I have an old Knight that looks a lot like that with the chrome chassis and black tube guard...I'll get to it one of these days, lol. Great video! Thanks for sharing!!
It was mentioned at the beginning of this video that you weren't sure whether this was the factory-wired version, or a kit. An easy way to check (and this applies to most all brands) is to examine how the chassis-mounted tube sockets are secured. If mounted with rivets, it was factory assembled. If mounted with machine screws & nuts, then it's a kit. Of course, if somebody did sloppy soldering with leads hanging all over the place, you could also make a safe assumption....
Great job, beautiful amp. Don't you just love these guys who sell things "completely restored and working great". I've received quite a few units from these guys and none have been restored. One radio I purchased was just a line cord replacement. I've since then have asked for pictures of the units before I buy them. Very few get back to me. 👍👍👍👍👍
You need EL37 or EL34 tubes for this. This is a nice amp I won 2 restored of them did the restoration by myself. Replaced all aged paper in oil caps with russian military pios and the electrolytics on the cirquitboards with new german F&T´s....the orignal multisection caps and even the single 16uF electrolytic high voltage caps reformed perfectly, no need to change. The electrolytic with that cardboard cover in fact is a solid electrolytic cap like a tantalum it does not age.
I'm glad you're back into circuits Mark. I have switched tubes on stereo amplifiers to see on scope if there's any changes in signal strength or whether there's distorted waves, noise etc. Bad solder joints, un-shielded audio cable, ungrounded wire, bad decoupling caps and bad elements in tubes causing noise and hum. I enjoyed the video. Thanks!
Thanks so much Mark! I’m really enjoying this trouble shooting series and the detail and reasoning you go into explaining what is happening as well as tracing where the problem is coming from. Keep up the great work!
That was a really interesting video and genuinely one of the best on the subject because you ran into real issues, diagnosed them, referencing the circuit diagram and clearly explaining your thought processes. You finished the video saying that you hope people learned something well I'm sure they will have done. Great job and thanks! :)
I love these videos! I know this is a nit-pick, but Mark told us to check his use of words, so... ... it's not a quarter inch "phono" plug, it's a quarter inch "phone" plug. Phone plugs were used with the old telephone switch boards and are used with electric guitars and other audio devices. Phono plugs are RCA plugs that carry the signal from a record player (turntable) to the phono input of a home stereo, with a low level signal and that funky lopsided equalization.
@@Blueglow The 16uf at 700v that goes across the GZ34 rectifier tubes, I always put in a 22uf @630v film cap in its place. The can caps I use the Authenticaps 550vdc which is a must. I always go up in capacitance after the choke and double it. I run the cathode bypass caps direct across the cathode resistors and I use 100uf 100v muse KZ.
Really enjoyed this and you’ve got a new subscriber here. Mistakes are all part of the fun and it’s instructional to see them so thanks for not editing out the tube snafu!
14:50 - Looking at V2, I don't see a phase inverter circuit. V2-A is a wide band inverting amplifier fed directly from the plate of the EF86 and V2-B is also an inverting amplifier being fed through a 1M/0.25uF low pass filter! Could you scope the outputs of those sections and prove that is a phase inverter? Meaning that the two output tubes are being driven with totally different signals! On the plates of V2 I would expect two identical amplitude sine waves, in 180 degree opposition on the two plates at all frequencies. I just don't see it with that circuit. Thank you in advance. In hind sight, IF the grid going to V2-B is pure DC, then the phase inversion is occurring in the current division on the cathode resistor as a classical differential amplifier.... Please confirm.
The most popular audio small signal pentode - EF86. Most popular general purpose small signal triode ECC83. No. of amplifiers using voltage gain with EF86 and a ECC83 phase splitter = too many to count. The Knight output stage isn't like the Mullard circuit. That was a wayward jump to say they were copies. I couldn't see it. I think you got a bargain too, an un-messed about with amp in excellent condition. I wouldn't have argued. I would have been happy as Larry. That was 1 in a million find.
@@rayislooking2 It wasn't a steal but wasn't worth the hassle of returning it knowing I would likely go through it anyway. More just trying to warn people that "restored" stuff on ebay may have had very little done to them.
