For Sale Verum 1 MKII Headphones Zebrano Brown + silver
- By pinnocchio
- Swap Meet
- 13 Replies
Attachments
For Sale UK - Neurochrome 686 - all boards - fully assembled and working
Neurochrome 686 fully assembled
All working as it should, no power on/off thumps just the quiet clicks from the relays
Case Dimensions in mm (approx)
450 wide v 410 deep x 190 high
Note: the sockets and switch add depth so allowing for cables etc front to rear depth in use is about 490mm
The Amplifier Includes:
2 x Neurochrome Modulus 686 boards
2 x Neurochrome Power supply boards – one for each channel, 88000uf per channel
1 x Neurochrome Intelligent Soft Start
2 x Neurochrome Guardian speaker protection – one for each channel
Green Ground/Earth Socket on rear
XLR inputs
4mm Speaker terminals
1 x Mains Transformer 800 watt with separate windings for each channel.
£2000 firm
All working as it should, no power on/off thumps just the quiet clicks from the relays
Case Dimensions in mm (approx)
450 wide v 410 deep x 190 high
Note: the sockets and switch add depth so allowing for cables etc front to rear depth in use is about 490mm
The Amplifier Includes:
2 x Neurochrome Modulus 686 boards
2 x Neurochrome Power supply boards – one for each channel, 88000uf per channel
1 x Neurochrome Intelligent Soft Start
2 x Neurochrome Guardian speaker protection – one for each channel
Green Ground/Earth Socket on rear
XLR inputs
4mm Speaker terminals
1 x Mains Transformer 800 watt with separate windings for each channel.
- 2 x 400 watts windings @ 25vac
- One winding for each channel
£2000 firm
Attachments
For Sale London UK: 2A3 SE amplifier, premium parts
- By andyjevans
- Swap Meet
- 12 Replies
For sale - my 2a3 SE amplifier with state of the art power supply - big Hammond transformer and choke, GZ34 rectifier, Black Gate bypass caps on the 2a3.
Input section is a 6N1P with teflon coupling caps, Kemet DC Link bypasses and Holco resistors. All premium parts.
Configured right now as just an amplifier but I can add a selector and volume control as needed to make it integrated.
Asking£485 excluding 2a3 valves. REDUCED to £460 including nearly new Sovtek 2a3s.
Situated Kensington, London. Auditions welcome. PM me with any questions.
Input section is a 6N1P with teflon coupling caps, Kemet DC Link bypasses and Holco resistors. All premium parts.
Configured right now as just an amplifier but I can add a selector and volume control as needed to make it integrated.
Asking
Situated Kensington, London. Auditions welcome. PM me with any questions.
JBL 2360 horn - Shape of entry
Hi all,
I have two JBL 2360 horns, and in the (near) future I want to purchase 2 CD's for them. What strikes me is the shape of the 2" horn entry, see the image below. It is certainly not circular (top to bottom: ~51mm, left to right ~47mm). Both of them look the same. Seeing this got me thinking: is it worth to invest in 600 euro drivers like the BMS or B&C coaxials for this horn? It feels a bit like using a highly advanced tight toleranced driver attached to a horn of the 'olden day's'. (Don't know what I get myself into by saying this) 🙂
Hopefully some of you can share their experience with this horn and/or give some insight of the effect of coupling a perfect circular 2" CD to this horn entry.
Thanks!
I have two JBL 2360 horns, and in the (near) future I want to purchase 2 CD's for them. What strikes me is the shape of the 2" horn entry, see the image below. It is certainly not circular (top to bottom: ~51mm, left to right ~47mm). Both of them look the same. Seeing this got me thinking: is it worth to invest in 600 euro drivers like the BMS or B&C coaxials for this horn? It feels a bit like using a highly advanced tight toleranced driver attached to a horn of the 'olden day's'. (Don't know what I get myself into by saying this) 🙂
Hopefully some of you can share their experience with this horn and/or give some insight of the effect of coupling a perfect circular 2" CD to this horn entry.
