My head's spinning, but it's good.

A case of PEBKAC (Problem Exists Between Keyboard and Chair)? Tell us about your war stories!
Post Reply
User avatar
PID_Stop
Posts: 491
Joined: Thu Apr 01, 2010 11:58 am
Location: Syracuse, New York
Contact:

My head's spinning, but it's good.

Post by PID_Stop » Tue May 22, 2012 1:48 pm

Spent the last week or so working on a Grass Valley 9510A sync generator shipped in from one of our stations (in and amongst everything else that goes on demanding instant attention and solutions). This particular unit would send the whole plant into spasms of instability when brought on line; and apparently I specialize in instability. :lol:

It appears that this box was a very early build for this model (circa 1986), and there are several traces omitted from the motherboard, which I corrected. Also turns out that one of those ceramic SIP amplifier modules is dead (boo hiss: they're largely unavailable or wickedly expensive), and a custom logic array isn't programmed correctly to allow the unit's genlock function to work. A bit of IC juggling to grab a working amplifier from an unused section of the board, removing one resistor and adding another to make the genlock gating work, plus wholesale replacement of the electrolytic caps, and voila: it's alive again!

Went through the calibration, and it's rock solid with the subcarrier frequency within 0.02 Hz, compared to our GPS-referenced master unit here. I'll ship it back to the station tomorrow after giving it some time to burn in.

It's a demonstration of why I really like older equipment: we have complete schematics, at least a certain amount of circuit description, and what isn't explained can be figured out with enough patience. And you can actually fix problems rather than trash entire assemblies. This box, which dates back to 2" quad VTRs, should be good for another 25 years. I wonder how much other equipment it will outlast...?

Okay, time to pack it in before I get a penalty for excessive celebration.

-- Jeff

User avatar
Deep Thought
Posts: 3211
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: My head's spinning, but it's good.

Post by Deep Thought » Tue May 22, 2012 2:53 pm

Amen, brotha.

I know I'm nuts, but it brings a unique sense of personal achievement when you can take a dead piece of equipment and troubleshoot/repair at the component level to bring it back to life under triage conditions. Much like getting the station back on the air using whatever happens to be around, MacGyver-style. I learned a lot from those old manuals that continues to be useful with newer, much less-documented equipment.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

eadler
Posts: 411
Joined: Mon Dec 15, 2008 2:23 pm
Location: Binghamton, NY
Contact:

Re: My head's spinning, but it's good.

Post by eadler » Fri May 25, 2012 12:56 pm

PID_Stop wrote:This box, which dates back to 2" quad VTRs, should be good for another 25 years.
What about Tri-level?

Also, a note: New Nautel transmitters come with full prints (at least, the NVs we got did).
Eric "tonsofpcs" Adler
http://www.videoproductionsupport.com/
Twitter: @eric_adler

User avatar
Deep Thought
Posts: 3211
Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL
Contact:

Re: My head's spinning, but it's good.

Post by Deep Thought » Fri May 25, 2012 1:31 pm

The XR6 I installed in Feb had full docs too.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

User avatar
PID_Stop
Posts: 491
Joined: Thu Apr 01, 2010 11:58 am
Location: Syracuse, New York
Contact:

Re: My head's spinning, but it's good.

Post by PID_Stop » Fri May 25, 2012 2:21 pm

eadler wrote:
PID_Stop wrote:This box, which dates back to 2" quad VTRs, should be good for another 25 years.
What about Tri-level?

Also, a note: New Nautel transmitters come with full prints (at least, the NVs we got did).
Quad machines don't use tri-level. :lol:

Seriously, by the time I'm done with the companion 9510A, I will have a redundant base reference that's more stable than a lot of brand new units -- and that I can repair if and when we need it. We can lock a Grass Valley ADVC G4 to it and get tri-level sync for about $650... which will improve the G4's nominal accuracy from ±4.0ppm to better than a tenth of that figure.