"Restored" means different things to different people. To the layman, restored could mean only that it was worked on and made functional, brought back to life, or resurrected. Always ask what was done and what was changed, adjusted, cleaned, etc... If you buy it under the your assumptions of what should have been done to meet basic standards of restoration and it fails to meet that, then be sure to communicate clearly what you expect when buying any used gear before buying. Lesson learned
Yah I call bs to on that was serviced by a tech I purchased a very nice Harman Kardon a250 epic and it was serviced by a tech and it sure was and done well to. Only repair I did was replace drifted resistors
@@Blueglow Hm. Okay. I would not give much credits to eBay-promises. I have bought stuff from eBay being aware of it could be useless. I have accepted the risks, usually because stuff are nor available otherwise.
I bought restored radios ,I was warned by another you tube when people say restored they sometime just do enough to get them working and sell them as restored ,also at the time couldn't you get help from pay pal or eBay ,all you would have to have done is like you did take the cover off it shows proof they were lying ,Me I hate to lose money ,also sometimes.it's hard to trust your fellow man ,so far I been lucky ,one because I will hitch about the problem and second I will take pictures to send as proof .
Devious ,dishonest,bull shitters lurk on ebay. Standard practice now is selling in non working /parts , even if it turns on and something works . Very disheartening.
I have an old Knight that looks a lot like that with the chrome chassis and black tube guard...I'll get to it one of these days, lol. Great video! Thanks for sharing!!
It was mentioned at the beginning of this video that you weren't sure whether this was the factory-wired version, or a kit. An easy way to check (and this applies to most all brands) is to examine how the chassis-mounted tube sockets are secured. If mounted with rivets, it was factory assembled. If mounted with machine screws & nuts, then it's a kit. Of course, if somebody did sloppy soldering with leads hanging all over the place, you could also make a safe assumption....
Great job, beautiful amp. Don't you just love these guys who sell things "completely restored and working great". I've received quite a few units from these guys and none have been restored. One radio I purchased was just a line cord replacement. I've since then have asked for pictures of the units before I buy them. Very few get back to me. 👍👍👍👍👍
You need EL37 or EL34 tubes for this. This is a nice amp I won 2 restored of them did the restoration by myself. Replaced all aged paper in oil caps with russian military pios and the electrolytics on the cirquitboards with new german F&T´s....the orignal multisection caps and even the single 16uF electrolytic high voltage caps reformed perfectly, no need to change. The electrolytic with that cardboard cover in fact is a solid electrolytic cap like a tantalum it does not age.
I'm glad you're back into circuits Mark. I have switched tubes on stereo amplifiers to see on scope if there's any changes in signal strength or whether there's distorted waves, noise etc. Bad solder joints, un-shielded audio cable, ungrounded wire, bad decoupling caps and bad elements in tubes causing noise and hum. I enjoyed the video. Thanks!
Thanks so much Mark! I’m really enjoying this trouble shooting series and the detail and reasoning you go into explaining what is happening as well as tracing where the problem is coming from. Keep up the great work!
That was a really interesting video and genuinely one of the best on the subject because you ran into real issues, diagnosed them, referencing the circuit diagram and clearly explaining your thought processes. You finished the video saying that you hope people learned something well I'm sure they will have done. Great job and thanks! :)
I love these videos!
I know this is a nit-pick, but Mark told us to check his use of words, so...
... it's not a quarter inch "phono" plug, it's a quarter inch "phone" plug.
Phone plugs were used with the old telephone switch boards and are used with electric guitars and other audio devices.
Phono plugs are RCA plugs that carry the signal from a record player (turntable) to the phono input of a home stereo, with a low level signal and that funky lopsided equalization.
Would love to see this brought back in another vid to see you go over the updates and upgrades. Another great video 👍🏻
I've ordered the can caps, will make a video on the restoration
@@Blueglow The 16uf at 700v that goes across the GZ34 rectifier tubes, I always put in a 22uf @630v film cap in its place. The can caps I use the Authenticaps 550vdc which is a must. I always go up in capacitance after the choke and double it. I run the cathode bypass caps direct across the cathode resistors and I use 100uf 100v muse KZ.
