BA-F1 Questions

I've finally gotten some available time, and scored the the 2nd (used, hopefully good) NMA1012 output that I needed to replace the incorrect NMA1216/NMC1216 transistors that are on one channel of this amp, so it is time to dive into a pretty complete refurbishing.

So, I have some of probably many questions to come regarding this project.

First, does anyone have any suggestions on replacements for the the 80v 220uf and 470uf caps that are on the PSU and Driver boards. The originals (and they are definitely original because there is a ton of severely deteriorated glue where they are mounted) are Nichicon, light blue case, no series marking.

Digi-Key seems to only have SMD and a couple of snap-in devices in these values; Mouser has a couple of radials- the Nichicon PM and United Chemi-con KZE, but not being the normally recommended Panasonic or Nichicon caps I'm hoping someone has some suggestions.

I guess it is also possible to slightly upgrade the voltage or capacitance values to widen the choices, but I am a little too uneducated to start guessing at suitable uprating amounts. Which actually brings me to my next question-

This amp has been used, and will be put back into a system driving some pretty uncooperative speakers- Infinity Renaissance 90's. Beyond the the 4ohm rating on the speakers and driving them from an amp rated for 8ohms, the Watkins woofers present some drastically low impedances and current demand. So although there seems to be no real consensus about replacing the main caps when people do a recap, I figure that now is the time to replace these 30 year old caps.

The direct replacement would be the Nichicon KG 63v 15000uf that only seems to be available from Michael Percy, but I am seeking the collective wisdom here about possibly upgrading to a higher capacitance and voltage to improve the power reserves. Also, I am not planning to get silly about "boutique" components, but I would like to hear any opinions about other available caps. This is a pretty rare and fantastic sounding amp, so I am interested in getting high grade parts into it and am willing spend some money to do so. There seems to be some popularity for Siemens, Philips and others that that have caps in these ranges, but sometimes it is hard to differentiate between solid, high-quality components and the exotic fringe.

And finally for today, I will replace the notorious "black flag" caps with silver micas as Echowars suggests, but I am wondering if I should also use the micas to replace the other "styrol" polystyrene caps on the driver board. In addition to the "black flags," there are also 200, 680, and 1000pf polystyrene film caps. I picked up a handful of 22pf mil-spec (I believe) CM05 Cornell Dubilier silver micas at All Electronics in Van Nuys the other day to replace one value of the "black flags." Unfortunately, they were closing so I didn't really get a chance to browse for other values, but they were inexpensive at 3/1.00, so I was thinking that if they had the higher values they might be a good candidate to replace the other styrol caps. Is it worthwhile to replace the ones that aren't the "black flags," and also, just out of curiosity, what is the difference between the construction of the "black flag" polystyrene and the polystyrene film caps. Their designation is the same in the schematic.

So, my apologies for this long-winded post, and thanks in advance for any help and suggestions. Herb

BA-F1, nice amp!

Check Digikey for 100V versions of the 220uF and 470uF caps. I was able to find them in Panasonic FC series, and both Nichicon HE and PW series, all of which are well-regarded, low impedance, long life caps. It looks to me as though the HE series are the longest-life. All are normal radials, not snap-in. 80V is an uncommon voltage rating. As long as it's higher (but not too much higher), you're fine.


Also, although there's not much info about the NMA1216's, it is my recollection from past research that they're very similar to the NMA1012's. Especially that they're the same high-bandwidth spec that is so rare today. So even though they're not exactly the same NMA1012 as originally installed, they're likely closer to it than anything else available today. Corrections on this are certainly welcome.

Also, the polystyrenes are good caps. The black flags are not styrenes. I think they're some kind of ceramic. Styrenes have very low dielectric absorption and are very stable over time. They're sensitive to heat, so be careful. Certainly silver micas are good replacement caps for the black flags (used for transistor stability) but they're inferior for signal path applications, as these likely are. I have never found a reason to replace them with anything more modern.

Best,
Collin

HDJR808 said:

I've finally gotten some available time, and scored the the 2nd (used, hopefully good) NMA1012 output that I needed to replace the incorrect NMA1216/NMC1216 transistors that are on one channel of this amp, Herb

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NMA/NMC1216 are substitutes for NMA/NMC1012

I thought I had read that the 2sc2607/2sa1116 pair was the Sansui recommendation to replace the 1012's, but I also seem to recall that the nma1216/nmc1216 pair was originally fitted to the AU-819, so they do make sense to be a close match, since the BA-F1 and AU-919 had the 1012's in common.

My guess on my amp is that the black flags went on the one driver board, and took out the original ouputs and someone put in the 1216's. Two of the black flags have been replaced with polystyrene film caps, and also a multijunction diode was replaced, so I guess there was some collateral damage. I can't say that I can tell a difference between the channels, but I would like to make it as original as possible, upgrading where it is beneficial. Last year I picked up NOS (1) nma1012 and (4) nmc1012, and just recently picked up a used nma1012, so I now have enough to make that one channel correct.