Thanks!
Vintage NAD 3020 amplifier history and simulation in LTSpice with possible simple improvements
- By pbilous
- Solid State
- 10 Replies
NAD 3020
The NAD 3020 amplifier, introduced in 1978 by New Acoustic Dimension (NAD), is a landmark in hi-fi audio history. Designed by Bjørn Erik Edvardsen, the NAD 3020 was a game-changer, challenging the notion that high-quality sound required a significant financial investment. At the time, the audio market was dominated by expensive, high-powered amplifiers. The NAD 3020, with its modest price and minimalist design, revolutionized the landscape by offering exceptional sound quality to a broader audience.
The NAD 3020 quickly gained a reputation for its remarkable performance. Despite its modest power rating of 20 watts per channel, it delivered much higher dynamic headroom, allowing it to handle musical peaks with impressive clarity and power. This capability enabled the amplifier to compete with higher-powered models, providing an audio experience that defied its wattage. Another key feature was its high current capability, crucial for driving difficult speaker loads and controlling speaker cones with precision. This resulted in detailed and accurate sound reproduction, making the NAD 3020 suitable for a wide range of speakers and musical genres.
A significant draw for vinyl enthusiasts was the integrated high-quality phono stage, which allowed turntables to be connected directly to the amplifier, offering a warm and rich analog sound without the need for an external phono preamp. The design simplicity of the NAD 3020, both externally and internally, contributed to its superior performance. By keeping the signal path clean and using high-quality components where it mattered most, NAD ensured the amplifier could deliver pure and uncolored sound, enhancing its reliability and longevity.
The most celebrated aspect of the NAD 3020's sound was its musicality and warmth. Renowned for its ability to reproduce music with a sense of rhythm and timing, it made listening enjoyable and engaging. Its warm sound signature added richness to the audio, making it a favorite among audiophiles and casual listeners alike. The NAD 3020 remains an iconic piece of audio equipment, revered for its groundbreaking approach to sound quality and affordability. Its unique blend of power, high current capability, and musical warmth set it apart from other amplifiers of its time, contributing to its legendary status. Decades after its introduction, the NAD 3020 continues to inspire and influence modern amplifier design, cementing its place in the annals of hi-fi history.
NAD 2150
The NAD 2150 amplifier, introduced in the early 1980s, is part of NAD's legacy of producing high-quality, affordable audio equipment. It employs the same foundational design concepts that made the NAD 3020 a legend in the audio world. Both amplifiers feature a singleton input stage with a constant current source, which ensures stable and low-noise operation. Next stage - VAS (voltage amplification stage) is using complimentary feedback transistor pair, which enhances linearity and reduces distortion, allowing for a more accurate and musical sound reproduction. And finally, both models utilize an emitter follower class AB output stage, providing a balanced mix of efficiency and sound quality.
However, a significant enhancement in the NAD 2150 is its use of higher current capability output transistors. These transistors enable the 2150 to drive more demanding speaker loads with greater control and robustness, resulting in improved performance, especially with contemporary, power-hungry speakers.
Another notable difference between the NAD 2150 and its predecessor is the absence of the preamp section in the 2150. While the NAD 3020 included a preamp, making it a versatile all-in-one solution, the 2150's omission of this section makes it particularly well-suited for modern audio setups. This design choice allows users to feed the signal directly from modern DACs and other high-quality sources without the additional signal path introduced by an integrated preamp. As a result, the NAD 2150 can offer a purer and more direct signal, aligning perfectly with the preferences of today's audiophiles who often favor streamlined, minimalistic systems for the highest fidelity audio reproduction.
Singelton input stage
The singleton input stage, as utilized in amplifiers like the NAD 3020, offers distinct advantages that contribute to its enduring appeal in audio design. Unlike the differential pair, which typically involves two transistors, the singleton input stage simplifies the circuitry. This simplicity often results in lower overall noise and distortion levels, crucial for preserving the fidelity of audio signals. Additionally, the singleton configuration can offer better phase accuracy and transient response, allowing for a more accurate portrayal of the original audio waveform. These characteristics make the singleton input stage particularly well-suited for applications where high-fidelity reproduction and transparency are paramount.
