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Quad Sansui problem; help???

Betomon

Betomon

Active Member
Hello guys, I wasn't having much luck at the SS forum, so I thought I would post here.

Yesterday my dad and I drove 3 and a half hours (one way) to buy and pick up a sansui system. It is composed of 4 SP 7500X, a FR-5080 4/2 really nice turntable, and a hugh jass QRX-9001. We had seen this posting on craigslist and discovered that the lady only wanted 75 bucks for the quad, while one was selling on ebay for 600+. She said that in her last move "something worked loose" and now it doesn't sound. So we woke up at 4 AM yesterday and drove down there to get it.. talked the lady into going a hundred less for the whole system and took it home :yes:

Anyway, now is where I have to ask you sansui experts about my problem...

The monster powers on, tunes to fm stations (stereo and all), pumps the VU meters to 200 watts, and puts out sound through the headphone jacks (2 for front and back.. both which turn off the speakers).

BUT, it does not put any juice out of the speaker terminals in the back. none whatsoever.... not even a scratch (literally). I tried plugging the 4 speakers in to both systems A or B (each "system" has 4 outputs) but I got nothing. :scratch2:

I noticed that one of the VU meters was not showing any power; the front left one. So I took the cover off and noticed that there was one fuse missing. Apparently it was for that channel. And when I tried to put a fuse in there, it blew it instantly........ :no:

The rest of the fuses look fine (4 fuse slots for 125v5a, 3 slots for 250v5a) as well as the power fuse.

I dont see any discoloration of the caps, wether it be the huge ones or the smaller ones.

At this point I'm thinking it has to be something blocking the speakers from getting any juice... wether that would be a short or some kind of relay. I'm willing to take the boards out (specifically the two Audio boards, and whatever else I would need to take out) to see what I can find os wrong or maybe replace a relay or something.

Can anyone relate to any of this? Or maybe had a similar problem? Could you provide some pointers or suggestions? Even if you can't, could you post something just for the hell of it? I need help :dunno:


Thanks in advance,
Albert
 
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Ok, first thing I'd advise is find the service manual, buy it and look it over.
You paid little for it, and it's the biggest Quad Sansui ever made. It's a complicated beast, if you are not an experienced technician I'd suggest you take it to someone who is, that thing isn't a project for someone without experience with vintage gear.
Please do search using the model number the posts here on AK, and settle in for a read....
Casey
 
If you're blowing a fuse likely you have a shorted output transistor in that channel. You'll need to pull them out one-by-one and test them with the diode function on your meter. Search AK on how to do that.
I'd also take a look at the contacts on the speaker protection relays and clean them. They make a thin burnishing file for that.
Don't forget to verify that the jumpers (if so equipped) are installed between the pre-out and main amp in RCAs on the back.

What is your skill level?
 
Ok I downloaded the service manual and schematic from hifi engine. I will most likely print whatever I need to print just to have it handy.

About the output transistors, that makes a lot of sense, and I will make sure to do that. I took a lot of pictures of the boards and things like that. Also, I took the two audio boards out to examine them, but didn't have time to test them (which I'll do soon). As far as visual examination goes, I didn't see any discoloration or shorts. But I haven't touched the output transistors. And by that you mean the main 8 that are attached to the heat sinks on the back? If I remember correctly my electronics/robotics teacher has about 3 boxes full of those (two pins I think).

And skill level in anything specific? Between me and my dad I am confident that we can fix this thing, and I'm sure I'll learn a lot of things in the way. I am not in any way going to rush this project because I know that it will be a sweet, sweet reward. Reminds me of a quote that is something about that conquering something that is difficult is glorious. (I can't remember the exact words or who said it.. maybe thomas jefferson?)

Anyway, I'm prepared to do whatever is necessary.. as well as ask my electronics teacher to help me out if I need it.

I'll upload some pics to imageshack and then post them here for you guys to see soon.
 
nosirrah said:
Ok, first thing I'd advise is find the service manual, buy it and look it over.
You paid little for it, and it's the biggest Quad Sansui ever made. It's a complicated beast, if you are not an experienced technician I'd suggest you take it to someone who is, that thing isn't a project for someone without experience with vintage gear.
Please do search using the model number the posts here on AK, and settle in for a read....
Casey
Click to expand...

The shorted output transistors would most likely have occurred by the speaker outputs shorting out. or something failing back in the driver section perhaps.
Transistors dont show any visible signs normally, that they have failed.
You have to test them with the diode function on your multimeter.

