Author Topic: Delay with channel 2 coming on.  (Read 594 times)

MagMan

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Delay with channel 2 coming on.
« on: June 01, 2016, 01:50:14 PM »
Hi, I'm excited to join the group and hope someone can help me with a problem. I have a 100 watt Magnavox AstroSonic I've just completed a re-cap on. Unfortunately, the recap did not fix a problem I was experiencing before with channel 2 being slow to start. I can hear a pop on this channel when I turn on the receiver, but it takes a few minutes before it comes on. Once it's on, it seems fine.  Any thoughts? Attached are the schematics for the amp. Thank you very much!

impaladb

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Re: Delay with channel 2 coming on.
« Reply #1 on: June 07, 2016, 10:19:32 AM »
Astrosonic 100 is a dual chassis model. With a preamp/tuner and separate amplifier mounted low in the cabinet. Switch the outputs from the preamp where they connect to the amplifier. See if the problem moves or stays with the same channel. That way you will know if the issue is with the preamp/tuner or the amp.

MagMan

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Re: Delay with channel 2 coming on.
« Reply #2 on: June 09, 2016, 10:37:58 AM »
Both outputs (left & right channels) work when connected to channel one on the amp, and demonstrate the same delay when connected to channel two on the amp. This would suggest the problem is with the amp, correct? Thank you for your help, Kent

Harbourmaster

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Re: Delay with channel 2 coming on.
« Reply #3 on: June 09, 2016, 01:46:56 PM »
yup.


Time to go back and double check your work... make sure that you didn't accidentally bridge a trace anywhere on the board, then it's time to start checking resistors etc.
-- Aloha, Ken

No Console Left Behind!

impaladb

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Re: Delay with channel 2 coming on.
« Reply #4 on: June 09, 2016, 03:17:34 PM »
Check your voltages to the driver transistors. They are the small preamp transistors, not the output transistors. If the voltage is OK, then suspect a transistor issue. These small germanium transistors have a tendency to go bad. I've replaced more than a few of them. I have a bag of 20 of them, along with high frequency germanium transistors for the tuners/fm osc.

Since you hear a "pop" when turning the unit on I would think the output transistors are good and a driver transistor is bad.

Did you replace the coupling caps for the speaker outputs?