I have a couple of Yamaha B-2’s that I use for bi-amping. Mods so far are recapping all electrolytics, new gold RCA jacks wired directly to the driver board (bypassing all front volume controls and switches), power supply caps bypassed w/polycarbonates, hardwired audiophile power cord, replaced speaker protection relays and installed new gold 5-way speaker binding posts. The power supply section uses Toshiba dual diodes S5151 & S5151R as a rectifier bridge. From what I can gather (can’t actually find a spec sheet), these are 200volt 5amp devices. Does anyone know if that is correct of sounds reasonable? It doesn’t appear that the fact they are ‘dual diodes’ means anything except maybe convenience of packaging and assembly. I’m planning to replace them with FRED’s spec’d to handle that voltage and amperage, is that OK? I want to be sure as I can't afford to toast the unobtainable VFET's.
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Yamaha B2-S5151 Diode replacement with FRED's
- Thread starter endeeinn
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Suggest you ask EchoWars directly on this.
Do you have any pic's of your work that you can post? That is almost exactly what I have planned for my B-2 amps. What do you think of your results thus far? That is problem with most of the amps of this vintage. Way too busy. Especially the B-1 with its 5 speaker channels, etc.
Do you have any pic's of your work that you can post? That is almost exactly what I have planned for my B-2 amps. What do you think of your results thus far? That is problem with most of the amps of this vintage. Way too busy. Especially the B-1 with its 5 speaker channels, etc.
get some pix next time its open
Don't have any pictures now but will take some next time I dive into it. There is a big difference removing the switches and volume controls as they were always dirty or not making good connections. Direct connection to vampire RCA jacks via Belden 89259. I disconnected power to one output relay as I only use one set of speaker terminals and to be sure there was suffiecent juice to the one left working. The next big difference (which I didn't expect or believe) was replacing the speaker protection relay, the old one was tarnished and discolored and the metal looked like it had it. The recap did some but was more for peace of mind, however, the polycarbonate by-pass caps was noticeable. The binding posts just provide positive and consistant connections. Somewhere I read the fuses get "brittle" over time ... don't know if that's real or not but for $2 each amp I changed all the fuses, if they last another 25 years I'll get my money's worth. Re-flowed the solder where it looked like it needed it ... someday .. maybe I'll re-flow and rewire all, but now I'm just listening.
Don't have any pictures now but will take some next time I dive into it. There is a big difference removing the switches and volume controls as they were always dirty or not making good connections. Direct connection to vampire RCA jacks via Belden 89259. I disconnected power to one output relay as I only use one set of speaker terminals and to be sure there was suffiecent juice to the one left working. The next big difference (which I didn't expect or believe) was replacing the speaker protection relay, the old one was tarnished and discolored and the metal looked like it had it. The recap did some but was more for peace of mind, however, the polycarbonate by-pass caps was noticeable. The binding posts just provide positive and consistant connections. Somewhere I read the fuses get "brittle" over time ... don't know if that's real or not but for $2 each amp I changed all the fuses, if they last another 25 years I'll get my money's worth. Re-flowed the solder where it looked like it needed it ... someday .. maybe I'll re-flow and rewire all, but now I'm just listening.
When the stock switches are clean and working well, there's not a lot to gain by bypassing them. I'm all for sensible modifications, but the B-2 is a rather special piece and I don't think I'd do what you have. But if you like it, my opinion means squat.
The dual diodes are just that...here's the schematic.
There are some FRED's in a bridge package. Might take a look at some that are rated for 10 to 20 amps, since you won't be able to fit heatsinking onto them.
The dual diodes are just that...here's the schematic.
There are some FRED's in a bridge package. Might take a look at some that are rated for 10 to 20 amps, since you won't be able to fit heatsinking onto them.
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Nakdoc
nakamichi spoken here
I agree with EW. There are certain sacred vintage pieces, and this is one of them. Mods are for mediocre gear that has room for sonic improvement IMO. I cannot, however, quibble with the polycarbonate bypass caps, as this process both sounds good and is reversable. I know the speaker jacks are not as good as 5 ways, but I hope you found a way to mount the posts without drilling the chassis.
rulerboyz
AK Member
I think that Nakdoc brings up an interesting concept: "mods are for mediocre gear". I think that the desire to modify something could be an indication that you are unhappy with the way it sounds. When you realize that you've programmed Partsconnexion into your speeddial and have become trigger happy, it could be time to consider investing the money instead on higher end equipment. Usually there is some tangible reason why you are not completely satisfied with the way a piece of gear sounds, such as "not enough detail in the treble from the phono section". If your main interest is listening to vinyl, perhaps a standalone phono preamp could be worth a try?
