8mm Forum: One last thing about the Sankyo 800. (I promise!)

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Posted by Jan Bister (Member # 332) on May 27, 2006, 06:51 PM:

Minutes ago, in my "lab" .....

YESSSSSSSS!!!!

Posted by Kevin Faulkner (Member # 6) on May 27, 2006, 07:11 PM:

Great news. So what was the answer? dont keep us guessing!

Kev.

Posted by Jan Bister (Member # 332) on May 27, 2006, 08:39 PM:

Refer to my other thread which I updated earlier today. [Smile]

But to make it brief, it was just a matter of replacing the green dual-diode rectifier (Toshiba 1B2Z1). Have just replaced the lamp connector as well - wouldn't want the same thing to happen all over again after all. [Wink]

Posted by Kevin Faulkner (Member # 6) on May 28, 2006, 08:37 AM:

So you now have a nice stereo machine.....nice. [Smile]

Kev.

Posted by Jan Bister (Member # 332) on May 28, 2006, 02:26 PM:

I hope so [Eek!]

there seems to be a problem with the right channel (track 2)... no speaker or headphone output, but LED VU meters appear to be working, so hopefully only the power amp is defective. As long as I can record on both tracks and play them back through the line-outs... Dangit, I need to dig up a film I can record onto, and patch cords to hook the thing up to my amp... (stupid 3.5mm mono jacks, why didn't they just use RCA jacks)... Ohwell, it can wait until later, I need to get a break from that Sankyo [Roll Eyes]

Posted by Kevin Faulkner (Member # 6) on May 29, 2006, 12:43 PM:

Could be the output IC for the right channel it also acts as the record amp. may habe been the cause of the original problem or was caused by the problem.

Still at least you have a second machine to take bits from. [Smile]

Kev.

Posted by Kevin Faulkner (Member # 6) on May 29, 2006, 12:43 PM:

Could be the output IC for the right channel it also acts as the record amp. may have been the cause of the original problem or was caused by the problem.

Still at least you have a second machine to take bits from. [Smile]

Kev.

Sorry about the double post it was a problem my end.

Posted by Rick Skowronek (Member # 385) on May 31, 2006, 01:16 PM:

Congrats Jan,

Glad it turned out to be one of those rectifiers. Should also change the filter cap if you're so inclined. Never hurts. Unfortunately, if I remember right from the schematic, Kevin is probably right in that the output amps also double as the record amps. I'll have to have a relook at them tonight and let you know. Sometimes they pull the record audio off of the preamps. At least you're more than halfway there.

That projector probably has more single posts than any other single projector on the forum. Ought to be in the hall of fame.

I'll let you know what I see on it.

Rick

Posted by Kevin Faulkner (Member # 6) on May 31, 2006, 03:56 PM:

Jan/Rick, Just checked the circuit diagram and the output IC for each channel drives either the LS output in playback or the record head in record. The drive comes from pin 10 and is then switched depending on the mode the machine is in.

Hope this helps, Kev.

Posted by Jan Bister (Member # 332) on June 01, 2006, 09:12 PM:

LS?

Drive?

Pin 10?

[Confused]

Posted by Rick Skowronek (Member # 385) on June 02, 2006, 08:18 AM:

I think what Kevin is telling you Jan is that the Output IC for the left channel does indeed drive either the LS (Left Speaker output) or the record head depending upon whether it's in playback or record. Pin 10 refers to the output pin on the IC that provides that "drive". Whatever the case, it's not necessarily good news if that output IC is blown as you will not be able to record (or playback) that channel. Just finding a good one could be quite a challenge.

Rick

Posted by Jan Bister (Member # 332) on June 02, 2006, 01:51 PM:

Ah, now I gotcha. I have to test it out some more to be sure (I don't even know for sure which of the internal speakers is which!) but even if worse comes to worst... there's always the other Sankyo. Anyway, I got a new rectifier to put back where I stole the original one from so I can get both machines going now, and see where to go from there. It's not a matter of if... just when. [Smile]

Posted by Kevin Faulkner (Member # 6) on June 02, 2006, 04:48 PM:

Jan, Rick was right thats exactly what I was trying to say. I dont have details of exactly what type number that IC is but a search on the internet may find you someone who has one in stock if it does turn out to be the IC. Fingers crossed it's not.

