Posted by Dal on September 17, 2003 at 08:23:50:
In Reply to: Help with Sansui 3000A.... posted by Pork Chop on August 06, 2003 at 21:26:29:
Hi Pork Chop.
There was a factory Service Bulletin which covered an important modification to the output stage of the 3000A. It has been at least 30 years since I performed this mod to my own 3000A so I can only tell you that it involved adding a small kit of components and a minor mod to the bias circuit and driver stage to correct a problem with DC instability.
An unmodified 3000A would only play for a year or two before developing problems in the output stage. After modification, my unit played for many years before further problems arose.
My guess is that your unit's been stored for a long time and missed out on the mod. Tannenbaum's have a service manual for 3000A and you can buy it online for $20 but I don't know if the Service Bulletin will be incorporated. It's worth a try.
As for capacitors, Japanese consumer-grade electrolytics from the 60's would have to be the worst capacitors ever made! After tracing / replacing several faulty electros in my 3000A, I just said "F... this" and replaced every damn one of them with modern types.
The difference this made to the amp's performance was unbelievable! (I'm listening to it as I write this) It went from sounding fuzzy and geriatric, back to seriously good -- maybe even better than new. Capacitors have evolved a lot since the 60's and they don't leak and dry up like the original parts.
The original values will not be readily available but that's no problem. You can safely "round up" the capacitance and voltage of any electrolytic in the unit to the nearest available value but don't change any of the small non-polar caps in any stage, (unless they're clearly faulty).
Modern electrolytics will be heaps smaller than the originals so you might have to play with the leads a bit -- all the PCBs are silk-screened with the + / - ends clearly visible so it's hard to go wrong. Just make sure you mirror any changes in both the left and right sides or the amp will sound unbalanced.
Sorry I can't be more specific about the output mod... About 10 years ago, the output stage in my unit finally failed in a way which I considered "Beyond Economical Repair". Because the amp looks so cool and had been with me for so many years, I decided to revamp the output stage completely.
For all I know, mine may be the only 3000A in the world with a MOSFET output stage! The rest of it remains fairly original though (except the caps) and it totally creams most modern amps for sound!
I wish you the best of luck solving the output problem. You can email me if you have any other questions that might jog my memory!
Dallas G. Clarke
: Hi all. I have just recently received a Sansui 3000A receiver from my uncle who purchased it while in the service (Vietnam). I don't know exactly where/when he bought it, but he was kind enough to give it to me, complete with a pair of SP-1500's. I'm looking for info/history on this unit that isn't on the panel. The ser# is: 119060618
: Also, I'm having trouble with it. About 30-60 seconds after powerup, it goes into "shut-down" mode. Trying to adjust anything on the front panel causes the shut-down instantly. However, for the first 30-60 seconds, it sounds great. Even with a few blown (I think) tweeters. It sat for about 10-15 years without being used, and given its age, could it be bad caps? I would love to get it working, as the amp is pristine. Not even one freakin' scratch!
: Many thanks in advance,
: Pork Chop
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