Going to give another go at my bad channel 3000a, need advice?

[wianieq]

Hi all. I have a Sansui 3000a that has the bad output issues that they issued a service bulletin modifivation for. My unit never had the mod done to it. I have a bad left channel and I think I tracked that down to a bad resistor and a coupe of transistors.

I have the service bulletin and that calls for replacing the sm 150 diodes with s-1.5-02. Anyone know what I can use for these? I couldn't tell if those numbers are values for volts, amps or etc. Need help.

I was trying to decide if I should try to get it up and running then do the cap mod, or just do the whole shebang before attempting to power it up again. I think I'm going to do a little more poking around and measuring, but I think I got my head wrapped around what needs to be done. I've including the schematics of the original and the service bulletin. Any advice on what to use for the diode replacements?

Thanks for any input.

 

[nosirrah]

Diodes

Hi all. I have a Sansui 3000a that has the bad output issues that they issued a service bulletin modifivation for. My unit never had the mod done to it. I have a bad left channel and I think I tracked that down to a bad resistor and a coupe of transistors.

I have the service bulletin and that calls for replacing the sm 150 diodes with s-1.5-02. Anyone know what I can use for these? I couldn't tell if those numbers are values for volts, amps or etc. Need help.

I was trying to decide if I should try to get it up and running then do the cap mod, or just do the whole shebang before attempting to power it up again. I think I'm going to do a little more poking around and measuring, but I think I got my head wrapped around what needs to be done. I've including the schematics of the original and the service bulletin. Any advice on what to use for the diode replacements?

Thanks for any input.

Sorry that I have no idea what diodes you need, but I'm thinking Echowars may know, did you try to cross it at Mouser or Digikey?
Please tell me how you posted the pdf scans to your message?
I often could help other members with service manual info if I knew how to do that.
Casey

 

[wianieq]

When I hit the manage attachments button, there is a pdf category. It has the highest memory limit. I still spent a bit of time trying to resize it so it was small enough. I think you can only do that kind of stuff if you have adobe acrobat, and not just adobe reader.

 

[wianieq]

All I can seem to find any info on is the sm 150 which the service bulletin says to replace. It looks like it is just adding a 1000uf 35w bipolar cap between the output transistors and the impedance switch and adding 10 ohm half watt resistors between prepower and output power transistors. It is beyond me to figure out what that is going to do to the circuit as far as what the replacement diodes should be.

I am going to try to include the whole service bulletin if it will let me.

Each channel has the two prepower to output transistors, but the schematic says to add the 10 ohm resistor between tr805 and tr802, but says .3 ohm between tr807 and tr 804. Is this a misprint? It never mentions any .3 ohm resistors. And there is only 4 10ohm and 4 1ohm resistors in the list of parts.

I have a bunch of those 1N4148 diodes, but I'm sure it wont be that easy.

Help.

 

[wianieq]

Fixed!

Well, I did the output modification a few nights ago. I had to replace one of the prepower transistors and one of the out put transistors. I powered it up and hooked up my crappy Bose test speakers and it worked! Both channels. The mod was a little intimidating for me, and I really didn't expect it to work.

I am having a few bias issues. This receiver must have lost the other channel before, because the prepower transistors where replaced with some that have no markings on them, the other two are 2sc696. When I first went at this a year or so ago, I got some outputs from NTE. One channel has the original pre power and outputs and I was able to adjust the bias down to 80ma. The other channnel, with the mystery prepower, and NTE130 outputs, could only be adjusted down to 130ma.

I have some extra of the 2sc696 that I will install in place of the mystery transistors, and I tested the old B-170008's that I removed a year ago, and one tested ok. So it looks like if I could find a B-170008 I would have all the stock transistors. I can't seem to find any though. Any ideas on where to go from here?

I love the sound of this thing. This is the unit I picked up that kind of got me started on all this vintage stuff. I got a 7070 soon after, and have recently been using my au888/tu888, but I think I like the sound of this one the best. I played a full side of a record at adecent volume then turned it off to feel the output transistors and they were colder than my hands where, I thought that the 130ma biased channel would be hot.

Thanks to all who chimed in to help me find replacement diodes for the mod. Does anyone have any more suggestions? Or Does anyone have an old, broken unit and wants to sell me a B-170008:yes: Or a selector knob, someone stuck an ugly plastic one on here.:thumbsdn:

 

[nosirrah]

3000a

Well, I did the output modification a few nights ago. I had to replace one of the prepower transistors and one of the out put transistors. I powered it up and hooked up my crappy Bose test speakers and it worked! Both channels. The mod was a little intimidating for me, and I really didn't expect it to work.

I am having a few bias issues. This receiver must have lost the other channel before, because the prepower transistors where replaced with some that have no markings on them, the other two are 2sc696. When I first went at this a year or so ago, I got some outputs from NTE. One channel has the original pre power and outputs and I was able to adjust the bias down to 80ma. The other channnel, with the mystery prepower, and NTE130 outputs, could only be adjusted down to 130ma.

