AU-9900 replacement parts recommendations?

[KeithD]

I'm starting to put together a list of parts to order from Mouser of replacement parts for my AU-9900. Everything is working fine, speaker relay was replaced by previous owner, but time to replace e-caps, trimmers, bad transistors, and other parts? There are a number of threads on this amp, but not a clear direction on a few items:

1. What line of replacement e-caps should I be getting? Nichicon, Elna, etc.? Specific line? I'd just like to hear what people's preferences are and briefly why.

2. There are many bipolar caps in there, and I assume the small value ones can be replaced with film caps? I have generally done Wima MKS2 series.

3. The Wima MKS2 series includes caps up to 10 µF last time a bought some. Can all e-caps in this unit with rating 10 µF and lower be replaced with the Wima films? I did that in my Eight, and seemed to work fine. Any reason not to?

4. Any suggestion for trimmers? Driver board appears to have 5 kΩ and 1 kΩ. I'm pretty sure the originals are adjusted from the top. (Also looking at getting replacement trimmers for a 5000X and a Seven.)

5. I've got plenty of KSA992FBU on hand. Assume those are ok with matched gain for replacement of 2SA798? That seems to be the recommendation. I've used the 992 in the past to replace 2SA726, same here where they are found?

6. Looks like a number of 2SC1313, and I've got lots of KSC1845FTA on hand. Assume these are ok?

Sorry I'm not listing these board by board in case those are not suitable in every location. I'm just trying to get as much on one Mouser order as possible rather than breaking things into multiple orders.

Will also be recapping the PS of my TU-9900. I've got a list for that, but would like to hear any suggestions for other things that might be needed with that tuner.

 

[ivandezande]

1: I use Nichicon PW, Nichicon EP for bipolars, and Nichicon KL to replace orange low leakage caps.
2: Yes, if you want. Most of them are big enough where a film cap won't work.
3: Should be fine, but kind of a waste of time and money. This was not a budget unit for Sansui. They used films where they saw it actually mattered.
4: Bourns 3386H-1-xxxLF
5: Yes, that's the best way to do it.
6: Yes.

Epoxy diodes need to go on the amp board. Lots of corrosive glue here as well.
Zeners on power supply, and most of the higher wattage resistors show heat fatigue and need to be replaced.

 

[sanjib]

Hi Keith
What a coincidence! I am going to get an AU-9900 by end of this week. According to the seller, it is working but needs work. I am going to follow this thread and every step.

 

[kevzep]

1: I use Nichicon PW, Nichicon EP for bipolars, and Nichicon KL to replace orange low leakage caps.
2: Yes, if you want. Most of them are big enough where a film cap won't work.
3: Should be fine, but kind of a waste of time and money. This was not a budget unit for Sansui. They used films where they saw it actually mattered.
4: Bourns 3386H-1-xxxLF
5: Yes, that's the best way to do it.
6: Yes.

Epoxy diodes need to go on the amp board. Lots of corrosive glue here as well.
Zeners on power supply, and most of the higher wattage resistors show heat fatigue and need to be replaced.

Yep, you saved me a bit of typing!!
This is what I do as well.....

 

[TupolevFan]

There is a good option now for 2SA798 . A nice Toshiba chip which is with adapter will be a direct replacement for 2SA798. It will also look nice. if you want I can supply you adapters for free ( I have quite a few of them - used PCB design software and ordered 200 of them as it was cheap.) you will just need to get this : https://www.mouser.com/ProductDetail/toshiba/hn4a06jte85lf/?qs=3kEcuH7qFheOWPWQLSYOfw==&countrycode=US&currencycode=USD
I got myself batch of 100. I installed first 10 on my adapters and the results are very nice. they fell into 2 groups so far for me. HFE around 400 and hfe around 500+ ( in reality was 540 to 570). What i also like about it is that datasheet contains noise graphs which you do not see often nowadays. I know 9900 has "millions" of 2SA798

for orange low leakage caps (and not only for them but in general for all e caps up to 10uF) in a signal path I mainly use film when space permits. Now if space does not permit and if you do it for yourself then you could use expensive option and use Rubycon MU series film capacitors which are smd type but it is very easy to attach leads on them. For example 10 uF X35 V is measured 5mm by 5mm and 3mm thickness. In my recent AU-717 resto i used 22 uF X 16V (two in parallel) to replace 47 uF bi-polar in control amp ( Actually there are 2 100 uF caps in series there and in Leestereo resto they get replaced by 1 bi-polar.) Those are very very expensive but again if you do it for yourself then it is up to you if you want to spend a bit more but kick another electro out )))

 

[KeithD]

Thanks for the feedback. Working on a parts list, and will post when I have further questions.

