8mm Forum: Sankyo 702 light died

This is topic Sankyo 702 light died in forum 8mm Forum at 8mm Forum.

To visit this topic, use this URL:
https://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=005199

Posted by Peter van Zand (Member # 1552) on January 20, 2010, 10:34 AM:

Yesterday when I was projecting some new shorts the lamp of my 702 suddenly quit. No problem, I thought, replace the lamp and on with the show. But it seems to be a power issue, no current is reaching the lamp. I checked the fuse and it's allright. Can someone maybe shed a light on this? The Sankyo was my favorite projector.. [Confused]

Posted by Steve Klare (Member # 12) on January 20, 2010, 02:56 PM:

Peter, how comfortable are you poking around circuits looking for voltages? (Especially when there is line level voltage present on the transformer and possibly the motor too?!)

This should be a pretty simple circuit: I bet we can find out where the problem is.

PS: What bulb does this machine use?

Posted by Peter van Zand (Member # 1552) on January 20, 2010, 03:24 PM:

Steve, I have a voltage meter but I wouldn't know where to measure. It's all packed tight inside and not very accessible, but I'm prepared to experiment and learn. Thanks for any suggestions.
It uses a EFR 15V 150W bulb

Posted by Mike Peckham (Member # 16) on January 20, 2010, 04:00 PM:

I had a similar problem on my Sankyo 800, turned out to be the lamp holder. I would suggest you trace the lamp holder wiring back to the transformer and with the motor running and the lamp on, test the voltage at that end.

If you get 15v you'll know that it's the lamp holder that's at fault, if you don't you'll need to look further...

Hope that helps.

Mike

Posted by Maurizio Di Cintio (Member # 144) on January 20, 2010, 04:38 PM:

Actually the lamp holder tends to gather dirt/oxide on the very contacts which touch the lamp's pins. When this happens it's not rare to have the lamp working again in pre-heat mode by gently moving the holder back and forth. This usually fix the problem (temporarily). For more consistent results, you need to clean the inside contacts of the lamp holder and possibly the lamp pins too: for the latter ones, I use extra fine sand paper; for the former I simply spray some contact clening fluid inside the lamp holder, and put the lamp pins in and out a few times after some minutes. Of course it is also possible to replace the whole holder. In any case I think this problem should not be underestimated as poor contact between the lamp socket and the pns might lead to over heating of the socket itself due to arching (in the worst circumstances).

Posted by Graham Ritchie (Member # 559) on January 20, 2010, 04:46 PM:

Peter
Just a thought, although I am not familiar with your projector I would remove your new lamp again and give the two lamp pins a really good clean with some fine wet/dry rubbing down paper. In most cases that should do the trick, in fact every time I change a lamp I clean those contact pins, if you dont have good contact you get resistance and that in turn creates heat which will in time cause the lamp holder to fail.

Graham.

Sorry Maurizio I was away from the computor so I didn't see your reply I think we were both saying almost the same thing. [Smile]

I would add a word of caution to Peter that some spray CRC contact cleaners are flammable so be carefull using those things [Smile]

Posted by Steve Klare (Member # 12) on January 20, 2010, 08:19 PM:

Peter,

Use the AC voltage ranges on your meter and for heaven's sake be careful!

If you can get to the point where the wiring enters the socket and touch the bare wires at that point, you can test the socket. Otherwise try to get the the other end of the socket wiring and measure what the voltage is doing there.

If you can find the switch that controls the lamp, the voltage across it should be zero when the switch is turned "on", and 15V when the switch is turned "off".

If all of these readings are zero, trace out the lamp wiring to where it is wired to the transformer and see if there is 15V present going in.

Something, somewhere is open circuit and getting all the voltage that should be on that bulb.

Is there one fuse for the whole machine or does the lamp circuit have its own?

Posted by Maurizio Di Cintio (Member # 144) on January 21, 2010, 10:54 AM:

Hi Graham. It's good to punctualize some sprays are flammable. I didn't, just because I usually wait until it is fully evaporated before operating the projector again so I assumed everybody would do the same [Frown]

Thank you

Posted by Peter van Zand (Member # 1552) on January 22, 2010, 01:57 PM:

Thank you all for your input, I am happy to say that I fixed the problem. It was indeed the lamp holder which caused the failure. I picked up a new one and some advise on how to go about it at Parallaxe today (see my post about that visit here: visit to Parallaxe and after replacing the socket all was dandy again [Smile]

It's great to have so many people chiming in to try to fix problems that other forum members encounter.

UBB.classic^TM 6.3.1.2