Martex M200 amps

Excellent, take a few with ya, .....!!!!!!!!!!!!


Is that an arduous process??
 
I'm thinking about just letting the amp off the DLT and see what happens. I compared the voltages of the differential amp transistors with the "good" side and there real close .I didn't find any real big voltage readings between sides . I ran amp on DLT it went to -117mV from -160mV and was about 10 to 15minutes it seem to balance out around-117mV and -116mV . Any ideas? or modifications ?
 
If ou still have it on DBT that could hold your offset high by limiting voltage to about 90 volts..
 
I mixed up the color bands on the diode on the base of Q3 (740 resistors on schematic) .From the Cathode edge its violet, yellow, brown . So 1N741 is 130v zener .Its across the +/-67v rails. I'm wondering if this could be leaking and effecting Q3's behavior ?
 
It passes the diode check yes and I get the same voltage drop across it has the good side . Something is causing the high DC offset on this side . The differential amp appears to be working but the negative voltage seems to strong so it doesn't balance out better ?
 
Do the voltage checks look the same from left to right on the front diff trans??
 
all but the base voltages on Q2 . Its -127mV on the bad side and -40mV on the good side
 
with the DLT in I have- 46v on the C of Q2 and -42v on the c Q1 It differs by 1volt each from the good side. Have to take it of the DLT it knocks the voltage to 46 -/+
 
What happens to the offset when ya come straight outta the wall on the AC?
 
Is the ground shell of the RCA jack really tied to the signal path downstream of the dominant pole cap(C4)???
 
It is the same as when on the DLT . Its 100mV higher than the good side. Its -140mV on turn on and it starts to head toward zero
 
That whole line from the base of Q2 to the negative speaker terminal connects to the center tap of the secondary winding ,there is no chassis ground. There are a lot on connections on it maybe that 100mV overage DC is from one of them . I disconnected the 22k(by RCA jack) from that line and offset went real high . That line should 0v right ?
 
A zener diode in that place is usually used as a voltage divider to for a lom voltage source. Just for kicks, put a 10K/half watt resistor in series with the RCA negative and the point it enters the board.
 
Which wire represents the transformer secondary centertap?
 
The schematic doesn't show it .I wasn't sure about it when I made the schematic. I should put a note on the line . I'll try the 10k , I did have the input jack wire(-&+) removed from the board at one time ,that made no difference in offset .
 
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