Help identify this McCurdy Board

I got one of this... all I know about is it came from a TV broadcast console, powered by split power supply. It is a McCurdy Line Driver.

Does anyone have any info about this, schematics, pin out diagrams?

Here's the picture


From the looks of it, it looks like 2 channels, transformer coupled outs (maybe balanced?). Probably Class A???

Owel,

McCurdy are still in business so try here:

http://www.mcradio.com/

--Bo

A big thank you Bo!

Wow... their site looks <ahem> sparse.

[quote author="owel"] transformer coupled outs (maybe balanced?). Probably Class A???[/quote]

Unless those hammond transformers are power transformers, and the heat-sinked transistors power regulators. That would explain the four fuses :shock:

A class-A transformer output stage would be a wierd combination with those dil-IC's..?

Jakob E.

Hmm,

Looks like an entertaining evening to me :grin:

When presented with a mystery board, look for little clues:

1. Identify the 0V rail- often this will be the largest/fattest trace on the board, and the shields of any screened cables may connect to it.

2. PSU rails will have decoupling caps- look for caps connecting from a rail to 0V and from another rail to 0V with its polarity reversed. Another good way of finding the PSU rails is look at the IC's- if you've got NE5534/5532/071/072's etc etc you can easily find the PSU rails and trace them back to the edge connector with eye/DMM.

3. Trace wiring of transformers to edge connector- finding how many taps there are and measuring their DC resistance can often tell you a lot about the unit.

4. Input and outputs...a little clue here is the screened (looks like single pair) cables running from edge connector to the front of the unit- this kinda yells "Input" to me (I may be wrong!), but if it is a linedriver with-gain, the input would need to be screened from the output, and the board looks like a low-level-at-front-high-level-at-back setup.....

5. Connection of input or output transformers...in this case, check to see where the circuit-side of the transformer windings go- if they connect to the power transistors with no rectifier(s) inbetween, then they are probably the output transformers, and the power transistors the output stages.

6. Divide and conquer! Draw out all the pins on the edge connector and start tracing them into the board. Just crossing out the ones that aren't use can be a good psychological start to a board-tracing mission.

7. There can only be so many connections to a line-driver:

Power +/0 or +/0/-
Signal Input Bal or Unbal
Signal Output Bal or Unbal
Remote Gain Control (digital or analogue)
Remote monitoring/shutdown etc

So with a bit of pondering, you should be able to get somewhere!

Mark

Hey Mark, it's a picture quiz! Isn't that the output amp from a Hurdy McCurdy synthesiser? Nah......that's Folk Music..........don't like Folk Music!
Stephen

Thanks for the tips Mark! You've read my mind.

I think it is a power output transistor (not regulator) because I see a diode glued in between the heatsinks.... which is a common thing to do with output transistors. and yes, that shielded cable looks like an input. I don't see anything that screams "rectifier diodes" and this came from a console, so the PSU is probably not on this PCB.

The two fuses may be along the (+) amd (-) voltage rails.

I haven't checked the numbers on this DIP ICs... But I don't think they're opamps. Maybe TTL logic chips? We'll see!

[quote author="StephenGiles"]Isn't that the output amp from a Hurdy McCurdy synthesiser? [/quote]

Surely that's "Hurdy Mc Gurdy" :wink:

Owel,

Yep, the diodes are probably the bias-compensation for the output transistors. The diodes will have the ~0.7V drop across them which will allow for the loss of ~0.7V across the bases of each transistor. By having the diodes in physical contact with the heatsinks, the Vbe and Vdiode will track approximately.

Let us know how you go with them,

Mark

[quote author="owel"]I haven't checked the numbers on this DIP ICs... But I don't think they're opamps. Maybe TTL logic chips? We'll see! [/quote]
Just feed the type number to Google, and you'll often get a hit.

Best regards,

Mikkel C. Simonsen

Mark you're right. Amazing sound though.
Stephen

Contact McCurdy directly. It might take a short while but chances are they have full doc's for this thing. Looks like part of distribution system (if memory serves me). High power output (chances are insanely high) and probably does sound really cool.

Got the info from McCurdy. Tommytones is right.

The unit you have is in the family of units based on the AM478T Monitor Amplifier. These units were identical except some of the components would vary in value between the different variations.

This board was designed as an output amplifier for the CS9000 series of broadcast intercom systems. The various variations of the board were sold for use in similar equipment.

Click to expand...

Question now is.... will there be any use of this in a studio? Headphone distribution amp????

> Got the info from McCurdy..... will there be any use of this in a studio? Headphone distribution amp????

You got the info. We didn't (except the obvious: part of a distribution system). Want to share, or can we make-up answers?

> Want to share, or can we make-up answers?

Huh? Share what? That's all the info I got from McCurdy... and that's what I quoted/shared.

if I want the full manual with schematics, I'd have to shell out $25. Now I'm deciding if it's worth getting the manual....

if this was a line preamp, I would. Now, I'm not so sure.

The email says "intercom". I don't think intercoms were made, even in a studio, to recoding quality standards. :guinness: :sam:

for the hell. I would get the manual. I bet if it´s not that good for proaudio and recording, you can mod it or use just a part of the circuit.

Or you can make a very impressive-looking intercom system :green:

Best regards,

Mikkel C. Simonsen

LOL... yeah... "paging the drummer... where are you? Your band is looking for you! "

I've seen those boards for sale as line drivers. Did you get them from Barry VE6SBS?