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Quad Sansui problem; help???

Ok, I will hold off the big order. I was going to just order it and not put them in until later.. but, either way I guess is ok.

We just finished replacing all the resistors that I got replacements for. But, we found several that were visibly burnt. Here they are:

R21
R11
R55
R59

We don't know the rating for them because on the parts list they dont show. And, the colors are gone.

Also, we found another blown & burnt TR. C1708 6XG
Whats the replacement for this one? There are 4 on each board I believe.

Thanks guys :)

UPDATE: Duh, sorry guys I forgot the other board's resistors were all fine. We figured this out based on color code:
R11=680Ω
R21=22Ω
R55=470Ω
R59=22KΩ
 
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Hi Betomon,
Sorry, I was busy last nite. Looks like you're doing well. One nice thing about the 9001 is that there are 2 driver boards, so you can compare one against the other. You can always compare a bad channel to a good one when you're making measurements. Looks like you'll be close to powering up that output section soon.

One thing about color code on real old parts. Sometimes the colors fade and it's possible to make a mistake. Do you have a copy of the schematic? All the values are on it. If you don't, you can get a copy at HiFi Engine. You have to join, but it's well worth it.
 
Trnsfmr said:
Hi Betomon,
Sorry, I was busy last nite. Looks like you're doing well. One nice thing about the 9001 is that there are 2 driver boards, so you can compare one against the other. You can always compare a bad channel to a good one when you're making measurements. Looks like you'll be close to powering up that output section soon.

One thing about color code on real old parts. Sometimes the colors fade and it's possible to make a mistake. Do you have a copy of the schematic? All the values are on it. If you don't, you can get a copy at HiFi Engine. You have to join, but it's well worth it.
Click to expand...


Thanks Jim. I have the hifiengine service manual, manual, and schematic. Also I have another copy of the schematic from a different website. I did not realize that the values were there :drool:

Thanks for this info, it is great.. as I noticed the service manual does not list MANY resistors.

The parts are on their way. To keep myself busy I put a ceramic resistor (15Ω10watt) in my advent's crossovers because the tweeters were just way too loud. It worked :))

But anyway, I still havent figured out a good way to secure the smaller 10000µf caps on the metal base. I'm thinking some kind of glue I can find locally? Or what do you guys suggest?
 
Hi,
I regularly glue the big caps to the same frame they were originally on. If you do it carefully and wire neatly, it looks good and professional. In this picture I have 4 10,000uf caps silicon glued to the subframe. The + and - connections are down, the ground is up, and I have a 12 uf polypropylene cap across the both banks of caps, from - to +.
 

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Trnsfmr said:
Hi,
I regularly glue the big caps to the same frame they were originally on. If you do it carefully and wire neatly, it looks good and professional. In this picture I have 4 10,000uf caps silicon glued to the subframe. The + and - connections are down, the ground is up, and I have a 12 uf polypropylene cap across the both banks of caps, from - to +.
Click to expand...

Very nice! I already wired them exactly in the same position the old ones were.. so do you think I could use silicon to glue them on the frame in the same position as the old ones? I just didn't know if I had to use any kind of special adhesives :D
 
If everything is clean, the silicon will hold very well. just try some different positions til you find something you like.
 
Ok cool, I'll get some tomorrow, unless there is some laying around. 100% silicone clear work fine? Because it seems pretty easy to do with a bottle of that
 
Ok guys, power supply(s) are recapped. Driver boards are recapped. Driver boards have all burnt resistors and transistors replaced. I did not replace the transistors on the good board. I bought and replaced all the fuses with the right specs.

Now, I believe its time to set the DC offset and bias correct? I remember you guys saying that before turning it on set the DC to 0. How do I do this? Please let me know. Thanks guys.
 
Good work, Betomon. sounds like you are ready to start the exciting part of the journey. This is where the amp diva, Kevin, comes in and leads us through the next part. I have a lot of experience with design and modification, but Kevin has more experience with problem and blown amps than anyone I have ever even heard of.


So, I think we can assume that the AC problem is fixed,that when you turn it on, it will power up. The unit was blowing fuses and there was one bad channel when last it powered up. So I don't have to read through a bunch of threads, can you tell us which channel is bad and what you have changed transistor-wise?

