counterpoint sa4 otl

[panelman]

does anyone have circuit diagrams for the counterpoint sa4.
thank you.
I have problem on 1 amp,it trips speaker relay out.any know what may be causing this.

 

[Koonw]

If the relay timer tripped maybe to look into what causes it to trip: too high DC offset, high distortion, abnormal bias and HT etc. You have to study the sch to find out.

 

[jazbo8]

What is this crazy contraption? Do people actual use it still?!

 

[Alastair E]

What is this crazy contraption? Do people actual use it still?!

Bloody horrible IMHO! Recipe for a tube eater--Now we know where all the 6LF6's went!.....

 

[panelman]

thanks for the sch,do u have it for the regulator board.i have one working super but other trips speaker protection relay out.

 

[Alastair E]

Prolly one o/p valve is stuffed,-As I said, Its a diabolical design IMO-A try see if still trips when you transfer output valves from one set to the other.

---A DC Coupled OTL--What kind of crack were they smoking!! Seems to use a Transistorised Servo--To keep it from self-destructing.....

 

[smoking-amp]

6FS5 remote cutoff guided grid RF tubes for the front end????????????

No equalization of gain for the top and bottom output tube banks????????????

Uhh, is this some 3rd world country design or something???????? Scrap box challenge?????

I would say that a TOTAL RE-DESIGN is callled for, DO NOT repair.

 

[smoking-amp]

Woops, I just noticed that it DOES have a bootstrapped splitter for gain equalization (V9 plate load). Looking a little better now. The 6FS5 for the V9 splitter is OK (low screen current and gm degenerated). But V10 has got to be non-linear.

 

[jazbo8]

It was designed by none other than Roger Modjeski of Music Reference, his first OTL design, he has got much better ones now.

 

[panelman]

well it may be a bad design but they sure do sound good,the working one I have sounds great,have tried swappimg tubes over and still trips speaker relay out.

 

[Alastair E]

Back to first principles of fault-finding then.

Voltage-checks etc....

 

[Unimog]

Also try a number of 12AX7 tubes. In my experience a 12AX7 tube somewhat out of specification will result in the amp not balancing. A lot of trouble-shooting may be avoided this way (I speak from experience).

 

[panelman]

counterpoint sa4

amps fixed,lots of faulty caps on driver board and a couple of blown zener diodes.both sound superb now.

 

[panelman]

anyone have any preferences on
krell kas 4 box monoblocks vs mark levinson ml2
undecided which ones to sell,i like both but need to sell one pair