I would like to reinforce the advice Casey has given, these amplifiers were Sansui's Quad flagship.
They are a complicated beast, so if you want to tackle it be sure you do your homework and be very meticulous and patient.
There are a bunch of us around here that can help, listen to the advice and dont jump ahead, thats when things can go wrong.
The problem with the amplifier could be fairly straight forward, as long as you follow the instructions it could be up and running in no time..........
Do you know how to test transistors?
 
Another issue common to this receiver are some soldered pass-thru joints.
The issue is that over time, due to thermal expansion and contraction the joints develop cracks, there are only 3 types of 9001 receivers, those that are cracked, those that will crack, and those that have had all those joints pinned with a small piece of wire, techs often use pre-tinned excess leads saved from caps and resistors they have changed, the only one I ever worked on, many moons ago, I used copper bell wire that I tinned. I think there are something like 53 joints to fix. Quadbob, a member here, is experienced in the repairs needed to fix this unit, he does them for others, but he is very expensive.
Google is your friend, google "transistor testing" and have a read, if you have an el-cheapo multimeter consider buying a good one, such as a Fluke or equivalent.
Search the forums here using your model number, and review the posts, that will give you an idea what you are up against.:yes:
 
I would like to reinforce the advice Casey has given, these amplifiers were Sansui's Quad flagship.
They are a complicated beast, so if you want to tackle it be sure you do your homework and be very meticulous and patient.
There are a bunch of us around here that can help, listen to the advice and dont jump ahead, thats when things can go wrong.
The problem with the amplifier could be fairly straight forward, as long as you follow the instructions it could be up and running in no time..........
Do you know how to test transistors?
Click to expand...

Yes I understand that completely. I have been reading up on it since I got it, and will keep on reading until I figure it out and fix it. I am so thankful that I have helpful people like you guys because this is one major time of need for me :yes:

And about "following the instructions", which instructions are you talking about?

Like nosirrah said google is my friend, so I will read up on transistor testing. Also i will get advice and help from my electronics teacher on doing that, and use his equipment to test whatever I need to test.

Another issue common to this receiver are some soldered pass-thru joints.
The issue is that over time, due to thermal expansion and contraction the joints develop cracks, there are only 3 types of 9001 receivers, those that are cracked, those that will crack, and those that have had all those joints pinned with a small piece of wire, techs often use pre-tinned excess leads saved from caps and resistors they have changed, the only one I ever worked on, many moons ago, I used copper bell wire that I tinned. I think there are something like 53 joints to fix. Quadbob, a member here, is experienced in the repairs needed to fix this unit, he does them for others, but he is very expensive.
Google is your friend, google "transistor testing" and have a read, if you have an el-cheapo multimeter consider buying a good one, such as a Fluke or equivalent.
Search the forums here using your model number, and review the posts, that will give you an idea what you are up against.:yes:
Click to expand...

These soldered pass-thru joints, could you maybe provide a picture showing an example of one? I am not too sure I know exactly what you are talking about, but it makes perfect sense. And how do i know which ones I need to fix? The pictures I'll provide should help maybe?

Thanks for all the help so far guys! Please continue if you can :D
 
The 9001 uses the same basic driver boards as the 9090DB. They will be prone to the same fuseable resistor failures. Do a search, there is a ton of information available.

Its a very complecated receiver. Definitely not a good choice for a learning mule. Find a dead 7070 or 8080DB to get your feet wet before you dive deeply into the 9001. They are much more common, better parts availability and a lot of guys here know them pretty well. Not the case with the 9001. Very hard to find parts so if you toast something, you are really screwed.

- Pete
 
Yes I have been doing searches and I think i came across that posting. And I have to agree, it is very very complicated. Especially for me. But I will go step by step until I find the problem/multiple problems.

As for today, I took it to my electronics class and tested the output transistors... and I camt to the conclusion that there was one output transistor that had very different ratings from all the others. (they are apparently matched in pairs, because the two center ones match measurements in the multimeter as well as matching numbers on the transistors themselves, while the 2 outer ones match too [this applies to both sides, remember 8])

Anyway, so I took the one that seemed bad out, got one that looked most like and most closely matched the measurements of the other ones... and put it in there, put the heatsinks back on, put a 2A (instead of 5A) fuse in the slot that was shorting.