Unfortunately, Kevin is burned out at the moment and continuing to do loud, offensive music shows, with his 100,000 watt + sound system. He told me he is very busy til Monday. He will probably join us, though.

But you never know, Earth to Kevin, are you there? :scratch2:
 
Betomon said:
Ok guys, power supply(s) are recapped. Driver boards are recapped. Driver boards have all burnt resistors and transistors replaced. I did not replace the transistors on the good board. I bought and replaced all the fuses with the right specs.

Now, I believe its time to set the DC offset and bias correct? I remember you guys saying that before turning it on set the DC to 0. How do I do this? Please let me know. Thanks guys.
Click to expand...

Before you think about applying power to this amplifier, what you need to do is build yourself a "dim bulb" tester.
What this does is enables you to power up the amplifier without the risk of blowing up transistors and other parts of the amp if there is a fault.
All it you do is put a lightbulb in series with the power.
You need a power socket then a lightbulb socket and a power plug. In your case you would start with a 100 watt bulb, if the amp runs then you could try a 60watt bulb, if thats good then you can plug the amp straight into the mains power.
You could mount it in a box of some kind......
What happens is if there is a short circuit in the main DC rails, the bulb will light up instead of the amp blowing outputs and the likes.

When you have that ready to go, you need to set the bias trimmers fully off. Jim will confirm but that is turning them fully clockwise, there is a possibility they might trim the other way as this seems to be the case with certin variations of driver boards. Jim will confirm this.
The DC offset trimmers need to be set at halfway or as we say in the trade, 12 O'Clock..........
Jim will chime in with how he uses a stereo 1/4" jack plugged into the headphone sockets to check the DC offset.....

Before I fire an amplifier up I always check the positive and negative DC supply rails are not shorting to ground.

You must carefully and slowly go through everything you have replaced and check it is in the right place too.....
You can never be too careful......

I'm sure Jim will be along soon soon with some guidance
 
Thanks Kevin. I can't remember anything any more, so I keep all this hard won info in a notebook. I can't even read the schematic without my notebook cause the schematic is so big.


Anyway, at the top of the 2624 board are 4 trimmers. The ones on the left do the left channel, on the right--the right channel. This board is so confusing because it is a mirror image board. everything on the right is a mirror image of what's on the left. The trimmers also turn up and down in mirror image one side to the other, or in opposite directions.

from left to right, across the top you have vr3, vr1 vr2, vr4. Vr1 and vr2 are the offset adjustments for the left and right channel. Offset is the amount of voltage the amp puts out when idling, with no signal. We want it to be 0, but within 10 milivolts of 0 is OK. Vr3 and vr4 are the bias trimmers. The bias is how much current the amplifier flows through the output section at idle, no signal. It needs to be set to 25-30 ma for lowest distortion.

So, you got it? the two center trimmers set offset, the two outer ones set bias. Kevin wants to set the two bias trimmers to minimum, so there will be the least chance of too much current when we power up. There are two different versions of the 2624 used in the 9001 and they have bias trimmers that turn opposite. so we need to know which board you have. I looked back through, and couldn't tell from the pictures. So, we need a top down view of your 2624 boards to go any further. A picture.

The other thing that kevin was mentioning is that we can measure the offset from the phone plug jack. If the 9001 is in protect mode, it breaks the connection to the speakers, but leaves the headphones hooked up. so we can measure the offset there. You need a 1/4" stereo phone plug to do it.

So take us a picture of your 2624 board(s). :smoke:
 
And, something that we have talked about before, but you must do, if you're going to use the low voltage method of the dim bulb tester to bring up the board. You must remove the two quad boards and remove or at least disconnect the CD4 board. Both these boards have logic chips on them and these chips can be destroyed if the voltage goes low enough for long enough. I am finding that fully about 1 out of 4 of the quad boards that I have come across have their chips blown due to the voltage drifting out of range.

The quad boards are the plug in boards that go right to left across the middle of the 9001. The CD4 board is accessible from the bottom of the unit. If you stand it up on the left end so that the power transformer is down, the CD4 board will be at the top, with a bunch of connectors plugged into it. I would just remove it and leave it out (with the quad boards) until you get the amp problems sorted out.

It would also not be a bad idea to remove the dolby board because it also has two IC's on it. It is right above the CD4 board when you have the unit open up as described.

