Sansui TU-9900 Restoration and Mods - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 24th March 2007, 10:01 PM   #1
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
Default Sansui TU-9900 Restoration and Mods

I just bought a very nice Sansui TU-9900 at a fair price. It is working perfectly.

The supply in mine was already repaired. TR01 and TR02 were replaced by NT152, see http://www.nteinc.com/

Check also these two sites:
http://www.antennaperformance.com/ mods section TU-9900

and this one in japan, but really good pictures of the restauration process: http://amp8.com/radio/tr-tuner/tu-9900.htm

I was planning the following restaurations, mods:

Replace all supply electrolytic with Panasonic FC,
Replace all Electrolytic in the audio path with BG
Replace 2 TA7136P op amps with OPA2604. I may build a small interface PCB to do so.
Install IEC320 AC connector and shielded AC cable.
Replace the supply rectifier diodes with fast discrete recovery diodes
Replace feet with good EAR one, as use with Bel Canto gears.

I have all the test gears to fully retune it, so I'll do that also.

I will describe the restauration process. It my be of some interest to others.
  Reply With Quote
Old 24th March 2007, 10:28 PM   #2
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
I've been with this tuner for a few days now, preparing and studying the schematics. First, for the price I paid, 525U$, it is a hell of a tuner. I worked for years in the RF field, and this tuner is a real beauty. It is almost a test equipment receiver. The front end section is a piece of art.

After reading the suggestions for mods on http://www.fmtunerinfo.com/DIY.html, I decided also to install a AC snubber circuit at the AC input ( two 10 ohms/5W resistors and 0.01uf, 400V caps). I will also insulate the power transformer from the case to reduce leakage current as decribded in the article.

Before replacing all the electrolytic caps, I studied the circuits, to determine what to use and where. First, there is more than a few type of caps used throught out all the circuit. I've been working for long enough with this kind of circuits to know that the engineers of these days were using all kind of tricks to improve analogue circuits. Some type of caps are used for a very specific reasons (low leakage, specific temperature drift or compensation, etc). It not always advisable to exchange capacitors type into RF analog circuits. It is even more critical with ceramic caps. Type NP0 or NP7 cannot be exchange for example.

I found that my version of tuner used 4 types of electrolytic and a few tantalum:

Blue Nichicon: Supply filtering
Grey Elna: Supply filtering and circuit used (coupling, osc, etc...)
Grey Elna Non-Polarize (NP): Audio Couplig
Orange Elna: Very specific circuit location (more on that later)
Tantalum: Very specific circuit location.

The Supply decoupling caps are no brainer. I will use Panasonic FC and a few Black-Gates.
The BG will be use at the supply PCB output caps. I will also increase the first filtering caps (C6-C7) and bypass them with WIMA MKS film caps. I won't bypass BG, they usually don't like it. A few of these caps are use in none critical section such as Power-On led supply filtering. I won't change those since they won't add anything to the sound.

For the NP caps I will use Type N, Black Gate, I will also increse their value from 10 to 33uF.

Since I don't know the design criteria for the circuit specific caps or how their value or specs may affect the circuit, I will keep them. It is the same for the tantalum. In one application they are part of a RF circuit. The two other caps are used only for the Low-Pass filter button selection, a rarely used function anyway. Changing them can change the filter parameter. So I keep these 4 tantalum caps as well.

I will post an extensive Excel file that list all my findings, type of caps, value, application and changes suggestions.

I already order the BG caps and the EAR feet. I have all the FC caps in stock.

Before exchanging parts I will test the tuner and measure its specs.
  Reply With Quote
Old 24th March 2007, 10:52 PM   #3
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
The ferrite antenna holder on the back was all cracked when I tried to remove it. I need to completely remove the rear panel to install the IEC320 AC socket.

Bingo, I just found a replacement part on ebay. Internet is just great
  Reply With Quote
Old 25th March 2007, 09:14 AM   #4
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
Interesting. I for one subscribed to this thread.

/Hugo
  Reply With Quote
Old 26th March 2007, 03:20 PM   #5
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
Hi Netlist. I hope it will be interesting. Well, before any measurements, the listening impressions. As noted on some other forums, I have to agree, the sound is great just like it is in many aspect, but some others can be certainly improve.

First the good part:
-Immediate and incredibly living sound. Just listen to people discussion. Voices are natural, fast, crisp. The sound is so there. It is no digital for sure.
-Timing is lightning fast, right on the beat. Music just swing.
-Sound stage is huge.
-Sensitivity: just one word, incredible! Without any antenna conencted, just sitting there in my basement I received plenty of stations. My better than my NAD 4300. With my noce little Dynalb antenna, I will receive the signal strong as a rock.

