Stage Line 500W amp repair project

[bikemech]

Are those the power transistors that you have removed?

Bob

where are you talking about Bob?

 

[BobK]

The transistors connected to red wires you are worried about.

Anyway, I looked at the schematic and they are not. Looks like part of the protection circuit.

Why do you think there is something wrong concerning the red wires?

Bob

 

[bikemech]

Yes Pete.

ok adam just did this and i can not get a steady reading!! ti is tempriture sensative, if i blow on Q46 the resistance shoots way up and slowly comes back down??

 

[BobK]

Adam asked you to measure current, not resistance. Or are you actually measuring current and deducing that the resistance is going up?

Bob

 

[bikemech]

Adam asked you to measure current, not resistance. Or are you actually measuring current and deducing that the resistance is going up?

Bob

that would be my bad then, i need to be on the vdc range?

EDIT: i was on the 200m range on my meter

 

[BobK]

No, you need to be on a current range. A or mA.

We are expecting around 3mA. But start on a higher range and go to lower ranges only if it reads 0 or 1 digit.

Bob

 

[bikemech]

No, you need to be on a current range. A or mA.

We are expecting around 3mA. But start on a higher range and go to lower ranges only if it reads 0 or 1 digit.

Bob

please remember, i am a beginner and the extent of my knowlage is not much more than this thread!!

 

[BobK]

Okay! What ranges does your meter have for current, if any?

Bob

 

[bikemech]

Okay! What ranges does your meter have for current, if any?

Bob

set it to the 200m on the right hand side, and i get no reading as in 00.0, have black probe in common and red in v Ω ma

 

[BobK]

And the probes are between the leg of R108 that you removed and the pad that it normally connects to?

Bob

 

[Arouse1973]

Adam asked you to measure current, not resistance. Or are you actually measuring current and deducing that the resistance is going up?

Bob

Thanks for helping Bob.
Adam

 

[bikemech]

And the probes are between the leg of R108 that you removed and the pad that it normally connects to?

Bob

Yes

 

[Arouse1973]

Hi Pete
Do this again and set the meter to 20 mA range. Is it still 0 mA?
Adam

 

[BobK]

I can think of one way to explain the readings we have been getting. If the upper side of R108 is not making contact and the lower side is shorted to the V+ supply. This would explain why there is no current through R108 and it reads 1K correctly when probed from the top. It also explains why the base is at V+.

Bob

 

[Arouse1973]

I can think of one way to explain the readings we have been getting. If the upper side of R108 is not making contact and the lower side is shorted to the V+ supply. This would explain why there is no current through R108 and it reads 1K correctly when probed from the top. It also explains why the base is at V+.

Bob

Yes that would be another reason Bob, good idea.
Adam

 

[bikemech]

Ok guys I appreciate everyone's help here, and you all have some really good input, am going to wait for kris to come back and see what he thinks , as he has been working on this with me from the start,and everything I have done so far has been from his instructions, please don't think I am being disrespectful, that is not my intention, I just find kris easy to follow and know he knows exactly where we're at with this project , thanks again guys and please don't think I don't value your input because I do,
Thanks again Adam/ Bob,
Pete.

 

[BobK]

Gee, thanks. I think I have actually identified the problem, but once again, you do not believe me. Good luck.

Bob

 

[bikemech]

Gee, thanks. I think I have actually identified the problem, but once again, you do not believe me. Good luck.

Bob

I do believe you know what your talking about, and I do appreciate your input Bob

I am just trying to not get confused with different people asking me to do different things, I am trying to learn , but it's going a little fast for me at the minute,

Again I am thankful for your help,

Reguards ,
Pete.

 

[bikemech]

could it have anything to do with this collector and emitter link still being in place on Q2

 

[Arouse1973]

Ok I know when I'm not wanted . Kris and Bob are far better at explaining things than me. I sometimes forget I am talking to a beginner. But I treat everyone the same so I may use terms you are not familiar with, but I don't know how much or how little you know. I find it better this way, so I don't come across as treating someone like a child.
All the best
Adam