I have serviced for over 4 decades and came up with solutions that involved using different case type transistors to solve problems that I encountered many times over my career. The performance was just as good as the original and often provided better specs.
Tony, thank you for this channel. The sunshine in your voice compliments your generosity and enthusiasm. I'm not a great audio enthusiast (r.f. is my thing) but I cannot miss anything you do and take a great interest in your work. It might be raining outside but you make the sun shine here.
I am such a big fan of Marantz's engineering! I just got an graphic equalizer (EQ551) from eBay for fixing and I couldn't be more excited. I will pair it with my P40SE that I recently fixed in order to complete the living room setup. Great video as always, Tony
When I was a young man in the late 60's we ran a pair of Klipsch Cornwalls off a 15w per channel amp playing Pinball Wizard. It sounded like the Who was playing in the room live!
Hats off to you a special amp indeed! funny I was thinking of a lm317 to92 for Q101 for a precision current limit source? my brother is retired and refurbished them what you said is reminiscent of what he did using a hp spectrum analyzer he does have a large lot of matched transistors he painstakingly sorted out for this amplifier he replaces all of the transistor in this amp the 14 enjoyed watching super job! take care
I had one of these amps in the early 1970s. I was using AR-3a speakers that are rated at 4 ohms impedance. They are actually close to 3 ohms at some frequencies. The overload lamps would light even at moderate volume with music that had strong bass in them. The amp still sounded fine with the red lights flickering, but I later got a Marantz model 250 which I still use.
Light bulbs actually are 'dynamic' resistors. Unlit, at low temperature, their resistance is relatively low, so they pass current quite easily. As soon as the filaments light up, their temperature along with resistance rises dramatically, which clamps the current. And since one can see when they are doing their job, that is a nice extra.
The 60Hz + 7kHz waveform shows an excellent case for the need for deemphasis (FM broadcast) & RIAA EQ curve (vinyl records), to reduce the bass amplitude, to make it fit within the limits of FM channel bandwidth, and a vinyl record groove ...
Another great video Tony! Although that ESR meter made my eyes light up.... I haven't seen it around anywhere! I have the MESR100 in circuit tester that many other people have which is available from eBay but I have never seen your one before! Where do I find one of those things? I love the simple analog meter on it... Also I should mention, I loved the great explanation of the amplifiers operation, a block diagram of the stages during the explanation would have made the explanation that much more better... I have an amplifier that started life as a kit from Electronics Australia magazine back in the early 70's that uses TO66 Fairchild transistors as it's output stage... Those things are really unobtainium... I purchased the amplifier with the idea that I was going to gut it and stuff it with some high powered class D amps, that before I realized that I really don't like the class D sound and how amazing this vintage 13W amplifier sounded! Thankfully the output transistors still function fine on this amplifier and I intend to keep it that way. Thank you once again for the amazing video... Looking forward to the next one!
Oh! I just found your ESR meter on eBay... I had to specifically search for it by it's name otherwise it won't show up! But it's price!!!! $400AU delivered is just a bit beyond me at this stage lol.. Shame though, it appears to have longer test leads compared to the cheaper MESR100 which makes it easier to use while testing in circuit, I tried to use longer cables with banana plugs on them but it knows that they are longer and asks for shorter cables... Kinda not so practical for in circuit capacitor testing because you have to keep the tester way to close. I wonder if there's a work around for the short leads? Otherwise it's not a bad bit of test gear even though I would prefer the wizard... Any chance of having a look inside it? I'm sure that it doesn't cost that much to make, they could potentially sell a lot more of them if they were cheaper.... Oh, and can it test capacitors over 470uf? The MESR100 won't measure above that capacity...
Although I like the way it works, the build quality was very poor when I received it. The wiring was very messy, as was the soldering job. Looks like it was quickly assembled on someone's workbench. That said, it works better than most of the other ESR meters I've tested, especially when doing in-circuit tests. They gave some very useful tips in the included instructions as well. I just wish the build quality was a bit neater for the premium price that you pay.
@@xraytonyb The test leads look to be a decent length... How long are they? The MESR100 that is available on eBay has very short test leads which makes it difficult to use as you have to continually move the unit around... It knows if you try to use longer leads and tells you to use shorter one's... Otherwise I can't complain for $64AU... I don't have the knowledge to try and modify the unit to accept longer leads... They don't have to be exceptionally long but longer than what they are would be nice... But the one that you have, I just love it's simplicity! It tells you if it's good, bad or ugly! Further testing can be performed out of circuit by other test equipment if necessary, but it gets you to where you need to be fast! And I like that... Maybe you should take it apart and clean up the inside a bit? While you are there.... Maybe you can reverse engineer the circuit? These things are essential tools for problem solving just as signal tracers are... Especially if the tracer has a very sensitive RF mode... Anyway, the video was great and as usual I learned something new while enjoying it at the same time.... Win win!
