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Topic: Fuses etc. - Sankyo Stereo-800
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Carlos Plaza
Junior
Posts: 22
From: Setauket, NY USA
Registered: Mar 2006
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posted March 12, 2006 10:50 AM
This reply is unrelated to this post item...I could not find the original... Posted by Jan Bister (Member # 332) on January 25, 2005
I picked up a Bolex SM8 for a song on EBay. If you are still interested...
Picked up the machine because I already had two 18-5's one standard, one Super 8, both great, etc., and needed Mag sound projector for my film transfer business (yes, I did come up with a way to get lip-sync on transfers to video/DVD, as sound and video capture are done separately).
This machine is built like a tank-and weighs it. It is driven by a fat round belt and the speed (18FPS and 24FPS) is adjusted with a dial that varies the diameter of the motor pulley. The film escapement, sprockets, and reels are all driven from worm gears on a central shaft.
Now, about how it performs:
Sound is not that good...lots of hum, even after replacing the filter capacitors, but has it all solid state components. For capturing sound from this machine, my best results came from adding a Neutrik Speakon connector, off the speaker output, to the case to totally isolate the speaker voltages. I then built a cable with a Speakon connector on one end, and the other end with a T/S phone plug, which plugs into an ground-isolated impedance converter, whih finally plugs into my mixer, which feeds my computer. All this because there is no Line Out.
Why did I do all this? For the fun of it!
Self-threading can be finicky-it seems OK with flexible leaders, but did not do well with a Blackhawk Film of 'The Dentist' until I spliced on some leader. Since I never record on the mag tracks, I cannot report on this.
I don't have a maintenance manual, so perhaps some adjustment would take care of the finicky self-threading, which could also affect the lower loop, sometimes causing the sound to be 'jerky'. When I replace my dead digital camera, I would be glad to send pictures of its innards. If anyone is interested, I do have the owner's manual.
Stay well!
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Jan Bister
Darth 8mm
Posts: 2629
From: Ohio, USA
Registered: Jan 2005
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posted April 02, 2006 10:38 PM
OK, this is interesting... I found nothing wrong with the small amplifier board, including the bridge rectifier. But when I looked underneath the large circuit board at the bottom...
...I noticed a copper trace that had busted open. Got curious, went and bridged the broken trace with a piece of green wire (as seen), plugged the Sankyo into the AC outlet, and it went POP. Nothing changed - no sound, but lamp and motor still working. Upon looking again, the other copper trace had blown open.
And both these are directly coming off the black & orange transformer wires which supply about 14-15V AC voltage, according to my voltmeter.
Hmm. So there's a short-circuit down there somewhere. Alas, I'm stumped now.... what could cause this? Another rectifier that was damaged and now presents a short circuit instead of supplying DC voltage to the sound board?
Comments? Thoughts? ...
EDIT
Here's what Michael Clark wrote about how it all started: "Last night I was watching a film, and all of the sudden the projector light went out. The film continued running, with sound, but no light. So I turned the machine off and checked the bulb. I forgot to unplug the machine first, and as I began to loosen the bulb, I heard a pop and sparks flew. Now, there is NO sound, and the smaller, dimmer light under the sound head doesn't work."
I'm beginning to think the pop and sparks was a complete coincidence and never had anything to do with the lamp... the lamp socket itself is in pretty bad shape and I've in fact had the bulb go on and off on me several times, sometimes I would have to wiggle it to get it to come on again. Something else caused a short circuit just as Mike was trying to pull the lamp off, perhaps brought on by mechanical vibrations. I only wish there was some visible evidence of where this happened...! ![[Frown]](frown.gif)
[ April 03, 2006, 01:00 AM: Message edited by: Jan Bister ]
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Call me Phoenix. *dusts off the ashes*
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Rick Skowronek
Expert Film Handler
Posts: 120
From: Marietta Georgia USA
Registered: May 2005
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posted April 04, 2006 11:06 AM
Hi Guys,
Been a lo-o-ong time since I've visited. With the hurricane we had here in S. Fla. (I'm still putting things back together) and me consulting full time 10-12 hours a day, my time seems to blow by. Biggest apologies to Dan Lail. I have a radio of his. Have at least a four hour alignment to do on the FM and still no guarantees.Will try to get to it within the next couple of weeks.