So, a bump up to 100v on the 220uf and 470uf caps would be reasonable? What dictates what would be too much of a bump? I guess this question also relates to my original question about uprating the main caps.

I am still unclear about exactly what the "black flags" are. The schematic identifies them with the symbol for a styrol (polystyrene) and they are also listed as such in the parts list for the board. But they are definitely not the same part as the other polystyrene caps on the board, which are identified exactly the same way.

The schematic in the service manual for the BA-F1 (or at least my copy of it) doesn't indicate the signal and feedback paths, and I don't understand nearly enough to figure it out, so I can't say whether the other polystyrene (not black flag) caps on the driver board are in the signal path. I'll try and post some of the schematic to see if anyone can identify if they are or not. And maybe if some knowledgeable person is really inspired, they could decipher the signal path for me.

Thanks- Herb

HDJR808 said:

I thought I had read that the 2sc2607/2sa1116 pair was the Sansui recommendation to replace the 1012's, but I also seem to recall that the nma1216/nmc1216 pair was originally fitted to the AU-819, so they do make sense to be a close match, since the BA-F1 and AU-919 had the 1012's in common.

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Yes you are right you have read about 2SC2607/2SA1116.
Recommendation for replacement is valid for AU-919 Export Model
see http://audiokarma.org/forums/attachment.php?attachmentid=20160&d=1152558556

HDJR808 said:

So, a bump up to 100v on the 220uf and 470uf caps would be reasonable? What dictates what would be too much of a bump? I guess this question also relates to my original question about uprating the main caps.

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It's only a 25% jump in working voltage. As working voltage goes up, so goes ESR/Impedance. These caps are by far better than what was originally installed in terms of impedance performance, according to the gurus here. Usually people go up to the next common voltage group. Beside,s your options for exactly the same part are limited, as you have found. The capacitance is the important thing to get exactly right, if possible.

HDJR808 said:

The schematic in the service manual for the BA-F1 (or at least my copy of it) doesn't indicate the signal and feedback paths, and I don't understand nearly enough to figure it out, so I can't say whether the other polystyrene (not black flag) caps on the driver board are in the signal path.

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Styrenes, ceramics, and silver micas are the kinds of caps that are available in very small values (low pF). It seems like you are able to locate which of the caps are black flags, based on their appearance as such. There's no way a styrene cap looks like a "black flag," they are cylindrical. Looking at the stock channel, establish a drawing of the stock black flag usage. Compare the value of the stryrenes that replaced the black flags (on the non-stock channel) for accuracy to the stock channel...if they're ok, you could leave them alone. Replace the remaining black flags with silver micas. If you're really into parity you could go through all the black flag locations and replace them uniformly with silver micas. The 919 sm called for ceramics in these locations.

Collin

Any word on the large PS caps?

No suggestions yet on the large PS caps, but following your logic on the 80v caps, a bump up from 63v would also be reasonable on the large caps. I'm still unclear on uprating the capacitance though. I've read that it can help the power reserves for large current demand, but also that there can be complications from increased inrush from the rectifiers. I'm trying to make sure that I tread a fine line- not trying to be smarter than the original designers, but still take advantage of incremental improvements based upon the collective wisdom in these forums.

I do intend to replace all the black flag caps, as echowars has advised for all occurences, including putting silver micas where the replacement polystyrenes have been fitted. Otherwise, I will leave the original polystyrenes.

I'm still curious about the part designations on the schematic- the black flags are definitely identified as polystyrenes. I'll post some clips from the schematic when I get a chance; right now I'm trying to figure out what I've screwed up in my c2101 that I've been refurbishing- which is likely to generate another thread.

Thanks-
Herb

Michael Percy Audio sells Nichicon KG Gold 15,000µf 63V caps that are perfect for the BA-F1 (essentially brand-new caps that are the same as the originals). But not cheap.

Thanks Echowars, I had seen the KG's at Michael Percy. I think they even go on special every once in a while, and they are definitely the prime candidate.

But I do wonder about the benefits/pitfalls of uprating these caps. My speakers are known to perform best with a lot of current, and the BA-F1 is really not the best match for them, but the combo just sounds great at low to moderate levels. I just fear clipping if I push it, and those emims/emits are scarce.

Thanks-

Herb

Uprating? If you mean higher voltage, there's no gain to be had here, and the caps will work better if used closer to their rated voltage, so the 63V caps are the way to go.

