Does anyone have the service manual for the HP/Agilent 'ColorPro' 7440A plotter? Also, the programming manual? I'll pay for either those, or good scans of them. eBay sellers aren't forcoming right now on that model.
The most important bit of info I want is the details of power supply to the four pins on the connector. The label on the base suggests 20VAC at 2A, but that seems unlikely in extreme! There are no rectifying and smoothing components inside, and each of the four pins seems to have its own track. Two of them have a capacitance across them, too big to safely put directly across 20VAC. The conflict between label and reality is too great to trust to anything but original info. I don't want to risk reverse engineering unless no info can be had at all.
You can list your needs on "E-Bay WANTED". I did that for a manual I couldn't find - it took a few months but I hit the jackpot. My "listing" there is about 5 months old or more - and I still get hits from it for equipment with the same model number.
"Michael A. Terrell" wrote in news: snipped-for-privacy@earthlink.net:
Thankyou. No good though, that plotter is 22 years old, they don't keep anything on it, except a passing reference in some other document for something else.
"CLFURENT" wrote in news:46c326a5$0$22488$ snipped-for-privacy@news.coretel.net:
I'm considering it, but as you say, it's possible to get mails indefinitely if the request is too braod so I want to try to get the information some other way first, even if just to narrow down what I ask for.
One small breakthrough:
formatting link
That describes the right power supply, and it's the same for many devices. I'm trawling eBay for adaters/psu's for those, without much success, I found one in Canada (I'm in the UK).
If anyone has any of those HP printers listed there, and is willing to get the PSU and let me know what the four pins are doing, i.e. which if any are commoned, or not connected, and especially, which are outputting 20VAC, that will be a great help to me.
I've had about a 50% sucess rate with their online manuals, but it never hurts to check, and check back, because they keep adding more old manuals. They have some a lot older than 22 years on there. :)
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
"Michael A. Terrell" wrote in news: snipped-for-privacy@earthlink.net:
Cool, I grant it's a nice way to look for stuff so I'll do it. Still hoping someone's got one of those PSU's to get me a pinout, but for the programming manual I can watch and wait, first thing is to get the thing started... Direct drawn PCB's. SMT, single sided and such. A cheap and effective way to make them, it seems. Good to learn with, if nothing else.
Bob Pownall wrote in news: snipped-for-privacy@corp.supernews.com:
Nice one. Thankyou. And yes, it is. I had a look inside yesterday, awesome thing, looks like it was made last week, not 22 years ago. No brittle plastics, wire sheaths are still flexibly plastic, no oxidised metal that I can see, belts are taut but not exerting strong constant strain, it looks like it could wait a century and still look good as new. Even the electrolytic caps look fine, but I won't know till I get power to it whether they are. I bet they are though.
says 2V 2A, but doesn't say AC or DC. It also lists some HP printers that used the same supply, and I MIGHT have a 120 VAC input supply in my pile of dead printers. I also have some old HP plotters in storage that might use the same supply.
formatting link
says: Power connector:
|o -> gnd |o -> ac1 |o -> vcc |o -> ac2
vcc and gnd -> 10Vdc @400mA
ac1 and ac2 -> 20Vac @1A
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
"Michael A. Terrell" wrote in news: snipped-for-privacy@earthlink.net:
Excellent find, that second info, it sort of confirms what I suspected, two power busses. Hard to see why 4 pins otherwise. Also, that capacitance I detected would likely be extra smoothing for the DC buss.
I'm after a 240V input PSU but I suspect cracking open the case might show a dual-primary transformer.
"Michael A. Terrell" wrote in news: snipped-for-privacy@earthlink.net:
Been inside. That info checks out, pretty much, except that's 2A as claimed by the other source, there's a bridge rectifier made of 4 diodes, and a 50V
2200µF cap before a 2A fusible resistor protecting what comes next. The other cap is a 3300µF so I guess the PSU is unusual in rectifying a 10V or
12V winding but not smoothing it.
I guess this is part of some common standard HP wanted so they could use the same PSU on so many devices.
I could probably wire something up now but this HP 7440A plotter is so awesomely perfect I want to treat it nice, so I'll try to get service and programming manuals and original PSU if I can. I'll try the eBay wanted ad soon if I don't get lucky here.