Hey thanks for your videos. I find your explanations of how this amplifier works to be fascinating. I see you curve matched the input transistors and I will assume that if you replaced the output transistors you would match those too. What I wonder about is are there any other transistor pairs in this amp that should be matched such as the drivers?
Hi Tony, have you ever considered hooking up a go-pro (or similar) to your head (attaching It on a baseball cap for istance) for shooting working sequences without having the camera in your way? Great content by the way.. It makes me want to start studying electronics at 42.. have a great day.
Nice video Tony. I never seen light bulbs in an amp before. It’s like having a dim bulb tester installed. I don’t like that the amp can fail and put that amount of DC to the speakers. Kinda scary.
It's not just this amp. Any amp is capable of sending almost full power supply voltage to the speaker when it fails, unless it's capacitor-coupled to the output terminals like some of the old mid-range Pioneers. eta: That's why newer amp designs started to include protection relays on the outputs. A circuit monitors the output and disconnects the speaker terminals if it senses DC voltage over a certain value. (Of course, that's assuming the protection circuit doesn't fail too, which does happen.)
Hi, big fan of your videos. Have a question on the MARANTZ 15 if you can help. Trying to figure out the diode sub for BTR1557 which I can't cross and is CR103, 105, 106, 107 can I use 1N4148 and for MR2360 which won't cross and is CR102, 108 can I use 1n4004-07?
40:24 : Don´t have such a digital scope but my understanding of Interference is, that in this case the sidebands are multiples of 60Hz. The fundamental wave is 60Hz, so i expect that the sidebands are +/- 60Hz, +/- 120Hz, +/-180Hz and so on. Taking the scaling of 125Hz/Div i measure app. +/-140Hz. Could it be only an artefact of the FFT caused by overdriving the AD-converter? Or is the "bandwidth" of the FT too big?
Many people think that doubling your amplifier gives you a lot more volume but it does not. Doubling your amp power only gives you a 3 decibel increase (barely noticeable). So, if you want more volume and you are only going to rely on more amplifier power to do it, I would suggest a minimum of tripling or quadrupling your power.
deekay2 The following information is from Georgia State University and Research on Human Hearing. “A useful general reference is that the just noticeable difference in sound intensity for the human ear is about 1 decibel. JND = 1 decibel In fact, the use of the factor of 10 in the definition of the decibel is to create a unit which is about the least detectable change in sound intensity. That having been established, it can be noted that there are some variations. The jnd is about 1 dB for soft sounds around 30-40 dB at low and midrange freqencies. It may drop to 1/3 to 1/2 a decibel for loud sounds. Caution must be used in applying the "one decibel" criterion. It presumes that you are increasing the same sound by one decibel. If you were adding a sound outside the critical band of frequency from this sound, you would be exciting fresh nerve endings, and the one decibel rule can't be presumed to apply. This causes some concern about the perceptual encoding schemes used with modern digital recording which might eliminate some significant audible content by the use of a "one decibel" criterion for dropping content.” Maybe this will clarify or confuse as to what is the minimum amount of chance in a sound that can be perceived or not.
When you’re measuring the voltage at the speakers, RU measuring “across” the terminals?, rather than to ground, as its normal on some amps to have voltage on the speakers terminals to ground.
Do you know if there were any Marantz service bulletins for this model? If so do you have them? I'm working on one and am trying to find them. I'm having lots of fun with this one as well. I have a bad hum in both amps, and a leaky output transistor.
(@32:00) I think you meant to say that the “...period of the 7 kHz tone is 1/4 that of the 60 Hz tone”, not that it’s “1/4 the amplitude.” And that’s way off, too. A waveform with a period 1/4 that of 60 Hz, would be (1/60)x(1/4) = (1/240), or 240 Hz, remembering that period and frequency are inversely proportional. So, it’s really (1/60) times x = (1/7000), or x=7000/60=116-2/3. So the ratio of frequency is 1:116.6666... between the 60 Hz tone and the 7 kHz tone. I hope you weren’t breathing in too much solder smoke, there. Of, course, you’re also going to get two beat frequencies at 7000 +/- 60, or 6940 Hz, and 7060 Hz, but - then - that’s what you get with Amplitude Modulation. 😎 HTH.
