On both of mine, the indicator lights are kept in with a dab of glue. I broke the glue (mostly) with an Xacto knife, then pulled the bulb out.
Sansui solid state 7000 repair, recap, and restore
On both of mine, the indicator lights are kept in with a dab of glue. I broke the glue (mostly) with an Xacto knife, then pulled the bulb out.
Now that is exceptionally helpful. I haven't gottten that far yet, so you may well have saved me the cost of s second set of labels. Thanks!
Will you post the BOM lists you made that are different than mine? If you do it here, please clearly state at the top "hey, these are for the OTHER style 7000 with (describe the boards)". Or start a new thread with that info and drop a link to it here. Either would be very helpful.
perryinva
IS it vintage????
I will, when I get back in there. I basically just replaced all the electrolytic audio caps except the large final coupling caps and the large PS caps. No tants or transistors replaced yet. I wanted to see what the progress so far sounded like, so I hooked it up to system #2, and all the pots and switches are now dead silent, and bass is punchy, and as mentioned, switching it to full power really left very little volume control at low levels. The problem is, the treble sounds like crap. Its hard to describe, but it feels over emphasized and has a tinny sound to it. Looks great, and no heat, but no way I can leave it in rotation sounding like this. Using the treble control, helps it a lot, but I can tell the attenuation curve doesn’t match whatever is going on. I pulled it from the stack and replaced it with my Mac1900, which blows it away as it currently is.
Hmm, I would have guessed any frequency-specific problem would come from a bad or failing cap, but you've replaced ALL the caps in the audio path...
That said, the final caps, the output-coupling caps, very much so influence the frequency response. If nothing else stands out, I'd look there to fix a tinny problem.
perryinva
IS it vintage????
Yes, I am really hoping it is those. It exists on all sources. But I would have suspected a bass issue, not a treble issue from that last cap. Still, they are almost 50 years old, so therefore suspect & I will replace them and see. It is quite obvious. I will also replace the small transistors (.old design/known to be noisy ) in the tone and output boards, in case they are turning the possibly increased treble clarity from the new caps to hash with low switching resolution. I will scope the output with a generated input and see if the effect is visible distortion.
Hi sansui guys,
please could you help me??
I am proud owner of sansui 7000 and many others. I like this old QC design. I modified my sansui 3300 also by implementaion baxandall diode with great result. I also tried to do that with my upgraded ( some trans, capacitors )sansui 7000 BUT after turning on the driver after about 3 seconds burned. I am pretty sure I used the BD in palce of 10 ohm resistor with direction of the diode to emitor of PNP tran. I used 100 ohm and 1N4004. For sure I minimased current bias before turning on to adjust it. the PNP tran, and output trans are out on one channel. pls, I do not know what could happen. Is it possible to modified also this drivers as 2000X , 3300 etc?? Or do I some mistake by direction or resistor value??
Thanks for your advice
please could you help me??
I am proud owner of sansui 7000 and many others. I like this old QC design. I modified my sansui 3300 also by implementaion baxandall diode with great result. I also tried to do that with my upgraded ( some trans, capacitors )sansui 7000 BUT after turning on the driver after about 3 seconds burned. I am pretty sure I used the BD in palce of 10 ohm resistor with direction of the diode to emitor of PNP tran. I used 100 ohm and 1N4004. For sure I minimased current bias before turning on to adjust it. the PNP tran, and output trans are out on one channel. pls, I do not know what could happen. Is it possible to modified also this drivers as 2000X , 3300 etc?? Or do I some mistake by direction or resistor value??
Thanks for your advice
Welcome to AK, you need to open your own thread, then you will get help.
Be very specific about what have you done with the unit.
Yes, please do open a new thread. You'll get a lot of support and I'm really interested in learning what a baxandall diode is.
smurfer77
Super Member
Some info here. The idea was developed in the late 60s and used in many amps. Several years ago it was brought up again over on DIYAudio. In terms of Sansui I've seen Conrad use it on the 2000X in the previous link and more recently Leestereo in an AU-555A. The mod should only be done, IMO, by those who understand circuits as you can affect more than distortion....
