Tektronix WFM90

I bet that's one of those self-contained buck converters. Like a 7812, but switching. Fetch it out, you should be able to work out what's input (probably from that L) & ground. The other will be the 12V output. Pop 12v in there, sensibly current limited, and see what happens. 

I suspect it's making that unpleasant noise because there's something loading it down. 

Hi Andy, this is the part.

Google says it's a relay, which I what I felt as it sounds like one when I put a screwdriver on it and the other end in my ear.

https://pdf1.alldatasheet.com/datasheet-pdf/view/158441/NAIS/TK1-12V.html

Ah indeed - Is your PSU limiting?

The manual is on Elektrotanya, power supply needs to be 12volt 1 amp unregulated.

OK, not sure if I've got it powered up, but I think it might be, though I've nothing on screen.

After seeing Stephen's info, I raised the voltage to 12V and current to 1A. I set OVP to 18V and OCP to 1.1A. Pushed the on button, buzz heard but instead of releasing kept holding. The supply drawn is on 3.61V and current drawn is 1.008A

OK, looking at the manual which has helped, thanks Stephen, it looks like this is toast. Glad I was careful as according to the manual there is H.T of 400VAC on the display backlight, which is dead, one of the bulbs not present.

Oh well, put that one down to experience. I'll have to hope I can find on in the UK and use this one for spares.

would be interesting to see what the bulbs look like, i have replaced many tubes and bulbs in backlights over the years from 2 inch to 19.

Then there is a possibility of an LED conversion. 

Not one to give up, I kept spamming the on button, Eventually it powered up taking 12V @606mA. What I thought was a broken backlight was not, it was just inset a lot further.

Unable to get the WFM90 to display the colourbars in colour, not sure if that is due to a config. As this was from the U.S. it thought maybe I need to set it all up for PAL, though if it were set for NTSC, would It not resolve at all? Anyway, looking through the manual, I cannot see any option to set standards.

I have hard-wired a 13.5V, 1,100mA wall-wart on the board. The unit powers up every time now.  I cannot get it to work from batteries, 6 x 1.5V C cells only amounts to 9V, looks like it has the option for a TEK rechargeable battery pack.

Still not sussed the colour problem to either a config error or fault. What I have noticed is if I call up the VectorScope I don't see the classic PAL pattern, is this a clue, are those circles no sync? Again I'm out of my depth here, and need broadcast engineers such as @hurty Adrian @cathovisor Mike or @mfd70 Mark to advise. Anyone know how to check if a WFM90 auto-detects standard or needs, like the TSG95, setting to a standard.

I tell you what, for 1997 I'm impressed with how TEWFM90 manages to simulate Phosphor. It certainly seems to simulate the characteristics of phosphor. As the signal is first received, it builds and shimmers.

@crustytv Looks like it's unlocked to me, there may be a setting to lock to incoming video rather than external sync, try setting the generator to a signal without colour and see if the burst is present on the display (the the two lines 90degrees apart). I haven't used one of these for a few years but I think it does need to be set to PAL or NTSC in a menu option.

OK, I've been all through the menus and there isn't an option I can find that sets it to PAL/NTSC.

I then thought there might be a key combination, like on the TSG95, that drops into a set-up to choose PAL or NTSC. On the TSG95 you hold the 'Lock Out' button down while pressing the 'ON' button to access the utility menu. Again, not yet found it anything in the WFM90 manual similar, I'm starting to think it auto configures.

There are three BNC connectors up top, Ref IN which I assume is for an external sync. Video IN with a switch to toggle between 75R & Hi-Z. Finally, a Video OUT, again with toggle switch for 75R or Hi-Z.

I checked the WFM90 menu, and the device is set to get internal ref, not external, so all is OK there. Yet when the vectorscope is activated, clearly no sync. I'm beginning to suspect there's a fault with the internal reference. I had this exact fault on a TEK 1428 Vectorscope, I never got that to resolve and gave up trying.

I wondered if the lack of colour on the WFM90 screen was a red herring, used the pass-through to a monitor. Low and behold, there is colour, so it looks like I have two further faults to find. No colour to the LCD and no internal reference. If only I had an external reference source. The courtyard CY420 I have I supposed to have one, blowed if I could get that to work when I was trying to feed it into the 1421.

Hi Chris,

nice bit of kit! Not sure if I’m looking at the right manual, there doesn’t seem to be a circuit diagram on it. Looking at the PCB in your video I notice it has some of those SMD electrolytics, they can be troublesome! I have a Sony mini LCD tv that I had to replace every single one of the damn things! I wonder if the earlier no power up/ high current draw was down to some of those playing up, probably in the backlight inverter circuit, as that part of the circuit is probably the most power hungry. Not sure on the no colour fault, might be worth examining the board under the microscope for any damaged components, or any that are missing, particularly where that DC connector had been removed.

 Regards 

Lloyd 

In the service manual, there is a flowchart for diagnosing an unlocked vectorscope waveform.

Check for vertical and horizontal sync pulses at J9 on Top Board. It further talks about checking the Subcarrier Regenerator Oscillator, and checking the IFsc signal. Again, SRO control voltage is at J9 on the top board, and should be approximately 1 VDC.

However, all roads lead to either top board, bottom board or both replacement, so I won't/can't be doing that, unless I find a scrapper.

As for input signal not being displayed in colour to the LCD. It would suggest there's no a fault with the LCD, it displays waveform, vector and menus in colour. Might that suggest there is a fault in the presentation of the picture signal path to the LCD, as on pass-through via the video out, it's perfectly fine, as shown above.

Anyway, that'll do for now.

Forgot to add and show, it came in the very nice TEK case, similar to the TSG95.

Posted by: @crustytv

Anyway, looking through the manual, I cannot see any option to set standards.

I have the horrible feeling that the WFM90 is NTSC only and the WFM91 PAL only.

Posted by: @cathovisor

Posted by: @crustytv

Anyway, looking through the manual, I cannot see any option to set standards.

I have the horrible feeling that the WFM90 is NTSC only and the WFM91 PAL only.

I think you are correct! I just googled the model number and came up with a website selling the things, and in their description it confirms your suspicion 🙁

Regards,

 Lloyd 

@cathovisor The TSG95 is PAL/NTSC, so it should be easy to test if it is NTSC only, just switch over the generator.

Well, I'm one stoopid ..... 🤡

That'll teach me not doing some basic research before diving in. It was the price guv, honest bargain clouded judgement.

OH, well

At least you aren’t going to spend ages chasing a non existent fault now! Maybe find a replacement DC socket, then sell it on at the going rate for a fully working unit, and look for a WFM-91 instead?

 Regards 

Lloyd