Bob Pownall wrote in news: snipped-for-privacy@corp.supernews.com:
Thankyou. I'm willing to pay, but I'll pass on those, having looked at them. They might not have any. Even if they do, they'll set the price to as high as they like the momemt I request a quote, then add all the surcharges and handling charges and brokerage charges they can think of.
I'll wait till someone on eBay offers one. Can't negotiate with people who run vast virtual carts. Maybe on eBay, I can. eBay also contractually binds a seller to have the item before trying to sell it for a start.
Lostgallifreyan wrote in news:Xns998EAA8D3B45zoodlewurdle@140.99.99.130:
LONG post alert. >:) Might be instructive though, or at least, amusing.
I just tried one of these strange outfits that say they have, or can get parts. First one I tried for the part in question, and sure enough, it really IS that bad! Read on if you're bored enough.....
Hi, I saw this on your site: Caritronics K-3000 TRANSFORMER PLY HV 3000VDC FS $87.00 Can you tell me any specs for it? 3000VDC is nice but how much current? I'd need to know before deciding on anything. Any info at all is welcome.
[Company details omitted, this is a fun post, not investigative journalism]
No, you don't need any of that. If you have the part, AND information to help me choose, I might be able to decide to buy. If you ask me for information that doesn't help me find the part or information about it, I won't go there, it's a waste of time, and a potential annoyance.
If you're able to get info on that part, just reply by mail as you already did, that's all you need. None of that other stuff is needed, no-one buys parts that way, they just buy parts. IF the information about them is forthcoming without obstacles, otherwise they go elsewhere.
Awesome! I found a couple for less than $50 including postage. I knew you weren't for real, and you just confirmed it MAGNIFICENTLY. What kind of outfit are you, really? You don't have the parts, do you, or even any access to them at all? You don't know a thing about them, do you? They don't weigh 3 lb each either, so you might want to correct that little detail on your site. Let me guess, you're one of these middlemen outfits who try to profit by inserting themselves between people and the things they are looking for, a bounty hunter for stupid people who don't really know what they want and have far too much of other people's money to spend. I'd have the same change trying to buy this part from a Nigerian email scammer, I imagine.
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Ok, maybe not all of them are like that but this should be a warning not to go to people like that, they'll slap you silly if you're daft enough to let them think you really want something from them.
I just joined the group today. I noticed that you are searching for a power adapter (or mains adapter depending on which side of the pond you're on) for an HP7440a plotter or at least info on power requirements.
Here is the link for the service manual from the very helpful and useful HP Museum (mentioned in Curt Carpenter's article in Circuit Cellar #202 about using the 7440a to do direct PC board resist layouts):
formatting link
I'm glad to have looked at this documentation since I was about to hook up a 20 vac transformer paralleling the inner and outer pair of pins as suggested by some forum on the net. This would have shorted the secondary winding(s) with unpleasant results. Actually paralleling any two pairs would guarantee shorting some part of the secondary.
The nitty gritty of the power supply:
--the transformer comes in many models to match the rated 100, 120,
220 and 240 input range. The secondary is 20 volts AC around 2A with a center tap of 10 volts AC-- and it must be a true center tap. If asymmetrical, one half of the winding will shoulder all of the digital circuitry load and the other will loaf along.
--the 20 vac is fed to a full wave bridge to C33 a 2200 uf filter capacitor to produce approx 26 vdc unregulated to drive the motors. This voltage is also monitored by support ic U6 which adjusts the gain of the plotter drive circuits to compensate for line voltage variations.
--the center tap produces a nominal 10 vdc through a center tap full wave arrangements (ie using two diodes) to power the digital logic. The circuit is a departure from the conventional (and more familiar) one which grounds thecenter tap and places a diode in each leg of the transformer secondary joining up at the filter cap. HP chose cleverly to connect the center tap directly to C32 a 3300 uf filter cap and ground each leg of the secondary through its own diode. The cleverness emerges when it becomes clear that these grounding diodes are already part of the full wave bridge! All of the necessary free-wheeling is already present to isolate the two full wave supplies and to prevent discharging any filter cap through a secondary winding.
--the on-board power supply has a charge pump to generate -9 vdc used by the encoders and RS232 circuitry.