However, it's essential to acknowledge that the singleton input stage has drawbacks compared to the differential pair. One notable limitation is its typically lower common-mode rejection ratio (CMRR) compared to differential configurations. This means it may be more susceptible to common-mode noise and interference, potentially impacting signal quality in environments with electrical noise. Additionally, the thermal stability and matching characteristics of the singleton input stage may not be as robust as those of differential pairs, which can affect performance consistency over varying operating conditions.
Despite these considerations, the NAD 3020 amplifier's historical success and revered sound quality stand as testament to the effectiveness of the singleton input stage when implemented with careful design considerations. The 3020's ability to deliver clean, natural sound with minimal coloration has solidified its place in audio history and continues to influence modern amplifier designs. Its enduring popularity underscores the viability and effectiveness of the singleton input stage in achieving high-quality audio reproduction, showcasing its strengths in the context of critical listening environments and audiophile preferences.
My story
After immersing myself in the rich history and technical details of vintage hi-fi equipment, particularly the NAD 3020 and its successor, the NAD 2150, I decided to delve deeper into this world by acquiring a NAD 2150 amplifier.
Intrigued by its renowned design principles I sought to explore its inner workings further. I obtained the service manual, complete with schematics, and delved into understanding how these components interact to produce the amplifier's distinctive sound.
Driven by curiosity and a passion for electronics, I took my exploration a step further by simulating the NAD 2150's circuit layout using LTSpice, a circuit simulation software. This exercise not only deepened my understanding of amplifier design but also allowed me to visualize how different components contribute to its overall performance. Sketching the circuit in LTSpice was both educational and enjoyable, providing insights into the amplifier's behavior under various conditions.
For those brave enough to open the amp and solder a few capacitors a significant improvement can be made by swapping input filter capacitors to 22uF + 22uF and DC coupling capacitor to 4700uF resulting in 0.002% THD@1kHz.
The NAD 3020 amplifier, introduced in 1978 by New Acoustic Dimension (NAD), is a landmark in hi-fi audio history. Designed by Bjørn Erik Edvardsen, the NAD 3020 was a game-changer, challenging the notion that high-quality sound required a significant financial investment. At the time, the audio market was dominated by expensive, high-powered amplifiers. The NAD 3020, with its modest price and minimalist design, revolutionized the landscape by offering exceptional sound quality to a broader audience.
The NAD 3020 quickly gained a reputation for its remarkable performance. Despite its modest power rating of 20 watts per channel, it delivered much higher dynamic headroom, allowing it to handle musical peaks with impressive clarity and power. This capability enabled the amplifier to compete with higher-powered models, providing an audio experience that defied its wattage. Another key feature was its high current capability, crucial for driving difficult speaker loads and controlling speaker cones with precision. This resulted in detailed and accurate sound reproduction, making the NAD 3020 suitable for a wide range of speakers and musical genres.
A significant draw for vinyl enthusiasts was the integrated high-quality phono stage, which allowed turntables to be connected directly to the amplifier, offering a warm and rich analog sound without the need for an external phono preamp. The design simplicity of the NAD 3020, both externally and internally, contributed to its superior performance. By keeping the signal path clean and using high-quality components where it mattered most, NAD ensured the amplifier could deliver pure and uncolored sound, enhancing its reliability and longevity.
The most celebrated aspect of the NAD 3020's sound was its musicality and warmth. Renowned for its ability to reproduce music with a sense of rhythm and timing, it made listening enjoyable and engaging. Its warm sound signature added richness to the audio, making it a favorite among audiophiles and casual listeners alike. The NAD 3020 remains an iconic piece of audio equipment, revered for its groundbreaking approach to sound quality and affordability. Its unique blend of power, high current capability, and musical warmth set it apart from other amplifiers of its time, contributing to its legendary status. Decades after its introduction, the NAD 3020 continues to inspire and influence modern amplifier design, cementing its place in the annals of hi-fi history.