The teacher told me to put the cover on it in case a cap blows (made me a bit scared)... but I turned it on for about 5 secs. and when I took the cover off.... smoke.
:no:
:sigh:
:thumbsdn:

so i looked around for something I toasted but didnt find anything. So i pinpointed the bad burnt smell to one of the audio boards. I took it out and examined it closer. Then I pinpointed the smell to one capacitor. one of 2 biggest on that board. It smelled pretty funky but was not blown. Apparently I saved it in time.. but I'm not sure. The burning smell was probably the cardboard stuff it has inside of it starting to burn because it got hot all of a sudden... but hopefully it didnt blow it. I could tell it got hot by the signs of a little bit of melting of the glue stuff on the bottom of it.



So now I'm not sure what to do again... I'm going to go ahead and order an output transistor to match the old one.

But what I dont understand is why did this cap do that? And why DIDN'T the fuse blow? Even though it was 2A, it still didnt blow... which leads me to believe that there is something wrong here that I dont know about, and it was not the output transistor that time because I put one in that was not shorted out or fried in any way.


Help? :sadwave:
 
Sir, you have to start by helping yourself. Read your post. How can anyone help you based on the information given? What cap, what board, something to identify that cap out of the literally hundreds of caps in that receiver. The short answer can only be it cooked because too much current was passing through it.

For that matter did your electronics teacher even mention that transistors come in two flavors, NPN and PNP and that test results will be opposite of each other? Did you even ask him/her to show you how to test a transistor or why the results you found didn't look right? Did you look at the part numbers on the transistors and identify their positions? If you swapped a PNP output into an NPN position, that could be why stuff is smoking.

At this point you are seriously dangerous and putting a rare and valuable receiver in great peril.

- Pete
 
LBPete is right with his post, I second that.
There are ways of testing work done so you know you are in a good position to power up the amplifier.
You also need the right test equipment, I have three fluke digital multimeters, a tone generator, a dummy load (2000watts) you dont need one that big though, 200watts is more than enough.
A Tektronik dual trace oscilloscope (100Mhz), a dual DC powersupply, a variac (with ammeter), a place to work with good lighting and also I use an opti-visor for close up small detail.
Also good quality tools.

There is no point blindly poking around in an amplifier like this, it is complicated and you need to have a good fundamental electronics understanding to undertake something like this.
Even though you have a service manual you need to understand the circuit, how it works and what your looking for.

There is normally a reason those fuses blow, its because an output transistor or driver transistor or both have shorted, that means about 50VDC has a dead short to earth.
In other-words your amplifier is trying to be an arc welder.
There are other possible faults too, but this is the most common.
Down rating the fuse to see if its still going to blow after fiddling around and swapping components is not going to prove anything, especially when it sounds like you may have got the NPN/PNP around the wrong way. All that will happen is more components will fail and you will be damaging this beautiful amplifier unnecessarily.

Semiconductors can fail faster than most fuses, i call them fuse protectors. Its a good thing to remember.

All these things can be done by applying logic, and following the advice and instructions from members on this site.
If you dont understand something, ask, dont start fiddling.

I recently helped a member get his G-22000 going, it was very satisfying for me because I felt he was listening and every time he went to do something he checked first to avoid further damage.
He knew his limits, and his patience and perseverance paid of.
We were both very patient and within a week he had his amplifier going.....
When we were running out of ideas, a couple of other members chimed in, it was a good thread.

If you want to fix this because you want to learn electronics, my advice would be get something a little more simple.

If you want to do this one, STOP. Be more descriptive, use part numbers and values, tell us what circuit board it is, for example TR01 on the F-2624 driver board or whatever the case may be.

If you want to do step by step, it can be slow on the forum because for example I am on the other side of the world and you have to wait for replies, or people get busy or whatever.
But you need to wait. While you are waiting you can do your research, google things about transistor testing, diode testing, basic electronic fundamentals. There is so much of it out there to be read.

There are members as I said before who will help you, or there are members who can do the work for you if you find its beyond you, and thats the key, to know when you are out of your depth.

So be logical re-read that last thread and post us something which gives enough information to help you.........

Good Luck...........
 
Idee:scratch2:: Why not trade this nice amp with issues for an other nice Sansui Receiver that is in good working condition? Is there no AK member that can create an win-win situation this way?

-John-
 
Betomon, I gotta agree with these guys, from your description of what's happened and what you have done so far it's only a matter of time till either you get hurt, or you destroy the receiver. If you were a subscriber you would see there's one, just like yours but has output most of the time to most channels for sale, it's $200, plus freight. Probably has the common issues as I told you earlier.
You may well have just toasted another transistor, and probably they are not available.

