50
http://cgi.ebay.com/ARRL-RADIO-AMAT...972413&_trksid=p3286.c0.m14&_trkparms=72:1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A1|294%3A50
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.
bright tube
Before I read your last post I swapped it with the one on the far right. Now niether of them is doing this.??? So there are some caps that should be replaced? How do I go about replacing all of the parts that are generally replacable, is there a kit or set of parts someone sells that if a person replaced everything in the "kit" would fix up the entire amp?
Before I read your last post I swapped it with the one on the far right. Now niether of them is doing this.??? So there are some caps that should be replaced? How do I go about replacing all of the parts that are generally replacable, is there a kit or set of parts someone sells that if a person replaced everything in the "kit" would fix up the entire amp?
Jeff,
The BBS software will not permit me to edit the "typos" in my previous post. So, the corrected portion of the text follows immediately.
Electrolytic capacitors literally dry out over time. Also, replacing the Selenium rectifier in the combined bias/heater negative supply with modern Silicon parts is MANDATORY. The OEM stuff is a ticking toxic time bomb.
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.
Shows what I know.
Since moving tubes around cleared the problem, it seems you had a contact problem at the socket.
Replacing the signal and PSU caps. is still a good idea. Refer to the 299B schematic. C35, C37, C66, and C68 couple the phase splitters to the PP "finals". McShane has probably worked on at least 1 specimen of this amp and will help you put a nice package together, at a fair price. Off the top of my head, I can see replacing those 0.1 μF. parts with 0.22 μF./630 WVDC 716P series "Orange Drops". Get Jim's opinion on the matter.
It's not exactly a state secret that signal sources have changed radically since the 299B was designed. Think CDP, etc. If you are in the least bit adventurous, replacing the source selector switch would allow you to get much better milage out of the OEM jack set. Were it my amp, I'd make the change in a heartbeat. The tape monitor loop is left intact. Wire a single pair of jacks straight into the magnetic device circuitry, which is configured exclusively for the RIAA (LP) curve. All other I/Ps would be configured for line level. Mouser stock #105-14572 is nice, modestly priced, candidate for the new selector switch.
The BBS software will not permit me to edit the "typos" in my previous post. So, the corrected portion of the text follows immediately.
Electrolytic capacitors literally dry out over time. Also, replacing the Selenium rectifier in the combined bias/heater negative supply with modern Silicon parts is MANDATORY. The OEM stuff is a ticking toxic time bomb.
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.
Shows what I know.
Since moving tubes around cleared the problem, it seems you had a contact problem at the socket.Replacing the signal and PSU caps. is still a good idea. Refer to the 299B schematic. C35, C37, C66, and C68 couple the phase splitters to the PP "finals". McShane has probably worked on at least 1 specimen of this amp and will help you put a nice package together, at a fair price. Off the top of my head, I can see replacing those 0.1 μF. parts with 0.22 μF./630 WVDC 716P series "Orange Drops". Get Jim's opinion on the matter.
It's not exactly a state secret that signal sources have changed radically since the 299B was designed. Think CDP, etc. If you are in the least bit adventurous, replacing the source selector switch would allow you to get much better milage out of the OEM jack set. Were it my amp, I'd make the change in a heartbeat. The tape monitor loop is left intact. Wire a single pair of jacks straight into the magnetic device circuitry, which is configured exclusively for the RIAA (LP) curve. All other I/Ps would be configured for line level. Mouser stock #105-14572 is nice, modestly priced, candidate for the new selector switch.
Wheeeew!!!!! my head is spinning!!!
Ok now, remember I am pretty new to this stuff. I know what a cap and resistor is but beyond that I get a little lost
I am taking that the PSU stand for power source unit or something like that. I have no idea what CDP means, or what a jack set is.
What do you mean by "Wire a single pair of jacks straight into the magnetic device circuitry, which is configured exclusively for the RIAA (LP) curve. All other I/Ps would be configured for line level."
I have done a lot of soldering in the past and I am pretty good with electronic schemata, I also understand the basics of most of the staple circut components like capacitors, inductors, resistors, diodes and a few other things, but amplifier circutry, esp tube, is all new to me. I think I could definitely find and replace the caps without incident, but the rest of all that will take some hand holding, if you will.
Also, are you suggesting changing the values from 0.1uf to 0.22uf?
Also, which C's on the schema are the PSU caps?
Thanks again,
Jeff Miller
Ok now, remember I am pretty new to this stuff. I know what a cap and resistor is but beyond that I get a little lost
I am taking that the PSU stand for power source unit or something like that. I have no idea what CDP means, or what a jack set is.
What do you mean by "Wire a single pair of jacks straight into the magnetic device circuitry, which is configured exclusively for the RIAA (LP) curve. All other I/Ps would be configured for line level."
