"New" Sony TA-N7B, need advice please

Having been infected with the Vfet bug some time ago, starting with refurbishing a Sony TA-5650 (with much advice from Echowars), I've been on the lookout for a TA-N7B. I finally purchased one a few weeks ago and it arrived today. Thankfully it was well packed and arrived safely . Except for a few minor cosmetic defects she is clean and appears unmolested. It looks to be an early model having serial #500064.

Upon arrival I observed that it is a 220v model with an IEC plug adapter. The U.S. seller ommited this information in his ad :thumbsdn:. I don't see this as a major hurdle, but I would appreciate suggestions on the best way to deliver power to it since I'm in the USA where 120v is the norm. Off the top of my head it seems I have a few options:

1. Use the schematic to wire it as shown for the USA/canadian model (I have the manual)

2. Buy a step-up transfomer (what brand/type would you recommend?)

3. Run a 220v line to where I want to use the amp. I am planning on some electical upgrades to my home soon anyway (new main service panel, extra outlets...)

Also, can I just connect a 220v electric dryer cord/plug to an IEC termination at the other end and plug the amp in to my 220v dryer outlet for testing? BTW, it does show 50/60 Hz on the back (photo).

Other things of concern are:

1. The fusible resistors which other members have mentioned are prone to drift in value on this amp. I want to replace these. Any recommendation as to brand/type?

2. I see in the schematic they show some double diodes. Are these like the ones in earlier Sony Vfet models that are prone to failure? I did not look yet to see if they appear to be the same.

3. I plan on recapping the amp with panasonic FM and/or FC capacitors. Are there any good replacements for the main filter caps out there that one of you has used? I don't know if I'll replace those yet, but would like to know if any of you has experience with a good substitute

4. I see the Vfet devices use an insulator that is soft like a modern Bergquist Kapton instead of Mica and grease. Should I leave these as is or would it be beneficial to switch to the Kapton?

I look forward to hearing from any other Vfet enthusiasts and will be happy to post photos as I progress. Please see an initial arrival set of pics below!

Congrats on finding one of these rarities!

I wouldn't switch it on until it's been given some proper care/maintenance. I used mine a couple of times after getting it, failing to notice one of the big caps had burst...

Not sure if 220V overthere is any different than the 230V we have here in Europe, so you might want to play it safe and use a decent step-up transformer ?

I replaced a whole bunch of stuff in mine (all credits go to Mirko Essling for his awesome support in this matter). All caps, big (Nippon Chemicon 27000uF) and small (Panasonic FM/FC), some diodes, some resistors (Cornell Dubilier, Vishay), pots (Bourne), all head pads (Bergquist Kapton), bipolar transistors (On Semiconductor), and every single fusible resistor (Phoenix) were replaced.

The foamy bits under the pcb's were also replaced as they had turned into a messy conductive crap that destroyed a couple of resistors in the process.

Later I also upgraded the crappy speaker clip thingies to decent binding posts.

It's been playing sweetly ever since (about three years ago now I think)

Thank You Stoffie. I appreciate your response. Having searched for posts and threads on Vfet gear I've certainly seen your enthusiasm for the TA-N7B.

Regarding available power here in the US, we run larger electrical appliances (stoves, dryers...) on 240v. I thought it was 220v, but I beleive that is incorrect. This is accomplished in the main juntion box in most homes by using two "legs" of 120v to create a 240v circuit. I'm not an electrician, but this is my basic understanding. We also use 60Hz and I think Europe uses 50Hz, but the unit is labeled for both. It is also my understanding from some posts that a 10% variation in voltage should not be a problem. I am hoping to define what is the best way to deliver power to this amp given my situatiuon with 120v or 240v available. I will be studying more over the holiday weekend.

Thanks for outlining some of the parts and the brands you used. I found a post where Unda Maris states the On Semi Bi-Polars to use are: D44H and D45H. Are these the ones you used? Digikey has them. However they come in 60v and 80v configurations. So far it looks like the original 2SC1173 (NPN) is 80v. Can anyone confirm? once again, I will continue to investigate.

When you say "some diodes" do you have a record of which ones? Do you have any order sheets from when you bought the parts that you could scan and share? If you have any record (numbers on the schematic) of the specific diodes and resistors (that aren't fusible ones) that were replaced it would be appreciated. I would like to make a record here for others who may follow in our footsteps so that these rare amps can be kept alive.

