McCurdy EQ155a schematic pin-outs etc

[mylesgm]

I've got a pair of the McCurdy eq155a discrete modules.  Nice looking units with switched low band, high band, a sweepable mid/presence niveau filter and a couple of switches that I'm not sure about.  Wondering if anybody has a schematic or a pinout.  The pin out I was given has the correct pins (or so it seems) for the i/o but has the power ails at 48v and that seems a little high.  especially as the positive rail goes to a resistor and then to a 35v cap.  All other caps are rated at 25v or less except for two that are rated at 50v but they seem quite deep in the circuit.  so a schematic or pinouts anybody?

Thanks.

 

[mylesgm]

nobody had any experience with these?

 

[Mike Cleaver]

I have a couple racked up with power supply buried in my storage locker.
As with most McCurdy Solid State stuff, they run on regulated 35 to 48 volt dc.
I don't have the schematics available, they're buried somewhere in the same locker

 

[mylesgm]

Hi Mike,

Just checking that you're sure that these run on +48v dc.  I racked a pair of 8995 eq's and they ran on +/-25v with regulators dropping the volts to +/- 18 on the module itself.

M

 

[evilcat]

From Gearslutz :

"McCurdy CANADA is still in business

http://www.mcradio.com/

give em' a call, Mccurdy archives all their schematics, dating all the back to even the 1940's"

 

[mylesgm]

but they charge for the schematics so I was hoping someone with experience on this particular unit would chime in and help out...

 

[mylesgm]

anybody?

 

[mylesgm]

Last call for help, any more info would be appreciated...

M

 

[mylesgm]

Well I fired them up on +12 to start with and no signal but it was clear that the voltage is immediately dropped to half the incoming voltage by dropping resistors.  Increasing voltage to +24 and got signal but was distorted. Increased supply voltage whilst listening to the output of module up to 35v and measuring the voltage after the dropping resistor.  Perfectly clear audio and the voltage post the dropping resistor was 18.5v.  Could probably go as high as 48v supply for a circuit voltage of 24 but my ps didn't supply more than 37 so I left it at 35.  Sounded great but sadly the second unit has problems and now I'll need to sort out replacing some of the transistors.  oh well, of course it couldn't be that easy.

 

[mjrippe]

I bit the bullet and bought the docs from McCurdy ($25).  They are posted in the Technical Documents section for posterity ;-)

The two units I had in for service got re-capped, new resistor in power supply section, and thorough switch cleaning.  Those rotary switches do have little holes to spray into.  One toggle switch was so bad it got replaced.

The low freq band on these is KILLER!  Balls without mud is one way to describe it.