I have done a lot of soldering in the past and I am pretty good with electronic schemata, I also understand the basics of most of the staple circut components like capacitors, inductors, resistors, diodes and a few other things, but amplifier circutry, esp tube, is all new to me. I think I could definitely find and replace the caps without incident, but the rest of all that will take some hand holding, if you will.
Also, are you suggesting changing the values from 0.1uf to 0.22uf?
Also, which C's on the schema are the PSU caps?
Thanks again,
Jeff Miller
PSU = power supply unit.
CDP = compact disk player.
C1, C2, C3, and C4 are the filter/decoupling parts in the B+ circuitry.
C5 and C6 are associated with the negative bias/heater supply.
Those PSU 'lytics are "twistlok" can multi-section. You can probably replace the B+ stuff with clamp mounted parts of current manufacture. OTOH, you may be forced to empty the contents of the negative rail cans and stuff them with modern parts. Please notice that the positive side grounding here can be a PITA.
Multiple magnetic source equalizations and I/Ps are part of the original design. Do you play 78 RPM records? Do you own an open reel tape transport that has a playback head, but lacks electronics? Those features made sense in 1960, but are inconsequential today. Remember, phono level signals are delicate. Eliminating parts and switches in that signal path will improve perfomance. If you take my advice, you end up with a single phono I/P and 5 line level I/Ps. Tape monitor loop operation is completely unchanged. BTW, don't try to drive a SS recording device, when records are playing. The phono preamp can't drive low impedance loads. You would have to construct an external buffer amp to record LPs. The recording O/Ps are directly connected to the O/P of the source selector switch.
The jack set is the group of RCA females on the back panel.
There are 3 trim pots. in the circuit. They set AC balance, DC balance, and bias. Read your documentation. Notice that there are test points around 18 Ohm resistors in each channel. You measure the voltage drop across the resistor and use Ohm's Law to calculate the "idle" current passing thru the pair of tubes. Replacing those 18 Ohm resistors with 1% tolerance 1/2 W. metal film parts is (IMO) obvious. Set the bias with some degree of precision.
Yes, your "Rat Shack" multi-meter is adequate.
CDP = compact disk player.
C1, C2, C3, and C4 are the filter/decoupling parts in the B+ circuitry.
C5 and C6 are associated with the negative bias/heater supply.
Those PSU 'lytics are "twistlok" can multi-section. You can probably replace the B+ stuff with clamp mounted parts of current manufacture. OTOH, you may be forced to empty the contents of the negative rail cans and stuff them with modern parts. Please notice that the positive side grounding here can be a PITA.
Multiple magnetic source equalizations and I/Ps are part of the original design. Do you play 78 RPM records? Do you own an open reel tape transport that has a playback head, but lacks electronics? Those features made sense in 1960, but are inconsequential today. Remember, phono level signals are delicate. Eliminating parts and switches in that signal path will improve perfomance. If you take my advice, you end up with a single phono I/P and 5 line level I/Ps. Tape monitor loop operation is completely unchanged. BTW, don't try to drive a SS recording device, when records are playing. The phono preamp can't drive low impedance loads. You would have to construct an external buffer amp to record LPs. The recording O/Ps are directly connected to the O/P of the source selector switch.
The jack set is the group of RCA females on the back panel.
There are 3 trim pots. in the circuit. They set AC balance, DC balance, and bias. Read your documentation. Notice that there are test points around 18 Ohm resistors in each channel. You measure the voltage drop across the resistor and use Ohm's Law to calculate the "idle" current passing thru the pair of tubes. Replacing those 18 Ohm resistors with 1% tolerance 1/2 W. metal film parts is (IMO) obvious. Set the bias with some degree of precision.
Yes, your "Rat Shack" multi-meter is adequate.
BTW, the metal shields on the 12AX7's should be removeable, and it probably wouldn't hurt to R&R the remaining tubes to get some fresh contact on the pins, since they have been sitting in their happy place for a few decades collecting oxidation.
Speaking of oxidation, get a can of electronics cleaner to attempt to clean up the scratchy pots. Spray it in the pot using the supplied squirter straw, an rotate the pot back and forth a few times. Some pots clean up and sometimes they need to be replaced.
As already mentioned, replacing the electrolytic caps is probably a good idea.
Speaking of oxidation, get a can of electronics cleaner to attempt to clean up the scratchy pots. Spray it in the pot using the supplied squirter straw, an rotate the pot back and forth a few times. Some pots clean up and sometimes they need to be replaced.
As already mentioned, replacing the electrolytic caps is probably a good idea.
More, More, More
Ok, now we are getting somewhere! A few more questions:
1) Is there a particular brand of electrolytics and level of tolerance you would use when making these repairs?
2) I plan to use only a CDP with this unit using the "Extra" input on the back for this. Is it therefore still
reccommended to make all those changes?
