[Sathimas]

Hi there,

as always when I build something, it doesn't work right away from the start

Well, I exagerate - bot sometimes it really seems so.

My e12 - newly added to my M³ does not work.
If I turn on power there no click, Voltage reading across the OPA pins is ~13,4Volts both (4/7)
and about half of that between pins 6/7.

Power supply is a s11, working correctly.

I already checked the position of the parts, orientation, no solder bridges.
What else can I look for?

greetings
Sathimas

 

[amb]

I assume that your voltage readings is from U1 or U2 pin 7 to VG and pin 4 to VG.
What did you use for the D1 zener diode? Should be a 24V zener...

 

[Sathimas]

The voltage I posted is measured between the pins 4 and 7 of each of the 2 OPAs.
(Where it should be ~ 24) Between pin 6 and 7 the multimeter reads about 6,4Volts.

I can't tell you what diode I used because it was part of a kit.
What's more - I built the e12 about 8 months ago and had no time for putting it into my M³.

 

[amb]

You probably got the wrong zener diodes, then.

 

[Sathimas]

How can I check that?

 

[amb]

Measure the DC voltage across the diode?

 

[Sathimas]

DC voltage across D1 is 21,4 Volts.

 

[amb]

What's the supply voltage across the V+ and V-?
Also measure the voltage across the B-E, C-E and C-B junctions of Q1 and Q2.

 

[Sathimas]

Ok, lets go:

Supply voltage is 22,4V

Q1
B-E 0,7V
C-E 1,03V
C-B 0,3V

Q2
B-E 7,7V
C-E 8,43V
C-B 0,66V

 

[amb]

Looks like your Q2 is blown.

 

[Sathimas]

ok, thanks for your help.

I'll try to get a new one...

May take some time.

 

[Sathimas]

ok, changed Q2 today - following effect

Voltage across Pin 4 and 7 of the OPAs - 7,3Volts

Q1
B-E 0,7V
C-E 0,95
C-B 0,24

Q2
B-E 0,54V
C-E 14,3
C-B 15V

well ... This is driving me crazy...

 

[amb]

Your Q2 is bad again (albeit in a slightly different way). Check carefully to make sure you don't have a solder bridge or short somewhere that might be causing Q2 to be blown. Are your tantalum caps installed in the proper orientation? If they are reversed, they could fail as a short circuit.

 

[Iniamyen]

What's the part number of the Q1/Q2 you got? I had identical symptoms and destroyed quite a few e12s before I realized the Q1/Q2 were the middle pin collector type.

 

[Sathimas]

What part number do you mean?
Order number at mouser or the number on the part itself?

Anyway, I'll look that up on Monday, I'm not at home this weekend.
Would be nice if the thing you discribe would be responsible for the error.
(Because it wouldn't be my fault then