Mangasync Movioala URS Sqawkbox Schem

[keninverse]

This is a long shot but I have scoured the interwebs and I can't seem to find this...So now I'm appealing to the diystompbox community humbly.  I'm looking for a schematic for moviola magnasync URS squawbox.  The only thing I'e came across is a modified schematic and some broken links unable to be restore by archive.org.  I would be so greatly appreciative if someone, somewhere can post this. 

[slacker]

Is it this http://en.wikiversity.org/wiki/File:Moviola_URS_schematic.JPG?

[PRR]

If it's what Ian posted: it's another way to build a Herzog. A high-gain Champ-like practice amp with output fed to the main amp. Such abuse will kill the Champ's OT unless you add a dummy load, and usually you want some adjustable attenuation between amps.

The difference between small sound-movie projector amps and a Champ is small. However in the fading days of tubes, old projectors may have been cheaper than a working Champ.

[keninverse]

Thanks Ian!  This is in fact the schematic for the amp that attached to a 16mm film editor. This would be my first foray into the field of modifying valve amps so please excuse my ignorance.  I should also preface by saying the extent of my tube amp workings is with just changing out tubes, biasing, replacing caps...basic stuff.  I picked up this amp for $40 so it is in fact significantly cheap project for me to try my hands at modifying and getting me back into some playing.  I have a fairly young family so my larger amps and cabs have been collecting dust for some time.  I'm digressing here...I'm planning on removing everything in front of the 12AX7 and changing out the front end to match impedance (68k input, 1M to ground), changing out the ac power cord, replacing older caps and then proceeding to other mods like changing the volume pot to 1M, true power switch and standby switch.  Again pardon my ignorance...Paul you mentioned adding a resistive load but how do I go about doing this?  Across the transformer secondary? You also mentioned adding some form of adjustable attenuation between the amps...would you mind explaining this as well? Let me say I've read a lot of your posts at GDIY and I'm humbled by your knowledge.  Please go easy on me.

[PRR]

> I've read a lot of your posts

Then you know I don't give out fish, I expect you to get your feet wet.

http://www.garnetamps.com/zog_story.htm

http://www.canadiandesignresource.ca/officialgallery/electronics/randy-bachmans-herzog/

http://www.tech21nyc.com/support/manuals/effects/AmericanWoman-OM.pdf

> changing out the front end to match impedance (68k input, 1M to ground)

You DO really-want to disconnect the high voltage to the optical sound head, both where it comes off the B+ line and where the audio goes to the first tube.

The "impedance" is fine the way it is. 1Meg, 470K, either is fine. The 68K (actually 34K) is useful when you go to different dives every night and one is under a radio tower (it cuts radio signals); but you don't go out much these days/nights.

The original circuit values are perfectly fine. Compared to Fender, it's a wee bit more gain and less clean... that's not wrong for a Herzog. And there may be mojo in the old parts. Unless the mojo burns out.

As claimed in the Garnett and Bachman tales, beating a tube amp HARD with 1Meg load on the 4 ohm tap will zap the output transformer insulation. Leaving the speaker connected is a lot safer, but may be loud. Go over to Radio Shack, get the 2-pack of 10 ohm 10 Watt resistors. Parallel them across the old speaker winding. The exact value is not too important, and we don't know if the amp was meant for 8 or 4 ohms. However we DO need "power". You may say one 6AQ5 only makes 4 clean watts, but when OVER-driven it makes nearly double that, so a 10W resistor. (At RS, the cheapest near-match is two 10r 10W for under a buck.)

3-wire cord, green to SOLID chassis screw, black and white to switch and fuseholder. (Inside an appliance, I don't distinguish black from white.)

50K pot across the dummy-load to output jack.



That's assuming the Moviola is in perfect shape. Smoke-test outside. Find voltage notes for a Fender Champ. The Moviola will be lower voltage all around but similar proportion.

Note that both the origin-story and the Re-Issue mention "selected parts". This could be a never-ending saga.