Dlucy
tell me one thing. For sure in my sansui 7000 I have to change the old driver Hitachi trans SA566 ( burnt) and sc680 . Is it better to find the same NOS driver trans or to use some new OnSemi MJE 15032 (33) as you did?? Could you hear some difference in sound? What about adjusting troubles? Thanks
tell me one thing. For sure in my sansui 7000 I have to change the old driver Hitachi trans SA566 ( burnt) and sc680 . Is it better to find the same NOS driver trans or to use some new OnSemi MJE 15032 (33) as you did?? Could you hear some difference in sound? What about adjusting troubles? Thanks
If there was a reliable and trustworthy supplier of the original parts, I'd say that is an option. I can't seem to find either at bdent, so I'm guessing they are not easily sourceable.
I chose the MJE15032/MJE15033 pair as I like modern parts, these two meet or exceed the original part specs, and they are made for each other.
I've never heard the original 7000, so I couldn't really say "yes, there is a difference" or "no, there is no difference". This is a subjective call.
Thats is a pity you could not hear the unmodified 7000. ...
I understand, I also like new semiconductors for vintage repairs. In sansui 7000 and also 3300 I used with great results KSC 1845 for all NPN trans (inputs of drivers and also on preamp board) and the sound chnanged dramatically - clear and gentle. But for bias tran ( originally sc984 with Hfe 75 - 85) I have worries using something new with much higher hfe. For sure in case of much higher Hfe of tis tran I should also recalculate resistors in bias circuit.
I understand, I also like new semiconductors for vintage repairs. In sansui 7000 and also 3300 I used with great results KSC 1845 for all NPN trans (inputs of drivers and also on preamp board) and the sound chnanged dramatically - clear and gentle. But for bias tran ( originally sc984 with Hfe 75 - 85) I have worries using something new with much higher hfe. For sure in case of much higher Hfe of tis tran I should also recalculate resistors in bias circuit.
You'll still need the TO-220 device to be thermally connected to the heatsink, so a mica insulator and non-electrically-conductive thermal grease on the backside, between the device and the heatsink. Then you solder a wire from the disconnected collector middle pin of the TO-220 to ground (likely to be the heatsink).
At least that's what I do.
Well... uh... that's a really good question. I've never really thought that through after seeing the instructions:
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Because in some cases this will make the heatsink 'live' and therefore at the same voltage as the collector of the transistor. Heatsinks are almost always grounded, but even if the collector of the T0220 device is grounded, maybe you don't want that particular ground path to be active. Thus, even though in some cases you may seem to be needlessly adding another thermal barrier, in the vast majority of cases it is best to use the insulator.
Another consideration is the use of NPN & PNP TO-220 transistors on a heatsink. In a fully complementary arrangement how are you going to decide which ones to use the insulator for and which ones not? Bearing in mind that the collector of the NPN will likely be at, or close to, full +ve rail voltage and the collector of the PNP at, or close to, full -ve rail voltage.
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Because in some cases this will make the heatsink 'live' and therefore at the same voltage as the collector of the transistor. Heatsinks are almost always grounded, but even if the collector of the T0220 device is grounded, maybe you don't want that particular ground path to be active. Thus, even though in some cases you may seem to be needlessly adding another thermal barrier, in the vast majority of cases it is best to use the insulator.
Another consideration is the use of NPN & PNP TO-220 transistors on a heatsink. In a fully complementary arrangement how are you going to decide which ones to use the insulator for and which ones not? Bearing in mind that the collector of the NPN will likely be at, or close to, full +ve rail voltage and the collector of the PNP at, or close to, full -ve rail voltage.
Thanks, John! Learn something new every day. (Now I just have to figure out how to remember all the stuff I learn....)