Really enjoyed this and you’ve got a new subscriber here. Mistakes are all part of the fun and it’s instructional to see them so thanks for not editing out the tube snafu!
Another much appreciated lesson, thanks Mark.
14:50 - Looking at V2, I don't see a phase inverter circuit. V2-A is a wide band inverting amplifier fed directly from the plate of the EF86 and V2-B is also an inverting amplifier being fed through a 1M/0.25uF low pass filter! Could you scope the outputs of those sections and prove that is a phase inverter? Meaning that the two output tubes are being driven with totally different signals! On the plates of V2 I would expect two identical amplitude sine waves, in 180 degree opposition on the two plates at all frequencies. I just don't see it with that circuit. Thank you in advance.
In hind sight, IF the grid going to V2-B is pure DC, then the phase inversion is occurring in the current division on the cathode resistor as a classical differential amplifier.... Please confirm.
You are correct, should have said inverter circuit. No argument on this one.
@@Blueglow Thank you.
It's a classic direct coupled long tail pair phase inverter, and is indeed a differential amplifier.
I always want to see the photos of the restoration. Asked a seller once to send photos and he said, "buy it or leave it." I left it.
The 4 Volts on the lower side of the coupling capacitor, is no leakage. They are supposed to be there. Look at the schematic.
66th week of 1952? lol, the old-timers say that was a L-O-N-G year...
I caught it before posting, made a note in the comments
Mark great video, thanks. You got outstanding patience.
Thanks for your time Mark
Really cool stuff thanks for going through this
The most popular audio small signal pentode - EF86. Most popular general purpose small signal triode ECC83. No. of amplifiers using voltage gain with EF86 and a ECC83 phase splitter = too many to count. The Knight output stage isn't like the Mullard circuit. That was a wayward jump to say they were copies. I couldn't see it. I think you got a bargain too, an un-messed about with amp in excellent condition. I wouldn't have argued. I would have been happy as Larry. That was 1 in a million find.
I'm sure he was happy with the price or he would have returned it?
@@rayislooking2 It wasn't a steal but wasn't worth the hassle of returning it knowing I would likely go through it anyway. More just trying to warn people that "restored" stuff on ebay may have had very little done to them.
66th week of 1952, do you mean 14th week of 53’?
🤦♂️ I’d love to know who “restored” the amp and put the tubes back in the sockets.
Obviously Mr. Nobodyatall.
great video mark
"Restored" means different things to different people. To the layman, restored could mean only that it was worked on and made functional, brought back to life, or resurrected. Always ask what was done and what was changed, adjusted, cleaned, etc... If you buy it under the your assumptions of what should have been done to meet basic standards of restoration and it fails to meet that, then be sure to communicate clearly what you expect when buying any used gear before buying. Lesson learned
If I may ask, how much did you pay for this model amp? Love the video and tnx as always!!
that looks great i love to have one.
hi Mark just emailed you the full original service manual for the amp and the preamp
Yah I call bs to on that was serviced by a tech I purchased a very nice Harman Kardon a250 epic and it was serviced by a tech and it sure was and done well to. Only repair I did was replace drifted resistors
Shame on you for not naming the A##hole who would sell something like this as restored
Howdy. No disrespect intended.
But sometimes one wonders if there are no limits to how naive one may be.
No idea what you are referring to?
@@Blueglow Hm. Okay. I would not give much credits to eBay-promises. I have bought stuff from eBay being aware of it could be useless. I have accepted the risks, usually because stuff are nor available otherwise.
good circuit don't know why people have to dishonest
I bought restored radios ,I was warned by another you tube when people say restored they sometime just do enough to get them working and sell them as restored ,also at the time couldn't you get help from pay pal or eBay ,all you would have to have done is like you did take the cover off it shows proof they were lying ,Me I hate to lose money ,also sometimes.it's hard to trust your fellow man ,so far I been lucky ,one because I will hitch about the problem and second I will take pictures to send as proof .
Devious ,dishonest,bull shitters lurk on ebay. Standard practice now is selling in non working /parts , even if it turns on and something works .
Very disheartening.
Great session!