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2 0 0   W i l l i a m s   D r i v e   •   R a m s e y   N J   0 7 4 4 6  
2 0 1 - 8 2 5 - 7 9 5 0   F a x   2 0 1 - 8 2 5 - 8 1 5 0  

 

Model:

 General Subject   

 

 

 

 

 

03/12/99

 

 

Classification:

 SERVICE TIP: 

 
BIAS TRANSISTOR ALOCATION or INSTALLATION. 
 

On models 

whose bias transistor may have been mounted far from the heat sink. 

Example: Picture shows TX-SV636 or TX-SV535 amplifier output bias transistor Q622, Q624 and at the center is Q616 
used for bias. 
 

 
 
 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
 

An amplifier assembly having its bias 
transistor far from the heat sink should 
be replaced and rearranged until the 
transistor body touches the heat sink. Put 
some heat sink compound between the 
transistor and heat sink assembly. Such 
exercise is basic and could provide 
stable bias at high temperature 
operation. TXSV636. 
  

Example: TXSV343 may run with higher bias 
than it should, causing power transformer to 
open. 
 
1. Idle current begins at no more than 3.5mv at 
given test points.  
2. The bias transistors should be placed up 
against the heat sink and heat sink compound 
should be added as shown. 
3. *** R582, and like resistor value may be best 
if changed from its current value 330ohm to 
270ohm.  

0399GENAMP_1