Finally rebuilding my Sansui G-8000, I’ll post all my questions here.

[saabracer23]

I don't care how much it costs within reason....No expense spared on my restorations, especially when its my own..

Completely agree, I would have initially gone with the 12,000 uF caps if I hadn’t been cautious with a large increase in filter capacitance. Now if I can purchase two types of cap that are somewhat similar and one is $10 and the other is $40 and I need to buy 8 I may be lead to the cheaper cap. If I only need 2 then I have no issue purchasing the more expensive cap.

Would you rather go for more capacitance or quality (ripple, esr)? Meaning I have to meet a specific physical size and I can either choose the 12,000 uF caps I purchased made by United Chemicon or I can go for the original ones I was going for. They were 6,800 uF Nichicon Gold Tune. 6,800 was the original value so it wouldn’t be like it was lacking, but people seem to really like to use the Fine Gold line. That was the only value that would actually fit as well.

I’ve also read that audio grade caps are a waste in the Filter section.

I was looking for that thread. I think I found it, but the pictures are all missing. Too bad Panasonic doesn't make those THA's anymore. I thought those were perfect for the G series.


The datasheets seem to indicate that the United Chemicons are better. I was going to recommend the Kemet ALT series, but I see for the one in your size, the price is double of the United Chemicons and double what I paid for mine in 15,000 uF. They were only $6 apiece and worked great in my AU-717.

Yes, I keep a large stock of these on hand for rebuilds. They are a very nice and inexpensive cap.




Dan

 

[kevzep]

Ive got some 22,000µF Kemet's in my G22000, they seem to get the job done, the original caps were 15,000µF...

The KG caps are intended for audio amplifiers, so I would say Nichicon may have paid close attention to the parameters that really matter for Audio applications...

 

[Hipocrates]

Ive got some 22,000µF Kemet's in my G22000

Oh man... you ruined that poor unit, is not good anymore, please send it to me for proper disposal.

 

[saabracer23]

Ive got some 22,000µF Kemet's in my G22000, they seem to get the job done, the original caps were 15,000µF...

The KG caps are intended for audio amplifiers, so I would say Nichicon may have paid close attention to the parameters that really matter for Audio applications...

Okay good to know, I’m sure they are good and I use them often, like in my HK Citation 19. It has four 15,000 uF KGs, originally it had 10,000s. It’s on my bench as I wait for the G8000 parts to get here.




But to answer my question, if you had to choose between the 12,000uF United Chemicon or the 6,800 uF Kg which would you choose? Only ones that could get to physically fit. More capacitance or more “audiophile” cap?

Dan

 

[kevzep]

But to answer my question, if you had to choose between the 12,000uF United Chemicon or the 6,800 uF Kg which would you choose? Only ones that could get to physically fit. More capacitance or more “audiophile” cap?

Yeah thats a tough call, but you know I would be inclined to go with the KG to be honest. I use them all the time, they are my go to Main Supply caps of choice...

 

[Kale]

Regarding the filter caps, I remember a nice thread from Kale, regarding the wiring of those caps, with some mods of ilizm... Sadly I can't find it anymore. I replace the wiring there and used some panasonics THA with some O-rings

I just made a new post in this my old thread, but with pictures about that....

 

[Hipocrates]

I just made a new post in this my old thread, but with pictures about that....

Awesome Kale, thanks a lot!

 

[saabracer23]

So I’ve been taking pics as I’ve done the rebuild. After I finished I was bringing it up on my variac and ran into an issue. So I did a full recap, all lamps, all relays, all four drivers (transistors, went with mje15034 and mje15035) and replaced all output transistors (there were literally 8 different transistor models and one pair was shorted. I went with mj21193 and mj21194. I figured the shorted pair was the reason why I got no output from the channel and blown fuse when I received it.) Coming up on the Variac I was reading a small measure of mV on the right channel and absolutely nothing on the left. Once I hit about 60V ac on the variac I heard a sizzle and I dialed it back down. I found two blown fuses on the board with the soft start resistor. The two that are ceramic.



I’ve gone over my work and figure I haven’t created any dead shorts.

I’m hoping to get suggestions on where to look, what I can do to narrow down the area where the issue lies. As soon as I get this figured out I’ll post the rest of my pics of the rebuild.

Thank you,
Dan

 

[Hipocrates]

Do you have an DBT, firts you need to be sure that the power supply section is working good.

 

[saabracer23]

Do you have an DBT, firts you need to be sure that the power supply section is working good.

I don’t, I thought a Variac would take place of a DBT. If I need a DBT to move forward I’ll build one tomorrow morning. Above when I said I was reading
A few mV on the right channel and nothing on the left I wasn’t too clear about that. I had my DMM on the test points for measuring bias.

Dan

 

[Hipocrates]

The DBT is important to limit current.

Once we are sure the power supply section is ok, we go from there.
Did you replace 10D diodes?

Pics can help specially with a nice resolution. (hundreds of eyes see better that two)

 

[kevzep]

Those driver replacements aren't suitable, they'll limit the bandwidth of the amplifier quite a lot and affect is slew rate.
You need to use 100mhz drivers, you'll get away with the 4mhz output transistors though.

 

[saabracer23]

The DBT is important to limit current.

Once we are sure the power supply section is ok, we go from there.
Did you replace 10D diodes?

Pics can help specially with a nice resolution. (hundreds of eyes see better that two)

Alrighty, working on the DBT right now. 10d diodes, you mean the single one on the board with the soft start resistor or every one in the amp? I could do them all. It looks like on audiokarma there are several suggestions for replacements. On hand I have 1N4001, 1N4004, 1N4007, 1N5408, and 1N5404 for some larger sized ones. Any of those you’d suggest? I can get pics posted, what would you like to see specifically?

