F 22 stereo and power relay

[pyonc]

Hi guys,

Have you heard about JBL F22 stereo balance and power relay? I'm curious about this vintage item.
To the best of my knowledge, it was used with JBL SG520 preamp in the 1960s...
I appreciate any comment from those of who actually used it or have some knowledge.
Thanks much in advance.

http://www.soundbox.co.jp/images/JBL_F22_12.gif

[Mr. Widget]

Well... you've come to the right place to find out, however I am afraid that is one obscure part.

I'll speculate that it may be some type of signal sensing device that activates power outlets for other equipment? Just a wild assed guess.


Widget

[grumpy]

http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/JBL-SG520.pdf

see pg 20. Power relay (energizer(s)), and unusual test/null (speakers) relay... If the
"balance" were off, you'd hear a signal while the test button was pushed. I assume you
can then tweak the balance control on the pre to maximize the null. Then release the test
button.

Sounds like a convenience really (power relay part), and (important!) only for use with
the intended equipment. The null thing sounds like an unnecessary set of relays in the
signal path, as well as an odd wiring requirement that would confuse most.

Neat thing to have with an SG520. But, for me, it would be to play with, then put away.

[Mr. Widget]

http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/JBL-SG520.pdf

see pg 20...Read the manual? Really! :D

Amazing age we live in with pdfs and Google...really!
Not to mention, Harman ain't so bad... posting ancient manuals on their service site.


Widget

[pyonc]

http://www.jblproservice.com/pdf/Vintage JBL-UREI Electronics/JBL-SG520.pdf

see pg 20. Power relay (energizer(s)), and unusual test/null (speakers) relay... If the
"balance" were off, you'd hear a signal while the test button was pushed. I assume you
can then tweak the balance control on the pre to maximize the null. Then release the test
button.

Sounds like a convenience really (power relay part), and (important!) only for use with
the intended equipment. The null thing sounds like an unnecessary set of relays in the
signal path, as well as an odd wiring requirement that would confuse most.

Neat thing to have with an SG520. But, for me, it would be to play with, then put away.

Thanks much, grumpy. Actually I've obtained one on ebay as I have a SG520 in nice condition.
You said "Neat thing to have with an SG520" but I find myself hesitating about putting it to test until I'm reassured.
Even without this power relay, I've had no problem with SG520...

[grumpy]

With the SG520 set to use this switch/relay, the pre
sends dc voltages on the line-out connectors (shield
-and- center conductor) to drive the relays... but so
the amp -shouldn't- see it if the circuit is all working.

I'd want to be sure this all was tested
as operating properly before attaching it to an amp.

Fortunately, the manual describes this.
Fun to have the set :) Interesting find!