8mm Forum: Bolex 18-5 voltage loss to lamp

»	8mm Forum » 8mm Forum » Bolex 18-5 voltage loss to lamp

UBBFriend: Email this page to someone!

Author

Topic: Bolex 18-5 voltage loss to lamp

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 09, 2018 10:26 PM

I mounted a bracket for a lamp conversion for this projector. Lamp was working fine. Returned a day later and lamp will not light. I tested the lamp and it is good. I'm only getting about 1 volt to the socket. Any ideas what may have caused this?

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted April 10, 2018 11:54 AM

There has to be a switch somewhere to control the lamp. Maybe the contacts have become burned, or maybe while you were doing the work its mechanical life came to an end it and just isn't switching properly anymore. (It's tough getting old!)

If you can get a meter across it and the voltage stays high in both "on" and "off", then you know.

-other than that, maybe some connection somewhere...isn't.

Transformer?...maybe...probably not.

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 10, 2018 02:51 PM

Hi Steve. My first thought was the switch. I unscrewd it and peeked u der it the best I could but could not see the connection. I agree it is the most likely issue. The switches on these units are a weak spot and are a real pain to work on. Carefully tapping on all visible wires at their connection at the back of the projector did not yield anything.

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted April 10, 2018 03:34 PM

Well,

Unplug the machine. (Please!)

If you plug an ohmmeter into the socket and flip the switch, you should see high and low resistance. I'm betting you won't.

If, while you still have it plugged in you can find where the socket is connected and put some kind of jumper across those points, you should now see a short. If not, then the socket is bad

If you turn the switch on and put the short across the transformer secondary for the lamp, the resistance will then drop if it's the transformer, but not if the switch or the socket is bad.

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 10, 2018 07:45 PM

At the socket connections, with the switch to of I get an ohm value of 26.04. When I turn the switch to On with lamp, reading drops to 00.00

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted April 10, 2018 07:56 PM

This sounds like the switch is at least trying. The 26 Ohms with the switch open isn’t what I expected. Is the lamp in circuit?

(Is there a high/ low switch?)

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 10, 2018 08:30 PM

There is no high/low switch. Not sure what you mean by "in circuit". It only comes on with the motor running, if that's what you mean.

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted April 10, 2018 08:45 PM

I'm imagining the lamp circuit: a simple one. There would be one side of a transformer secondary, then a switch, then the lamp socket and after that the other socket lead goes back to the transformer.

With the switch open and looking into the socket, you should see an open circuit: literally billions of ohms. (This can dip into the millions or thousands if fingers join the action! -been there, done that!)

26 Ohms is really low. I thought maybe you were measuring the socket with the lamp still plugged in, or maybe there's other circuitry.

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 10, 2018 09:18 PM

No, lamp was not in the socket. Measurement was taken from the two wires connected to the socket. Both are red, so I'm guessing that means it is "in circuit".

To further clarify, the mains is not plugged in.

I've got a couple other 18-5s that work. I'll get a reading from one of them in the morning.

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 11, 2018 08:35 PM

Well, the flood protection just wiped out my post. I am getting sick of it.

Anyway, I had some time to mess with Bolex again. I plugged in mains and measured voltage at empty light socket with motor and light switched on. Read a little over 10 volts but motor would not run. Installed lamp and tried again. Motor ran fine but lamp did not light. Socket read just over 1 volt.

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted April 12, 2018 08:57 AM

The thing between the lamp and the motor is kind of funky. I don't know this machine. Can anybody who does chime in?

To me it sounds like you are loading down the transformer and it can't support the motor and the lamp at the same time.

Is it easy to get a voltmeter on the transformer terminals?

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 12, 2018 09:38 AM

Hi Steve. Here is a pic of the transformer and terminals. The heavy red wire is for the lamp.

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted April 12, 2018 09:44 AM

OK, it looks like an easy grab with alligator clips or EZ-hooks. (Please be careful, there is 117VAC somewhere here...)

If you can measure the voltage between the two transformer lamp terminals lamp on and lamp off it should tell us something.

By the way, have you changed the type of lamp you are installing?

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 12, 2018 10:27 AM

I'll measure a bit later today. The lamp I was installing was just hooked up via alligator clips. It lit at one time and then did not. The original socket is still in place and untouched. I can install the original bulb in it and that is what I am using now.
UPDATE: Took some measurements. They were taken at the transformer terminals as suggested. Mains on. I took them with the bulb in and bulb out, and with the motor and lamp on simultaneously and with the motor on but the bulb off.
Bulb Installed:
Bulb and motor ON: 0.141v
Bulb OFF motor ON: 10.64v
With the bulb installed, motor ran fine.

Bulb Removed:
Bulb and motor ON: 10.64v
Bulb OFF motor ON: 10.63v
With the bulb removed, motor would not run.

[ April 13, 2018, 12:30 PM: Message edited by: Barry Fritz ]

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 13, 2018 12:26 PM

Steve, do the above values shed a light on anything? No pun intended!

| IP: Logged

Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003

posted April 13, 2018 09:31 PM

Well,

The good news is it sounds like you've exonerated your lamp circuit!

The bad news is it sounds like you have kind of a fundamental power supply problem!

It's acting as if the lamp is wired in series with the motor.

[ April 13, 2018, 10:57 PM: Message edited by: Steve Klare ]

--------------------
All I ask is a wide screen and a projector to light her by...

| IP: Logged

Barry Fritz
Phenomenal Film Handler

Posts: 1061
From: Burnsville, MN, USA
Registered: Dec 2009

posted April 14, 2018 09:32 AM

Thanks Steve. I am at a loss how that happened. I did not do any rewiring of anything. I just used alligator clips to temporarily connect my converted lamp to the wires on the original socket, and have since removed them. All wiring that I can see is intact. Thanks for you help. Looks like I now have a mint display unit!

| IP: Logged

All times are Central

Printer-friendly view of this topic

UBB.classic^TM 6.3.1.2