Kev.

Posted by Jan Bister (Member # 332) on June 04, 2006, 12:06 AM:

Well - I'm happy to report that the first Sankyo (hencetoforth referred to as Unit A) plays back stereo tracks beautifully through the external line-out, as tested with Roger Rabbit in Tummy Trouble. And wow, what a sound!

As for recording... still can't say for sure. Track transfers from 1 to 2 work. Actual line-in recording to either track turns out to be a pain - what in blazes was Sankyo thinking putting dual 3.5mm mono jacks on the machine, I have zillions of patch cords and adapters and yet can't seem to make a connection to these! [Mad]

Time to go shopping for a set of two RCA-to-3.5mm adapters I guess [Roll Eyes]

Ohyeah, and then there's Unit B... put in the new rectifier (to replace the one used to fix Unit A)... fully working but no voltage supplied to the motor, thus no transport. This has me puzzled.

I may need you guys to bring me back to Earth before I lose my sanity over either machine and will have to be led away in a straightjacket as I giggle madly on my way to the padded room! [Big Grin]

Posted by Kevin Faulkner (Member # 6) on June 04, 2006, 05:55 PM:

Jan, Think this is going to be more difficult to diagnose. Again there is another rectifier and cap just for the motor. This then goes via the switches and goes into the Motor Control Unit. This circuitry also has a driver transitor and Thyristor. The transistor is marked as a 2SD385...I think. The scan i have is not clear enough to see the fine details of type numbers etc. Also it doesnt include the Circuit of the Control unit.

Maybe Rick has a better diagram etc.

Kev.

Posted by Jan Bister (Member # 332) on June 04, 2006, 06:11 PM:

Well, perhaps not a problem... because I went ahead and picked up a full service manual for the Sankyo 800 on eBay today (the only one that was available, at that). I'm determined to get both machines working now, but I'll take my time with it. [Smile]

Posted by Rick Skowronek (Member # 385) on June 05, 2006, 01:51 PM:

I believe I do have a schematic for the motor control, I think. I'm pretty certain I saw it on one of two or three I have. I'll run through them and see tonight. If so, on to Jan it will go.

As to getting stereo playback via line out on the repaired one Jan, you will. That output is "tapped" off before the output ICs and thus the blown one will not impact it. However, I believe you will find that that channel will not record since it does use that IC to feed high level audio to the record circuitry.

I'll let you know on the motor circuitry.

Rick

Posted by Jan Bister (Member # 332) on June 05, 2006, 09:39 PM:

You are correct... playback works on both channels, recording *appears* to work (both LED VU meters show a signal) but upon subsequent playback the left channel (track 1) is silent.

Anxiously awaiting the motor info... thanks in advance. [Smile]

Posted by Kevin Faulkner (Member # 6) on June 06, 2006, 03:43 AM:

Once again Jan, I think the VU meters are tapped off before the output IC so you still may have a duff IC. If you record and dont hear anything on that track via the line out then I would say that IC is dead or some other component local to that IC [Frown]

Kev.

Posted by Jan Bister (Member # 332) on June 06, 2006, 08:20 PM:

Yes, yes... I was agreeing with you and Rick all along, Kevin. [Wink]

Posted by Rick Skowronek (Member # 385) on June 07, 2006, 07:13 PM:

If you haven't, check your email Jan. Blown up part of the schematic I sent you in April clearly shows the Motor Control circuit. Let's keep our fingers crossed it's either the bridge rectifier or the output transistor. Both usually available as replacement parts of one sort or another.

Otherwise, boat anchor time if it's the M/C IC.

Rick

Posted by Jan Bister (Member # 332) on July 01, 2006, 11:16 AM:

OK, it's been a while but I just got around to checking over Unit B (dead motor) again.

