Please help me!!!

I have built the intercom circuit found at (
http://www.uoguelph.ca/~antoon/circ/intercom.html ), but it does not
work.

I have it connected to two 8 ohm speakers that I have used in another
intercom circuit that worked.

When I turn either switch on the corresponding BC558 transistor gets VERY hot!

I took the audio transformers off to try it that way, but all that did
was add extra noise on the line.

I cannot see anything I have hooked up incorrectly. Do you have any suggestions?

Thanks
-Chad

 

Originally posted by crivoli@May 6 2006, 08:14 AM
Please help me!!!

I have built the intercom circuit found at (
http://www.uoguelph.ca/~antoon/circ/intercom.html ), but it does not
work.

I have it connected to two 8 ohm speakers that I have used in another
intercom circuit that worked.

When I turn either switch on the corresponding BC558 transistor gets VERY hot!

I took the audio transformers off to try it that way, but all that did
was add extra noise on the line.

I cannot see anything I have hooked up incorrectly. Do you have any suggestions?

Thanks
-Chad

[post=16837]Quoted post[/post]​

Suggestion #1- Do NOT turn the switch on
Suggestion #2- If you turn the switch on...don't touch the transistor
Suggestion #3- Contact Jan H. and complain

 

Originally posted by dbwgwee@May 7 2006, 03:08 AM
Suggestion #1- Do NOT turn the switch on
Suggestion #2- If you turn the switch on...don't touch the transistor
Suggestion #3- Contact Jan H. and complain

[post=16841]Quoted post[/post]​

What a helpful response.

Now for some help. Did you connect the audio transformers the correct way around with the 8 Ω speakers? The schematic says "No 8 Ω without audio transformer". Having such a low resistance in the emitter of Q1 and Q3 would explain why the transistors are getting hot.