Another sick Sansui 3000A.

Hi all,
This is my first post here. I usually work on tube radios an TVs from the 30's-50's. But this weekend I picked up this Sansui 3000A.


Upon getting it home I cleaned it up and did a test to see if it would power up, which it did. One of the dial lamps was burned out. As it was an odd bulb and I figured I could wire something else in, I did so. I am really embarrassed about this, but its important to what's going on with the set: I somehow inexplicably wired the new lamp in wrong and thus created a short. So when I flipped the power again what occured was that all four of the fuses that are mounted to a board inside for the 4 channels instantly blew.

Seeing this I figured well, I'll just remove the bulb I had soldered in and that would solve the issue. Nope. Now every time I install new fuses, they will blow as soon as the set is turned on. So something must have shorted out when the dial lamp shorted.

I did some research about this amp and it seems they have some common problems. One is that the output transistors tend to go bad and when they do, that can ruin the speakers its connected to. I also read somewhere that these used some poorly designed bias diodes and these also have a high failure rate.

I checked the voltage going to each of the fuses. All showed about a 37-40 volt variation. I then checked the voltage on many of the other components in that circuit. Again, all around 40 volts. So there is either too much current being drawn through the fuses or there could be some sort of surge on initial powering up.

Lastly, this has all of the original electrolytics. Like any piece of vintage equipment I assume its probably not a bad idea to replace these- especially some of the super high capacitance units, some of which show as much as 3,000uF.

How good are these BTW? I have a Marantz amp I use for my home stereo and it sounds great. Would this be an improvement or is it no match?

Any help would be appreciated. I am going to do some more digging into this set over the next few days.

There are guys that love them and guys that dont love them as much.....

I am the latter, while they have quite a good tuner, pretty much the rest of the unit is a fail in my opinion.
The power-amp can be a real nightmare if it hasn't had the output coupling cap mod (factory mod).
It appears when these amps first came out they had a fairly high failure rate and because the output s direct coupled they were burning up speakers...
If you were to take a picture of the unit with the bottom off, we can tell you if it has the mod....
There is a AK member here working on a power amp drop in replacement for these....
I had one, and once I got the FM section running properly I recapped my unit and got the power-amp running as stable as possible, then one day I turned it on and watched the cones on my Pioneer speaker pulse forward and stop, so I turned it off, and found I had 30VDC on the output of the amp......
The output transistors were OK, it was a driver failure, and basically as soon as i fixed one thing, then something else would go wrong...
The longer it ran the more things went wrong, pre-amp transistors went noisy etc etc.....
So I gave mine away free with a couple of cassette decks I sold.....

In my opinion, if you want one as a project, be prepared to completely re-work the power amp....standard, they are a hazard to your speakers, I dont care what anyone says....

But, when it was running, I thought it sounded pretty good, nice old warm sound, great at low volumes.....but at the end of the day, not my cup of tea so to speak....

Oh by the way, welcome to AK........:thmbsp:

I traded a Marantz 2245 (which sounded good but was not making the rotation) for a 3000A (which has the "mod" and a little other work done on it) and a totally recapped Harman Kardon 330B. I am very happy with the trade. I would have been happy with a straight across Marantz for 3000A trade if the values had been closer. I like the 3000A's sound quite a bit better than the Marantz. This is personal opinion of course.

Hmm... the concerns I've read from numerous people with these 3000 series amps is a bit worrisome. I have a Fisher tube amp in the garage and a Marantz in the house. This was possibly going to be swapped out with the Marantz, but I'd be annoyed if they destroyed the Bose speakers I just picked up for a steal at a yard sale. I guess for me its more about working on something new and learning more about solid state electronics. Compared to some of the awful early PCB tube electronics I've worked on, this Sansui looks pretty nice as far as ease of getting to stuff.

I don't know if I want to blow a ton of money on this as there are A LOT of big capacitors in there and with cap prices these days, I could see just those running into the $100+ range easy.

I believe the club I belong to has a bunch of vintage transistors sitting around that might work for this. Its a shame that these have somewhat notorious reputations. The front face plate and the knobs are made out of solid machined aluminum. So it at least 'seems' nice.

looking at the schematic for the 3000 .+ - 40v is the correct voltages going through f1 to f4 .
the 3000 is apparently more or less the same as the 3000a .
i don't know what you did to blow all the the 4 fuses .
if you have the manual there is an in depth fault finding part to it . best i have seen as it happens .

bobwilson77 said:

Hmm... the concerns I've read from numerous people with these 3000 series amps is a bit worrisome. I have a Fisher tube amp in the garage and a Marantz in the house. This was possibly going to be swapped out with the Marantz, but I'd be annoyed if they destroyed the Bose speakers I just picked up for a steal at a yard sale. I guess for me its more about working on something new and learning more about solid state electronics. Compared to some of the awful early PCB tube electronics I've worked on, this Sansui looks pretty nice as far as ease of getting to stuff.

I don't know if I want to blow a ton of money on this as there are A LOT of big capacitors in there and with cap prices these days, I could see just those running into the $100+ range easy.

I believe the club I belong to has a bunch of vintage transistors sitting around that might work for this. Its a shame that these have somewhat notorious reputations. The front face plate and the knobs are made out of solid machined aluminum. So it at least 'seems' nice.

Click to expand...

The build quality of these units is pretty good, and they did put a lot of thought into the design, but its weak point unfortunately is the most important part which is the stability and reliability of the power-amp.
They knew the blew it with the design because they released the cap coupling mod....

petehall347 said:

looking at the schematic for the 3000 .+ - 40v is the correct voltages going through f1 to f4 .
the 3000 is apparently more or less the same as the 3000a .
i don't know what you did to blow all the the 4 fuses .
if you have the manual there is an in depth fault finding part to it . best i have seen as it happens .

Click to expand...

It will be the drivers response to the possible intermittent bias/DC offset trimmers.....
There is probably a few diodes gone because of it too.....

The build quality of these units is pretty good, and they did put a lot of thought into the design, but its weak point unfortunately is the most important part which is the stability and reliability of the power-amp.

Click to expand...

I find this one fascinating because due to its age it is from the era when a lot of the Japanese electronics firms were trying to get a solid foothold in the market and as such, and at least to me some of the electronics from the likes of Sony, Sansui, and Teac were excellent from this era. But this is fairly early. I'd say this is not as nice as the older 50's era Fisher amp I have. But its still pretty nice.

I took the amp apart tonight. Here are a few images of the innards. I also did a simple resistance test on the four output transistors. The readings were all over the place. Two showed as open. One showed about 1900 ohms. The last showed about 200 ohms. No telling whats going on with that.

Could that be the original factory protective plastic on that bezel? It sure looks like the way I remember it.

I hope your 3000A doesn't turn out to be the PITA that my 5000 is turning out to be.

Looks to be an unmodified unit. Careful there. Speaker VCs can be set on fire with that. Need to check all components in the driver amps and outputs. Can't imagine blowing all four fuses, but strange things happen. Having the protective tape still on the face is pretty rare after 45 or so years. Probably well worth repairing.

I like it. Fix it! There’s one on Ebay for a buck, $36.00 shipping. It may have the coupling mod! Ask the guy.