Is the feeling that the Nichicon UPW and UKL series caps are as good as the UFG series, or that you would not hear the difference between UFG and the others?

 

[ivandezande]

Thanks for the feedback. Working on a parts list, and will post when I have further questions.

Is the feeling that the Nichicon UPW and UKL series caps are as good as the UFG series, or that you would not hear the difference between UFG and the others?

Completely wrong way to look at it. Is it good for the application is the real question. PW is low impedance long life. KL is low leakage.
It’s not “are as good” or “can hear a difference”. Can’t just go sticking “audio” caps in everything.

 

[KeithD]

Can’t just go sticking “audio” caps in everything.

Well, some people do, so that's why I asked!

 

[kevzep]

Thanks for the feedback. Working on a parts list, and will post when I have further questions.

Is the feeling that the Nichicon UPW and UKL series caps are as good as the UFG series, or that you would not hear the difference between UFG and the others?

The UPW are thew right cap for Power Supply applications, the UKL are one of the best low leakage caps for audio path applications.
The UFG are in a similar category to the UKL, but the UKL out-perform UFG in my experience.

You definitely don't want to use the UFG in power supply applications.

 

[KeithD]

The UPW are thew right cap for Power Supply applications, the UKL are one of the best low leakage caps for audio path applications.
The UFG are in a similar category to the UKL, but the UKL out-perform UFG in my experience.

You definitely don't want to use the UFG in power supply applications.

Yeah, I have only used UPW for power supplies. I'll have to look for the "orange" caps mentioned for UKL replacements. Don't know which ones those are just from the SM list. I've got quite a few UPW caps on hand and a number of UKL and MKS2 films.

I used MKS2 films and UFG in my Sansui Eight recap (UPW in PS). That's the first receiver I've used the UFG in.

 

[TupolevFan]

I'll have to look for the "orange" caps mentioned for UKL replacements. Don't know which ones those are just from the SM list.

Usually those will have "BRN" next to their value and voltage rating.

 

[Hyperion]

Don't know which ones those are just from the SM list.

I advise you NOT to use the SM list - the schematic is generally more accurate.

 

[KeithD]

I advise you NOT to use the SM list - the schematic is generally more accurate.

Thanks John. I was going to use the SM as a starting point, then cross check with the schematic. First I have to check which driver board I have, then start a spreadsheet...

What line of caps did you use in your restoration of an AU-9900? Did you document that process in a thread here? Would love to see that if you did.

 

[Hyperion]

I was going to use the Schematic as a starting point, then cross check with the Unit, and then the SM lists. First I have to check which driver board I have, then start a spreadsheet...

There, I fixed that for you.

What line of caps did you use in your restoration of an AU-9900? Did you document that process in a thread here? Would love to see that if you did.

I know I used 10,000µF Nichicon KG ('Super Through' I think...) for the main filter capacitors, but this was quite a while ago, so I didn't document it. At the time I was a big fan of Panasonic FC and FM, and if I had thought of it, would have used Wima film capacitors to replace all the 3.3µF bipolars scattered around in the earlier stages of the amplifier.

 

[KeithD]

There, I fixed that for you.
I know I used 10,000µF Nichicon KG ('Super Through' I think...) for the main filter capacitors, but this was quite a while ago, so I didn't document it. At the time I was a big fan of Panasonic FC and FM, and if I had thought of it, would have used Wima film capacitors to replace all the 3.3µF bipolars scattered around in the earlier stages of the amplifier.

Hmmm... do you really take the whole thing apart to confirm specific caps before ordering parts? Is the SM/schematic that unreliable on this unit? Some boards are easy to inspect, while others are pretty buried and would require disassembly.

My plan was to use MKS2 films for all of the small caps, certainly the 3.3 and 1 µF positions. Any reason not to use them for the 4.7 µF positions? I also used 10 µF MKS2 films in a couple of positions in my Eight. I found the lead spacing was not a problem. Would this not be recommended in general or in this application?

