HP85B awakens

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HP85B awakens

Postby kaimaiguy on Sat Jul 16, 2011 3:25 am

Dear fellow forum members

I have a few pics I am trying to attach of an HP85B I have just begun to retore. Might I ask how does one attach pics to a post? Many thanks

Cheers

Rick
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Re: HP85B awakens

Postby tezza on Sat Jul 16, 2011 7:07 am

Hi Rick,

The forum itself is not set up to host pictures. I suggest using any free photo hosting service such as flickr (http://www.flickr.com/) or something similar and post a link here. If you are able to use a direct link from a photo hosted on the web elsewhere, you can use the Img tag here.

It would be great to see pics of the HP85B.
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Re: HP85B awakens

Postby lizardb0y on Sat Jul 16, 2011 7:57 am

Hi Rick,

It's great to read that you're having a go getting it running. :)

I have an HP85B myself, though I haven't powered it up for quite a long time. If there's anything I can help with just let me know.
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Re: HP85B awakens

Postby kaimaiguy on Tue Jul 19, 2011 1:50 am

Good MOANing all!

Well many thanks for the flicker lead I have managed to upload a few pics of the machine but still trying to figure out how to make them accessable from here.

I have managed to get a display so fears of a totally dead CRT have abated however tis little more than so much goobly gooch with a steady stream of Ps and # . Probably a problem with the logic board or DIPs themselves I would imagine. There is no actual boot up the LEDS on the printer light up and the occasional display. there is also a DIP missing in what I believe may be the memory bank on the logic board but not quite sure as I still have no board layout info and no schematic.

I suppose also I expected to hear a fan upon power up but doesn't seem to exist here. prolly becuase the older CPUs may not have been as hot so didnt require them again not sure.I actually recall seeing similar DIPS hanging on the component racks of Radio shack back in the states years ago. Would love to attempt a replacment but now that they are most likely considered museum display subjects themselves would most likely be hard to locate and a tad pricey at any rate.

Be well Gentlemen and have the finest of days

Cheers!

Rick
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Re: HP85B awakens

Postby tezza on Tue Jul 19, 2011 12:54 pm

Hi Rick,

Glad to see you got the video going. How did you do that? Was it just a case of de-oxidising some connectors or a larger job?

The missing DIP may or may not be significant. Sometimes sockets are included on machines for extra ROMs and the like. However, if you know it’s a socket for a memory chip and it’s the only one missing in a bank of them then that is suspicious. RAM was often organized in banks corresponding to rows on the circuit board. Unexpanded vintage machines might have a bank empty but seldom just one socket.

Apart from swapping chips and checking for broken connectors it’s quite hard to progress without a circuit diagram or a manual showing the mode of operation. Did you try to hook up with some of those other HP85 users in some of the Internet groups? I’m sure one of them will have some schematics scanned.

One fairly generic thing you can do is to check the CPU with a multimeter to see if it’s working. (Power, clock, RESET line etc.). However the machine does have a proprietary CPU so finding just what pin does what might be a problem. If it was a Z80 or 6502 it would be a lot easier.

To my knowledge the HP85 units never had a fan. The processor is actually quite slow and it probably doesn’t get hot enough to warrant one.
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Re: HP85B awakens

Postby lizardb0y on Tue Jul 19, 2011 1:02 pm

Hi Rick, I don't have a schematic but I can take a high resolution photo of my HP85 board this weekend if that well help. It should let you identify what chips go where at least :)
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Re: HP85B awakens

Postby tezza on Tue Jul 19, 2011 1:20 pm

Rick,

In looking around the web I found a repair manual here:
http://www.series80.org/PDFs/HP85-RepairCourse.pdf

It's actually a detailed "training guide" for technicians, and it has the theory of operation and circuit diagrams etc. Should be useful!

The site has quite a few user manuals too. Have a look.
http://www.series80.org/Manuals/index.html

Good luck!
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Re: HP85B awakens

Postby kaimaiguy on Tue Jul 19, 2011 1:59 pm

Dear Sirs

N ladies n Germs

I am so grateful for your kind input and for all the time you have taken to respond to my posts. As I said before I lack the lot tools, resources and know how. So when you suggest that I use a multimetter to check the whatsis on the CPU it's very vague to me.
So far what I detect is a ticking sound which seems to be originating down in the right center of the power supply. This is s steady beat tick tick tick then sometimes it's not there at all. The diplsay is not steady either and only appears on occasional basis.

The interior is very clean and I see little in the way of corrosion but probably doesn't rule out a good clean. Just hoping to be able to get downtown sometime to get some alcohol hopefully.

Also unfortunately my own internet machine is riddled with problems I have a very slow rural dial up connection with Kiwionline which makes surfing truly a miserable experience can't use Utube etc just too slow. Can't find this page can;t find explorer and can't even access my email half the time. MY ISP knows nothing.

Aside from the one chip missing all else seems to be there on the logic board and so far there are no apparent visable signs of any problem areas. This is why my thoughts remain with probable bad Logic etc.

Thank you for the URL to the tech manual I already downloaded it and many others that is why I felt ok about starting out on the project clear concise and proper disassembly instructions. Ian emailed me and suggested that the machine may still be trying to access the other box it was connected to while in it's former use and that I might try to connect the interface that came along with it. So I guess nothing tried nothing gained. If this starts getting into a money thing I will simply have to ditch the project. I just don't like seeing a thing of beauty sleeping like this when it can be wide awake and enjoying it's continuing cyber life.