Thanks again for you advice. I'm glad your amp is restored and working properly. I will heed your warnings in hope that I'll soon be enjoying a TA-N7B too! :thmbsp:

This has some interesting info on how US 240V and European 230V are wired a bit differently and what to look out for. Apparently it has mostly to do with how the neutral is connected differently in both systems.

If you PM me your email addy, I'll send you some more info on the components, I do have a list handy with references to the service manual.

Thanks for the link Stoffie! That is very good information. I will PM you shortly. I appreciate you sharing your infomation.

You're welcome, keep us posted on progress!

I hope everyone had a great holiday.

I've been looking up some of the parts for the TA-N7B, having already received a great "leg-up" from Stoffie, and am not sure of a couple things and can't find any main filter caps for this application.

1. For the DC balance and DC bias variable resistors (pots), part numbers RV101, RV201,RV102 and RV202, I am looking for Bourns replacements of the cermet type. Can anyone recommend the proper series? The manual doesn't state the watt rating. My assumption would be 1/2w? How many turns would you recommend? Here's the one I'm considering for RV101 and RV201: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3339P-101LF-ND . Is this a good canidate or are there better options?

2. I am also curious about the double diodes at position D101,201,102 and 202. They are labeled a MV12N diode, but look very similar to the double diodes that were in my TA-5650 that are known to fail. The ones in the TA-5650 are labeled as VD1221. Are the MV12N's reliable or should they be replaced like the VD1221's with a series of 1N4148's like in the TA-5650. Any experience here would be appreciated.

3. I'm having trouble finding replacements for the main filter caps. The originals are 22000uf 71v, 50mm diameter X 100mm with screw terminals. I've looked for 22000uf 80v and 27000uf 80v, but none of the ushual sources have any of either in stock. Anyone know where I can source these?

Thank You

The big cans can be problematic to find, especially if you only need four. Mine were ordered in bulk, and the spare ones I have were also sourced as a 20+ order (neither order was done by me).

If you really can't find any, I might be willing to part with mine to help out. Maybe Echowars here can point you in the right direction for most of your questions ?

Re-Cap has begun

Just a quick update. I've ordered and received all my parts from Digikey.

First I replaced all of the original silicone insulators for the Vfets and the TO-220 devices mounted on the heatsinks with Bergquist Kapton/Silicone ones. I had used these on my TA-5650 and TAN-8550 previously. Although they are expensive, I think they are worth the cost for better heat transfer and less mess (no "grease").

Next I replaced the original RCA input connectors and the spring type speaker connectors. I didn't get too fancy here (no WBT or Cardas). I used decent quality ones (read: reasonably priced) from Parts Express. I've used them before and found them to be an extremely good value. I believe they are brass that is 24k gold plated. They are definitely an improvement over the ridiculously cheap ones supplied by Sony. They won't oxidize and these binding posts will give a much better bite on some decent quality cables.

Before the purists hang me, I do appreciate the historical aspect of this amp and saved the originals parts which could be put back. I did no drilling, enlarging of holes in the chassis or anything that couldn't be put back to the original configuration. When I got the amp one of the spring clips for the speakers was not gripping properly and this is what prompted me to make the inprovements. The new RCA's just mounted in the holes for the originals. For the binding posts I had to make some custom mounting plates out of black ABS plastic that matched the chassis holes. I "sandwiched" the chassis between two plates (one of which had a "filler" on the back to take up the space of the original mounting hole) to which I mounted the binding posts. The screws that hold them in place go through the original opening for the spring clip assembly, so that no modifications had to be made to the opening or any holes drilled for mounting the new binding post assembly. See the photo below.

Now I am in the middle of re-capping, replacing all of the fusible resistors and replacing the original Alps adjustment pots with Bourns multi-turn cermet types. See the photos below which show the left channel (now finished) and the right channel which I've yet to start.

I've got some more questions, but I'll save them for now. If anyone could help on the previous diode question I'd be grateful.

Stoffie: Thanks for your support. I think I may have found a large capacitor that I can use to replace the main filter caps. I'll post about it next time.

