I worked for the bedini brothers in the early 80's. May even have built this amp. ( Built as in assembled the PCB, assembled the entire amp and even shipped the units!) I started machining the heat sinks and soon moved into assembly of all circuit boards, and building the amps, preamps, and Lazer couplers. For a while I was the only employee doing everything. Just happened on this video and felt like commenting. As for this amps issue, it was my thought it was a bad transistor or diode. Anyways, this is a old video, so not expecting any chatter, cool seeing the inside of one of our amps again. ( By the way, bedini was my first job, work for a few years for them but got cought up in personal issues with Gary's girlfriend and it became a bad deal. It was to bad, we were for a while like family..)
I like the way you do things,and your channel and very much appreciate you uploading the videos,what I found funny was the expense your friend went to with the power cable,but inside the amplifier were all the 5% tolerance resistors and ceramic disk capacitors,but great video all the same,look forward to your other videos.
Thanks for the flashback memories of Bedini amplifiers. Your particular model is not an original 25/25 (circa 1974), but the 25/25 DE (diode emitter) from the early 1980's. I owned the larger 100/100 DE from that era (there was also a 50/50 DE). They used diodes (e.g., 1N 4004 on the output transistors) instead of resistors on the emitters. The 100/100 DE had MJ15024 outputs instead of 2N6254's used in the original 45/45 and 100/100. All Bedini amps used non-complementary output stages and all invert absolute signal polarity, complicating listening comparisons to noninverting power amplifiers. Bedini preamps also inverted signal polarity, so the Bedini preamp/amp combinations complemented each other. Otherwise, I had to switch speaker cable polarity to correct for the inversion.
tafkasteve : now that is interesting. I really don’t have much experience with Bedini amps and certainly never came across a diode used on the emitter. I would really like to see the schematic, but it’s like finding hens’ teeth. Thanks again.
I looked through my 35 year-old notes and I have a schematic, but it is general for the 45/45 and 100/100 series amps and does not include many component IDs and values, especially for the DE series. I made a mistake in my original post, as the diodes on the output transistor emitters are MR 852's. I visited the Bedini factory in Sylmar, California (before they moved to Idaho) and John Bedini didn't explain his rationale for replacing emitter resistors with diodes. He just remarked that people would say that it couldn't be done and he had done it. He said that bias was approximately correct when the voltage across the MR 852 was around 0.63 V.
tafkasteve : I like the way the creators of exceptional products usually do so without the customary overthinking that later is applied to their creations. It’s quite funny actually: what he states is the normally bias voltage across the diode is merely the normal forward bias of a silicon diode, so he must have had a good sense of humor as well as technical creativity. Thanks for your input.
@@tafkasteve Can you please sed me Schematic and more info re Bedini 45/45 ? I have one Bedini 25/25 and 45/45...I like to Oversize Power module un Bedini 45, and need more info. Regrads marianisimo@gmail.com
It was a very interesting careful troubleshooting that brought your research to success after having troubled about the schematic diagram which apparently was difficult to find..! any way congratulations for your accurate research for such a small diode that gave you the inspiration to look for it.
These very personalized units are always poorly documented in the net, so we have to do more research on the unit itself to assist in the fault-finding process. Also, when you do find a schematic, it does not necessarily correspond to the one you’re working on. The consistent aspect is always the quality of the sound. Amazing!
I think that those small signal diodes, that are not present in any of my two schematics of that amp, must be two back to back parallel connected diodes, for protection, between the bases of each long tail pair. They must have been put there as an afterthought after the schematic drawn. If shorted, one of the input long tail pair transistors will have no drive. From my back memories I remember to hear this Bedinni at a friend's system, driving QUAD ESL 63 and playing the José Afonso album "Cantigas do Maio" and it sounded really good. Very nice video, once again, and I'm looking forward to the next one.
the middle driver is the bias transistor. I talked to John and he said that he uses the same transistor as the output devices for the bias transistor so it tracks more accuratly
If I remember correctly, there is a driver, and may also have a voltage regulator in there. It’s been a while since I did this one, so can’t remember exactly
Hello! Thank you for the great video! I have a short question. Do you know which BIAS has to be set to a Bedini BA 803? I found some posts which say 35 Ma, but is this possible? Mr. Bedini often wrote 35 Ma but said this for the BA 802, BA 803, 250/250 and so on. So could this be possible that all these amps have the BIAS set to 35 Ma? Thank you very much!
@12:34 since the offset between the two channels is still high, I would replace the same diode on the other channel, thinking that they may be overworked and started to leak over time.
Sir,I 'm a owner of Bedini 25+25 amplifier too,mind I ask where can I get the schemactic to do service for it.Possible you have one to share.I am from Malaysia.Thank you anyway.
