The Sinclair QL Forum

Hi,
My rekindled interest in my QL is turning into a bit of a trial. ( Could be said to be normal for me, by someone!!)

20 yrs ago I had a pretty good setup.
QL + the Medic i/face + built in to a box with 2x floppies + hard wired 'real' keyboard to modified membrane connectors+ battery backed clock. Failed m'drives removed.
Plus Qjump Eprom programmer.
I bought a backplane and after some trouble had the whole lot working together.
Many hours of fun burning eproms when playing with the OPD.
Looked a bit of a tangle but it did work.
After my hiccup pulling the ROM cartridge out I swapped the 8301 for another and found they both worked.
More fiddling got me past the memory check but to a white screen.
More fiddling and I had the QL up and running half the time with no clue as to why only half the time.
At this point it's a bare QL.
I think there is a problem with either the power in socket or the 78S05 socket/chip. Will replace.

MOVED to a backup QL which starts up every time.
Works with the backplane inserted.
Works with the Medic i/face inserted but NOT both.

The backplane is pretty messy but did work for years.
Went over it with a meter and 'ha!, found!' it a couple of times, but no luck.
Also, I don't remember why at all, but I've run a wire from one pin on the backplane to either ground or one of the other pins on the 7805.
I think it's the ASL line. The L means Low so I'm wondering if it needs to be on 0v?

Question.
Is there anything special about a backplane? Is it not just all the tracks diverted and duplicated to one or more extra connectors?
I would strip the backplane down but there are nearly 200 solder joints so I'm a touch reluctant.
The backplane works without a card in it so I don't think anything is 'shorting out' Might be wrong.

As usual any help much appreciated

Dave[img][/img]

Ha!
Further investigation shows that the track to ASL has definitely deliberately been cut. So there was some connection from the ASL to the 7805 in order to get the Medic card to work. No solder on the 7805 input so that leaves me with Ground or ( i guess ) 5v.
Dave

KINGCHEF wrote:Is there anything special about a backplane? Is it not just all the tracks diverted and duplicated to one or more extra connectors?

A back plane should pass all wires straight through effectively being inert to signal paths it is down to the attached boards to do the logic. I would make all wires go straight through to start with a good backplane then see what doesn't work when attached. The ASL is an address select output from the CPU isn't it? Connecting an output directly to a rail will blow it.

KINGCHEF wrote:Further investigation shows that the track to ASL has definitely deliberately been cut. So there was some connection from the ASL to the 7805 in order to get the Medic card to work. No solder on the 7805 input so that leaves me with Ground or ( i guess ) 5v.
Dave

I don't understand this statement. A 7805 is a voltage regulator or are you talking about something else?

Hi,

Short time after my post I gave it another try.

The track on the backplane connecting ASL on the expansion connector has been cut.
The, now isolated, pin in the socket for the peripheral board has been hard wired to the GND on the 78S05 voltage regulator.
The board works.
I do not remember doing this 20yrs ago, who told me to or why it is necessary.
The medic board works O.K. plugged directly into the expansion connector after removing the backplane.
! suppose that I could remake the track but as it is working I will not mess with it.
The only thing I can think of, and I don't necessarily know what I'm talking about, is that the backplane somehow weakens the ASL signal.
Does that sound at al likely?
Dave

KINGCHEF wrote:The track on the backplane connecting ASL on the expansion connector has been cut.
The, now isolated, pin in the socket for the peripheral board has been hard wired to the GND on the 78S05 voltage regulator.
The board works.

So the peripheral board doesn't use the ASL but if other boards do they won't work in the backplane is what you are saying. Since it works for what you want your are a winner. The chopping of tracks should really be done on the peripheral board to keep the backplane standard and other boards would work on it if they use the ASL.

Hi,
I've got a 512kb through expansion. I'll give that a try and report back

Dave

So......
This is starting to annoy.

