I got a Sansui 8080DB in from a friend because it quit on her. I found a boat load of old caps inside and went ahead and replaced every electrolytic in the driver and amplifier boards, Also did the two giant cans. My repair got it to quit popping fuses! A small success. I noticed upon turning on the amp that the driver board began to smoke out of the left channels bias and DC offset pots. (immediate power-down) Looked down and saw that one of the transistors is quite a bit different in color than its mate for the right channel. Meter shows a short, Problem is, I have no idea what transistor to order. The numbers on it are...
A899 V
S JN
Looks to be a typical transistor, with an emmitter collector and base. I must admit I know very little about transistors because all my amps use tubes. I was able to successfully diagnose that the transistor is bad but I am clueless on what to order.
Any help would be appreciated
A899 V
S JN
Looks to be a typical transistor, with an emmitter collector and base. I must admit I know very little about transistors because all my amps use tubes. I was able to successfully diagnose that the transistor is bad but I am clueless on what to order.
Any help would be appreciated
Look familiar? 2SA899 Semiconductor (Transistor, diode, IC) Cross reference
This page gives some cross references that may substitute for it, if that's the type it is.
This page gives some cross references that may substitute for it, if that's the type it is.
I believe you can substitute 2sa899 by 2sb649, which should be available.
Try MCM Electronics.
Last edited:
First place to start is to get a schematic, so you can see how the parts are used. There's one on Hifi Engine - Sansui 8080DB | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
A quick look at that shows that 2SA899's are used as the VAS transistor in what is a pretty typical "Lin" or "Blameless" topology solid state amp. The data I found on the 2SA899 suggests it's a TO-126 package transistor, pretty typical figures for VAS use - fairly high voltage (100Vceo is typical), medium current (typically 50-100mA), medium power dissipation (the TO-126 package is typical) and fairly fast fT of ~100MHz.
My suggested replacement would be the Fairchild KSA1381. If you want to do a quick test, an MJE350 should serve.You may have to increase the value of the Miller compensation capacitor (C11-12) to ensure stability. The original 15pF seems a bit low to me - I'd put at least 47pF there.
The thing to consider is what caused this transistor to fail. Typically the VAS fails as a consequence of driver or output transistor failure, especially where a VI limiting circuit is implemented. You will want to check the drivers (TR11-TR14) and the outputs (TR701-TR704) to make sure they are OK before replacing this. Check also the components in the limiter circuit (TR15-18, D13-16 and associated resistors) to make sure they're intact.
A quick look at that shows that 2SA899's are used as the VAS transistor in what is a pretty typical "Lin" or "Blameless" topology solid state amp. The data I found on the 2SA899 suggests it's a TO-126 package transistor, pretty typical figures for VAS use - fairly high voltage (100Vceo is typical), medium current (typically 50-100mA), medium power dissipation (the TO-126 package is typical) and fairly fast fT of ~100MHz.
My suggested replacement would be the Fairchild KSA1381. If you want to do a quick test, an MJE350 should serve.You may have to increase the value of the Miller compensation capacitor (C11-12) to ensure stability. The original 15pF seems a bit low to me - I'd put at least 47pF there.
The thing to consider is what caused this transistor to fail. Typically the VAS fails as a consequence of driver or output transistor failure, especially where a VI limiting circuit is implemented. You will want to check the drivers (TR11-TR14) and the outputs (TR701-TR704) to make sure they are OK before replacing this. Check also the components in the limiter circuit (TR15-18, D13-16 and associated resistors) to make sure they're intact.
found the culprit
Someone has been here before i found all 4 output transistors were mismatched one was completely shorted out. Going to replace all 4, repair the driver and try again. I found old stock replacements from an american source, ordered them and the fusable resistors. It will be good to be done with this so i can get back to playing with toobz
Someone has been here before i found all 4 output transistors were mismatched one was completely shorted out. Going to replace all 4, repair the driver and try again. I found old stock replacements from an american source, ordered them and the fusable resistors. It will be good to be done with this so i can get back to playing with toobz
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.