This is why I have never brought up a 9001 with a low voltage method. With these boards all removed, nothing will be left but analog, and it should all handle the reduced voltages just fine.
 
Ok here are the pics of the boards





But, before we go any further.. I need you guys to know this: I took the two 3.9k resistors out because I just had a hunch that I needed to test them out of circuit. They both tested very very weirdly.. the numbers were all over the place... eventually settling on like 150-170 range (set on 2000k). But sometimes it just showed no resistance, sometimes showing an ever-lowering resistance. I believe this is a problem.... my teacher has 10 watt ceramic resistors, but I don't know the ohms just yet.. I'll look monday.

But in the meantime, if I have time tomorrow I will set the DC and bias, disconnect the quad boards, and also make that light bulb thing :D

Hopefully I'll also have a new set of aluminum function buttons machined by my buds in machine trades.
 
Oh, sorry I forgot to answer this. The front left channel was out. tr 899 and c1708 were burnt. Also the resistors on their path. These have been replaced. I left all the other trs alone. The fuse all the way to the left 5A 125V was burning and the meter for the front left channel never showed power back when it used to turn on.


But guys, my hunch with the 3.9's based on the schematic is that without these being the right rating the entire unit will not power on because the current is off. Maybe too little current to the relay so it never makes contact? Or too little current to make anything turn on? I'm just thinking that without these replaced.. I can't go much further.
 
Betomon said:
Ok here are the pics of the boards



But, before we go any further.. I need you guys to know this: I took the two 3.9k resistors out because I just had a hunch that I needed to test them out of circuit. They both tested very very weirdly.. the numbers were all over the place... eventually settling on like 150-170 range (set on 2000k). But sometimes it just showed no resistance, sometimes showing an ever-lowering resistance. I believe this is a problem.... my teacher has 10 watt ceramic resistors, but I don't know the ohms just yet.. I'll look monday.

But in the meantime, if I have time tomorrow I will set the DC and bias, disconnect the quad boards, and also make that light bulb thing :D

Hopefully I'll also have a new set of aluminum function buttons machined by my buds in machine trades.
Click to expand...

Glad you took the pictures. You have the rarer version, with diode biasing. If you want to see a schematic of these boards, download a schematic for a 9090 on Hi Fi Engine. These boards are different than the schematic you have.

Now, are you talking about the the 3.9 ohm 3 watt resistors on the Power supply board? They are 3.9 ohm, not 3.9 kohm. Notice they read 3.9 ohm K. when the k is after the ohms it means a tolerance spec. I thought you ordered new resistors, 3.9 ohm to replace the bad ones on the power supply. Did you order 3.9K ohm instead? Please clear up my confusion.

And, here's the deal on the diode bias 2624 boards. The bias pots turn the opposite direction from the transistor bias boards. For minimum bias Vr3 gets set full CCW and Vr4 gets set full CW.
 
Trnsfmr said:
Glad you took the pictures. You have the rarer version, with diode biasing. If you want to see a schematic of these boards, download a schematic for a 9090 on Hi Fi Engine. These boards are different than the schematic you have.

Now, are you talking about the the 3.9 ohm 3 watt resistors on the Power supply board? They are 3.9 ohm, not 3.9 kohm. Notice they read 3.9 ohm K. when the k is after the ohms it means a tolerance spec. I thought you ordered new resistors, 3.9 ohm to replace the bad ones on the power supply. Did you order 3.9K ohm instead? Please clear up my confusion.

And, here's the deal on the diode bias 2624 boards. The bias pots turn the opposite direction from the transistor bias boards. For minimum bias Vr3 gets set full CCW and Vr4 gets set full CW.
Click to expand...



Ok good to know about the boards..

And, I did not order the 3.9s because they were not available. :S

UPDATE: Wow I so totally did not see the 280-CR5-3.9-RC available one... Idk what happened to me..... ugh :SS

So then do you think I could replace them with 4Ω? I'll look for these too in school then, but I dont know why I thought they were 3900 then :S

And I set the bias. Is the DC offset the same as other boards?
 
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The offset pots get set in the middle, or alternatively, if you haven't replaced them, just leave them exactly where they were, as the new settings, once you get it working, will be very close to the old.

Yes, you could use 4.0 ohm resistors. That's well within tolerance. Make sure they are at least 3 watts each. You have to replace these, as it will not power up without them.
 
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