NAD 2150
The NAD 2150 amplifier, introduced in the early 1980s, is part of NAD's legacy of producing high-quality, affordable audio equipment. It employs the same foundational design concepts that made the NAD 3020 a legend in the audio world. Both amplifiers feature a singleton input stage with a constant current source, which ensures stable and low-noise operation. Next stage - VAS (voltage amplification stage) is using complimentary feedback transistor pair, which enhances linearity and reduces distortion, allowing for a more accurate and musical sound reproduction. And finally, both models utilize an emitter follower class AB output stage, providing a balanced mix of efficiency and sound quality.
However, a significant enhancement in the NAD 2150 is its use of higher current capability output transistors. These transistors enable the 2150 to drive more demanding speaker loads with greater control and robustness, resulting in improved performance, especially with contemporary, power-hungry speakers.
Another notable difference between the NAD 2150 and its predecessor is the absence of the preamp section in the 2150. While the NAD 3020 included a preamp, making it a versatile all-in-one solution, the 2150's omission of this section makes it particularly well-suited for modern audio setups. This design choice allows users to feed the signal directly from modern DACs and other high-quality sources without the additional signal path introduced by an integrated preamp. As a result, the NAD 2150 can offer a purer and more direct signal, aligning perfectly with the preferences of today's audiophiles who often favor streamlined, minimalistic systems for the highest fidelity audio reproduction.
Singelton input stage
The singleton input stage, as utilized in amplifiers like the NAD 3020, offers distinct advantages that contribute to its enduring appeal in audio design. Unlike the differential pair, which typically involves two transistors, the singleton input stage simplifies the circuitry. This simplicity often results in lower overall noise and distortion levels, crucial for preserving the fidelity of audio signals. Additionally, the singleton configuration can offer better phase accuracy and transient response, allowing for a more accurate portrayal of the original audio waveform. These characteristics make the singleton input stage particularly well-suited for applications where high-fidelity reproduction and transparency are paramount.
However, it's essential to acknowledge that the singleton input stage has drawbacks compared to the differential pair. One notable limitation is its typically lower common-mode rejection ratio (CMRR) compared to differential configurations. This means it may be more susceptible to common-mode noise and interference, potentially impacting signal quality in environments with electrical noise. Additionally, the thermal stability and matching characteristics of the singleton input stage may not be as robust as those of differential pairs, which can affect performance consistency over varying operating conditions.
Despite these considerations, the NAD 3020 amplifier's historical success and revered sound quality stand as testament to the effectiveness of the singleton input stage when implemented with careful design considerations. The 3020's ability to deliver clean, natural sound with minimal coloration has solidified its place in audio history and continues to influence modern amplifier designs. Its enduring popularity underscores the viability and effectiveness of the singleton input stage in achieving high-quality audio reproduction, showcasing its strengths in the context of critical listening environments and audiophile preferences.
My story
After immersing myself in the rich history and technical details of vintage hi-fi equipment, particularly the NAD 3020 and its successor, the NAD 2150, I decided to delve deeper into this world by acquiring a NAD 2150 amplifier.
Intrigued by its renowned design principles I sought to explore its inner workings further. I obtained the service manual, complete with schematics, and delved into understanding how these components interact to produce the amplifier's distinctive sound.
Driven by curiosity and a passion for electronics, I took my exploration a step further by simulating the NAD 2150's circuit layout using LTSpice, a circuit simulation software. This exercise not only deepened my understanding of amplifier design but also allowed me to visualize how different components contribute to its overall performance. Sketching the circuit in LTSpice was both educational and enjoyable, providing insights into the amplifier's behavior under various conditions.