Anyway, Jan, I do have the Sankyo 800 wiring diagram from Mike Peckham. Unfortunately, it's resolution sucks. You can make out the wiring runs butjust barely adequate. I am sending it to you by email tosee if it gives you some guidance. I believe Kevin (as usual) is spot on with his diagnosis. To blow copper traces of that size so quickly means a dead ass short across the transformer windings. Since this is amplifier power and probably other circuits as well, probably means in this order - 1. Bridge rectifier (although somewhat unusual as two diodes in the bridge must fail shorted and they usually fail open. 2. a filter capacitor on the output of the bridge to smooth the rectified AC (more likely) and last, the dreaded output transistor in the audio amp shorted out. If you see no other smoke or burned components those are the likely suspects. Since I don't have any 800 board/circuit schematics all I can tell you is that is most definitely the power for a majority of the electronics (mostly audio) and is a dead short so it shouldn't be too ridiculous to track down. Drag out the ohmeter compadre.
I'll try and help where I can.
Rick
PS - I found the schematic and wiring diagram and have forwarded those to Jan by email. In looking at the schematic, it does not bode well for that projector as the orange lead feeds AC to a bridge rectifier (as suspected) and a filter capacitor then directly (do not pass Go) to the power in the IC type audio power amps. If any one of those four ICs are shorted, it would be nigh impossible to find replacements for them.
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Rick Skowronek
Expert Film Handler
Posts: 120
From: Marietta Georgia USA
Registered: May 2005
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posted April 04, 2006 07:26 PM
Well Mad Doctor, do understand that applying any DC to a shorted circuit will only get you the fireman's award. The objective here is to find out exactly where the short is.
Hopefully, it's the rectifer or capacitor. If it's not, there are ways to circumvent the output ICs. Not easy but possible. From that you can put outboard amps to take the preamped audio and feed it elsewhere. One of the major problems with this is that those same output ICs also feed the Record circuits. Not for the novice, my friend, but possible. It's either this, after troubleshooting, and if it is one of the four output ICs, you now have one of the original Mike Clark boat anchors. You wouldn't be able to Record but may be able to Play back movies. Still probably more trouble than the machine is worth. Sorry for that diagnosis, but sadly may be true. Personally, I hate to give up on anything electronic but, alas, there are those times now with non-servicable electronics.
Rick
PS - Forgot to comment on this - there are 4 ICs in the audio output Jan. Not one. They are the same ICs but they are hooked up in 2 ICs per channel in a push-pull configuration. One IC works for negative going signal and the other works in positive signal. Gives roughly twice the audio output power of a sngle chip. So, basically, you have 4 chips each hooked to the output of the positive voltage from that 14 VAC bridge/capacitor combo. Any one of those shorted can create the problem.
As I said, good luck.
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Jan Bister
Darth 8mm
Posts: 2629
From: Ohio, USA
Registered: Jan 2005
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posted May 06, 2006 12:24 AM
OK... (much time has passed once again!...) well, I'm 99% certain it's either the rectifier or capacitor, as shown here...
This is located right behind the AC power socket, neatly tucked away on the main board. (So neatly I had a tough time shooting these pics!) The suspects are a large 25V/4700uF capacitor and a green rectangular rectifier (there is another black one next to it as well).
Anyway... I don't have replacement parts, nor the patience or energy to take the whole projector apart just to even get down there... so my options are 1. have Rick Skowronek perform a repair for me or 2. put it on eBay as a parts machine.
Rick, would you be willing to have a go at it? I'll pay shipping both ways plus a bit extra if you think there's a good chance of repairing the machine... and I do think that the sound board, including ICs, is OK otherwise...
[ May 07, 2006, 01:56 PM: Message edited by: Jan Bister ]
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Call me Phoenix. *dusts off the ashes*
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Topic Closed
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and who knows, if I can identify the exact parts that I need, I can replace them myself and then see what happens (btw, yes... you're right, they do look fried). Right now it's not a high-priority item on my to-do list anyway... it's not going anywhere and I have other stuff to play with in the meantime. 
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