Again I thank you all for everything

Have the finest of days.

CHEERS!

Rick
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Re: HP85B awakens

Postby tezza on Tue Jul 19, 2011 2:08 pm

kaimaiguy wrote:The interior is very clean and I see little in the way of corrosion but probably doesn't rule out a good clean. Just hoping to be able to get downtown sometime to get some alcohol hopefully.


Is this to clean the corrosion or for medicinal purposes when you come to a blind alley in the diagnosis? :)

I'm glad you have that manual. A ticking sound in the PSU is not a good sign. In fact I would start there. Make sure the right voltage is coming off the PSU (be careful where you probe). It's best tested with the motherboard plugged in so it has some load. If the voltages being supplied to the board and VDU aren't correct and steady then this will cause a whole host of problems including all of the ones you describe.

P.S. Be VERY careful measuring around the VDU. There is high voltage around those things. Hopefully that manual will suggest where to measure to check that you're getting correct power levels.
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Re: HP85B awakens

Postby kaimaiguy on Tue Jul 19, 2011 3:06 pm

Hi

Thank you very much for your Post

As I said before I have no clue as to how to do many of these operations. Not sure where to put the probes etc and exactly what I am looking for. What do you mean by " the right voltage" what is the right voltage are we talking mains voltage , board voltage etc etc?

Also you say that the ticking is not a good sign what could some of the causes be?

The alcohol was suggested by another older member here to clean up the boards, circuits etc.
again however there is really no signs of visable corrosion.

Thanks for all

Rick
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Re: HP85B awakens

Postby ZL2AOX on Tue Jul 19, 2011 3:53 pm

The ticking sounds like high-voltage arcing due to insulation breakdown. If a damaged or discoloured component isn't apparent, it might be easier to spot in darkness.

However, I'd strongly reiterate Tezza's cautions - be very careful what you touch!
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Re: HP85B awakens

Postby tezza on Tue Jul 19, 2011 8:08 pm

kaimaiguy wrote:As I said before I have no clue as to how to do many of these operations. Not sure where to put the probes etc and exactly what I am looking for. What do you mean by " the right voltage" what is the right voltage are we talking mains voltage , board voltage etc etc?


Your manual should help with this. Normally 240V goes into the PSU and DC voltage goes out to the mainboard. Just what this is and just how many DC lines there are depends on the computer. There is amost always a 5V one and often there is a 12V one and a -5V one also (on a computer as old as yours). However, it's possible some of those voltages could be generated on the board itself. Anyway these DC voltages should be at the levels stated in the manual and stready. Check the manual and see where these lines connect to the mainboard. Measure them where the connect or close to where they connect, but before they go through any components. There are lots of other places you could also measure the voltages but you'd have to use the schematic to find them. I'm assuming you know how to use a multimeter?

I agree with ZL2AOX that it sounds like your PSU is shorting. It certainly shouldn't be ticking. It's possible that a capacitor has shorted perhaps or (more seriously) the insulation. If the voltages are out of wack on the board, that would confirm it.

Your PSU would also have a (high voltage) lead to the screen. Unless you really know what you are doing it would be prudent to stay way from this. There are high (lethal) voltages in that area, and the power doesn't even need to be on. I would advise strongly not to go near it with a probe (or anything) until you are a lot more skilled. In fact, a PSU (especially a shorting one) can also be dangerous to novices so I would advise not poking around the PSU as well.

Given the risk factor here, consider that this might be just a bridge too far. I was at about your level when I started tinkering around with these machines but I started on a really well known and well documented machine (Apple II+), had duplicate machines, and the issues were neither PSU or screen. I also had an electronics mate (Philip Avery) to explain and assist from time to time. It took me a while to build up expertise before I would go near a screen or PSU. Even now they still make me nervous.
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Re: HP85B awakens

Postby kaimaiguy on Wed Jul 20, 2011 10:00 pm

Good evening mates

Well I believe I have found at least one of the major ailments located on the logic

There is a battery of of 3 silver cylinder caps which are C1 C2 and C3. Two of these caps are blown out on one end the positve end of C1 and the negative end of ajoining C2. The leads appear to have been fried being a dark brown colour. These caps I believe supply/regulate the voltage to the CRT ribbon cables which connect the Logic PCA to the large CRT PCA. This is also the exact area where I believe I heard the ticking sound.

Still looking for further dead soldiers which I expect to find but very hopefully do not. The very next hopeful thing is to be able to find replacements or suitable subs. I also believe that U21 PM021 (the missing DIP) may have been essential ROM to the machine thus another finger missing from the hand. This I am however unsure of as to whether or not this chip is essential to drive the neccessary logic to make the machine operational.

WIll keep all posted on progress

I thank you all again for your help and kind support during this first of my sojurns into bringing another ole timer back to the world of the living.

Cheers!

Rick
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Re: HP85B awakens

Postby tezza on Wed Jul 20, 2011 10:08 pm

Sounds like good progress. Be very careful around that PSU and Screen. Caps can blow out because they are old, but they can also blow out if there is a sort circuit somewhere else.
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Re: HP85B awakens

Postby kaimaiguy on Wed Jul 20, 2011 10:19 pm

Thanks Heaps Tezza

The mentioned caps are monuted on the logic board itself which has been removed from the system so at least for now don't have to worry too much about the PSU/CRT peril Going to call Jaycar Electronics about the replacements, We have a store here in Tauranga.

Always appreciate your help Tezza

All the best sir have a relaxing and enjoyable night.

Rick
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