For those brave enough to open the amp and solder a few capacitors a significant improvement can be made by swapping input filter capacitors to 22uF + 22uF and DC coupling capacitor to 4700uF resulting in 0.002% THD@1kHz.
Hello!
- By rzsantiago
- Introductions
- 2 Replies
Hello everyone!
I've always been passionate about music (just listening) and recently I began to be more interested in the equipment aspect to enjoy it more and better.
I started by making my own speakers, a version of the 'Overnight Sensations' by Paul Carmody. I tried them only with a class D amplifier and the first listening experience was incredible. From there I acquired an old Kendwood KA-300 amplifier in very good condition and again, the experience was better than the previous one and the loudness function helped a lot to better balance the sound of the speakers since I usually listen to them in a very small environment.
I'm really enjoying this journey of baby steps improvements😅 so I hope to continue improving my equipment and creating new ones.
Thanks for reading!
I've always been passionate about music (just listening) and recently I began to be more interested in the equipment aspect to enjoy it more and better.
I started by making my own speakers, a version of the 'Overnight Sensations' by Paul Carmody. I tried them only with a class D amplifier and the first listening experience was incredible. From there I acquired an old Kendwood KA-300 amplifier in very good condition and again, the experience was better than the previous one and the loudness function helped a lot to better balance the sound of the speakers since I usually listen to them in a very small environment.
I'm really enjoying this journey of baby steps improvements😅 so I hope to continue improving my equipment and creating new ones.
Thanks for reading!
2017 VFET kit - 2ea 2SK82/2SJ28 - SOLD
I'm selling the kit I purchased back in 2017 with matched VFETs and circuit board. I REALLY want to build the amp but I just don't see it happening any time soon and would like to pass it on to someone who will actually put them to good use. Purchased direct from diyaudiostore. Thanks for looking!
Edit: forgot the price: $250 including shipping. It was the 'essentials' kit that has the matched VFETS, PCB's and some screws
Edit: forgot the price: $250 including shipping. It was the 'essentials' kit that has the matched VFETS, PCB's and some screws
Magnetic cartridge preamp
- By Tube Radio
- Analogue Source
- 40 Replies
Is there a good quality small magnetic cartridge phono preamp board that can run on up to 12Vdc?
The B+ to the 45 player is +12Vdc as I needed to replace the stock motor with a DC brushless motor due to it inducing hum in the cartridge. I can use a LM-317 to derive any voltage under +12Vdc.
I've got an RCA 45 player I converted to a stereo magnetic cartridge and wanted a built in preamp so that I can plug it into any line level input.
The board needs to be relatively small as there's only a small place for it to fit.
Pictured is where the board has to go and also a previous attempt from a few years ago that didn't work so good. The existing board is 3" X 2 1/4", but there's enough space to where it can be 3" X 2 1/2".
The B+ to the 45 player is +12Vdc as I needed to replace the stock motor with a DC brushless motor due to it inducing hum in the cartridge. I can use a LM-317 to derive any voltage under +12Vdc.
I've got an RCA 45 player I converted to a stereo magnetic cartridge and wanted a built in preamp so that I can plug it into any line level input.
The board needs to be relatively small as there's only a small place for it to fit.
Pictured is where the board has to go and also a previous attempt from a few years ago that didn't work so good. The existing board is 3" X 2 1/4", but there's enough space to where it can be 3" X 2 1/2".
Mod/fix a vintage two way kit
About 30 years ago I've built a pair of bookshelf speakers based on Audax drivers. Recently, I got back to diyaudio during Covid. I felt It was dull so I bypass R1 but it is too hot. I've used it like that for few years, now the tweeter is dead on one channel.
The original Audax tweeter is hard to find now but there are similar design from local manufacturers with 4ohms impedance. I'm thinking of just put an attenuating resistor in series with new tweeter. Maybe a 2 ohm resistor so about -3.5dB at 6 ohm instead of -6dB at 8 ohms in original design.
Would that work? Do I need to think about phases?