I am kind of curious to find out how much better $30/pair RCA jacks can make it sound?
I am kind of curious to find out how much better $30/pair RCA jacks can make it sound?
I happen to agree with endeeinn. While the B-2 is the best amp I've owned/listened to, it is too busy. Switches and pots on the input side and terrible speaker terminals on the output. I will eventually be doing exactly the same thing (perhaps not the diodes, but certainly taking all the useless parts out of the signal path) to my B-2 amps.
The speaker terminals on the B-2 are the pits. They only accept skinny little wires (14-16 gauge) or pins. I drilled mine out (the plastic) so could fit some 12 gauge wire in them. But, they still suck and having modern, gold-plated terminals that allow one to lock in spades or banana-plugs will make them much easier to use and will allow much greater flexibility in choice of speaker cables.
endeeinn - as soon as I can get some time I'll be having some plastic blocks machined for the new speaker terminals. They will be bolt-in replacements. Won't be next week or two, but eventually.
The speaker terminals on the B-2 are the pits. They only accept skinny little wires (14-16 gauge) or pins. I drilled mine out (the plastic) so could fit some 12 gauge wire in them. But, they still suck and having modern, gold-plated terminals that allow one to lock in spades or banana-plugs will make them much easier to use and will allow much greater flexibility in choice of speaker cables.
endeeinn - as soon as I can get some time I'll be having some plastic blocks machined for the new speaker terminals. They will be bolt-in replacements. Won't be next week or two, but eventually.
Exactly. The block will be predrilled for something like the WBT (I was sort of thinking Cardas, but WBT would also work well). And it would also be pre-drilled with countersunk hole to use the original mounting screw holes that are located between the pairs of stock speaker terminals. As stated, should be a bolt-in replacement that consists of making four (4) solder connections - one per terminal. I'm undecided on the exact layout. I can probably have them predrilled for the two sets of terminals, like the stock amp has. However, I will probably has them predrilled with only four (4) holes for my use and use one with no holes drilled (a blank) to replace the speaker terminals for the second set of speakers, for which I have no use. I'm thinking that the block for the terminals will be fairly thick (~0.5") and the blank will be about half that.nbourbaki said:
Anyone who might be interested in these blocks should send me a PM with your interest. Am sure we will get a much better price if we order as many as possible at the start.
The FRED's are in and sound great!
Completed replacing the PS diodes with FREDs in all three of my B2's and the results are very noticeable. The only words I can use are "detail" and "delicate", not that I didn't hear detail before but now the 'before detail' is more mainstream and the 'delicacy' surrounding that detail has appeared. My opinion, I'm happy and believe it was worth it. I used 600v/30A Fairchild 'Stealth' diodes (Fairchild's term for FRED) and they run stone cold without a hint of heat. This is what they look like, got indivduals and not a bridge so they fit in the original PCB holes.
The picture also shows some of the other mods - new caps, PS bypass caps and new protection relay. Since I only use one set of speakers I disconnected the 2nd relay so the 12v supply only needs hold one relay in.
This shows the muffin fan powered by a walwart with dropping resistors so the fan just bearly turns and runs quite. The fan is mounted in place of the existing B2 rear plate. Also shown are the 5-way binding posts which use the B2 speaker plate for mounting.
This is a picture of the rear showing the Vampire RCA's, muffin fan, 5-ways and HD power cord. The front & rear speaker/meter switches are removed from the circuit and the RCA's are direct connected to the driver boards shown below.
Also new 10-turn adjusting pots have been added to the driver board and as a result I'm able to get idling current and DC balance on all 3 amps to 40mv and 0mv respectively. For the purists, all modifications can be undone as no extra hole were drilled on parts distroyed. The only exception is the HD power cord where the inlet hole had to be enlarged.
Completed replacing the PS diodes with FREDs in all three of my B2's and the results are very noticeable. The only words I can use are "detail" and "delicate", not that I didn't hear detail before but now the 'before detail' is more mainstream and the 'delicacy' surrounding that detail has appeared. My opinion, I'm happy and believe it was worth it. I used 600v/30A Fairchild 'Stealth' diodes (Fairchild's term for FRED) and they run stone cold without a hint of heat. This is what they look like, got indivduals and not a bridge so they fit in the original PCB holes.
The picture also shows some of the other mods - new caps, PS bypass caps and new protection relay. Since I only use one set of speakers I disconnected the 2nd relay so the 12v supply only needs hold one relay in.
This shows the muffin fan powered by a walwart with dropping resistors so the fan just bearly turns and runs quite. The fan is mounted in place of the existing B2 rear plate. Also shown are the 5-way binding posts which use the B2 speaker plate for mounting.