-- Jeff


Funny: this must be sync generator week. I just finished repairing the power supply from a 1984-vintage Lenco; that was so much fun I changed out the filter caps on its backup unit.

Baylink
Posts: 438
Joined: Wed Dec 15, 2010 3:21 pm

Re: My head's spinning, but it's good.

Post by Baylink » Sat May 26, 2012 1:14 pm

So... did you mark up the doco as-rebuilt, so the next guy has a clue? :-)

[The job isn't over til the paperwork's done]

User avatar
PID_Stop
Posts: 491
Joined: Thu Apr 01, 2010 11:58 am
Location: Syracuse, New York
Contact:

Re: My head's spinning, but it's good.

Post by PID_Stop » Wed May 30, 2012 7:33 am

Baylink wrote:So... did you mark up the doco as-rebuilt, so the next guy has a clue? :-)

[The job isn't over til the paperwork's done]
But of course! Copied the original drawings, made the revisions, and put both the originals and revisions back in the binder along with a memo detailing exactly what I had done, and why. Actually, though, my restoration work mostly was aimed at correcting early revision bugs, so that the unit matched the original schematics -- except for working around several non-available parts.

One thing I've learned over the years: do the drawings and writeups first for any project, because once the equipment is installed or back in service, everyone expects that you're fair game for their next emergency... and you'll never get the time to go back.

-- Jeff

User avatar
RGORJANCE
Posts: 1387
Joined: Mon Dec 31, 2007 7:48 am
Location: RACINE, WI

Re: My head's spinning, but it's good.

Post by RGORJANCE » Wed May 30, 2012 7:45 am

It is really great to read about how you are documenting things! So many times I have encountered a problem, only to find the books missing. "The previous engineer took them home" In recent years, I worked with a guy that installed the equipment at a station and took the books with him back to the "home office", He got real upset when I gave him an "old time chewing out". Like he felt it wasn't necessary for the books to be where the equipment was. Took three or four sessions, and a real threat from his boss to get him to leave the docs. He quit working for the company about 6 months later.

Another famous one was where the engineer "kept the documentation at home, or in his head for job security". They wouldn't dare fire him because he had all the information.

One of the most helpful things I do is to have a spiral binder at every xmttr site and put notes in it at each visit. Helps me and other guys who work the sites.

Fossil

User avatar
PID_Stop
Posts: 491
Joined: Thu Apr 01, 2010 11:58 am
Location: Syracuse, New York
Contact:

Re: My head's spinning, but it's good.

Post by PID_Stop » Wed May 30, 2012 1:24 pm

RGORJANCE wrote:It is really great to read about how you are documenting things!
It's self preservation. I serve a regional group of stations; between each station and the centralcasting hub (where my office is), it's nearly impossible to remember what's at each facility and how they are wired.

Heck, some days I can't even get from my office to the control room without forgetting why I was going, by the time I get there. Fortunately, smoking equipment has a way of jogging one's memory... :lol:

-- Jeff

User avatar
PID_Stop
Posts: 491
Joined: Thu Apr 01, 2010 11:58 am
Location: Syracuse, New York
Contact:

Take two...

Post by PID_Stop » Fri Jun 01, 2012 2:40 pm

Well, the sync generator got sent back to the station and put into service; its companion arrived yesterday for a similar refurb and recalibration. I somewhat expected to have to perform the same field updates (turns out I don't), but I didn't expect to find this:

Image

That's the power regulator module, under all that... er... stuff. Instead of replacing the module when it failed, someone simply tied the unregulated ±15v feeds from the frame to the (supposedly) regulated ±10v card buses, using a string of diodes to drop the voltage to roughly the right value. I can't get the module any more, so I designed a plug-in replacement; the circuit board should arrive from ExpressPCB on Wednesday, and it should take about half an hour to populate and install. No point in spending the time to calibrate something that's going to drift as the AC line voltage changes...

:shock:

-- Jeff

Post Reply