NAD C 720BEE - worked great initially and then entered protected mode...solution included
- By Pernas
- Solid State
- 2 Replies
Hi!
Just wanted to share my experience from a few days ago when I found myself a rather nice (IMHO) looking NAD C 720BEE together with a C 525BEE CD player.
The amp was acquired as a replacement for the NAD 302 which I'm now a bit hesitant to leave running for longer periods due to it's lack of any protection circuit.
(More on that later).
The C 720BEE was cleaned and then tested without any issues whatsoever. However, a few days later when starting the 720BEE it remained in red (protected mode) regardless of speakers connected or not and I thought, bummer, time for a re-cap then.
(The SM only guided me to check the protection circuit to proceed though, not very helpful here).
However, before starting with the re-cap I really wanted to find the actual cause for this sudden regression - and soon found that the -18V supply was only at -1.16V when ON.
Ok, then tried to trace all possible caps involved in with the -18V supply without any success. Also, there was no obvious indication of abnormal current draw from the -37V either...
Strange I thought and then my wife suddenly appeared in the doorway and I quickly explained what I was doing and trying to find and then she out of the blue (she's very intuitive and smart) told me that I might be searching in the wrong place(s) and asked me about the circuit board and suggested that I should take a look at that instead:
...and she was right, the circuit board was to blame for this regression and the reason for the missing -18V was due to
that R414 didn't have any connection with the +18V side as the schematics below indicates:
The fix was a rather crude one with a link soldered to remedy the above and then it was back to the living!
(The soldering on this board didn't look too nice to start with, this unit could have been a lemon 😉)
Now I'm just awaiting new 2x15000uF caps for the power supply to arrive to finish the re-cap.
(Horrible that these 15000uF caps are live even when the AMP is in standby mode, it's really time since one of them has a small bulge...)
More to follow when AMP has been fixed up to specs!
Thanks for reading,
Per
Just wanted to share my experience from a few days ago when I found myself a rather nice (IMHO) looking NAD C 720BEE together with a C 525BEE CD player.
The amp was acquired as a replacement for the NAD 302 which I'm now a bit hesitant to leave running for longer periods due to it's lack of any protection circuit.
(More on that later).
The C 720BEE was cleaned and then tested without any issues whatsoever. However, a few days later when starting the 720BEE it remained in red (protected mode) regardless of speakers connected or not and I thought, bummer, time for a re-cap then.
(The SM only guided me to check the protection circuit to proceed though, not very helpful here).
However, before starting with the re-cap I really wanted to find the actual cause for this sudden regression - and soon found that the -18V supply was only at -1.16V when ON.
Ok, then tried to trace all possible caps involved in with the -18V supply without any success. Also, there was no obvious indication of abnormal current draw from the -37V either...
Strange I thought and then my wife suddenly appeared in the doorway and I quickly explained what I was doing and trying to find and then she out of the blue (she's very intuitive and smart) told me that I might be searching in the wrong place(s) and asked me about the circuit board and suggested that I should take a look at that instead:
...and she was right, the circuit board was to blame for this regression and the reason for the missing -18V was due to
that R414 didn't have any connection with the +18V side as the schematics below indicates:
The fix was a rather crude one with a link soldered to remedy the above and then it was back to the living!
(The soldering on this board didn't look too nice to start with, this unit could have been a lemon 😉)
Now I'm just awaiting new 2x15000uF caps for the power supply to arrive to finish the re-cap.
(Horrible that these 15000uF caps are live even when the AMP is in standby mode, it's really time since one of them has a small bulge...)
More to follow when AMP has been fixed up to specs!
Thanks for reading,
Per
-
Locked
Speaker recognition and how to remove the face from the mount, please.
- By jfmusic
- Introductions
- 4 Replies
Hi, I purchased a used set of 6422cfp, and they came with tweeters.
Anybody know what they are and how to separate the unit from the mount frame?
I have a heavy hand and am notorious for oops...
Thanks in advance
Anybody know what they are and how to separate the unit from the mount frame?
