Film-Tech Forum ARCHIVE: Soundhead upgrades for my Devry XD

This is topic Soundhead upgrades for my Devry XD in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=005065

Posted by Sean Weitzel (Member # 244) on 07-07-2003, 04:13 PM:

I am now fed up with the sound issues from my beloved Devry XD 35mm machine. It's all still totally original with the original Photo Electric cell and the toolbox sized tube amplifier. The sound quality was very nice for a long time. Variable density newsreels sounded nothing short of amazing with Lowell Thomas's booming voice filling my living room. Recently, it seems like the actual sensitivity of the amplifier (or soundhead) has gotten weaker and weaker up until now only where only loud passages from the soundtrack will actually make it all the way to the speaker. Anything quiet gets lost completely into a sea of silence or crackling. The odd thing is that the sound that does make it to the speaker is at the proper volume level. Turning the volume up just makes the noise very loud so i don't think it's a problem with the output stage. I've replaced all of the capacitors in the amplifier, checked the voltages and wiring, and made sure there wasn't any gunk stuck in the exciter slit lens. I'm at the point where i suppose it could be a bad tube or two, or maybe a failing photo electric cell? but I am at a point where I think i want to get away from the PE cell and tube amp completly. Replacement tubes are going to cost close to $50 bucks for all of them, and I can't even find a source for a replacement PE cell. Who here was working on a stereo retrofit for the Devry machines? Any news or progress? I can't watch films at this point anymore so I need to get something going here soon. Can anyone help out or have any suggestions for me?
Thanks.

Posted by Stan Gunn (Member # 554) on 07-07-2003, 05:50 PM:

can you send a picture of the sound head? The impossable just takes a little longer. [Smile]

regards

Posted by Mark Gulbrandsen (Member # 72) on 07-07-2003, 06:31 PM:

Actually Sean,
We are a week away fomr having the prototype reverse scan pickup available for the DeVry. It will utilize a special short optic scanner made by C.E. and the rest of the stuff....red led mount and mount for the pickup is being produced in our shop. It will be reasonably priced too.
Mark @ CLACO
CLACO Equipmwnt And Service
1212 South State St.
SLC, UT
801-355-1250

Posted by Sean Weitzel (Member # 244) on 07-07-2003, 07:47 PM:

I just now was able to verify that the PE cell is not bad and the problem is in the amp somewhere. I discovered that the original Devry PE cell is the same as the PE cell used in Precision mag/optical bench soundtrack readers so I swapped the one in my reader with the Devry and the same results. Mark, Since I've been running all this time on a standalone amp, if I invest in a retrofit kit once it's available, will it be possible to say, tie this into a pro-logic home receiver somehow? or is it going to need it's own preamp?

Posted by Bruce McGee (Member # 131) on 07-07-2003, 08:50 PM:

I bet that the first or second stage amplifier tube has died. One of the smaller ones. Have you got access to a tube checker somewhere?

The tubes that are so expensive are the outputs. The 6L6G's, etc.

Posted by Mike Fitzgerald (Member # 1304) on 07-07-2003, 08:53 PM:

Any idea on what the price level will be.

Posted by Sean Weitzel (Member # 244) on 07-07-2003, 09:01 PM:

I *did* have access to a tube tester at a local electronics surplus store, but when I went there this afternoon I was told that a man came in Thursday and bought the entire collection of tubes and the tester too!!! I went into my box of misc tubes in the garage and found a NOS 6J7 and plugged it in and noted no difference. That leaves a 6F5 and a 6N7 to track down. We'll see. Yes, Mark, any idea on what this retrofit will cost?

Posted by Ken Layton (Member # 133) on 07-07-2003, 10:20 PM:

You can get tubes at Antique Electronics (www.tubesandmore.com). Yes it's posible that one of your preamp tubes has decided to crap out or you might have a resistor in the front end change value. Did you change just the electrolytics or the electrolytics AND coupling caps?

Posted by Sean Weitzel (Member # 244) on 07-07-2003, 10:30 PM:

I replaced all of the caps. The huge 500 volt can caps as well as the smaller coupling caps. It did seem to have a noticable effect on the overall volume and crispness of the audio, but the weak sensitivity of the soundtrack remains. I bit the bullet and ordered a 6n7 and a 6F5. we'll see what happens.

Posted by John Anastasio (Member # 607) on 07-08-2003, 04:03 PM:

I agree with Bruce. When the pre-amps lose their emissivity, they go grossly non-linear and do exactly what you described.

Posted by Sean Weitzel (Member # 244) on 08-06-2003, 11:04 AM:

O.K., Here's the final verdict. After nearly $40 in tubes and replacement caps, and the problem still persisting, I finally managed to figure out what the problem was - The speaker I was driving with my amp was blown! AAGH!, however, with all these new components, the audio sounds great and has a very rich fidelity now. Maybe I'll stick with the PE cell setup for a while, but I still eventually want to convert so I can go stereo with it. Thanks for all the suggestions

Posted by Jeff Stricker (Member # 224) on 08-06-2003, 03:37 PM:

It might be worthwhile checking the output of your amplifier to be sure there's no DC voltage present. I'm wondering what caused the speaker to go kaput in the first place. Of course it could be just old age.