Please, any other TA-N7(B) owners out there? Your input would be most welcome. :yes:

Nice work Jeff! Your binding posts look very similar to mine, and I pretty much did what you did! RCA's are exactly the same too

I think you'll be hard pushed to find any other TA-N7B owners on here (there are a couple, also an ex-owner, but haven't posted on here in quite some time). I could up their emails if you wanted though

Stoffie said:

Nice work Jeff! Your binding posts look very similar to mine, and I pretty much did what you did! RCA's are exactly the same too

I think you'll be hard pushed to find any other TA-N7B owners on here (there are a couple, also an ex-owner, but haven't posted on here in quite some time). I could up their emails if you wanted though

Click to expand...

Yes well done Jeff! I also used Mirko's kit on the advice of Stoffie to rebuild/update my N7 done by Andy Reynolds who did a great job and like Stoffie he photographed the whole procedure. He subsequently replaced the RCA's and speaker outlets and after a weeks burn in it sounds great. Before the rebuild I was going to sell the amp, it did not sound as good as the other amp's I had been using and now I'm driving the top cabinet biwired to tweeter and midrange. Well worth the effort and increasing it's value and saleability!

Nice of you gents in the Vfet camp to chime in. Thanks for the encouragement!

I hope you are right about the diodes Vint Age. I'm glad to hear you are enjoying your TA-N7B Fitzy. It's encouraging to hear your story. Thanks to Stoffie's kind help and Mirko's knowledge, I hope to be enjoying musical bliss in 2011 .

Stoffie, Fitzy: did either of you replace the diodes I asked about? I mentioned that I found replacements for the large filter caps. They are here: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=338-2039-ND. They are "snap-in", but have two lugs for positive and negative. I plan to bridge the two with a piece of high purity copper which I will drill and tap in the middle to make screw mounts. The dimensions are very close to the originals in size at 50mm X 105mm and they are rated at 3000 Hrs @ 105°C!

I'll have more tomorrow. I've got to get to bed. Thanks Again.

OK, so tomorrow turned into next week! Last week ended up leaving little time for Vfet fun.

I did get around to re-capping the R-CH Power Amp Board and replacing all of its fusible resistors Sunday and last night. Now I'm back to my question(s) I wanted to ask a week ago. It concerns the adjustable resistors and, mainly, RV102 and RV202. These are for the DC Bias.

For better reliabilty and easier adjustability I bought Bourns cermet series 3339P 1/2 watt types. The original Alps ones were rated to 22K. I purchased Bourns that were rated to 20K. Before removal (in circuit) RV102 measured 11.42K ohms from the wiper to one leg. The other leg is connected to the wiper through the PCB.

NOTE: RV102 and RV202 were NOT connected to the PCB as shown in the manual's diagram! I'm guessing this may not matter as one leg is connected to the wiper through the PCB, but this caught me a little off guard. I did notice that on top of the board itself the print for the installer showed it diagramed as it was installed.

When I installed the Bourns replacement for RV102 the most I could get was 10.17K ohms (in circuit). I checked the Alps that I removed and it measured over 22K ohms and was, obviously, "maxed out" to that side. I have not removed RV202 yet, but it measures 11.13K, so I assume it is nearly maxed to one side as well.

My first thought is that I just need to get the next higher Bourns pots that go to 50K ohms, but I wondered why Sony would use a 22K unit that would have to be adjusted to its max (or near so). In case you are wondering if they were adjusted after they left the factory, the evidence would say "no". The factory applied, white paint from the top of the pot to the PCB was intact and had no sign of ever having been disturbed. The inside of the amp showed no signs of having been disturbed ever. Do any of you TA-N7B owners (Service Techs) remember anything about the measurements of these two adjustment pots when you refurbished yours? Am I worrying unnecesarily. Should I just get the 50K ohm units set them to equal the Alps unit readings and move on?

On the RV101 and RV201 adjustable resistors (DC Balance) the originals were rated at 100 ohms and the Bourns replacements are as well. However the Bourns, as tested, have less range than the original Alps units. When I try to match the original setting it will match on one side but be low on the other. Should I split the difference or set it accurately to one side in particular for the initial set-up?

Maybe I'm being too anal, but I don't want to take any chances with the Vfets . As always, any help is appreciated.