Never mind, I was looking at the original waveform, and wondering what you we’re talking about; the audio and video got out of sync during playback for some weird reason. Even after seeing the AM modulated signal, it didn’t sink in... at first. My apologies. 😔
I have a Marantz SR8002 that might have been damaged by a power surge. We had a power outage and was using a 6600W generator to power the house, some time after the power came back on I noticed the red power light blinking in protect mode. I perform the reset procedure and then the unit turns on for about 3 seconds and then goes back into protect mode. During the three second window I can adjust the volume and change inputs. What could be wrong or could you fix it if you live/work close enough? [It would cost a fortune to ship it out of state. I live in Northern California near Redding but also travel to southern California... Riverside/Orange/LA counties once a month. I do have the service manual.
Just found this site describing the history of Marantz: www.whathifi.com/us/news/60-years-marantz-are-all-about-music This Model 15's vintage is 1966!": "Anyway, back to the history, and 1965 had seen the arrival of the first solid state Marantz products, in the form of the Model 7T preamp and, a year later, the Model 15 stereo power amp, and in 1968 came another of those classic Marantz products, and the start of a long line of receivers: the $595 Model 18."
You could, but I think it's necessary for this amp to reach a certain ambient temperature for optimal stability. I'm not positive on this, but I suspect this to be the case.
I have serviced for over 4 decades and came up with solutions that involved using different case type transistors to solve problems that I encountered many times over my career. The performance was just as good as the original and often provided better specs.
Tony, thank you for this channel. The sunshine in your voice compliments your generosity and enthusiasm.
I'm not a great audio enthusiast (r.f. is my thing) but I cannot miss anything you do and take a great interest in your work. It might be raining outside but you make the sun shine here.
I am such a big fan of Marantz's engineering! I just got an graphic equalizer (EQ551) from eBay for fixing and I couldn't be more excited. I will pair it with my P40SE that I recently fixed in order to complete the living room setup. Great video as always, Tony
When I was a young man in the late 60's we ran a pair of Klipsch Cornwalls off a 15w per channel amp playing Pinball Wizard. It sounded like the Who was playing in the room live!
Hats off to you a special amp indeed! funny I was thinking of a lm317 to92 for Q101 for a precision current limit source?
my brother is retired and refurbished them what you said is reminiscent of what he did using a hp spectrum analyzer he does
have a large lot of matched transistors he painstakingly sorted out for this amplifier he replaces all of the transistor
in this amp the 14 enjoyed watching super job! take care
That was sn awesome video Sir.
Only 80 thumbs up and over 1K views, what's wrong with these people?
Have they no gratitude?
👍👍👍👍👍
Very cool repair on a very special amp. Thanks for sharing it!
I had one of these amps in the early 1970s. I was using AR-3a speakers that are rated at 4 ohms impedance. They are actually close to 3 ohms at some frequencies. The overload lamps would light even at moderate volume with music that had strong bass in them. The amp still sounded fine with the red lights flickering, but I later got a Marantz model 250 which I still use.
Good repair video, Tony. (And I dare you to play the Portsmouth Sinfonia version of the Suite #1 ;-) )
Thanks, two more great video's, learn something new everytime...DA.
Great video, love the Foghorn Leghorn reference
Light bulbs actually are 'dynamic' resistors. Unlit, at low temperature, their resistance is relatively low, so they pass current quite easily. As soon as the filaments light up, their temperature along with resistance rises dramatically, which clamps the current. And since one can see when they are doing their job, that is a nice extra.
Loverly vid...cheers!
Had one with a 7T driving it, both worked great till I sold them. Had the wooden cases for both and they looked great together.
great amplifier chassis design 😍🔉🔊🎵🎶
The 60Hz + 7kHz waveform shows an excellent case for the need for deemphasis (FM broadcast) & RIAA EQ curve (vinyl records), to reduce the bass amplitude, to make it fit within the limits of FM channel bandwidth, and a vinyl record groove ...
Another great video Tony! Although that ESR meter made my eyes light up.... I haven't seen it around anywhere! I have the MESR100 in circuit tester that many other people have which is available from eBay but I have never seen your one before! Where do I find one of those things? I love the simple analog meter on it...
Also I should mention, I loved the great explanation of the amplifiers operation, a block diagram of the stages during the explanation would have made the explanation that much more better...
I have an amplifier that started life as a kit from Electronics Australia magazine back in the early 70's that uses TO66 Fairchild transistors as it's output stage... Those things are really unobtainium... I purchased the amplifier with the idea that I was going to gut it and stuff it with some high powered class D amps, that before I realized that I really don't like the class D sound and how amazing this vintage 13W amplifier sounded! Thankfully the output transistors still function fine on this amplifier and I intend to keep it that way.
