Knight C-577 Compressor- anyone ever seen one?

[Bow]

I picked Knight C-577 Compressor up at a local hamfest a while back... she is an oldie for sure...

I got some time to throw it on the bench today... signal generator input, monitored the O'scope on the output... it works.... and doesn't take much at all to drive it

The meter needle has broke off the movement, and it uses 1/4" TRS for input and output.

However, I would like to find a schematic on it...

Anyone have any leads? My Google-Fu has come up dry

 

[Bow]

Here it is in action...

1KHz @ 30mv drive
9vdc power

Bypassed signal

Lowest Compression setting

Highest Compression setting

 

[Shadetree Mechanic]

Looks like it is overdriven on high?

 

[mrgumby]

 

[Bow]

Looks like it is overdriven on high?

Not overdriven.. it is a clipping circuit

 

[Bow]

View attachment 29598

Thank you sir! Where did you find that?

 

[mrgumby]

https://www.americanradiohistory.co...rimenter/Radio-TV-Experimenter-1966-02-03.pdf

 

[mrgumby]

Page 61

 

[nomadradio]

I'd venture to say that the sideways S-meter from a derelict mobile CB is probably a decent match for the broken meter.

Replacing all the electrolytic caps in there would probably clean up the waveform at a high drive level.

73

 

[Bow]

Swapped the only electrolytic (C2 in the schematic) it was a 50uf/10V, I had a 68uf/10V close enough

Looks like the gain dropped a tad, looks like it cleaned up the signal a bit.

 

[nomadradio]

I'd replace all five, but if you saw a difference changing just one, that's a hint.

73

 

[Bow]

Yup, I agree, they are all pretty common...
the others are
3 are 0.1uf
1 is 0.0033uf

 

[nomadradio]

Hmm. Counted five caps with that "+" symbol alongside them in the schemo. But no capacitance values visible.

If they are aluminum electrolytics, age is your enemy.

73