Hi,

I'm looking to fix an AC3 RF output to my newly acquired CLD-97 (after 22 years I finally scored one! woo hoo!).

Is anybody in this wide world still selling a DIY AC3 board?

I'm willing to take on the soldering risk, but need a board.

Alternately, I have the AC3 output mod from my deceased Mcintosh 7020, but detached, and I can't make out where all the 8 connections are. I found the solder points for all 8, but not sure which is which without a schematic.

Any help greatly appreciated.

Thanks, and rock on laserdisc diehards!

Can you post good top and bottom pics of the AC3 board from the 7020 and maybe I can help decipher what each wire is for? If it’s easy to figure out, then you will have a board for your 97.

And in regards to buying DIY boards, they aren’t being sold anymore from what I can tell.

Could have pulled the audio board out of the 7020 and swapped it directly into the 97 and just drill the hole in the back. They are the very same audio board.

ldfan, thanks for the very kind offer!

I'm attaching 3 pix: obverse, reverse, and see-through. Hopefully these are clear enough.

I looked over the pics for the last hour or so and I think these are the correct points.

SP1 = AC3-RF Out (to middle pin of RCA jack on back panel)
SP2 = AC3-RF Out GND (to GND of RCA jack on back panel)
SP3 = +5vdc
SP4 = Audio FM In
SP5 = Not used (possibly meant for a Mute Active Low player)
SP6 = Mute Active High
SP7 = -5vdc
SP8 = GND

However, I am not 100% certain about SP7 as the boards I have made I always sent -5vdc to the what would be the SQ1 transistor but this circuit design sends it to SQ2 instead (a possible reason is that this SQ2 might be an NPN type transistor and I usually use a PNP type on my boards).

If Kurtis could possibly confirm my analysis, we'll know for sure.



As for your adding the AC3-RF to your 97, here are the points as written up by invenio...

https://drive.google.com/file/d/0B3Or4a ... VzRFk/view

Good luck for when you get your 97 modded. I'll probably mod my 97 in about a year or so; too many other projects I need to work on .

A thousand thanks, ldfan! I'll give it a shot and report back.

Hope I am right about the points. Just let me know if you need help. Didn't realize you live in SF as well .

OK, I got the Mcintosh board wired up to my CLD-97, initial results are promising but not yet conclusive.

First of all, nothing blew up. I can't begin to convey what a relief that was.

The board seems to be working insofar as I read +3.6V on the AC3 output coax jack when a disc is playing, and 0V when not.

However, no legible signal from the jack itself. No voltage on the meter and no AC3RF light on the demod.

So at present I am analyzing the RCA jack board extracted form the McIntosh and of which I didn't post photos before cause it looked too simple - just the terminal of the AC3RF line wired to the center and sleeve of a RCA jack in parallel with a small capacitor. Can you see anything obviously wrong? If I don't find something I can fix on that board I'm tempted to just wire the terminal to a cut off end of a coax extender cable with an RCA jack on it and see what that does.

Anyway if you do have a minute to share any thoughts I would be most grateful.

Assuming that the jack board is fine, should I try altering the wiring? I followed your deduced pin assignments and matched to the audio board solder points in invenio's document.

I'll keep poking around with the multimeter and see if I can find any unexpected readings.

Thanks again for your generous and invaluable assistance.

-Jeremy

P.S. Yes I am in SF in the Outer Mission. This 97 was a Craigslist score -- a very nice person out in the Sunset sold it to me for a very fair $400 considering its condition is excellent except for the broken bottom door hinge, and everything works, plus he included his modest but delightfully quirky collection of discs including a Criterion Seven and Video Essentials which made me very happy, and a eyebrow-raising title called PRETTY BABY which I had never even heard of but turned out to be a top-shelf historical drama on a very seldom treated theme....

If you are getting the switch in voltage as you say, then it's obvious that the board is functioning correctly. However, you also mention no voltage on the voltmeter right after you said you had voltage so that kind of confuses me. Were you trying to get a reading off of the RCA jack and that is where you found no voltage?



The board w/ the RCA jack looks fine to me. The purpose of that cap is for GND isolation from the chassis and it shouldn't cause any issues. Just have to make sure the wire for the center pin goes to SP1 and the wire for the RCA GND goes to SP2.

The only other issue that comes to mind is that the point for SP4 is not correct or possibly SP4 really wasn't the AFM input as I thought (but I don't think so since you are getting the 3.6v for play and 0v for pause/stop).

Oops yes looks like I misspoke there. I DO get voltage measured on the wire itself, or actually on the connector on the RCA jack board just where the wire terminates, but NO VOLTAGE measured on the RCA jack itself (shoving a probe in the jack hole and clipping the other one on the metal sleeve. I'll check the measurements on the board again verify +/-5 are where they're supposed to be, and all solder joints are ok, and maybe if that fails I'll try a different RCA jack.

It feels like I'm getting close. Thanks again.

Ok. Sounds like a simple connection issue between the RCA jack and the AC3 board in that case. You probably should remove all that hot glue on the RCA jack board as it could be hiding a broken connection for the jack.

If you need to use a different RCA jack, you’ll have to wire it more or less like this....



The white piece you see in the pic is the same as the yellow cap on your board so you can recycle that.

so that's a capacitor wired in series between the RF ground lead on the board (SP2) and the shield on the RCA jack?

That is correct. Here is a diagram that might help explain it better (look at C4).



So on my RCA jack, I have the green wire stuffed between that bracket for chassis GND. The McIntosh jack board essentially does the same.

I see cold solder joints at the plug connector pin, I see possible open connections.
You need to take a small piece of wire and connect the proper points together. I would not trust the connections in the connector board.