Thank you once again for the amazing video... Looking forward to the next one!
Oh! I just found your ESR meter on eBay... I had to specifically search for it by it's name otherwise it won't show up! But it's price!!!! $400AU delivered is just a bit beyond me at this stage lol.. Shame though, it appears to have longer test leads compared to the cheaper MESR100 which makes it easier to use while testing in circuit, I tried to use longer cables with banana plugs on them but it knows that they are longer and asks for shorter cables... Kinda not so practical for in circuit capacitor testing because you have to keep the tester way to close. I wonder if there's a work around for the short leads? Otherwise it's not a bad bit of test gear even though I would prefer the wizard... Any chance of having a look inside it? I'm sure that it doesn't cost that much to make, they could potentially sell a lot more of them if they were cheaper.... Oh, and can it test capacitors over 470uf? The MESR100 won't measure above that capacity...
Although I like the way it works, the build quality was very poor when I received it. The wiring was very messy, as was the soldering job. Looks like it was quickly assembled on someone's workbench. That said, it works better than most of the other ESR meters I've tested, especially when doing in-circuit tests. They gave some very useful tips in the included instructions as well. I just wish the build quality was a bit neater for the premium price that you pay.
@@xraytonyb The test leads look to be a decent length... How long are they? The MESR100 that is available on eBay has very short test leads which makes it difficult to use as you have to continually move the unit around... It knows if you try to use longer leads and tells you to use shorter one's... Otherwise I can't complain for $64AU... I don't have the knowledge to try and modify the unit to accept longer leads... They don't have to be exceptionally long but longer than what they are would be nice... But the one that you have, I just love it's simplicity! It tells you if it's good, bad or ugly! Further testing can be performed out of circuit by other test equipment if necessary, but it gets you to where you need to be fast! And I like that... Maybe you should take it apart and clean up the inside a bit? While you are there.... Maybe you can reverse engineer the circuit? These things are essential tools for problem solving just as signal tracers are... Especially if the tracer has a very sensitive RF mode... Anyway, the video was great and as usual I learned something new while enjoying it at the same time.... Win win!
all the film caps go wonkey in these
Hey thanks for your videos. I find your explanations of how this amplifier works to be fascinating. I see you curve matched the input transistors and I will assume that if you replaced the output transistors you would match those too. What I wonder about is are there any other transistor pairs in this amp that should be matched such as the drivers?
Q102 and Q103 are the only two that need to be matched.
great video ..... very informative ....thanks alot sir
Great morning coffee watch
Thank you. very nice Amp. Good job.
You have very good informative videos. By any chance did you measure the voltage drop across the emitter resistor when you set the idle current?
Hi Tony, have you ever considered hooking up a go-pro (or similar) to your head (attaching It on a baseball cap for istance) for shooting working sequences without having the camera in your way? Great content by the way.. It makes me want to start studying electronics at 42.. have a great day.
That’s a very interesting amp design
Where did you buy the parts for and the parts number? Great video.
Thank you
Nice video Tony. I never seen light bulbs in an amp before. It’s like having a dim bulb tester installed. I don’t like that the amp can fail and put that amount of DC to the speakers. Kinda scary.
It's not just this amp. Any amp is capable of sending almost full power supply voltage to the speaker when it fails, unless it's capacitor-coupled to the output terminals like some of the old mid-range Pioneers.
eta: That's why newer amp designs started to include protection relays on the outputs. A circuit monitors the output and disconnects the speaker terminals if it senses DC voltage over a certain value. (Of course, that's assuming the protection circuit doesn't fail too, which does happen.)
Man learned so much Thanks a lot
Hi, big fan of your videos. Have a question on the MARANTZ 15 if you can help. Trying to figure out the diode sub for BTR1557 which I can't cross and is CR103, 105, 106, 107 can I use 1N4148 and for MR2360 which won't cross and is CR102, 108 can I use 1n4004-07?
Excellent!
Top jop... got one of these.... type 14... love it...
Nice. How about a repair video on your presonus audio interface. I have a trashed one also.
40:24 : Don´t have such a digital scope but my understanding of Interference is, that in this case the sidebands are multiples of 60Hz. The fundamental wave is 60Hz, so i expect that the sidebands are +/- 60Hz, +/- 120Hz, +/-180Hz and so on. Taking the scaling of 125Hz/Div i measure app. +/-140Hz.
Could it be only an artefact of the FFT caused by overdriving the AD-converter? Or is the "bandwidth" of the FT too big?
