A Specific Question about Recapping a Vintage Tuner

[lorne]

• I recently scored a Sansui Tu-207 tuner. This is the Sansui TU-217 that most of you will be more acquainted with. Of course, the 207 will be in the Japanese bandwidth. (I live in Japan.)

• The tuner has not yet arrived, and I don’t know how it is working except the seller says it powers up. At ¥1,000 plus delivery from Osaka, I thought it was a viable purchase ... cuz ...

• ... this basic 3 gang tuner is apparently punching way above its weight on strong stations. And here in urban Sendai, I really have only 3-4 stations on the dial ... and the ones I listen to are very strong. (Japan does licence a lot of broadcasters.) I don’t need a DX unit, and selectivity is not really an issue. Moreover, I don’t have an obstructive single path for FM broadcast. NHK is my mainstay and there are times of the day when their signal is superb.

• Tuner information Center has made some very favourable comments about this tuner’s sound performance on strong strong signals. This has been mentioned before here on AK in reference to TIC’s ‘shootout’ section. Its admirable sound is attributed to the simplicity and directness of the audio path.

• Moreover, there is a “mods” article for the tuner written by ‘Jim’. He did the shootout article and later rebuilt the TU-217 he bought for the exercise. He reports signifcant improvements in sound. If interested, you can follow up on the particulars here:

htt.ps://www.fmtunerinfo.com/DIY.html#TU-217

• Because I intend to rebuild this tuner, and perhaps have it aligned by the tech who is currently aligning my Pioneer TX-8800II [TX-8500II], I have some questions I hope members can help me with concerning the parts values that ‘Jim’ used in his restoration.

Here is the parts list as found on the Tuner Information Center site:

* Red = NO change in value; other colours refer to specific brands / cap series

Power supply, meter supply and wiring used off-the-shelf parts, no real exotics.
D101, 102 with UF4007 diodes or Schottkys.

C102 470 µF changed to 1500 µF
C106 220 µF changed to 560 µF
C17 47 µF changed to 100 µF
C28 1 µF to 1 µF
C78 47 µF to 120 µF
C79 47 µFto 120 µF (schematic mistake lists C78 twice)
C43 330 µF to 560 µF
C47 10 µF to 10 µF
C48 10 µF to 10 µF

Audio path - choice caps were chosen:
C34 47 µF to 47 µF - Sanyo Oscon
C35 4.7 µF - Sanyo Oscon
C49 10 µF to 10 µF - Nichicon MUSE
C50 10 µF to 10 µF - Nichicon MUSE
C51 6.8 µF to 10 µF - Nichicon MUSE
C52 6.8 µF to 10 µF - Nichicon MUSE

QUESTION -1: About the increases in the power supply caps. What are your opinions about the huge increases? I’ve increased power supply caps in tuners before. But I’ve always followed a policy of not exceeding a 25% increase. I don’t have a technical objection about the increase here, cuz I’m not that knowledgeable. I just know that you don’t want to exceed the specs of the transformer ... and maybe not do something nasty downstream?

QUESTION-2: The audio path: C51, C52: they look to me to be coupling or smoothing caps for signal out. The increased value is not so radical ... but why the increase? (Please see attached). I think J. Was trying to get rid of a spike he measured when using the ON/OFF. Citation follows:

“Listening this morning while going over the schematic, I wondered why I really needed the pair of caps after LPF 01 (caps C51 and C52). C49 and C50 block 4.8 volts DC each, but I saw no DC offset after the LPF. Figuring Sansui didn't put these two caps here just for fun, I tried all switching to get a DC offset pulse. Turning the on/off switch, I was able to get a very quick, short 1 volt spike before C51 and 52, read on a digital VM. It was still there as .4 volts after C51/52, though. I decided to bypass these last two caps. Bypassing C51/52 puts R51/52 in parallel with R53/54, so I lifted R53/54 from ground. I don't recommend strapping out C51/52. It is just an exercise I had to try. I'm listening this way now, and it sounds great.”

NOTE: The parts list accounts for 18 caps, so I guess he did not change out all of them.

By the way, the TU 317/307; 417/407 both use the same basic circuit. The 317 is the same tuner, but with dial scale lights. (Oooo - luxury!)