Casey
 
kevzep said:
LBPete is right with his post, I second that.
There are ways of testing work done so you know you are in a good position to power up the amplifier.
You also need the right test equipment, I have three fluke digital multimeters, a tone generator, a dummy load (2000watts) you dont need one that big though, 200watts is more than enough.
A Tektronik dual trace oscilloscope (100Mhz), a dual DC powersupply, a variac (with ammeter), a place to work with good lighting and also I use an opti-visor for close up small detail.
Also good quality tools.

There is no point blindly poking around in an amplifier like this, it is complicated and you need to have a good fundamental electronics understanding to undertake something like this.
Even though you have a service manual you need to understand the circuit, how it works and what your looking for.

There is normally a reason those fuses blow, its because an output transistor or driver transistor or both have shorted, that means about 50VDC has a dead short to earth.
In other-words your amplifier is trying to be an arc welder.
There are other possible faults too, but this is the most common.
Down rating the fuse to see if its still going to blow after fiddling around and swapping components is not going to prove anything, especially when it sounds like you may have got the NPN/PNP around the wrong way. All that will happen is more components will fail and you will be damaging this beautiful amplifier unnecessarily.

Semiconductors can fail faster than most fuses, i call them fuse protectors. Its a good thing to remember.

All these things can be done by applying logic, and following the advice and instructions from members on this site.
If you dont understand something, ask, dont start fiddling.

I recently helped a member get his G-22000 going, it was very satisfying for me because I felt he was listening and every time he went to do something he checked first to avoid further damage.
He knew his limits, and his patience and perseverance paid of.
We were both very patient and within a week he had his amplifier going.....
When we were running out of ideas, a couple of other members chimed in, it was a good thread.

If you want to fix this because you want to learn electronics, my advice would be get something a little more simple.

If you want to do this one, STOP. Be more descriptive, use part numbers and values, tell us what circuit board it is, for example TR01 on the F-2624 driver board or whatever the case may be.

If you want to do step by step, it can be slow on the forum because for example I am on the other side of the world and you have to wait for replies, or people get busy or whatever.
But you need to wait. While you are waiting you can do your research, google things about transistor testing, diode testing, basic electronic fundamentals. There is so much of it out there to be read.

There are members as I said before who will help you, or there are members who can do the work for you if you find its beyond you, and thats the key, to know when you are out of your depth.

So be logical re-read that last thread and post us something which gives enough information to help you.........

Good Luck...........
Click to expand...



Thank you, and this is what I will do. I was stupid for trying something without knowing enough about it. But I will keep doing research and wont care if it takes me a year to finish, as long as I do it right. I know the value of this and how great it can be.. as well as how much is at risk. Please keep in mind that we can all be foolish at times, and I have been foolish so far. If I could load AK at school I would, but all forums are blocked on the network. Anyway, I can still write things down on paper then bring it home to post here. I will post the capacitor that I believe started to get damaged, and what board its on. If I'm allowed I'll try to take a picture too.


In the quote above, you mentioned there are ways to test the amp before turning it on. Could you please be a little more specific? I will be doing a lot of testing before powering it on from now. In fact, I wont power it on for a while.. until I have determined that it is ready (with you guys' help of course).

Anyway, please do not give up on me. This has all helped me very much. I am going to study the schematics of the driver boards as well as information on transistors, diodes, etc. I am going to be as careful as possible to make sure I don't fry this beautiful beast. That means I wont do stupid things out of random ideas that pop into my head. I will follow your advice.

Question: What is the "diode function" on a multimeter? Is it the it the same as a "continuity" test? And, I can test transistors with an ohmmeter correct?

Lets say I'm starting over.. but now, I know a few things more, and we can all go from there.


1. There is apparently one output transistor that is showing odd readings compared to all the others. I should order a new matching one correct?

2. There was a fuse blowing. The fuse was apparently blowing because of the shorted out (I will confirm this with a resistance test tomorrow) output transistor.

I am assuming that the fact that the transistor was shorting out, the protection circuit kicked on and prevents all channels from sounding correct?

3. I have read in lots of places, including here, that this unit has "cold solder joints."

My understanding of this is that there is not a good weld on some joints because it was done at a lower temperature, therefore not allowed to bond correctly. And that I can identify a lot of them with a magnifying glass. These joints can cause outputs to go out periodically or for good.

Now, my question about this is, should I look for these joints and fix them now? And, is my understanding correct?