3) Is the "Extra" input on the back the proper input to use for a CDP?
4) The 18ohm resistor...Replace it with another 18 Ohm "1% tol 1/2 watt" resistor correct? I ask this b/c you stated
earlier to change a 0.1uF part with a 0.22uF part.
5) The negative rail cans, any benefit to changing those out anyways. If so, reccommended brand and tol. percision?
6) the twistlok PSU multi-section "cans"...where can i get new ones with the exact values?
7) The owners manual I bought online, I don't see anywhere whe it gives any values to adjust these 3mm trim pots, where then can I find this info?
Thanks for your help, I would probably be tearing out my eyeballs by now if someone was asking me all these questions!
Sincerely,
Jeff Miller
Ok, now we are getting somewhere! A few more questions:
1) Is there a particular brand of electrolytics and level of tolerance you would use when making these repairs?
2) I plan to use only a CDP with this unit using the "Extra" input on the back for this. Is it therefore still
reccommended to make all those changes?
3) Is the "Extra" input on the back the proper input to use for a CDP?
4) The 18ohm resistor...Replace it with another 18 Ohm "1% tol 1/2 watt" resistor correct? I ask this b/c you stated
earlier to change a 0.1uF part with a 0.22uF part.
5) The negative rail cans, any benefit to changing those out anyways. If so, reccommended brand and tol. percision?
6) the twistlok PSU multi-section "cans"...where can i get new ones with the exact values?
7) The owners manual I bought online, I don't see anywhere whe it gives any values to adjust these 3mm trim pots, where then can I find this info?
Thanks for your help, I would probably be tearing out my eyeballs by now if someone was asking me all these questions!
Sincerely,
Jeff Miller
Don't be fooled into buying DESIGNER parts
JEFF: There is a lot of HYPE out there in this loony market. Most of the coupling capacitors in the signal circuitry can be replaced with SBC 716P orange drop capacitors. The 716P series have solid copper leads. The 715P series are not solid copper. You can spend a great deal more on capacitors and not get a better cap. These are avaliable from ANTIQUE ELECTRONIC SUPPLY among others. There are also modern replacement CANS for C1-C4. But cans are not being made any more by many manufacturers so you might as Eli suggests have to stuff a can with radial electrolytics to make your unit cosmetically pleasing as looking original. You can get the radial electrolytics from DI-GI KEY or MOUSER. Replace the bias selinium rectifier (these things age and drift also) with 1n4007 with a .01 ceramic disc and a 470K-1/2w resistor in parallel with it. Ray
JEFF: There is a lot of HYPE out there in this loony market. Most of the coupling capacitors in the signal circuitry can be replaced with SBC 716P orange drop capacitors. The 716P series have solid copper leads. The 715P series are not solid copper. You can spend a great deal more on capacitors and not get a better cap. These are avaliable from ANTIQUE ELECTRONIC SUPPLY among others. There are also modern replacement CANS for C1-C4. But cans are not being made any more by many manufacturers so you might as Eli suggests have to stuff a can with radial electrolytics to make your unit cosmetically pleasing as looking original. You can get the radial electrolytics from DI-GI KEY or MOUSER. Replace the bias selinium rectifier (these things age and drift also) with 1n4007 with a .01 ceramic disc and a 470K-1/2w resistor in parallel with it. Ray
Parts questions
Look at the PANASONIC LOW ESR 105 degree caps from DI-KEY or MOUSER or you could use NICHICON 105 degree just make sure they are the same rating as to mfd and voltage. Resistors should be replaced with the same wattage but I would use metal films or metal oxide around the power supply. Carbon comps change value with age and the ones that are flexed (heated up) the most will drift the most AND THEY ARE AROUND c1-c4. If fact just soldering them will cause them to change a little.
Eli makes the case for bypassing the old selector switch circuitry which takes a sonic toll. There is simply too much switching going on and these old selector switches are ONE OF A KIND. If they are oily and dirty then you may have to make a design change with a new switch like a GRAYHILL. The best place to find these is on ebone. Ray
Look at the PANASONIC LOW ESR 105 degree caps from DI-KEY or MOUSER or you could use NICHICON 105 degree just make sure they are the same rating as to mfd and voltage. Resistors should be replaced with the same wattage but I would use metal films or metal oxide around the power supply. Carbon comps change value with age and the ones that are flexed (heated up) the most will drift the most AND THEY ARE AROUND c1-c4. If fact just soldering them will cause them to change a little.
Eli makes the case for bypassing the old selector switch circuitry which takes a sonic toll. There is simply too much switching going on and these old selector switches are ONE OF A KIND. If they are oily and dirty then you may have to make a design change with a new switch like a GRAYHILL. The best place to find these is on ebone. Ray
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