As always, any answers greatly appreciated — Cheers, Lorne

 

[painttoad]

i can not answer anything specific for your tuner but i do have a sansui t-60 that i had already done a recap on by the time i had seen that page and i saw my tuner listed, so i said what the hell.

i notice zero difference from a stock value recap to "upgraded" values and the fast diodes in the power supply.

if you have the correct value of a decent cap to use in the signal path, i wouldn't make a special order to get the polymer caps or the muse caps either. . just use ukl, ukt, ufg,ufw..etc.

nichicon does make a decent polymer cap that i used to replace sanyo oscons in a computer soundcard if you choose to go that route but i think it's kind of pointless in a tuner's signal path. in my case they were in a section of the dac.

one more thing...when i had recapped my tuner, i did not have the stock i now have . i did not have any "audio grade" caps to put in the signal path for the output decoupling caps. stock ones measured higher esr and had drifted so i used uvz...when i replaced them with ues, i heard no difference.

 

[Punker X]

Question 1: Yes going larger for filter caps in the power supply. You could go even larger. May consider some fast recovery diode too.

Question 2: The larger audio cap give you better low frequency response.

 

[j!m]

And, if you do any capacitor changes with the tuner board, you absolutely have to have the tuner re-aligned.

I have heard of cases where a tuner board re-cap rendered the tuner unable to pull in much of anything. I don't touch them personally for this reason. It might be worthwhile to have the alignment tech replace the caps and then do the alignment himself. That's my plan. It'll cost me more than only an alignment, but the tech will have much more experience and understanding of exactly the implications of each change he makes. I'm sure you can make suggestions for what brand he uses, but otherwise, defer to his experience.

 

[lorne]

And, if you do any capacitor changes with the tuner board .... >>> SNIP >>> It might be worthwhile to have the alignment tech replace the caps and then do the alignment himself. >>>SNIP >>> ... the tech will have much more experience and understanding of exactly the implications of each change he makes. >>>SNIP>>>

I think that is prudent advice. But, I was forced into retirement in accordance with the usual Japanese practice. Money is tight. I think I'll change out the caps and see what I get. Then I'll have Iwata-san try to align it.

This TU-207 at $10 is an affordable experiment. If it turns into an albatross around my neck, I'll rely on my silver face Pioneer TX-8800II that Iwate san is working on now. I recapped it years ago. Recently, the stereo light failed to light. I tested the diode — OK. Looked for cold joints; saw no suspects. I think that channel separation and imaging could be better, so I suspect alignment issues.

I also have a Dynaco FM-3 I used in Canada for 20 years. When I moved here, I had a tech recalibrate it for the Japanese bandwidth (apparently not an easy thing). It developed PS issues and is parked until I get back to it

If I'd been more flush, I'd have hunted down a L-02T or something.

Thanks j!m, Punker and paintload for the answers so far. Good fun!

 

[j!m]

When you pick up the one he's working on, maybe have a chat with him.

My dad had a foreign auto repair shop and a sign on the wall:

X$/hr labor rate

XX$/hr if you watch

XXX/hr if you tried to fix it yourself first...

Point is, you might actually save money letting him handle it (for the tuner board anyway). Amp and preamp- go for it, and then set bias and offset.

But I know those tuner boards can be extremely sensitive (they have to be!), particularly to capacitor changes.

Just because you paid a small amount for the item, doesn't mean it's not worth restoring. My SX-880 was a dumpster dive (possibly the main unit at the local sewerage treatment plant) special flipped to me on eBay. But I repaired and restored it and it's my office receiver now. I even replaced the wood grain vinyl!

These old things, even the "low end" stuff is worth it. Comparing my SX-580 (Craig's list capture that actually WAS in someone's trash pile- seller told me after I had paid my money) to a modern home theater receiver, and it's 1/10th the wattage yet at least double the weight. Build quality was there, and much more pride in ownership than the black plastic box.

 

[lorne]

These old things, even the "low end" stuff is worth it. >>>SNIP >>>

I quite agree.