Things to improve:
-Bass is full but can be better controlled --> Supply improvement?
-Highs sound solid state --> Probably to old opamp and coupling caps.
-Medium also can be more sweet --> op-amp and coupling again.

Problem on my own tuner, Power supply ripple noise. Traced it to the repaired supply. In fact a not so well repaired supply I'm afraid. Noise is coming from the +13V, ripple of 70mV! I replaced this supply with my own bench supply and no more noise. Just silence. Need to work on this one. Since this supply is very basic, I may replace the +13V regulator with a more modern LM317 regulator.

The audio noise dissapear if I supply the +13V with my own supply just the MPX and Low Noise Ampl PCB. The rest of the circuit probably has RC sub filters that remove the ripple.
  Reply With Quote
Old 26th March 2007, 03:22 PM   #6
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
Just found locally the almost exact power supply replacement transistor. They had in stock the original 2SD213, which is identical to the original 2SD214 except for the VCBO that is 110V instead of 130V. It is not a problem in this circuit. I will replace it and see.
  Reply With Quote
Old 26th March 2007, 03:34 PM   #7
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
More on the caps. Reading some more I found into the original parts list that there is 3 types of electolytic caps. The one in Orange are "Low noise" cap. I may keep them. There is just a few.

The two 1.5uF tantalum are not used for the LPF function, as I originally thought, but rather to couple the last RF subcarrier to the MPX decoder output to the LPF module just before getting decoced Stereo FM audio. They probably used tantalum cap to get hi freq response and large capacitance value. So they must have a big impact on te final sound. I really need to replace those.

Just found locally some nice film cap ERO MKT1817, 0.47uF, 63V. They are probably much nicer on the sound. I have also 0.47uF, Wima MKS-3 caps. I will combine three of them in parallel to get 1.5uF, try both and compare the sound. I would expect that they will perform better that these awfull tantalum ones.
  Reply With Quote
Old 26th March 2007, 03:40 PM   #8
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
Found also the perfect caps for the new snubber I want to install at the AC inlet. They are 0.0047uF, 400V, X1 caps. I'll use two in parallel to get about 0.01uF. The X1 specs is important because they are approved to be used directly on the line voltage. It is a must, see this nice site for details: http://www.justradios.com/safetytips.html

Quote from this site:

"Class X capacitors are used in “across-the-line” applications where their failure would not lead to electric shock. Class X safety caps are used between the “live” wires carrying the incoming AC current. In this position, a capacitor failure should not cause any electrical shock hazards, rather, a capacitor failure “between-the-lines” would usually cause a fuse or circuit breaker to open."

"Class Y capacitors are used in “line-to-ground” (line bypass) applications where their failure could lead to electric shock if a proper ground connection were lost. The failure of a “line-to-ground” capacitor would not open any safety fuse. In other words, the failure of a line bypass capacitor could create a 120 volt “hot” chassis that could give you a potentially fatal shock."
  Reply With Quote
Old 26th March 2007, 04:06 PM   #9
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Quote:
Originally posted by Algar_emi
The two 1.5uF tantalum are not used for the LPF function but rather to couple the last RF subcarrier to the MPX decoder output to the LPF module just before getting decoced Stereo FM audio. They probably used tantalum cap to get hi freq response and large capacitance value. So they must have a big impact on te final sound. I really need to replace those.
Don't be so eager to replace those "old" parts. Some of them are much better sounding than present day substitutes. When I was modding Accuphase T-101 I put back some of the blue tantalums into signal coupling as they were better than BG N. So always compare the sound of new vs old for best results. I was also very selective about other parts replacement.

I also have TU-9900 and did some mods to it, might post some pics later. Make sure that deemphasis switch is set correctly, it should be 75us for America and it is often set incorrectly (like in my T-101)

After modding, TU-9900 sounds pretty close to TU-X1, but TU-X1 does not not need any mods (except for potentiometer bypassing) to sounds great
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 26th March 2007, 05:11 PM   #10
diyAudio Member
 
Algar_emi's Avatar
 
Join Date: Oct 2002
Location: Canada, Qc
Thanks Peter. I'll keep that in mind. Did you replace the audio op-amp?

Bye...

SB
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sansui AU-317 restoration project - 56k warning Nordic Solid State 60 14th December 2012 03:12 PM
Sansui TU-9900 schematic Acoustat Solid State 2 4th March 2009 03:14 PM
Sansui TU-9900 AMV8 Solid State 3 23rd January 2007 09:36 PM
Sansui TU-717 Mods Jeff Wong Analogue Source 2 28th April 2004 03:58 PM


New To Site? Need Help?

All times are GMT. The time now is 06:57 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2