I have a heavy hand and am notorious for oops...
Thanks in advance
VTL IT-85 Schematic Needed
- By ampexperts
- Tubes / Valves
- 10 Replies
I'm in search of schematic for IT-85.
Peculiar problem between V101 and V102, intermittent loss of signal, V101 has a signal on pin 1, but it's not making it to V102. I see there are a couple of relays in there.
In addition, the other channel does not mute when the amplifier is warming up or after shutdown.
I've been over the solder joints that are accessible, but the next step is major disassembly to get that PCB out for inspection/repair.
A schematic would at least tell me what's in the signal path between those two tubes.
Problem suspected to be somewhere under the mass of wires and switch on the right hand side of this photo:
Peculiar problem between V101 and V102, intermittent loss of signal, V101 has a signal on pin 1, but it's not making it to V102. I see there are a couple of relays in there.
In addition, the other channel does not mute when the amplifier is warming up or after shutdown.
I've been over the solder joints that are accessible, but the next step is major disassembly to get that PCB out for inspection/repair.
A schematic would at least tell me what's in the signal path between those two tubes.
Problem suspected to be somewhere under the mass of wires and switch on the right hand side of this photo:
Adjusting an old bias pot did some damage and I am unsure how to proceed
- By 62vauxhall
- Solid State
- 248 Replies
The unit is a Sony TA1150 integrated that I've had since 2018. It was unwell when I bought it but it did power up and it did pass signal. I did not use it per se, just hooked up for the odd listen over a couple of years then there came a time when it stopped amplifying.
I learned some transistors failed, outputs and drivers so i replaced them with those which were recommended. I also replace the electrolyltic capacitors associated with the power supply. At that point the amplifier was working well enough to leave connected in a small "hobby room" system.
Not long ago, the pilot lamp did not light up. I did the disassembly necessary to repair that and thought it was a good time to replace all the electrolytic capacitors and that task spanned several days. When all the new electrolytic capacitors were in place, I used a 40 watt DBT to check for shorts and there were none. It went dark almost immediatly after turning on the power switch.
Since a number of components were new, I decided to check and if necessary, re-set the bias. Since the DBT went dark right away and my understanding was not to use a DBT when setting bias, the amplifier was plugged dirctly in to wall power.
As per the service manual, the target is 25mv and the left channel bias was pretty close. The right channel was nearly 60mv so I attempted to adjust that channel's bias pot.
As I rotated the pot, both 1.6A fuses blew and I noticed the telltale odor of an overheated component. Even now, I fail to see anything that shows heat damage.
My next step was replaing the fuses and turning the amp on using a DBT which went bright and stayed bright so there was now a short.
I pulled all eight output transitors, which are now four MSJ15032G and four MSJ15033G. One 15032 and one 15033 in the right channel were damaged. At that point I ordered new 1K ohm bias pots. When they arrived, I installed them and I replaced the two bad output transistors.
Again with a DBT, I turned on the power. DBT went bright, stayed bright and both fuses blew again. As a shot in the dark, I replaced all eight of the output transistors one more time on the off chance that some others were injured and would fail under load. There was no change, DBT wet bright, stayed bright and both fuses blew.
My last attempt to trouble shoot the short was to remove all eight output transistors and see what the DBT did in conjunction with a variac but that too changed nothing. DBT got bright with the variac around 50 volts. I went no further so fuses are still intact.
I am unsure at this time what to do next. My hope is that some knowedgable person here can point me towards the cause of this shorting problem. I don't particulary want to junk this amplifier, I bought it for a reason. A Sony TA1150 was the very first brand new amplifier I ever bought. That was in 1973 and I was 20 years old.
Doing the math, that makes me 71 and my intention was to make this TA1150 my final amplifier. A kind of ironic twist that only I would appreciate.
I learned some transistors failed, outputs and drivers so i replaced them with those which were recommended. I also replace the electrolyltic capacitors associated with the power supply. At that point the amplifier was working well enough to leave connected in a small "hobby room" system.