Those driver replacements aren't suitable, they'll limit the bandwidth of the amplifier quite a lot and affect is slew rate.
You need to use 100mhz drivers, you'll get away with the 4mhz output transistors though.

Oh well that’s a bummer, I searched the audiokarma Sansui section to see what others mention would make a good replacement for the stock 2SA968 and 2sc2238. I found four that were suggested that I had on hand, MJE15032, MJE15033, MJE15034, MJE15035. As far as the outputs, those were suggested by EW and I did have to order those, but his knowledge seems to be trusted here.

Any suggestions for drivers?

Dan

 

[ManyMoonsAudio]

You may have got one of the driver boards plugged in one pin off. Be very careful plugging them in.

 

[Hyperion]

Alrighty, working on the DBT right now. 10d diodes, you mean the single one on the board with the soft start resistor or every one in the amp? I could do them all. It looks like on audiokarma there are several suggestions for replacements. On hand I have 1N4001, 1N4004, 1N4007, 1N5408, and 1N5404 for some larger sized ones. Any of those you’d suggest? I can get pics posted, what would you like to see specifically?

You absolutely do not need to replace these. If you want to be absolutely correct none of the 1N4xxx series are correct because they are only rated at 1.0A. Also the 1N54xx are also wrong because the current rating is too high, meaning that the leads of the device are too thick to go into the original holes.

If you absolutely, definitely, totally want to replace them, then the exact correct device is 1N5392, 100V & 1.5A just like the original 10D1.

(Note: you will see on AK where I have used 1N4003 to replace 10D1 - this was where they were used across relay coils to quench back emf from the coil in order to protect the relay driver transistor. But for ordinary rectification duties the correct substitute should be used).

 

[Hipocrates]

Alrighty, working on the DBT right now. 10d diodes

Test them to see if you have something going on there. if they are ok just move on (on both I did were previously replaced with 1N series) and the reason I ask is to try to guess if something is going on there.|
Hyperion is right about replace them, unless they are bad.

2SA968 and 2sc2238.

IF yours are good I would use them, I haven't look for more suitable replacement, on both I did they were good and strong.

 

[saabracer23]

You may have got one of the driver boards plugged in one pin off. Be very careful plugging them in.

I thought of that as well, it looked aligned, but I’ll be double careful when I put it back together.

You absolutely do not need to replace these. If you want to be absolutely correct none of the 1N4xxx series are correct because they are only rated at 1.0A. Also the 1N54xx are also wrong because the current rating is too high, meaning that the leads of the device are too thick to go into the original holes.

If you absolutely, definitely, totally want to replace them, then the exact correct device is 1N5392, 100V & 1.5A just like the original 10D1.

(Note: you will see on AK where I have used 1N4003 to replace 10D1 - this was where they were used across relay coils to quench back emf from the coil in order to protect the relay driver transistor. But for ordinary rectification duties the correct substitute should be used).

So they don’t necessarily need to be replaced? If they did need to be replaced and I didn’t want to have to wait a week for parts to come in I could technically use the 1N54xx if I enlarged the holes? I have a bit set made specifically for PCBs and enlarging holes. It doesn’t look like I need to make them all that much larger.

Test them to see if you have something going on there. if they are ok just move on (on both I did were previously replaced with 1N series) and the reason I ask is to try to guess if something is going on there.|
Hyperion is right about replace them, unless they are bad.


IF yours are good I would use them, I haven't look for more suitable replacement, on both I did they were good and strong.

Alright, I’ll pull pull the ones on the power supply boards and measure them to see if they’re good. If they are then I’ll leave them in.

As far as the drivers go, two were replaced at some point using a 2sa490 and a sk3929. I just thought it would be nice to have all of them be matching devices.




Got the DBT finished up and ran down to the local hardware store and picked up an assortment of bulbs. I got 40w, 60w, 150w, 200w, and 300w. I was told 75w and 100w are no longer being produced which was sad to hear. I went to two other stores and they didn’t have any either, in fact the incandescent bulb selection was quite sad. Probably 75% or more were L.E.D.

Also, what would you like to see a detailed photo of?

Dan

 

[Hipocrates]

That's good looking DBT, well done.
If you enlarge the holes for the little diodes going to be ok, I would just test if they are shorted.
Regarding the drivers:
You can work with the one that you got to to keep the unit going.
Let me see if I can come up with more suitable replacements. I've seen some people using some Toshiba but who knows where they found them.

I think 60W bulb will work if not the 150W.

The pictures are just to see what in there and the work done (kind of visually inspect the unit).

 

[kevzep]

Oh well that’s a bummer, I searched the audiokarma Sansui section to see what others mention would make a good replacement for the stock 2SA968 and 2sc2238. I found four that were suggested that I had on hand, MJE15032, MJE15033, MJE15034, MJE15035. As far as the outputs, those were suggested by EW and I did have to order those, but his knowledge seems to be trusted here.

Any suggestions for drivers?

They won't hurt the amplifier at all, but you wont be getting anything like the best performance from it.
A lot of people recommend those transistors, but they are not the right ones....
You'd be able to see if you ran a 10khz square wave through the amp, the speed of the amp is compromised.
I'll have to look up an alternative, or you can get them off the german seller on the bay, I've got them from him before and they are genuine. (that is the Toshiba 2SC2238/2SA968)

 

[Hyperion]

Kev is absolutely right, the driver transistors are important, it won't sound right until you have the correct ones.

I used the MJEe's on a couple of amplifiers, and was unhappy with the results, but changing them for the correct type made a difference.