@@electronicsoldandnew , ok you can help-me? i need adjust bias, in trimmer my bedini 100/100 is 2k pot-trimmer, but one channel , with multimeter in output speakers on amp, read.. positive 100mv dc and other channel read neagtive -25mv, dc I turn the trimmer it only gives negative reading, and the channel heats ,..What can be wrong with the channel? I have not tested transistor 2N5416 AND 2N3440 sorry my english,
All this stuff about hearing the difference in power cables is rubbish. It has been around for years. Even read that one person swore by painting the ends of the 13A fuse in the UK plug with a SPECIAL brand of marker pen. Give me a break. There was also an article in a hi fi mag in the seventies about the best cartridge in the world being carved out of a solid lump of wood by one old man who lived in Japan. Is it always April Fools day in Hi Fi world???
The right power cable, "Can" make a very large difference in a rigs sound. But only if your rig "as a whole", is resolving enough to allow you to hear that difference. Contemporary physics modeling can now "partially", explain how and why. Your kids will grow up knowing why. In fact, (We are working on the changes to the physics texts as I write this). So unless you are in point of fact, an "All knowing being"? Then you shouldn't talk in such "absolutes", as you have. Especially when it comes to subjects you know little about. But I do understand your frustration. "At least to a point". As I had a hard time accepting "Quantum Theory" as reality too. Probably as hard a time as those in the past, whom just "knew", the world was "flat"! "Progress" is much like the "Mac Truck". Because if you insist on standing before it, when it is coming straight at you? It will simply just crush you flat beneath. As it rolls "inevitably" forward........
As I said in response to Benters, “people can really get carried away”, either by lack of knowledge or by the Mac Truck 😊 The absolutes in the world of audio are, like religion and sexual preference, an argument that I do not partake in. I know that minds will not be swayed. I’ve heard it all: someone defending that he could hear the improved quality of an audio system while listening to it on a youtube video on his phone; someone claiming that a good quality volume pot made no difference to the sound quality. You see? There’s a delusion (or absolute truth) in every position, so I let everyone have their own.
I worked for the bedini brothers in the early 80's. May even have built this amp. ( Built as in assembled the PCB, assembled the entire amp and even shipped the units!)
I started machining the heat sinks and soon moved into assembly of all circuit boards, and building the amps, preamps, and Lazer couplers. For a while I was the only employee doing everything.
Just happened on this video and felt like commenting. As for this amps issue, it was my thought it was a bad transistor or diode.
Anyways, this is a old video, so not expecting any chatter, cool seeing the inside of one of our amps again. ( By the way, bedini was my first job, work for a few years for them but got cought up in personal issues with Gary's girlfriend and it became a bad deal. It was to bad, we were for a while like family..)
Thanks for commenting, and it is indeed interesting to find someone who worked on these personally.
I like the way you do things,and your channel and very much appreciate you uploading the videos,what I found funny was the expense your friend went to with the power cable,but inside the amplifier were all the 5% tolerance resistors and ceramic disk capacitors,but great video all the same,look forward to your other videos.
There’s sometimes no logic in the world of hi-fi 😊
Thanks for the flashback memories of Bedini amplifiers. Your particular model is not an original 25/25 (circa 1974), but the 25/25 DE (diode emitter) from the early 1980's. I owned the larger 100/100 DE from that era (there was also a 50/50 DE). They used diodes (e.g., 1N 4004 on the output transistors) instead of resistors on the emitters. The 100/100 DE had MJ15024 outputs instead of 2N6254's used in the original 45/45 and 100/100. All Bedini amps used non-complementary output stages and all invert absolute signal polarity, complicating listening comparisons to noninverting power amplifiers. Bedini preamps also inverted signal polarity, so the Bedini preamp/amp combinations complemented each other. Otherwise, I had to switch speaker cable polarity to correct for the inversion.
tafkasteve : now that is interesting. I really don’t have much experience with Bedini amps and certainly never came across a diode used on the emitter. I would really like to see the schematic, but it’s like finding hens’ teeth. Thanks again.
I looked through my 35 year-old notes and I have a schematic, but it is general for the 45/45 and 100/100 series amps and does not include many component IDs and values, especially for the DE series. I made a mistake in my original post, as the diodes on the output transistor emitters are MR 852's. I visited the Bedini factory in Sylmar, California (before they moved to Idaho) and John Bedini didn't explain his rationale for replacing emitter resistors with diodes. He just remarked that people would say that it couldn't be done and he had done it. He said that bias was approximately correct when the voltage across the MR 852 was around 0.63 V.
tafkasteve : I like the way the creators of exceptional products usually do so without the customary overthinking that later is applied to their creations. It’s quite funny actually: what he states is the normally bias voltage across the diode is merely the normal forward bias of a silicon diode, so he must have had a good sense of humor as well as technical creativity. Thanks for your input.
@@tafkasteve Can you please sed me Schematic and more info re Bedini 45/45 ? I have one Bedini 25/25 and 45/45...I like to Oversize Power module un Bedini 45, and need more info.
Regrads marianisimo@gmail.com
It was a very interesting careful troubleshooting that brought your research to success after having troubled about the schematic diagram which apparently was difficult to find..! any way congratulations for your accurate research for such a small diode that gave you the inspiration to look for it.