This is a picture of the rear showing the Vampire RCA's, muffin fan, 5-ways and HD power cord. The front & rear speaker/meter switches are removed from the circuit and the RCA's are direct connected to the driver boards shown below.
Also new 10-turn adjusting pots have been added to the driver board and as a result I'm able to get idling current and DC balance on all 3 amps to 40mv and 0mv respectively. For the purists, all modifications can be undone as no extra hole were drilled on parts distroyed. The only exception is the HD power cord where the inlet hole had to be enlarged.
Excellent work! Thanks for the pic's and details on the diodes. Am a few months behind you. I'll be using Cardas RCAs and WBT terminals.
OK......after doing quite a bit of looking around and trying to decide exactly which binding posts I want to use in the back of my B-2s, I have pretty much decided on these: http://www.cardas.com/content.php?area=oem&content_id=10&pagestring=Patented+Binding+Posts I like their design better than the WBT and they will fit in the space better than the WBT. Am awaiting a reply from Cardas with info on exact dimensions, and then will get the machined plastic binding post mounting block drawn up for fabrication. My plan is to do about the same as endeeinn. Remove the extraneous controls, add the FREDs (have all ready been recapped) and better RCAs http://www.cardas.com/content.php?a...Female RCAs+(closeup)&content_id=6&part_id=35 with the speaker terminals shown above.
I will be ordering the parts this week for mine. Will order the machined plastic bits for anyone who is interested at the same time. I buy my Cardas parts through Welborne Labs.
I will be ordering the parts this week for mine. Will order the machined plastic bits for anyone who is interested at the same time. I buy my Cardas parts through Welborne Labs.
energyandair
Active Member
I was thinking of leaving the stock binding posts in place and mounting modern terminals on the removable blank plate to the side. This looks easy and completely reversible.
David
David
energyandair
Active Member
Have you had a chance to A-B the modified B-2 before and after with an unmodified one that initially sounded the same, or are you depending on memory of how it sounded before?endeeinn said:
Have you had a chance to A-B it with modern high end amps, and if so, how well did it match up with some well known names?
David
So will the change I am planning. Will use the original screw holes from removing the stock terminals to mount the new terminal block. Will use the original holes to feed the signal leads and back of the new binding posts. Am planning to remove both sets of speaker terminals and replace with a single set, putting a blank plate over the holes left by the removal of the second set of terminals, which I would never use.energyandair said:
I also notice that you are asking about the sound before and after. While I think there is a sound improvement after with just the recap done thus far in my B-2, the primary reason I will be making the mod's, such as up-grading the FREDs, is reliability. I have listened to many more modern amps and like the sound of the B-2 the best. And that was when it was stock. Did an A/B listening test with an MX-1000 I had at the time and after about two weeks of comparison I sold the MX-1000, which was a much more powerful amp. I have also done a similar A/B with a Yamaha CA-2010 and Sony TA-5650 (also a VFET amp), both recapped by EW, as was my B-2. Again, the B-2 simply has a bit more 'magic' than does the others.
The Cardas website just calls them the "Patented Binding Post". On the Welborne Labs they are the part # CPBRS. The RCA is part #GRFA.nbourbaki said:
nbourbaki
Active Member
I was looking for something like the Cardas CCGRS. I was going to use both outputs and use WBT locking bananas. I like being able to A/B speakers with the B-2. I'm afraid there wouldn't be enough room for two sets of spades. I do like the positive contact you get from spades.
Yes......it may be too tight if both outputs are on the same block. As I plan on doing the 'full endeeinn', I will mount one of the binding posts where the lower terminals are now and the other where the upper terminals are located.
Again, the only 'hacking' I envision is a larger hole where I will swap out the power cord for something a bit more substantial. Like Sony of the same era, they are really crappy AC cords. But......at least they aren't brown.
EDIT: Here is a less expensive place to buy the Cardas parts. http://www.diycable.com/main/default.php?cPath=26_44_49&Cid=d9ecbf41e93d3b0941ec3df26686a3b5
EDIT 2: Everything (FREDs) but the plastic block and Cardas parts are on order. Cardas has always been very good at responding to any questions I've had in the past, so expect to hear back from them early in the week.
Again, the only 'hacking' I envision is a larger hole where I will swap out the power cord for something a bit more substantial. Like Sony of the same era, they are really crappy AC cords. But......at least they aren't brown.
EDIT: Here is a less expensive place to buy the Cardas parts. http://www.diycable.com/main/default.php?cPath=26_44_49&Cid=d9ecbf41e93d3b0941ec3df26686a3b5
EDIT 2: Everything (FREDs) but the plastic block and Cardas parts are on order. Cardas has always been very good at responding to any questions I've had in the past, so expect to hear back from them early in the week.