Lexel 88 problems - Help please

[smogthemog]

Been on holiday last week and will now be back 'giving it a go'

Must get this thing lit before the LEM or my ass is gravy

Again, thanks SO much!!! for all of your help through all of this Steve.

[mixedgas]

You better get it lit, I'd hate to have to take my tax return and have to buy a ticket and come fix it....

Thinking about a long overdue vacation...

Steve

[smogthemog]

Waow!!!

You have around 11 days to decide that Steve That is if you are refering to the Surfleet LEM - which is pretty imminent?

That would truly be awesome mate - you would be most welcome as I am sure you would imagine! Not only to light the Lexel, but to have a gas laser guru such as yourself over on this hallowed isle would be rather cool

You could bring Ben with you

[smogthemog]

Lift R32 and see if that voltage goes away. If it does, reconnect it, and your ready for testing. If it does not, you still have a problem.

You've done fine on the diagnosis/repair, most people would have never gotten as far as you have now.

Steve

OK Steve I lifted R32, which is actually a 560K and not a 360K as Sam has written, which incidentally is situated across the back of TP2 & TP3!, and the 34v went away

I presume now I am OK for testing?

I don't want to go any further without your guidance - for obvious reasons

[mixedgas]

Seems like your good to go, not all Lexels have that resistor.

Tap accordingly, try to start at higher currents, and watch to keep reg volts in the green.

Steve

[smogthemog]

OK Steve, thanks.
I am just going to check components within the head before I do finally let loose with thick style wiggley AC current

I want to check the HT caps in the starter cct and the coil resistance/continuity.

[smogthemog]

I checked the 3x caps and the 2x resistors and all seemed OK.

I made sure everything was plugged in, filament switch checked and set, voltage taps set and then applied power and water, switched on and waited for the ready light.

I noticed that the 34v wasn't there so I switched off and re-checked everything.

I powered up and hit the start button..............

It did exactly the same as it did before I started

It strikes and lases for a second or so but makes a horrible 'oscillation' type noise then goes out until you re-press the fire button. Once you have done this a few times it lases for longer periods each time until eventually it stays on. It is still making the horrible noise. The noise emanates from the HV strike coil in the head. Again, I haven't run it for any longer than 5 seconds before switching off.
When it lases the current/power output is totally unadjustable from the PSU, current controlled, and it's pulling about 25A, according to the PSU meter. The Pass bank voltage is still very low, around 14V, according to the PSU meter.

I can, as before, completely remove the current board from the PSU and it still does as I have described.

I powered everything down, slammed shut my shed door and went inside in front of the telly.

I am very sad

I am officially confused.

[mixedgas]

OK Steve, thanks.
I am just going to check components within the head before I do finally let loose with thick style wiggley AC current

I want to check the HT caps in the starter cct and the coil resistance/continuity.

Please consider leaving the starter alone, its so overbuilt it never fails.

check the magnet for 50-80 ohms or so.

Steve

[smogthemog]

The mag coil is 53.5 Ohms.

I had a closer inspection of the crimped connections in the head this afternoon and found the below:

I don't know yet whether it is the problem as of yet, haven't had a chance to test it but it certainly wont help! The black wire fell out of the back of the crimp when I unscrewed and moved it. I am now fitting individual crimps to each wire and not having 2 wires into one crimp - always a recipe for disaster!

[mixedgas]

[QUOTE=smogthemog;144520]The mag coil is 53.5 Ohms.

I had a closer inspection of the crimped connections in the head this afternoon and found the below:

End QUOTE;

Good, magnet is within spec.

Steve