All of my system is vintage, except for ancillary modules I either built or wired up and boxed. Amps, pre-amp, tuner, DAC, outboard transformers and cabling have all been overhauled, repaired or worked on by me. Mind you, I make no claim at all to any expertise or good knowledge of electronics. In fact, I'm embarrassed. (I used to be better at cars and motorcycles before they were electronically controlled.)

As for my tech guy ... well this is Japan and a whole different culture. I give the stuff to him. He repairs it. I pay what always seems a fair bill. He speaks no English, and whereas I can usually have conversations in my awful version of Japanese with many other people, I find communication with him very difficult. Moreover, he is quiet and very difficult to understand. Fortunately, he knows his stuff and is a consummate professional. He was an engineer at Sansui ... and then the company went bust.

I'm off my own topic ... but this might explain where I'm coming from. Still, I think your advice is the most rational and prudent. Sure, I could ask him about recapping the TU.

Thanks.

 

[lorne]

And BTW, I was looking at the TU's schematics. There are more capacitors in the TU than are mentioned above — quite a few more. Some are marked as C.E., T.C., and P.C. respectively. If anybody can explain these signatures, I would be grateful for the lesson. I tried referencing the abbreviations and got nowhere.

(Yes, I know about the old 'CE' company name for canned multi-caps — a new entity is currently using acquired, antique machinery making 30 versions of canned caps.

 

[j!m]

You can look at them to confirm, but my guess is tantalum, film and ceramic. Which is which I’m not sure. (That’s where the visual part comes in)

 

[lorne]

Well, there there are usually a pile of Tantalum and lots of ceramic caps in tuners. Here is a photo I picked up off the internet. This was the "before" photo ... before recapping. I always liked the way Sansui stuff looked under the hood. The caps pegged with glue, not so much.

Here I see a couple of those blue tantalums. Also I see about six of the orange, low leakage electrolytic caps used back in the days — often Elna LL's I think. I was really curious to see the innards and couldn't wait for the delivery.

Sansui TU-217

 

[gadget73]

The audio path: C51, C52: they look to me to be coupling or smoothing caps for signal out. The increased value is not so radical ... but why the increase?

that one is actually easy. Nichicon doesn't make a Muse in 6.8uf.

https://www.mouser.com/datasheet/2/293/e_ukz-1513448.pdf

lowest you get is 10uf at 100 volts. At 25 volts they don't exist smaller than 33uf.

 

[lorne]

that one is actually easy. Nichicon doesn't make a Muse in 6.8uf.
lowest you get is 10uf at 100 volts. At 25 volts they don't exist smaller than 33uf.

Thanks ... that makes sense. I looked at the schematic and C51, C52 are stock 6.8 uF, 50 Volts. By doubling the capacity and voltage, I wonder if he gets any advantage? I could check if the data for the old caps still existed.

 

[lorne]

Just to let you all know:

The TU-207 arrived the other day from Osaka. ¥1,000 for the tuner + ¥1,600 for shipping. So say $26. And what I got:

Everything works. I put it on the DBT and an isolation X-former for 20 minutes or so. The tuner is rated at 5 Watts, so I used a 10 Watt incandescent bulb. The test went perfectly and there were no bad smells or ozone. The finish is unblemished but for a bit of unobtrusive corrosion on the bottom plate. I washed the hood in the sink and wiped the bottom plate with benzine. I inspected the board and all looked visually OK. I've not yet looked at the solder side. The clear plastic and tuning windows have neither scratches nor scars. I polished the RCA plugs. The plating came up like bright chrome. I take this as evidence that it was rarely used, or had a very polite life. This is all excellent, considering I bought it as a "junk" item — no guarantees or returns.

Both AM and FM bands work. The stereo lamp lights up. With a very simple dipole antenna, NHK tuned on the dial to exactly the local broadcast frequency of 82.5 MHz. Signal strength was indicating 4.5 / 5 (almost pegged). The signal tuned exactly in the middle of the legend.

Sound: initial listening was really good. There was a program of Baroque opera. The violas, cellos, bass, harpsichord and recorders were all announcing themselves on a soundstage with the soprano and tenor. The soprano was a bit shrill in the ear, but the Kenny/Trio L-0M5 mono amps just do that despite having been recapped and having the Melos tube pre-amp in front to tame them. (Perfect amps for metal ))

I'm really pleased so far. This promises to be the most enjoyable broadcast instrument since my much favoured Dynaco FM-3. Good, uncompressed FM is just a blast!