Long time, no post. I did figure out the potentiometer solution and just stepped up to the next one in the range (50k) and all is well. I've been enjoying this amp tremendously. First through Yamaha NS-1000's and Now through 1964 Bozak B-302a's (upgraded from B-300's with the B-209B mid).

So far I've used a step-up transformer to supply it with 220V and it has worked just fine. I'm ready to do my final part of the restoration now by installing new main filter caps. I wanted to wait until everything checked out "OK" before I spent nearly $100.00 on these caps. It's hard to find replacements for the ones in this amp. Especially if you are only buying four. However, I did find these at Digikey: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=338-2039-ND. The originals are 21,000uf - 71V. The ones from Digikey are 27,000uf - 80v. These should work just fine. A key factor is that they are the exact same dimensions as the originals (50mm dia. X 105mm long).

The biggest obstacle to overcome now is that these are "snap-in" types whereas the originals have screw terminals. The new snap-ins have two pins for positive, two for negative and one mounting pin. I'm going to make my own "screw terminals" by bridging each set of pins with a 1/8" thick piece of copper and tapping a hole in the center to receive the original mounting screws (4mm X .70). In order to position them correctly I measured the originals mounted in place (drain/discharge them first!) to find the distance between the two inner screw terminals that are joined by a copper bridge. This way they will install exactly as the originals.

See the photo below. I made an 8mm spacer to place between the two capacitors that will be joined by the copper bridge when installed. This is the spacing between them when mounted in the TA-N7B. Then I taped them together to hold the positioning/spacing. Now I was ready to place my homemade copper terminals on the capacitors pins such that when installed there would be 52mm between the tapped holes just like the originals to match the mounting holes in the copper bridge. The outer terminals won't be critical in positioning, but these inner two inner ones must be done this way to use the original copper "bridge" that connects each pair of filter caps when installed. If anyone wants more details on this process I'd be glad to help.

Once I get them installed I would like to "adjust the bias current slightly above the value Sony recommends" as (Mirko) "Unda Maris" recommends here: http://www.audiokarma.org/forums/showthread.php?t=208592 in post #9. Sony recommends 30-70mv. Stoffie (anyone) do you know how far above 70mv Mirko recommends?

Nice going Jeff! Glad you are enjoying one of Sony's finest, at last

I don't really remember how much I set mine for, haven't checked in a few years. I do know I set it for at least 70mV. Mirko is an elusive man, but you could try to contact him to ask for advice

Hi Stoffie,

Nice to hear from you. I'll try a PM to Mirko. Meanwhile, I installed the new main caps last night. It got late so I didn't turn it on and set the bias yet. The manual says to set it between 30 and 70mv. I think I set it on 50mv originally because I was not aware of Mirko's recommendation to go a little higher. If you know you set yours at 70mv (at least) I think I will set mine at 75mv tonight and give a listen. I'll report if I get a response from Mirko. Thanks for the support!

Great job, all. I placed one of the big orders for those large large caps a few years back and shipped most to Europe for Stoffie, Mirko and a couple of others and have one (1) of them left, if anyone needs it. TA-N7B is a terrific amp. However, I've just gone back to my favorite amps of all time to bi-amp the Sony SS-M3 speakers. Sounds so good that I wish I still had the set of SS-M7 speakers so could try bi-amp with them.

MX117.MC7150,

Nice of you to check in. The TA-N7B is very enjoyable. I have a pair of SS-M7's not getting any use at the moment. I don't want to have to ship, but if there's a will.....I would accept a very reasonable amount if you're interested and could make arrangements (Pony Express?). PM me if it's worth exploring.

BTW, what cap did you buy for the TA-N7B main filter caps? Thanks

Thanks, but just bought a set of PMC TB2i monitors to compare. Want to stay with monitors as I prefer to listen in the near-field. You might want to try your SS-M7s in bi-amp (vertical) mode. Quite a striking improvement with the SS-M3 and might be the same with the SS-M7.

The caps we used are the Nippon Chemi-Con U36D 80v 27,000uf 0742L 96, which are the largest we could find that fit directly into the Sony cans without modification. Think we did a total of ten (10) TA-N7B amps at the time, four (4) here and six (6) in Europe.

:drool: