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» 8mm Forum   » 8mm Forum   » Repairing a Sankyo Stereo 800 - The Journey (Page 9)

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Author Topic: Repairing a Sankyo Stereo 800 - The Journey
Graham Ritchie
Film God

Posts: 3816
From: New Zealand
Registered: Feb 2006


 - posted October 02, 2017 09:42 PM      Profile for Graham Ritchie   Email Graham Ritchie   Send New Private Message       Edit/Delete Post 
Janice I am certainly not an expert in amps...but my guess would be if you can hear hum from the speaker when cranking the volume to full running the motor as well then the amp is working...no hum.. no amp [Smile]

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Janice Glesser
Film Goddess

Posts: 3218
From: Sunnyvale, CA USA
Registered: Sep 2011


 - posted October 03, 2017 12:37 AM      Profile for Janice Glesser   Email Janice Glesser   Send New Private Message       Edit/Delete Post 
Well Graham then I know one more thing...

There's no hum...so no amp [Frown]

It's sad to see such a nice stereo projector so crippled. I just don't know enough to intelligently troubleshoot where the disconnect is located. Even having all the circuit designs hasn't been much help.

I know something blew when I touched a metal bar by mistake. Poof!... and it went silent.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Graham Ritchie
Film God

Posts: 3816
From: New Zealand
Registered: Feb 2006


 - posted October 03, 2017 02:07 AM      Profile for Graham Ritchie   Email Graham Ritchie   Send New Private Message       Edit/Delete Post 
Hopefully someone will come to your rescue Janice.

Just thinking, is the pre-amp still ok? If the main amp is gone and the pre-amp is ok then by pass it to a aux out, then run the leads to a external amp..or get one of those amp kits you can buy and build a new one. Another thought an old cassette tape deck scrap it and take the pre-amp out of it and wire it to projector sound head..to a aux out...external amp [Roll Eyes]

I think you will get there in the end, it might even be nothing more than a blown transistor..but I think you need to take it to an electrical repair to fix it.

Anyway food for thought...

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Janice Glesser
Film Goddess

Posts: 3218
From: Sunnyvale, CA USA
Registered: Sep 2011


 - posted October 07, 2017 11:23 AM      Profile for Janice Glesser   Email Janice Glesser   Send New Private Message       Edit/Delete Post 
Just when I think the plot points in this novel (actually this is a documentary) have gone dry... a small spark of hope emerges [Smile]

Graham... you got me brainstorming again that this might be as simple as a blown transistor. I had been spending hours and days trying to learn about amplifiers and the components. However, I decided last night to go back and re-read this thread. I don't know how I missed it...but Pete Richards had suggested replacing the green Toshiba 1B2Z1 rectifier. In the same area as that rectifier I had already replaced a large capacitor and added a fuse. I never followed up on identifying and replacing that rectifier. I guess at the time I didn't know what that green thing was (: . Anyway... I also located an old thread from 2006 http://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=001730
Here Jan Bister had almost the identical problems with his Sankyo 800. He mentions replacing that same rectifier and it restored the sound to his projector.

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After this epiphany at 1 a.m. in the morning... I found the part on Ebay. It should arrive by next Friday.

Crossing fingers....Stay tuned for this next chapter [Smile]

[ October 07, 2017, 08:55 PM: Message edited by: Janice Glesser ]

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Janice Glesser
Film Goddess

Posts: 3218
From: Sunnyvale, CA USA
Registered: Sep 2011


 - posted October 17, 2017 06:16 PM      Profile for Janice Glesser   Email Janice Glesser   Send New Private Message       Edit/Delete Post 
I replaced the Green Rectifier yesterday...but unfortunately "no joy." I've now ordered a replacement for the black rectifier that sits right next to the green one. It measures correctly with the ohm meter...but Pete Richards says it may not work under a load.

Granted I'm disappointed...but I did learn something about a rectifier stack and it's polarity. Unlike a bridge rectifier that has 4 terminals...a rectifier stack only has 3 with the center terminal being common... positive or negative. On the Sankyo 800...the green rectifier has a positive common...where the black one has a negative common.

The new black rectifier is coming from the UK and will take a couple of weeks. I'll report back then.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Janice Glesser
Film Goddess

Posts: 3218
From: Sunnyvale, CA USA
Registered: Sep 2011


 - posted November 05, 2017 07:03 PM      Profile for Janice Glesser   Email Janice Glesser   Send New Private Message       Edit/Delete Post 
Got the replacement black rectifier installed... but still complete silence [Frown]

Graham...How do I test to see if the pre-amp is working?

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Thomas Knappstein
Film Handler

Posts: 99
From: Erwitte, Germany
Registered: Oct 2017


 - posted November 07, 2017 11:44 AM      Profile for Thomas Knappstein   Email Thomas Knappstein   Send New Private Message       Edit/Delete Post 
I dont have this Sankyo 800 machine but the same Rectifiers are in my Elmo GS 1200. The green one and the black one together make a normal Bridge Rectifier because there are two Diodes in the Green one and two diodes in the black one.
If you have changed both of them and canged the big Capacietor there must be a Voltage about 15-20Volts measuring on the Capacitor. If it is not check the AC Voltage on the Transformer. I dont think that the Preamp is defektive. I think if it´s not the Power Supply it could be the End Transistors ore Hybrid Part. Because If the Preamp is defektive and enything else is ok than you must here a Hum in the Speakers but no Sound of the Film. And you say that there is no Hum so it could be an Idea.

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Janice Glesser
Film Goddess

Posts: 3218
From: Sunnyvale, CA USA
Registered: Sep 2011


 - posted November 07, 2017 07:21 PM      Profile for Janice Glesser   Email Janice Glesser   Send New Private Message       Edit/Delete Post 
Hi Thomas...I greatly appreciate your thoughts. I haven't checked the voltages since I got the motor running on this machine. I'm always hesitant to test with the AC plugged in...that's how I blew it in the first place. [Eek!]

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Thomas Knappstein
Film Handler

Posts: 99
From: Erwitte, Germany
Registered: Oct 2017


 - posted November 07, 2017 10:24 PM      Profile for Thomas Knappstein   Email Thomas Knappstein   Send New Private Message       Edit/Delete Post 
I hope you will fix this Problem and it will run once a Day.

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Janice Glesser
Film Goddess

Posts: 3218
From: Sunnyvale, CA USA
Registered: Sep 2011


 - posted January 12, 2019 02:22 PM      Profile for Janice Glesser   Email Janice Glesser   Send New Private Message       Edit/Delete Post 
It's been a little over a year since I updated this thread and I'm happy to announce that I finally have a fully working Sankyo Stereo 800. Here is how it went:

I was able to buy a second "non-working" Sankyo 800 for a very low price. The sound was working on this projector, but the motor wasn't running.

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I pulled out the power board and discovered that like the first projector...the bridge rectifier was cracked...

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...and the PCB trace was burnt.
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In hopes that with the repairs I had already done to the power board on the first projector would be suffient... I decided to switch out the boards.

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When possible I try and number the connectors and the wires so I don't have to guess later on when reconnecting.

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SUCCESS!!!! The projector motor started right up...the arm spindles were turning and the sound lights all turned on.

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I'm happy to have a working projector, but feel bad I couldn't get the sound working on the original machine.

Thanks everyone who contributed to this thread. It has been a wonderful learning experience and I hope others can benefit from the information. [Smile]

[ January 12, 2019, 06:15 PM: Message edited by: Janice Glesser ]

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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James N. Savage 3
Phenomenal Film Handler

Posts: 1373
From: Washington, DC
Registered: Jul 2003


 - posted January 12, 2019 07:15 PM      Profile for James N. Savage 3   Email James N. Savage 3   Send New Private Message       Edit/Delete Post 
Thanks so much for the update Janice! So glad to get a happy ending on your Sankyo project. Hope you will enjoy your machine for many years as I have too.

James

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Janice Glesser
Film Goddess

Posts: 3218
From: Sunnyvale, CA USA
Registered: Sep 2011


 - posted January 14, 2019 09:52 AM      Profile for Janice Glesser   Email Janice Glesser   Send New Private Message       Edit/Delete Post 
I'm glad to finally wrap up this project James and thanks for your interest. Sankyo has made some great projectors and I've owned several models. The Sankyo Stereo 800 is the top-of-the-line and a pleasure to run.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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