[codefox1]

Well, a vintage audio generator that'll give you sine, square, etc is nice to have, usually only a few bucks at meets, etc... Bet someone here has a spare to gift or let go for postage, I only have one, an ancient Heathkit. I also have a distortion analyzer that I never figured out how to use.

And some non inductive power resistors, or even a mess of wirewounds series/paralleled to give you, say 4 or 8 ohms to act as load whilst testing. I wouldn't hook up any speakers you want to keep whilst poking around.

As stated, you can read output wattage and just about any working scope will show you the shape of the output (and compare it to input) so you can see clipping. You can confirm waveform is good at input then go stage by stage to output to see if there is an intermediate point of distortion, or proceed backwards from output to input, (well, I was taught to start with the speaker and go backwards to the antenna to fix radios after determining there was light and B+, way back when.)

[Ron Ramirez]

Thanks Fox (Bill), as always. Perhaps when I get back to work I'll consider buying an audio generator.

[Ron Ramirez]

One word: SUCCESS!!!

[Image: http://www.philcoradio.com/images/phorum...0-T_18.jpg]

[Image: http://www.philcoradio.com/images/phorum...0-T_19.jpg]

This afternoon after putting in my study time, I decided to try again to troubleshoot the multiplex decoder in my 440-T.

It turned out to have multiple issues. Q402 was bad and I replaced it with a used, tested 2N2614 pulled from another, dead multiplex board. Then I wasn't getting any B+ voltage to the collector of Q401. That turned out to be poor solder joints at Z402. I went over the entire board with the soldering iron and solder, touching up every solder joint on the board.

I reconnected the LED Stereo Beacon, following this diagram as I used on my 4400:

[Image: http://www.philcoradio.com/images/phorum.../led02.jpg]

Then, I hooked everything up...and it was off to the races. The Stereo Beacon seems a bit dim to me, but it is otherwise working very well; when tuned off station, the LED goes out immediately.

Let's see...that took only a year and 17 days from start to finish...but at least it is done and seems to be working well.

Oh, and no, this is not the same face plate that I started out with. This one is very dull on the edges but all of the lettering is good, as is the Fisher logo.

[PhilcoMike]

Ron,

Was this the one with the distorted audio on one channel or do you have two Fishers on the bench?

Good luck!!!

Mike

[Ron Ramirez]

PhilcoMike

This one had severe distortion in both channels until I discovered the speaker fuse was missing (see page 5, post #68, this thread).

I wrapped up a 700-T a few evenings ago after tracing a channel imbalance to the volume control.

And I had previously started a thread on a 170 that has distortion in both channels with speakers but plays fine through headphones. I had set it aside last summer and more or less forgot about it. Maybe I should get it out and try to figure it out again.