8mm Forum: Bell & Howell 642 Lamp Holder

»	8mm Forum » 16mm Forum » Bell & Howell 642 Lamp Holder

UBBFriend: Email this page to someone!

Author

Topic: Bell & Howell 642 Lamp Holder

Paul Mason
Jedi Master Film Handler

Posts: 540
From: Aldershot, Hampshire, UK
Registered: Nov 2013

posted September 03, 2014 04:19 AM

After replacing the exciter and pilot lamps on my 642, the main lamp has stopped working. The lamp is OK as it lights up in my 644 projector and I rely on one mains lead for both projectors so it can't be that. This leaves either the lamp holder/base or the control switch. has anyone had trouble with the switch or the lamp holder? Is it straightforward to replace? Many thanks.

--------------------
Paul.

| IP: Logged

Martin Jones
Phenomenal Film Handler

Posts: 1269
From: Thetford , Norfolk,England
Registered: May 2008

posted September 03, 2014 04:26 AM

If this has the "valve" type base with pins, try working it up and down in the holder to clean the internal contacts of the holder. A little Servisol contact cleaner on the lamp pins first will assist with this.

--------------------
Retired TV Service Engineer
Ongoing interest in Telecine....

| IP: Logged

Simon McConway
Phenomenal Film Handler

Posts: 1085
From: Doncaster, UK
Registered: Jun 2004

posted September 03, 2014 07:28 AM

I had to replace the whole switch which was a fiddle. Starting currents are high with this lamp which can produce arcing across the contacts. This causes damage over time. The lamp holder could also have been damaged by arcing if a lamp had previously not been pushed fully home during the past life of this machine.

| IP: Logged

Paul Mason
Jedi Master Film Handler

Posts: 540
From: Aldershot, Hampshire, UK
Registered: Nov 2013

posted September 03, 2014 09:57 AM

Thanks Martin and Simon,
I tried moving the lamp up and down to rub the pins as Martin suggested and it does now light up. As Simon says it is easy to not push the lamp fully home. I suspect corrosion in the base was always the most likely as the lamp didn't come on in forward or reverse whereas a switch fault would probable only affect forward. I may try gentle cleaning with a needle file as well

--------------------
Paul.

| IP: Logged

Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007

posted September 03, 2014 11:08 AM

The pins are very fragile. Handle with extreme care.
Don't forget that the lamp is always live, the switching is on the neutral. Only handle the in/out of the lamp with the mains plug disconnected.

--------------------
Maurice

| IP: Logged

Terry Sills
Phenomenal Film Handler

Posts: 1423
From: Weymouth,Dorset,England
Registered: Oct 2012

posted September 03, 2014 11:22 AM

Maurice
Is that true of all projector lamps?
Terry

| IP: Logged

Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007

posted September 03, 2014 01:14 PM

Fragile pins, or live connection? I assume you mean the latter.

This applies to all 16mm Bell & Howells from the 641 onwards, until the TQ models appeared. They can be distinguished by their 4-pin mains sockets. By the use of a special transformer 115 volt lamps can also be used. The wiring is so designed for this. The separate wire direct to the lamp can also be used for a change-over arrangement.

I am referring to the A1/205, A1/206 and A1/207 lamps.

--------------------
Maurice

| IP: Logged

Paul Mason
Jedi Master Film Handler

Posts: 540
From: Aldershot, Hampshire, UK
Registered: Nov 2013

posted September 03, 2014 02:17 PM

The Bell & Howell 643/644 instructions warn that the mains supply should be disconnected before removing or replacing the lamp. I remove the plug from the projector or the mains socket. There is a shock risk with lamp voltages over 30volts but it applies to all projector lamps since an accidental short-circuit can weld metalwork if a high current is passed similar to that caused by car batteries. The pins of G17 type bases are delicate but with care should allow the lamp to be moved vertically in and out of the holder without damage.

--------------------
Paul.

| IP: Logged

All times are Central

Printer-friendly view of this topic

UBB.classic^TM 6.3.1.2