I have some extra of the 2sc696 that I will install in place of the mystery transistors, and I tested the old B-170008's that I removed a year ago, and one tested ok. So it looks like if I could find a B-170008 I would have all the stock transistors. I can't seem to find any though. Any ideas on where to go from here?

I love the sound of this thing. This is the unit I picked up that kind of got me started on all this vintage stuff. I got a 7070 soon after, and have recently been using my au888/tu888, but I think I like the sound of this one the best. I played a full side of a record at adecent volume then turned it off to feel the output transistors and they were colder than my hands where, I thought that the 130ma biased channel would be hot.

Thanks to all who chimed in to help me find replacement diodes for the mod. Does anyone have any more suggestions? Or Does anyone have an old, broken unit and wants to sell me a B-170008:yes: Or a selector knob, someone stuck an ugly plastic one on here.:thumbsdn:

I may be able to help, but you have to wait a bit, see my post in D&S {Opinion}for the sordid details but I may have a 3000 parts unit, don't know if the tranny you need is the same, but you did me a favor recently, and Karma abounds!
Casey

 

[Sam Cogley]

Well, I did the output modification a few nights ago. I had to replace one of the prepower transistors and one of the out put transistors. I powered it up and hooked up my crappy Bose test speakers and it worked! Both channels. The mod was a little intimidating for me, and I really didn't expect it to work.

I am having a few bias issues. This receiver must have lost the other channel before, because the prepower transistors where replaced with some that have no markings on them, the other two are 2sc696. When I first went at this a year or so ago, I got some outputs from NTE. One channel has the original pre power and outputs and I was able to adjust the bias down to 80ma. The other channnel, with the mystery prepower, and NTE130 outputs, could only be adjusted down to 130ma.

I have some extra of the 2sc696 that I will install in place of the mystery transistors, and I tested the old B-170008's that I removed a year ago, and one tested ok. So it looks like if I could find a B-170008 I would have all the stock transistors. I can't seem to find any though. Any ideas on where to go from here?

I love the sound of this thing. This is the unit I picked up that kind of got me started on all this vintage stuff. I got a 7070 soon after, and have recently been using my au888/tu888, but I think I like the sound of this one the best. I played a full side of a record at adecent volume then turned it off to feel the output transistors and they were colder than my hands where, I thought that the 130ma biased channel would be hot.

Thanks to all who chimed in to help me find replacement diodes for the mod. Does anyone have any more suggestions? Or Does anyone have an old, broken unit and wants to sell me a B-170008:yes: Or a selector knob, someone stuck an ugly plastic one on here.:thumbsdn:

What diodes did you end up using for the mod? I picked up a 3000A last night and I'd like to get it going. If it works, it might become part of my gear or it might go to my godson.

 

[iamdoctorron]

Just so you all know, I found an AWESOME parts source in NJ called American Microsemiconductor at <www.americanmicrosemi.com>. These guys sell to the big boys (mobo manufacturers, PSU mfrs, audio component companies, etc). They WILL sell to us little guys...and they have EVERYTHING and spec sheets/xref for parts. They even, to my surprise, carry about EVERY valve (electron tube) ever made. I was VERY impressed.

Just a satisfied customer--my first time doing business with this great parts company! I swear upon my Adcom GFA-555 that I am in no way affiliated with them!

DocRon

 

[McGowdog]

Fixed!

Well, I did the output modification a few nights ago. I had to replace one of the prepower transistors and one of the out put transistors. I powered it up and hooked up my crappy Bose test speakers and it worked! Both channels. The mod was a little intimidating for me, and I really didn't expect it to work.

I am having a few bias issues. This receiver must have lost the other channel before, because the prepower transistors where replaced with some that have no markings on them, the other two are 2sc696. When I first went at this a year or so ago, I got some outputs from NTE. One channel has the original pre power and outputs and I was able to adjust the bias down to 80ma. The other channnel, with the mystery prepower, and NTE130 outputs, could only be adjusted down to 130ma.

I have some extra of the 2sc696 that I will install in place of the mystery transistors, and I tested the old B-170008's that I removed a year ago, and one tested ok. So it looks like if I could find a B-170008 I would have all the stock transistors. I can't seem to find any though. Any ideas on where to go from here?

I love the sound of this thing. This is the unit I picked up that kind of got me started on all this vintage stuff. I got a 7070 soon after, and have recently been using my au888/tu888, but I think I like the sound of this one the best. I played a full side of a record at adecent volume then turned it off to feel the output transistors and they were colder than my hands where, I thought that the 130ma biased channel would be hot.