If you mean higher capacitance, consider that these 15,000µf caps are already a nice degree of overkill for a 100WPC amp, and the 'F1 does not have any sort of soft-start to reduce power-up stress to the power switch and rectifiers. In other words, the amp is already overbuilt WRT the energy available from the power supply. Stick with the stock values.

So, for the 80v caps the same would apply? Probably OK to go to the next higher voltage, but performance is optimal closer to the original 80 volts?

Any opinion on the Nichicon PM series? I know you typically recommend other Nichicon series or the Panasonics, but the PM series does include the values that I need.

Also, just because I waste too much time wondering about these kind of things :scratch2:, I am attaching some jpegs regarding the service manual description of the "black flag" caps in this amp.

As can be seen in the parts list, both the very small (2pf,3pf etc.) caps which are the black flags and the slightly larger (200pf, 100pf) caps are designated as "P.C." caps. There is no abbreviation list in the BAF1 manual, but the attached list from the B2101 manual shows the P.C. as a Polystyrene Cap.

Also, as seen in the schematic, both the C10 and C11 caps have the "Styrol" cap symbol, seen in the legend attachment, and as seen in the photo, one is a black flag, one is actually a polystyrene.

None of this actually matters- I'm going to replace the black flags with silver micas. I just am curious about exactly what kind of cap those black flags are and why they would be labeled as styrol caps. Despite the reputation for inaccuracies in the these manuals, I'm surprised that there would be such consistency in the mislabeling.

Thanks- Herb

HDJR808 said:

So, for the 80v caps the same would apply? Probably OK to go to the next higher voltage, but performance is optimal closer to the original 80 volts? Any opinion on the Nichicon PM series? I know you typically recommend other Nichicon series or the Panasonics, but the PM series does include the values that I need.

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Honestly, I can't sit and blindly go over the schematic to figure out which caps you're talking about. My previous post was specifically referring to the four large power supply caps. For the smaller radial lead caps, modern values skip the 80V range, so the jump is from 63V to 100V. If you need an 80V cap, use a 100V cap. My selection process can be distilled as this: http://audiokarma.org/forums/showpost.php?p=2526347&postcount=12

Also, just because I waste too much time wondering about these kind of things :scratch2:, I am attaching some jpegs regarding the service manual description of the "black flag" caps in this amp.

As can be seen in the parts list, both the very small (2pf,3pf etc.) caps which are the black flags and the slightly larger (200pf, 100pf) caps are designated as "P.C." caps. There is no abbreviation list in the BAF1 manual, but the attached list from the B2101 manual shows the P.C. as a Polystyrene Cap.

Also, as seen in the schematic, both the C10 and C11 caps have the "Styrol" cap symbol, seen in the legend attachment, and as seen in the photo, one is a black flag, one is actually a polystyrene.

None of this actually matters- I'm going to replace the black flags with silver micas. I just am curious about exactly what kind of cap those black flags are and why they would be labeled as styrol caps. Despite the reputation for inaccuracies in the these manuals, I'm surprised that there would be such consistency in the mislabeling.

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Your theshold for surprise needs to be raised a bit...you're working on a Sansui. As far as the Black Flag caps, I suspect that they are a stacked ceramic. The 'Styrol', or polystyrene, are pretty reliable, and rarely need to be replaced. They are sensitive to heat, so treat them nicely if you have some need to remove them from the board and plan to reinstall them.

EchoWars said:

Your theshold for surprise needs to be raised a bit...you're working on a Sansui.

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:lmao:

Honestly, I can't sit and blindly go over the schematic to figure out which caps you're talking about. My previous post was specifically referring to the four large power supply caps. For the smaller radial lead caps, modern values skip the 80V range, so the jump is from 63V to 100V. If you need an 80V cap, use a 100V cap. My selection process can be distilled as this: http://audiokarma.org/forums/showpos...7&postcount=12

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Sorry, didn't mean to suggest that at all. It was only specific in that it referred back to the 80v 220uf and 470uf caps mentioned in my original post. It was really a general question following the logic that pertained to maintaining the voltage in the large can caps; whether to use the stock voltage in cap series (PM) that I have not seen anyone in the forums refer to, or jump up a range and go for something like the Panasonic FC and FM.

If the advisability of either maintaining the stock voltage or moving up a range is dictated by the specifics of the circuit, I was not aware, and was not asking for individual analysis. No that I would be able to follow it anyway

Your theshold for surprise needs to be raised a bit...

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Hey, I work in the movie business, so I can assure you that I am not surprised by anything. :sigh:

I guess I should have said that it seemed impressive that Sansui could have so consistently maintained an inaccuracy.

Thanks for everybody's help- Herb

Gotcha. I hope that the explanation that 80V caps have pretty much disappeared in the radial leaded family clears things up. Replacing with the original voltage is generally preferred, but in some cases that isn't an option. Go from 80V to 100V for these small caps and don't worry about it.