To understand all of this more easily I would recommend printing out the schematics. They are complete but because of their size they are broken up into sections. To prevent serious migraines I would recommend trimming and taping together the sections so that the entire power supply circuit paths can be viewed at once. Note that there are two versions of the 7440a. Option 001 is RS232 and Option 002 is HPIB. The RS232 version's power supply simply adds one current limited
+9v supply for the serial interface. I sincerely hope you don't have the HPIB version unless your computer speaks this protocol!
The Bottom Line:
--find an original adapter. PRO: guaranteed compatibility CON: limited availability and unlimited price!
--find a suitable transformer with appropriate primary voltage and 20 vac center tapped with a 2A rating. PRO: certainly cheaper and will likely work especially when care is used to make proper connector pin hookups CON: not a common voltage/current rating especially center tapped
--find two identical transformers each with a single 10 vac winding at
2A and wire in series (wire the primaries in parallel of course and check the phase of the secondaries) PRO: more likely to find these transformers (you may even have them in your junk box or spares bin) CON: care must be taken to turn both transformers on and off simultaneously so that digital and motor drive circuits will do likewise, additionally there is the temptation to use 12.6 vac transformers which may produce excessive voltage from the full wave bridge especially since this voltage is continually monitored by U6. I would avoid this temptation and I decline to take responsibility for any information in this post -- use at own risk!
--find a non-center tapped 20 vac 2A secondary and use to power the full wave bridge while using an independent 10 vdc (must be DC!) at approx 0.5A source connected to the positive end of C32 the 3300 uf cap (with the negative end of the source connected to circuit ground of course) PRO: presents another availability and reasonable-cost option CON: the same caution about powering everyhing up and down at the same time.
The choice is yours. I have deliberately left out pin number references. Powering up this device in any do-it-yourself manner is not a cookbook proposition. Complete understanding of what you are doing and a healthy measure of experience are required. Good luck and proceed at your own risk!
PopMed wrote in news: snipped-for-privacy@k79g2000hse.googlegroups.com:
My hero! And I don't even beleive in them. Thankyou, that is very awesome, an amazing stash.
I agree, finding the original adapter seemed wise once I learned of the unusual arrangement of 4 terminals. Even with the centre tap the fourth terminal is not yet clear to me, but it will be with those schematics.
I got a supply, WITH a deskjet printer. :) Won it on eBay for the cost of postage, I added a couple of quid because no-one else bid and the seller was willing to change his postage conditions to send it to me.
If I do have to make a second supply, I'd probably use a 12V 2A toroidal and take out enough turns to drop the voltage. As they have two separate secondaries, they are ideal for this.
I got lucky btw, NEW (mothballed) ex-MoD (Navy) device with RS-232. It looks and works like it was built last week, not over 20 years ago. Got it for price of postage, again, only thing wrong was no power supply.
With 8 Staedtler Lumocolor refills and a few Lumocolur pens to raid various width tips from to refit plotter pens with, I'll be making boards soon.
There's a service tweak I discovered/invented for these plotters which you might possibly find useful.
The paper motion (in the "Y" direction) uses several cylindrical rubber wheels, which hold the paper against individual rollers on the other side the paper. On the used plotter I bought, the plotter had been stored with the paper drive mechanism in the "engaged" position, and the pressure from the rollers had flattened the rubber on the wheels enough to create a distinct "dimple". This caused paper motion to be uneven and unreliable - the roller/wheel interface would lose pressure when the roller hit the dimple in the rubber.
Trying to buy replacement wheels from HP seemed out of the question.
I found a solution at a local hobby store - a soft, flexible silicone- rubber tubing (translucent blue in color) which is used as a fuel line in radio-controlled airplanes. I was able to dismount the existing rubber-coated wheels and scrape off all of the old rubber (it's pressure-molded onto a ridged core/axle), cut off a short length of the silicone rubber tubing, and force the tubing over the core of the wheel.
When re-mounted on the plotter, the new silicone-rubber wheel surface proved to work very well.
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
snipped-for-privacy@radagast.org (Dave Platt) wrote in news: snipped-for-privacy@radagast.org:
Good cautionary point. I caught myself reading a manual the other day while leaving the paper engaged, and disengaged it thinking of exactly that problem. I'm slightly conditioned to thinking of this risk and preventing it, having a bandsaw, those too can go agly if you leave them under tension and static for a significant period. I also used to repair tape decks...
Nice idea. I think polyurethane might also be good, or that kryptonic stuff used for skateboard wheels, but not so easy to find in a tube, perhaps.
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