And wouldn't you know it, turns out it's the same old thing again - rectifier gone bad, shorting things out and busting a copper trace underneath the motor control board. This is getting ridiculous - why didn't Sankyo put fuses in either of these two machines [Roll Eyes]

It does make for an easy fix, though (hopefully) so I'll once again be hunting for a replacement part on eBay.

More to come. [Smile]

Oh, and Rick, I never said thanks for your email, so thanks. [Smile]

I'm saving it just in case the rectifier isn't the only issue preventing the motor from running... I do have the complete service manual now which gives me a well-readable hardcopy of the entire wiring diagram... very nice for a xerox copy, indeed.

Now a small favor... since there are three separate topics dealing with this whole Sankyo mess, could we combine them all into one (in chronological order)? That would be 1. Bulb Issues started by Michael Clark, 2. Fuses etc. which I opened, and finally this one which I guess I just linked to itself even though that doesn't make sense. [Big Grin]

Thanks!!!

Posted by Kevin Faulkner (Member # 6) on July 01, 2006, 11:22 AM:

Hi Jan, I dont know of a way of linking threads. What you could do is to close them (unless thats only an option we moderators have) but put a link at the end of each of the other two pointing to this thread and a link in this thread back to the other two.

Kev.

Posted by Jan Bister (Member # 332) on July 02, 2006, 12:07 AM:

A two-way link... good idea. Well, I just posted links to the first two threads here so I'll go and put links from there back to here... and then you can close them (you're right in that only you and Doug and Brad can do this).

In other news, I went and simply exchanged the motor control boards between both machines - so now Unit B is fully working (the motor runs perfectly!) whereas Unit A will receive the defective board once I have a new rectifier in place - and then I'm almost there: Two fully working Sankyos, with only the left-channel recording issue on Unit A left to be fixed. Woohoo!

Posted by Rick Skowronek (Member # 385) on July 03, 2006, 09:24 AM:

Hi Jan,

You mentioned the blown rectifier again on the second unit. You can easily replace this with a Radio Shack full wave bridge rectifier. One with a value of a couple of Amps at 50 or more volts should be fine. Their part - Model: 276-1173 should be more than adequate at $2.49. Just watch and insure you get the plus DC out of the rectifier on the plus bus to the capacitor. Check your schematic.

Should save you time and hunting.

Rick

Posted by Jan Bister (Member # 332) on July 03, 2006, 06:33 PM:

Wow, Rick, thanks. [Smile]

I was all set to get a rectifier through eBay which would have cost me $7 or so, good thing I didn't do this yet. [Smile]

All in all I have been quite successful... Unit B is now completely functional, and Unit A will be as well once it has a new rectifier, which leaves only the dead left channel to worry about. That reminds me - which IC is it that is responsible for playback and recording on that channel? (where is it physically located?)

Posted by Jan Bister (Member # 332) on July 22, 2006, 10:15 PM:

Strange...

Put in the new rectifier, plugged 'er in, POP... capacitor was shorted (should've tested it first). Replaced capacitor, verified that the rectifier survived unscathed, and plugged 'er in again. No POP this time, and the multimeter indicates voltage is present on the DC side. All is connected properly and I know the motor is good, too.

Still, it won't come on when I put the machine in forward or reverse.

Strange...

I've half a mind to just power the motor externally, with a projector-independent DC supply. [Roll Eyes]

Posted by Kevin Faulkner (Member # 6) on July 23, 2006, 05:17 AM:

By doing that Jan you will have no speed control.

Can you not swap the motor control boards between machines to see if the fault moves between machines? this is asuming the machines have a seperate control board.

This is a problem that has to be watched on machines of this era, capacitors especially electrolytics will be tiring and when they have voltage applied to them after a long time of no use this is the sort of problem to expect.

Kev.

Posted by Jan Bister (Member # 332) on July 23, 2006, 08:37 AM:

I did swap the boards between machines, that's how I got Unit B to run. Unit B was originally the one with the "dead" motor, so now it's a 100% working unit including recording on both channels.
Since Unit A (the current problem machine) was also running fine before the swap, it stands to reason there is yet another issue with the control board itself. There are some more electrolytic capacitors so I'll pay special attention to those. [Smile]

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