Thanks to all who chimed in to help me find replacement diodes for the mod. Does anyone have any more suggestions? Or Does anyone have an old, broken unit and wants to sell me a B-170008:yes: Or a selector knob, someone stuck an ugly plastic one on here.:thumbsdn:

You had me at "crappy Bose speakers" .

 

[nij2514]

Thanks for the helpful information. Everything that is received is useful in every topic. But still can't catch the right direction on what topic to do, thank you

 

[dly66]

Used the On MJ21194 for replacement output transistors in mine. It is back in the project queue since last time I tried to use it it went into protection after a period of playing. Turned it off and back on it was playing normally but did not trust it. Will try to figure it out sometime in the future after completing some other projects.

 

[RodantKapoor]

I was fortunate to buy a 3000A with the modification already performed. I really enjoy the sound this Sansui puts out, and it looks very nice as well.
Enjoy!

 

[Billy1973]

I picked up a Sansui 3000a some years back, probably on Ebay. My dad has one that he brought back from overseas in the late 60s, I liked the looks of it so that's why I picked one up. It just sat in the closet for about 10 years. I am now in the process in restoring the 3000a. I also just acquired a set of late 60s Sonics as-300 speakers that I will also be refurbishing. At the moment I am measuring 32 VDC on the output of the 3000a, so I think I have my work cut out for me.

 

[tom3]

Usually you'd have a resistance load on the outputs, but that's a scary voltage. Good that you checked before hooking up speakers.

 

[Billy1973]

I

Usually you'd have a resistance load on the outputs, but that's a scary voltage. Good that you checked before hooking up speakers.

I will post picture as I start and finish the refurbishing process on my Sansui 3000a. I hope all goes well. I found a restored and refurbished Sansui SR-4050c turntable that I am considering buying. Here are a couple of not so good pics of the Sonics as-300 speakers I will be refurbishing.

 

[tom3]

You've probably seen this before but be sure to replace the 8 (?) diodes on the driver amp board. One of those goes bad and stuff starts smoking.

 

[Watthour]

I picked up a Sansui 3000a some years back, probably on Ebay. My dad has one that he brought back from overseas in the late 60s, I liked the looks of it so that's why I picked one up. It just sat in the closet for about 10 years. I am now in the process in restoring the 3000a. ... At the moment I am measuring 32 VDC on the output of the 3000a, so I think I have my work cut out for me.

I'm thinking that the outputs are either shorted or are being driven to the moon by the 2SC696s. The drivers in that amp are sketchy. So are the outputs and their bias circuits.

I pulled the TO-5 can drivers and their six pounds of hardware and sockets, the installed much heavier TO-220s along the sides of the heat sinks instead (BD241CG). Of course, the original outputs were baked as a result of the drivers experiencing electronic diarrhea, and those were replaced with MJ21194Gs instead.

The 1971 factory service bulletin upgrades are highly advised, although you won't need all those special mounts and brackets since it's not 1971 any more. The new components will fit nicely in the space behind the amp section and rear wall of the unit.

The output coupling capacitors will not prevent the Rice Crispies falling out of your 'Sui, but will have a chance of keeping your speaker voice coils from melting. Obviously, those are not installed in your unit, which leads me to believe it has been untouched since it left the Post Exchange in 1969.

 

[Billy1973]

I'm thinking that the outputs are either shorted or are being driven to the moon by the 2SC696s. The drivers in that amp are sketchy. So are the outputs and their bias circuits.

I pulled the TO-5 can drivers and their six pounds of hardware and sockets, the installed much heavier TO-220s along the sides of the heat sinks instead (BD241CG). Of course, the original outputs were baked as a result of the drivers experiencing electronic diarrhea, and those were replaced with MJ21194Gs instead.

The 1971 factory service bulletin upgrades are highly advised, although you won't need all those special mounts and brackets since it's not 1971 any more. The new components will fit nicely in the space behind the amp section and rear wall of the unit.

The output coupling capacitors will not prevent the Rice Crispies falling out of your 'Sui, but will have a chance of keeping your speaker voice coils from melting. Obviously, those are not installed in your unit, which leads me to believe it has been untouched since it left the Post Exchange in 1969.

Thank you for the pictures and advice. I appreciate any info I can get on this Sansui 3000a and the Sonics as-300 speakers. I hope to start opening her up in a couple of days.

 

[Billy1973]

You've probably seen this before but be sure to replace the 8 (?) diodes on the driver amp board. One of those goes bad and stuff starts smoking.

Yes I have read the 1971 CE-007-A Service Bulletin, it says to replace the eight SM-150 diodes with S-1.5-02. I can not seem to source the S-1.5-02 diodes, would you happen to know an equivalent replacement for the SM-150 or know of a place to source the S-1.5-02?

 

[tom3]

Don't have the number right now but those are just standard diodes. And you might want to give the 4 fuses and holders a good cleaning while you're in there. Mine were some corroded and losing some current flow.