And at this point I am starting to think that my electronics/ROBOTICS teacher is not of too much help. He was not familiar with testing transistors. And I found out myself that there are two types. (I will still use all of his equipment, tools, and parts though) But how can I tell the difference between them using something like a multimeter, if it is possible.


For now, I will use his nice big magnifying glass to look for cold solder joints, until I buy the output transistor and get some more input from you guys. I want to do this right. I am prepared and willing to listen, be patient, and very very careful.


Now, what would your suggestion, other than selling it, getting it fixed, trading it, etc, be for what I should do next?

-Awaiting instructions.

Ps. Thank you very much for the input so far.
 
I like your enthusiasm, but please reread what has been posted. You have already gone from bad to worse. Your best bet is to find someone local and ask for some hands on help. Well that's my two cents.

Just
Scott
nosirrah said:
Betomon, I gotta agree with these guys, from your description of what's happened and what you have done so far it's only a matter of time till either you get hurt, or you destroy the receiver. If you were a subscriber you would see there's one, just like yours but has output most of the time to most channels for sale, it's $200, plus freight. Probably has the common issues as I told you earlier.
You may well have just toasted another transistor, and probably they are not available.

Casey
Click to expand...

Betomon said:
Thank you, and this is what I will do. I was stupid for trying something without knowing enough about it. But I will keep doing research and wont care if it takes me a year to finish, as long as I do it right. I know the value of this and how great it can be.. as well as how much is at risk. Please keep in mind that we can all be foolish at times, and I have been foolish so far. If I could load AK at school I would, but all forums are blocked on the network. Anyway, I can still write things down on paper then bring it home to post here. I will post the capacitor that I believe started to get damaged, and what board its on. If I'm allowed I'll try to take a picture too.


In the quote above, you mentioned there are ways to test the amp before turning it on. Could you please be a little more specific? I will be doing a lot of testing before powering it on from now. In fact, I wont power it on for a while.. until I have determined that it is ready (with you guys' help of course).

Anyway, please do not give up on me. This has all helped me very much. I am going to study the schematics of the driver boards as well as information on transistors, diodes, etc. I am going to be as careful as possible to make sure I don't fry this beautiful beast. That means I wont do stupid things out of random ideas that pop into my head. I will follow your advice.

Question: What is the "diode function" on a multimeter? Is it the it the same as a "continuity" test? And, I can test transistors with an ohmmeter correct?

Lets say I'm starting over.. but now, I know a few things more, and we can all go from there.


1. There is apparently one output transistor that is showing odd readings compared to all the others. I should order a new matching one correct?

2. There was a fuse blowing. The fuse was apparently blowing because of the shorted out (I will confirm this with a resistance test tomorrow) output transistor.

I am assuming that the fact that the transistor was shorting out, the protection circuit kicked on and prevents all channels from sounding correct?

3. I have read in lots of places, including here, that this unit has "cold solder joints."

My understanding of this is that there is not a good weld on some joints because it was done at a lower temperature, therefore not allowed to bond correctly. And that I can identify a lot of them with a magnifying glass. These joints can cause outputs to go out periodically or for good.

Now, my question about this is, should I look for these joints and fix them now? And, is my understanding correct?

And at this point I am starting to think that my electronics/ROBOTICS teacher is not of too much help. He was not familiar with testing transistors. And I found out myself that there are two types. (I will still use all of his equipment, tools, and parts though) But how can I tell the difference between them using something like a multimeter, if it is possible.


For now, I will use his nice big magnifying glass to look for cold solder joints, until I buy the output transistor and get some more input from you guys. I want to do this right. I am prepared and willing to listen, be patient, and very very careful.


Now, what would your suggestion, other than selling it, getting it fixed, trading it, etc, be for what I should do next?

-Awaiting instructions.

Ps. Thank you very much for the input so far.
Click to expand...
 
It isn't a matter of cold solder joints, that's when a solder connection gets moved before the solder cools, giving the joint a frosty appearance.
It's an issue of the design, connections go from one board to another via a pass thru joint, where typically theres a brass rivet thru a connection that has been soldered. Thermal expansion and contraction, over time cracks this solder joint, sometimes you can simply re-flow the solder joint but if you don't put a wire in there it will crack again.
Do you have a good meter?
Go to a thrift store near you, buy an el cheapo clock radio, take it home, make sure it works.
With it up-plugged, desolder and remove a couple of resistors, and a couple capacitors, clean them up and re-install them. See if it still works.
look at the manual for your meter to see how the diode function works.
Tell us about what equipment/tools you have.
 
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