fluke 45 - Page 1
Forum section: electronics / repair

author: ant17
author_rank: Regular Contributor
timestamp: August 14, 2022, 01:43:26 am
content: hi guys i have a fluke 45 and it has no display on the vfd at all. i have checked all the power supplies and all voltages seem to be there according to my service manual but for further investigation into what might be wrong. i need the correct display board schematic as the nec processor is different to my schematic and my schematic shows a 4.1mhz crystal on the board but my one does'nt it only has 3.6 mhz crystal on the main board all my schematics are from the attached service manual. i was wondering does anyone no if there are revision services manuals or schematics

author: alm
author_rank: Super Contributor
timestamp: August 14, 2022, 10:05:17 pm
content: I'm pretty sure that Fluke has made a service manual and/or change sheet for this hardware revision, but whether someone scanned and published it is another matter. I guess your best chance is to try to find as many copies as possible and hope one has the correct schematic, or otherwise troubleshoot without the correct schematic.Did you already check the getter if the VFD is still vacuum? A vacuum fluorescent display that's not vacuum is not going to be fluorescent either

author: ant17
author_rank: Regular Contributor
timestamp: August 14, 2022, 11:35:46 pm
content: ok will try thanks

author: ant17
author_rank: Regular Contributor
timestamp: August 15, 2022, 06:24:21 am
content: hi guys i have an updatei was measuring the main oscillator crystal on the main cpu on main board u6 HD630A3Y03 just see if the main processor u6 had good clock signal. that was preventing it from working properly a found it to be hard to measure and noisy i was measuring the pins also on the vfd and i made a measurment of the fillament voltage to ground with a multimeter and found something wierd. The display lit up which i found really weird and could not explain. so i looked all around the fillament citcuit and could find anything out of order. so i put it back together and then found if i applied a little pressure to the back of the board in certain spots the whole screen would light up brightly like norma.l i went and had lunch and then came back to it repeated the same test but got nothing but i am starting to doubt the crystal anybody else got any ideas thanks

author: J-R
author_rank: Super Contributor
timestamp: August 16, 2022, 12:40:02 am
content: Keep poking things with a non-conductive stick until you find the culprit? Probably a loose solder joint.

author: ant17
author_rank: Regular Contributor
timestamp: August 16, 2022, 06:05:18 am
content: ok thanks for the encouragement

author: floobydust
author_rank: Super Contributor
timestamp: August 16, 2022, 06:35:39 am
content: I would spend some time looking at the PCB with a magnifer and touch up any bad solder joints.A common problem is fractured solder joints on a VFD. The pins are Kovar with some weird plating that does not solder great at the factory. At the far ends of the tube, the filament connection pins are high current and tend to be a problem at the pc board pads.You can also take a plastic pen or poker and gently tap around to find the bad connection.

author: ant17
author_rank: Regular Contributor
timestamp: August 20, 2022, 12:51:31 am
content: hi guys thanks for all your help. i have update i did find pins in the vfd that did break away from the solder joints so fixed them. but it still did not come to life but microprocessor /Vfd driver on all the pins going the vfd were showing -37volts dc and not much of any data signals. also i noticed that when i put my finger on particular pins the vfd would light up with random numbers any ideas?