 

[Hyperion]

Hmmm... do you really take the whole thing apart to confirm specific caps before ordering parts? Is the SM/schematic that unreliable on this unit? Some boards are easy to inspect, while others are pretty buried and would require disassembly.

Personally, I haven't used the SM lists recently for any pre-recap assessments, I occasionally refer to them as a last resort when other information sources have failed. I find them hopelessly incomplete, unreliable, and sometimes just plain wrong.

I can usually get the vast majority of component values and type numbers with the use of a dentist's mirror and a small torch. Those that don't yield to this approach do require some strategic disassembly, but I feel this is a small price to pay for absolute accuracy. I also have some components held in stock for the occasional 'under the board' mounted components that surprise me sometimes.

Any reason not to use them for the 4.7 µF positions?

Completely Ok to do that.

 

[KeithD]

Personally, I haven't used the SM lists recently for any pre-recap assessments, I occasionally refer to them as a last resort when other information sources have failed. I find them hopelessly incomplete, unreliable, and sometimes just plain wrong.

I can usually get the vast majority of component values and type numbers with the use of a dentist's mirror and a small torch. Those that don't yield to this approach do require some strategic disassembly, but I feel this is a small price to pay for absolute accuracy. I also have some components held in stock for the occasional 'under the board' mounted components that surprise me sometimes.

Thanks for your insights, John! The driver board and PS boards look easy to access, but the tone controls will necessitate taking off the face plate and removal to to get at. Things are pretty tight in there and its just a few caps on each board. I do have a decent stock of UPW and some UKL caps, so if there is a discrepancy, I may have what's needed. This will be an after Christmas/January project, so just want to get ready with parts well in advance. I probably won't have time to complete my Mouser list until some time next week. I've just started my spreadsheet.

Completely Ok to do that.

Yeah, from what I've read the double stack films are as good as e-caps and should last longer than e-caps, since there is nothing to leak. So, I replace all 1 µF e-caps with films, and have done so with e-caps up to (and including) 10 µF in the last re-cap I did (Eight).

 

[TupolevFan]

Hmmm... do you really take the whole thing apart to confirm specific caps before ordering parts? Is the SM/schematic that unreliable on this unit? Some boards are easy to inspect, while others are pretty buried and would require disassembly.

My plan was to use MKS2 films for all of the small caps, certainly the 3.3 and 1 µF positions. Any reason not to use them for the 4.7 µF positions? I also used 10 µF MKS2 films in a couple of positions in my Eight. I found the lead spacing was not a problem. Would this not be recommended in general or in this application?

IMHO in most cases film caps prefered in signal path. Whenever you can replace electro with film do it. I do not see too many 10uF electro in this unit. However if regular Wima cap does not fit you can use this
https://www.mouser.com/ProductDetail/Rubycon/35MU106MD35750?qs=T3oQrply3y%2BcmT4yat/O1A==
see attached how i installed them in my recent AU-717.Those particular are 22 uF x 16V and I had to use 2 in parallel to imitate near 50 uF which was previously done by 2 100uF electro in series

Now you have C601 and C602 in preamp and similar in phono which are blocking or baypas caps for power supply. I would leave them electro and increase their value to 47uF same or higher voltage rating.

 

[MacMillan]

Hi Keith....
....looking forward to your BOM on the AU9900. have started one this past summer and am not finished as yet...I initially started out buying a kit put together and sold on Ebay...
thought this was a good way to go...not so...I did get a few Caps to use but most of them were audio grade Nichicon FG and Muse...now I find out that these are not the best or should be used in say the power board.
it can be frustrating for a person new at this......I will reorder Nichicon UPWs .
.....something also I have noticed is that each AU9900 may have a different board from another...such as the PS 2568..which mine has
....there is no unsoldering of any wires on this board to access it...
....as you can see in pic , there is some glue to remove...seems to be my only board with it though..
....will try to take pics as I go and share with you if you like...

 

[KeithD]

Well, no surprise, @Hyperion was right. Checked PS and driver boards and there were discrepancies between SM and what was actually in there. I'll take these one board at a time. Here is my list for F-2568



Replacements in blue are what I have in stock, black I'll have to order. C18 capacitance is what is actually on the board and is different from SM. I did not check all of the transistor since I have all of the replacements on hand. @ivandezande recommended replacing the zener diodes. What are the suggested replacements?