Well, I was hoping I'd never have to deal with this, but my 5 1/2 year old 7900 has finally acquired a "clog" which I cannot clear using the normal recommended cleaning methods. It's in the Green channel, and I'm missing a small block of about 3 lines (one of them partial) in the lower half of the nozzle check pattern. This is the first time ever that I've not been able to easily clear missing nozzles.
I'd been printing fine with my Green 350ml cartridge at 1% before this showed up, but since in the past I've seen problems when cartridges get low I put in a new Green cartridge to be sure I wasn't having ink starvation or pressurization issues. I should also mention that the replaced Green cartridge was dated 2009 so it has been there for quite a while, though I routinely agitate the cartridges in my printer every 6 weeks, and I typically print at least once or twice a week. So far the heaviest clean I've done is a CL4 in Service Mode on the O/G pair. I've also printed a few solid Green blocks (using the nice QTR-based ink purge utility contributed here on LuLa a while back) to see if possibly there is air in the line which needs to get pushed out (which I've also seen happen when cartridges are replaced). Still missing the same nozzles, though occasionally on one of the many nozzle test patterns I would see a few nozzles come back and others drop out in the same part of the pattern. And a few nozzles appear to be very faint, as if some ink is getting out, but not the normal amount. I don't see any evidence of a deflected nozzle which is printing in the wrong place.
I've done quite a bit of reading and research to determine my next step. Since the service manuals clearly recommend replacing dampers every year, and since I have never replaced them, I'm leaning towards doing an Ink Selector replacement. I understand that bad dampers typically cause full loss of a color, not just a few lines, but I've also seen comments here (and elsewhere) that bad dampers can result in other symptoms as well. In any case, I've done service work on equipment similar to these printers and I feel quite comfortable doing the work myself. I have the Service Manual and Field Guide, and I've also reviewed Eric's novel and videos for his great advice on head replacement and wiper replacement. (By the way, I have been replacing my wiper at least once a year.)
So, now to my questions...hopefully someone here has done this and can give me some pointers:
1. The Service Manual says that the ink lines must be purged of all ink before replacing the Ink Selector using special drain cartridges. It's clear that the ink lines must be disconnected from the Ink Selector to replace it, but I'm wondering if it is really necessary to drain the lines. This means wasting a ton of ink, not to mention the expense of purchasing the set of drain cartridges. Does anyone have a different approach that would save the ink in the lines while the Selector is installed or would that be pure folly and prone to a total mess of ink?
2. Any comments on pros/cons of replacing the Ink Selector in my scenario? For sure it is possible my head is bad, but it seems to me that the combination of a) low cost for the Selector (vs. a new head), and b) the fact that I've never replaced something that is recommended for yearly replacement suggests that I should try the Selector first. What do you experienced technicians think?
Thanks in advance,
Dave
