VFD Display - Good segments, bad segments? - Page 1
Forum section: electronics / repair

author: dundee
author_rank: Regular Contributor
timestamp: September 15, 2015, 04:15:20 pm
content: Hey Guys!Im trying to repair a Teufel Cinebar (Soundstation).The power Supply (5V, 12V, 32V) was faulty. Changed some capacitors and now it's working.Sound is good, but i have a little question to the VFD-Display.Some segments are clear to read, others look a little bit dim.Is this the "normal" aging process of VFD Displays or could it be another reason?I know the aging problem from some of my Test-Equipment but i have never seen different lightning up segments.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 15, 2015, 04:23:35 pm
content: Dirty Cathode/Anode voltage, however they are doing it, caused the symptom as you show, in a few devices I have seen in the past. Replace capacitors in the inverter circuit if you can and check again.In lieu of that a driver problem.

author: dundee
author_rank: Regular Contributor
timestamp: September 17, 2015, 06:24:34 pm
content: Thank you for the hint.I checked the voltages for the VFD: 30V DC and 4.4V AC. They are fine.I swapped the Display-PCB to my fully working cinebar. Same problem.So it must be the Display or the Display PCB.There is not much to see. The Voltages go directly to the PT6311 Chip.Datasheet here:http://www.ec66.com/market/sheet/PT6311.pdfShould I try to change the chip? Found on ebay for around 10€.

author: Macbeth
author_rank: Super Contributor
timestamp: September 17, 2015, 06:49:51 pm
content: I doubt it is the driver chip. Have you found a test mode to highlight all the display segments? Sometimes just switching stuff on gives this briefly. Film it, then look at the freeze frame. It's pretty obvious that certain filaments have been left on for a long time and burned in while others seldom used do not suffer this.In your case the device is displaying COAXIAL. My guess is this is not the normal operation and it would display something else when idle - and then all the segments will be equally dull.A new VFD is needed rather than the IC.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 17, 2015, 07:09:17 pm
content: Normal voltages yes, but are the -30V and +5V clean (on a scope) on the VFD & IC, i.e. no high ripple? If it isn't clean, it could cause a phased blanking effect. Is the -30V coming from the mains or from an inverter?Not a fan of Princeton IC's. I bought a few for exotic stoof but haven't used them yet. Cheap enough, too many projects right now, soon.Quote from: dundee on September 17, 2015, 06:24:34 pm

author: dundee
author_rank: Regular Contributor
timestamp: September 17, 2015, 10:20:38 pm
content: Macbeth, coaxial is the right text.This is one of the inputs. (Coaxial, Optical, Aux 1, Aux 2)Quarlo Klobrigney, as I said I swapped the Display to my working cinebar ( have two of them).Therefore I think it can't be the power supply. But I will look, if they are clean.It's a switched mode power supply...

author: Macbeth
author_rank: Super Contributor
timestamp: September 17, 2015, 10:48:28 pm
content: Quote from: dundee on September 17, 2015, 10:20:38 pmExactly - you have just confirmed what I said. I bet "OPTICAL" is all nice, even, and equally dull, so this device has been running on OPTICAL for most of its life. The dull/bright segment contrasts seem to support this.

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 17, 2015, 10:48:48 pm
content: By display do you mean just the glass or the whole board? Also is the switchmode on board or off board?

author: wraper
author_rank: Unknown
timestamp: September 17, 2015, 10:50:58 pm
content: Quote from: dundee on September 17, 2015, 10:20:38 pmMacbeth means that usually there is something else shown on the display. Those segments which are lit most of the time burn out more and become more dim than others. The only way how to fix this is to replace VFD display itself (glass).

author: dundee
author_rank: Regular Contributor
timestamp: September 17, 2015, 11:38:14 pm
content: Ahh, now I know what you mean! Will examine it tomorrow.By display I mean the complete board...The SMPS is off board.There are a total of three boards: Power Supply, Amplifier and the Display-PCB.Many thanks for the support

author: dundee
author_rank: Regular Contributor
timestamp: September 18, 2015, 11:26:55 am
content: 100 Points to Macbeth!Looks like i have no chance to get a display. Googled the Part-Number but no results....

author: Quarlo Klobrigney
author_rank: Super Contributor
timestamp: September 18, 2015, 06:05:59 pm
content: I didn't see the info. When you said you swapped boards you didn't say whether the problem followed the board. So I was under the assumption that it worked in the other good unit. I'm lost.......

author: dundee
author_rank: Regular Contributor
timestamp: September 18, 2015, 06:30:45 pm
content: Quote from: Quarlo Klobrigney on September 18, 2015, 06:05:59 pmYeah, sorry... my English is not the best...