Not long ago, the pilot lamp did not light up. I did the disassembly necessary to repair that and thought it was a good time to replace all the electrolytic capacitors and that task spanned several days. When all the new electrolytic capacitors were in place, I used a 40 watt DBT to check for shorts and there were none. It went dark almost immediatly after turning on the power switch.
Since a number of components were new, I decided to check and if necessary, re-set the bias. Since the DBT went dark right away and my understanding was not to use a DBT when setting bias, the amplifier was plugged dirctly in to wall power.
As per the service manual, the target is 25mv and the left channel bias was pretty close. The right channel was nearly 60mv so I attempted to adjust that channel's bias pot.
As I rotated the pot, both 1.6A fuses blew and I noticed the telltale odor of an overheated component. Even now, I fail to see anything that shows heat damage.
My next step was replaing the fuses and turning the amp on using a DBT which went bright and stayed bright so there was now a short.
I pulled all eight output transitors, which are now four MSJ15032G and four MSJ15033G. One 15032 and one 15033 in the right channel were damaged. At that point I ordered new 1K ohm bias pots. When they arrived, I installed them and I replaced the two bad output transistors.
Again with a DBT, I turned on the power. DBT went bright, stayed bright and both fuses blew again. As a shot in the dark, I replaced all eight of the output transistors one more time on the off chance that some others were injured and would fail under load. There was no change, DBT wet bright, stayed bright and both fuses blew.
My last attempt to trouble shoot the short was to remove all eight output transistors and see what the DBT did in conjunction with a variac but that too changed nothing. DBT got bright with the variac around 50 volts. I went no further so fuses are still intact.
I am unsure at this time what to do next. My hope is that some knowedgable person here can point me towards the cause of this shorting problem. I don't particulary want to junk this amplifier, I bought it for a reason. A Sony TA1150 was the very first brand new amplifier I ever bought. That was in 1973 and I was 20 years old.
Doing the math, that makes me 71 and my intention was to make this TA1150 my final amplifier. A kind of ironic twist that only I would appreciate.
EAR 869 Input Blocking Caps
- By juancho
- Tubes / Valves
- 15 Replies
Hi,
Can anyone help me identify the input blocking capcitor on the attached photo? I've tried tracing the pcb but jsut getting a headache!
Thanks in advance!
Can anyone help me identify the input blocking capcitor on the attached photo? I've tried tracing the pcb but jsut getting a headache!
Thanks in advance!
For Sale Sanken 2SA1859A and 2SC4883A NOS
I bought these several years back when I had some restoration to do and bought all that BDENT had in stock. Gotta clear some of this stuff out. Don't get beat up by buying knock-offs and fakes from who knows where. I have 47 of each. Many MFGR's used these like Sansui, Marantz etc.... I know many of you like to keep the original components. I'll be listing more hard to find parts soon.
PayPal FF preferred.
$4.00 each with free shipping on orders of 10 or more. Same day shipping if purchased before my mailman comes (about noon). US Shipping only
PayPal FF preferred.
$4.00 each with free shipping on orders of 10 or more. Same day shipping if purchased before my mailman comes (about noon). US Shipping only
Cascading two low-pass filters
Has anyone ever seen this kind of loudspeaker's crossovers in this picture?
It looks like there are two second-order low-pass filters cascading. I'm not sure if it is aimed for creating the half-way system or not, i.e., 2.5 or 3.5-way speaker system.
If it is meant for the half-way system, then, are there any formula for calculating those L1, C1, L2, C2 parameters? Assume WF#1 and WF#2 are identical.
It looks like there are two second-order low-pass filters cascading. I'm not sure if it is aimed for creating the half-way system or not, i.e., 2.5 or 3.5-way speaker system.
If it is meant for the half-way system, then, are there any formula for calculating those L1, C1, L2, C2 parameters? Assume WF#1 and WF#2 are identical.