These very personalized units are always poorly documented in the net, so we have to do more research on the unit itself to assist in the fault-finding process. Also, when you do find a schematic, it does not necessarily correspond to the one you’re working on. The consistent aspect is always the quality of the sound. Amazing!
I think that those small signal diodes, that are not present in any of my two schematics of that amp, must be two back to back parallel connected diodes, for protection, between the bases of each long tail pair.
They must have been put there as an afterthought after the schematic drawn. If shorted, one of the input long tail pair transistors will have no drive.
From my back memories I remember to hear this Bedinni at a friend's system, driving QUAD ESL 63 and playing the José Afonso album "Cantigas do Maio" and it sounded really good.
Very nice video, once again, and I'm looking forward to the next one.
Yes, the sound is amazing, especially when well matched to the rest of the system, as well as the album itself.
the middle driver is the bias transistor. I talked to John and he said that he uses the same transistor as the output devices for the bias transistor so it tracks more accuratly
👍
How come there are an odd number of output transistors on the heatsink. I would expect 4 or 6. Where does number 5 come from?
If I remember correctly, there is a driver, and may also have a voltage regulator in there. It’s been a while since I did this one, so can’t remember exactly
Hello! Thank you for the great video! I have a short question. Do you know which BIAS has to be set to a Bedini BA 803? I found some posts which say 35 Ma, but is this possible? Mr. Bedini often wrote 35 Ma but said this for the BA 802, BA 803, 250/250 and so on. So could this be possible that all these amps have the BIAS set to 35 Ma? Thank you very much!
I’m afraid I don’t know at this stage. That amp has been out of my possession for quite some time now.
Beutiful handmade amp.
@12:34 since the offset between the two channels is still high, I would replace the same diode on the other channel, thinking that they may be overworked and started to leak over time.
👍
1:39 because cats are awesome!
Thank you for todays lesson:)
You’re welcome. I learnt something as well.
Very good job 👌
Sir,I 'm a owner of Bedini 25+25 amplifier too,mind I ask where can I get the schemactic to do service for it.Possible you have one to share.I am from Malaysia.Thank you anyway.
I’m afraid all I have to give is in the videos.
This is great! Love this video! I have one of these amps and need the schematic! Do you happen to have it?
It’s been a while, but if I remember correctly, none was available.
Nice repair. What value that shorted diode or zener-diode was?
saarike : mentioned in the video. It was a 1n4148 silicon diode.
Ok. Thank you! :)
hello i have one amp bedini 100/100 i need schematic, you have? thanks
I’m afraid I don’t. Sorry.
@@electronicsoldandnew , ok you can help-me? i need adjust bias, in trimmer my bedini 100/100 is 2k pot-trimmer, but one channel , with multimeter in output speakers on amp, read.. positive 100mv dc and other channel read neagtive -25mv, dc I turn the trimmer it only gives negative reading, and the channel heats ,..What can be wrong with the channel? I have not tested transistor 2N5416 AND 2N3440
sorry my english,
@@juliusc.m.5552 I have heard that there are no, "Real" schematics for these. All were handmade. All a bit different. But you can "Work it out".
I always found one of these driving a pair of LS 3/5A or a clone thereof.
All this stuff about hearing the difference in power cables is rubbish. It has been around for years. Even read that one person swore by painting the ends of the 13A fuse in the UK plug with a SPECIAL brand of marker pen. Give me a break. There was also an article in a hi fi mag in the seventies about the best cartridge in the world being carved out of a solid lump of wood by one old man who lived in Japan. Is it always April Fools day in Hi Fi world???
Benters : there’s a believer for every story. People can really get carried away.
The right power cable, "Can" make a very large difference in a rigs sound. But only if your rig "as a whole", is resolving enough to allow you to hear that difference. Contemporary physics modeling can now "partially", explain how and why. Your kids will grow up knowing why.
In fact, (We are working on the changes to the physics texts as I write this). So unless you are in point of fact, an "All knowing being"? Then you shouldn't talk in such "absolutes", as you have. Especially when it comes to subjects you know little about. But I do understand your frustration. "At least to a point". As I had a hard time accepting "Quantum Theory" as reality too. Probably as hard a time as those in the past, whom just "knew", the world was "flat"!
"Progress" is much like the "Mac Truck". Because if you insist on standing before it, when it is coming straight at you? It will simply just crush you flat beneath.
As it rolls "inevitably" forward........
As I said in response to Benters, “people can really get carried away”, either by lack of knowledge or by the Mac Truck 😊
The absolutes in the world of audio are, like religion and sexual preference, an argument that I do not partake in. I know that minds will not be swayed. I’ve heard it all: someone defending that he could hear the improved quality of an audio system while listening to it on a youtube video on his phone;
someone claiming that a good quality volume pot made no difference to the sound quality.
You see? There’s a delusion (or absolute truth) in every position, so I let everyone have their own.