 

[lorne]

Perhaps this post is superfluous, but it's a sort of conclusion. Moreover, there is a very slight chance it will be read by other owners of a Sansui TU 207 / 217. And because I recorded all the capacitor replacements anyway … so why not?

For this project, I bought fresh Nichicon and Nippon Chemicon general purpose caps, as well as Nichicon FG audio caps — just what I could get from local retail supply. Other caps such as the films and Oscons came out of my parts bins. Tuning and signal strength was completely unaffected by the capacitor replacements.

I tried to match the original values as much as possible. I mostly managed to do that, albeit with greater voltage ratings.


C17: Nichicon H7730L 47uF 16v 85° > Sanyo Oscon 47uF 20v
C25, C26, C28: Nippon Chemicon SL 75(4) 1uF 50V > rectangular plastic cased poly cap, manuf. unknown (yellow) 1uF 63V
C43: Nichicon H772H6L 330 uF 16V > Rubicon PK A2038 PET 330uF 25V 85°
C47, C48: Nichicon 17726L 10uF 16V > Nichicon FW 10uF 50V 85°
C65: Nippon Chemicon SL 4.7uF 25V > Rubycon YK 4.7uF 50V
C66: Nippon Chemicon SL 3.3uF 50V > Rubycon YK 4.7uF 50V
C78: Nichicon H7730L 47uF 16v 85° > Sanyo Oscon 47uF 20v
C79: Nichicon H77726SL 100uF 6.3 V 85° > Nichicon FW 100uF 35V
C102,103: Nichicon H7708L 470UF 35V 85° > Nichicon FG 480uF 35V 85°
C104: Nippon Chemicon SL CE04W 100uF 25V > Nichicon FW A0721 PET 100uF 35v 85°
C106: Nippon Chemicon SL CE04W 220uF 16V > Nippon Chemicon KMG 220uF 25V 105°


ORANGE NICHICON ‘(low noise’ ) CAPACITORS NOT YET REPLACED

These caps (see photo) are the original, very low leakage caps. There was discussion in these forums about low noise vintage caps that are found in some pieces of old equipment. One member did some testing and recorded some comparative measurements with modern audio capacitors. This contribution, as well as the thread discussion as a whole, was convincing — at least to me. I came away with the conclusion that it was better to leave these orange caps in place, or replace them with modern supply that matches or exceeds the leakage specification. Accordingly, at a later date, I’ll order some Nichicon UKL capacitors and install them.

The ‘TU’ sounds great on the strongest broadcast in my area (Sendai Japan): NHK @ 82.4 MHz. — in fact quite astonishing for an online purchase of ¥1,000 plus ¥1,600 shipping.

ORIGINAL ORANGE COMPLEMENT

(2) 10uF @ 25V
(2) 6.8 uF @ 50V
(1) 10 uF @ 25V
(1) 4.7 uF @ 50V
(2) 0.47 uF @ 50V

 

[gadget73]

can always use film in place of the LL caps. Those will have extremely low leakage, and should perform better than an electrolytic in basically any way except cost.

 

[lorne]

can always use film in place of the LL caps. Those will have extremely low leakage, and should perform better than an electrolytic in basically any way except cost.

I can probably manage to find one or two of the values in my bins. But, I'm thinking that finding say 10uF small enough to fit may be really difficult.

 

[lorne]

Well, nothing in the pantry ... high voltages and in the nF values.

 

[gadget73]

Up to about 10uf at 50v can be had in a reasonably small package, beyond that it starts getting pretty big. 11x16mm seems to be the package size with 5.5mm lead spacing.

MKS2B051001N00MSSD WIMA | Mouser

 

[lorne]

Up to about 10uf at 50v can be had in a reasonably small package, beyond that it starts getting pretty big. 11x16mm seems to be the package size with 5.5mm lead spacing. >>>SNIP>>

Thanks! Your URL link helped me get to the page I was looking for. I was just going in circles and finding specs for large VDC capacity — large packages. I gotta pull the hood and start modelling. I hope there is supply in Japan. The current exchange rate (product +shipping) is murderous.