Many people think that doubling your amplifier gives you a lot more volume but it does not. Doubling your amp power only gives you a 3 decibel increase (barely noticeable). So, if you want more volume and you are only going to rely on more amplifier power to do it, I would suggest a minimum of tripling or quadrupling your power.
deekay2 The following information is from Georgia State University and Research on Human Hearing.
“A useful general reference is that the just noticeable difference in sound intensity for the human ear is about 1 decibel.
JND = 1 decibel
In fact, the use of the factor of 10 in the definition of the decibel is to create a unit which is about the least detectable change in sound intensity.
That having been established, it can be noted that there are some variations. The jnd is about 1 dB for soft sounds around 30-40 dB at low and midrange freqencies. It may drop to 1/3 to 1/2 a decibel for loud sounds.
Caution must be used in applying the "one decibel" criterion.
It presumes that you are increasing the same sound by one decibel. If you were adding a sound outside the critical band of frequency from this sound, you would be exciting fresh nerve endings, and the one decibel rule can't be presumed to apply. This causes some concern about the perceptual encoding schemes used with modern digital recording which might eliminate some significant audible content by the use of a "one decibel" criterion for dropping content.”
Maybe this will clarify or confuse as to what is the minimum amount of chance in a sound that can be perceived or not.
Maybe it does give you a lot more volume but our ears just can't notice a difference ?
Hi I have a marantz model 15 it works and sounds great but the two red lights don't light up at all
When you’re measuring the voltage at the speakers, RU measuring “across” the terminals?, rather than to ground, as its normal on some amps to have voltage on the speakers terminals to ground.
Nice repair video. Are those current-limiting Incandescent light bulbs visible through the front panel when they light up?
I think so, there seems to be some kind of see through strip in the front panel.
Yes they are. The red lenses on either side of the power indicator lamp are positioned directly in from of the bulbs.
Do you know if there were any Marantz service bulletins for this model? If so do you have them? I'm working on one and am trying to find them. I'm having lots of fun with this one as well. I have a bad hum in both amps, and a leaky output transistor.
(@32:00) I think you meant to say that the “...period of the 7 kHz tone is 1/4 that of the 60 Hz tone”, not that it’s “1/4 the amplitude.” And that’s way off, too. A waveform with a period 1/4 that of 60 Hz, would be (1/60)x(1/4) = (1/240), or 240 Hz, remembering that period and frequency are inversely proportional. So, it’s really (1/60) times x = (1/7000), or x=7000/60=116-2/3. So the ratio of frequency is 1:116.6666... between the 60 Hz tone and the 7 kHz tone. I hope you weren’t breathing in too much solder smoke, there. Of, course, you’re also going to get two beat frequencies at 7000 +/- 60, or 6940 Hz, and 7060 Hz, but - then - that’s what you get with Amplitude Modulation. 😎 HTH.
Never mind, I was looking at the original waveform, and wondering what you we’re talking about; the audio and video got out of sync during playback for some weird reason. Even after seeing the AM modulated signal, it didn’t sink in... at first. My apologies. 😔
Habe you ever done any work on a Sansui G-8000 ? Thanks for the video ?
I have a Marantz SR8002 that might have been damaged by a power surge. We had a power outage and was using a 6600W generator to power the house, some time after the power came back on I noticed the red power light blinking in protect mode. I perform the reset procedure and then the unit turns on for about 3 seconds and then goes back into protect mode. During the three second window I can adjust the volume and change inputs.
What could be wrong or could you fix it if you live/work close enough? [It would cost a fortune to ship it out of state. I live in Northern California near Redding but also travel to southern California... Riverside/Orange/LA counties once a month.
I do have the service manual.
you are amazing !
4:30 and PLEASE redraw that diff-amp stage! :)
I'll put it on the never-ending list :)
Just found this site describing the history of Marantz: www.whathifi.com/us/news/60-years-marantz-are-all-about-music
This Model 15's vintage is 1966!":
"Anyway, back to the history, and 1965 had seen the arrival of the first solid state Marantz products, in the form of the Model 7T preamp and, a year later, the Model 15 stereo power amp, and in 1968 came another of those classic Marantz products, and the start of a long line of receivers: the $595 Model 18."
Great information! Thanks for sharing!
Couldn't' you just tweak the bias until the crossover notch goes away? That 30W power-consumption measurement is very round-about!
You could, but I think it's necessary for this amp to reach a certain ambient temperature for optimal stability. I'm not positive on this, but I suspect this to be the case.
Any way you could tell me how to find the schematic for different amps
hifiengine.com
Why not repair that PreSonus interface?
“Zen”er, and the Art of Amplifier Maintenance ...
Moussorgsky would be disappointed.
It was the orchestra's Conductors fault!
Fascinating, Great 2 hour session.