Uni-watt Transistors Identification

Rotoflex4

Active Member
I've read here that the Uni-watt transistors should be replaced. I'm not 100% sure if what I am looking at are the dreaded uniwatts. They are marked "C1124" and "A706", on the driver board of my AU-11000. Can anyone confirm??? Thanks.
 

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Great. Thanks! I have some extra MJE340 and MJE350 laying around. Do you think they would be suitable subs? Other posts recommend the KSA1220 for the A706, and KSC2690 for the C1124. I'd have to order the KSA1220/KSC2690, but that's not too big a deal.
 
Great. Thanks! I have some extra MJE340 and MJE350 laying around. Do you think they would be suitable subs? Other posts recommend the KSA1220 for the A706, and KSC2690 for the C1124. I'd have to order the KSA1220/KSC2690, but that's not too big a deal.
Use the KSC/KSA, those MJE are no good.....
 
I'm looking to proactively replace the A1124/A706 pre-drivers in my AU-9900 ..
While the KSC2690 is available, the KSA1220 is obsolete ( !! ).
Can anyone suggest a good, currently available, sub for it - or the pair ?
Thanks...
 
I'm looking to proactively replace the A1124/A706 pre-drivers in my AU-9900 ..
While the KSC2690 is available, the KSA1220 is obsolete ( !! ).
Can anyone suggest a good, currently available, sub for it - or the pair ?
Thanks...
I found this in my notes. Someone here posted this, but I don't know who. I recently completed an AU-11000 and can confirm these are good subs:

When repairing AU-11000 and AU-9900 amps the following work should be done:
I have found the pre - driver transistors in these and other Sansui amps to be failure prone, at least when they get this old. They are the ones that have a tab on the top, but they are not TO-220 case. Motorola used to call this case "Uni-Watt" because they had a 1 watt power rating. I have found that they go intermittent and sometimes fail outright, causing possible damage to the rest of the power amp. I recommend replacing them with KSC3503ESTU and KSA1381ESTU, available from Mouser Electronics.
 
I found this in my notes. Someone here posted this, but I don't know who. I recently completed an AU-11000 and can confirm these are good subs:

When repairing AU-11000 and AU-9900 amps the following work should be done:
I have found the pre - driver transistors in these and other Sansui amps to be failure prone, at least when they get this old. They are the ones that have a tab on the top, but they are not TO-220 case. Motorola used to call this case "Uni-Watt" because they had a 1 watt power rating. I have found that they go intermittent and sometimes fail outright, causing possible damage to the rest of the power amp. I recommend replacing them with KSC3503ESTU and KSA1381ESTU, available from Mouser Electronics.

Hi Ray,

Re the KSC3503/KSA1381 advice as a suitable replacement for the “uni watt” transistors - these are rated at 100ma max collector current, whereas the original 2SA706/2SC1124 are rated as 1amp collector current. There are some “uniwatt” transistors that are rated at 50ma max collector current, and the KSC3503/KSA1381 are suitable replacement for these.

The KSC3503/KSA1381 aren’t equivalent to the KSC2690/KSA1220 and TTA004/TTC004, these alternatives are rated at 1amp max collector current.

Cheers
John
 
Hi Ray,

Re the KSC3503/KSA1381 advice as a suitable replacement for the “uni watt” transistors - these are rated at 100ma max collector current, whereas the original 2SA706/2SC1124 are rated as 1amp collector current. There are some “uniwatt” transistors that are rated at 50ma max collector current, and the KSC3503/KSA1381 are suitable replacement for these.

The KSC3503/KSA1381 aren’t equivalent to the KSC2690/KSA1220 and TTA004/TTC004, these alternatives are rated at 1amp max collector current.

Cheers
John
Good to know, John. I didn't even look at the specs, as they were recommended by someone whom I trust.

I'll be sure to check before just blindly stabbing them into anything that used Uniwatts!
 
If a 0.9W power rating (at ambient) will suffice, KSA1013 and KSC2383 are worth considering. They're good for 1A and pretty high voltage. And they're available! They are a "long" TO92 package, so they aren't suitable if a tab is needed for mounting.
 
I'm looking to proactively replace the A1124/A706 pre-drivers in my AU-9900 ..
While the KSC2690 is available, the KSA1220 is obsolete ( !! ).
Can anyone suggest a good, currently available, sub for it - or the pair ?
Thanks...
TTA/TTC004b
TTA006B/TTC011B
TTA008B/TTC015B

Any of this should work fine
 
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