Not getting anywhere really so I removed the home wired through connector from the backplane. Didn't help . Still checking track integrity with the meter and looks O.K.
Back to square 1 as they say.
I have 3 Ql's
1, Built into a box JS ( my daily use before )
2. Bare bones unmodified JM
3. Bare bones with Minerva.
I have 3 expansion cards
1. Qep3 eprom programmer
2. Medic 512 Disc i/face
3. Sandy thru-con RAM card 512k

MINERVA QL
All cards worked
JM QL
2 out of 3
disk i/face produced a green screen
JS QL
AS JM

Playing with the backplane on my BOXED QL shows there must be a fault in it so back to the soldering iron.
However, I wondered about the power to the expansion bus

The 9v pins all measure around 9.5v pins 32a+b, 31b
BUT the 12v and -12v are both reading minus 7.9v. pins 31a&30a
I thought the meter must be playing up but it measures dry cells O.K.
Is this normal?

Also,
My real desire is to get the system running again with the eprom programmer BUT the ROM images are on disc so that has to work as well.
Most are 256k but a few are 512k

How can I achieve this? Only with a backplane?
If so then how on earth were eproms programmed on a standard QL even with 512k memory?
A microdrive only holds around 100k .

I'd buy a new backplane but the one on offer won't let me run the disc i/face and programmer together because of size constraints.
Is there an alternative?

Thanks, thanks,

Dave

You said

KINGCHEF wrote:The board works.
The medic board works O.K. plugged directly into the expansion connector after removing the backplane.
! suppose that I could remake the track but as it is working I will not mess with it.

Now what are you saying, nothing works? If the back plane bells out and has no shorts then the peripheral boards have the faults and since it sounds like they are intermittent check the boards for bad or broken solder joints. As I said before keep the back plane as straight through wires and do mods for boards on the peripheral boards assuming they don't affect the bus. If the expansion ram works directly on the QL board it should work on the backplane and give you confidence it works then you have to find the board faults. Old electronics with an expected life of under 10 years is fun isn't it.

When checking the backplane, Are you you just checking the tracks, or are you checking from 'pin' to 'socket'.

I am wondering if you have a problem inside one of the connectors.

Another thing you might want to check out. Is the PSU OK. If the 9v has ripples on it, it might measure 9V on a meter, but cause the 5V regulator to drop out sometimes.

Especially with different expansion boards having different load on the supply rails.

Hi,
As the disc i/face is now not working with 2 of the QLs and only with Minerva I thought I would look at that first.

The board has multiple socketed chips and the memory is arranged in 2 distinct banks. The sockets for the memory chips are of two different patterns, one being of the turned pin type.
It may be that the board was sold with 256/512 options or that a previous owner had added memory later.
Anyway, as connections become tarnished and unreliable with age I lifted all the chips one by one and replaced them firmly.
Minerva is now throwing up multiple memory address errors so some of my problems must lie there. I'll do the lot again with proper contact cleaner.

On the subject of modifying the backplane or the expansion board there is a paradox. If the peripheral works with a standard QL , as it did when I set off on this adventure, then to modify it to make it work with my backplane might well prevent it working anywhere else without reversing the mod. This would make it difficult to test on second machine in the event of another fault that may or may not have anything to do with the backplane. My problems have increased the more I try to fix them. Once I get the i/face board stable again I can re-assess.

Checking the backplane connections were done from pin to socket using a dummy connector to get to the socket pins. I started furthest away from the QL and worked inwards. It was my idea that perhaps I was getting a voltage drop through the backplane. Connections all checked out multiple ways as the pins are exposed in 4 different locations and I checked them all.
I have seen pins in these connectors push out of their locations deeper into the socket and thus not making the connection but all checked out with the plugs and sockets in place.

It is possible that I have a problem with the 78s05 regulator and I'm awaiting delivery of a replacement. There may also be a problem with the QL to regulator socket/connection. I'll redo that when the regulator arrives.
I'm more interested in the +12v and -12v readings which are much lower than that. How/where is it regulated and what is it used to power? Does it actually power anything in the peripheral board?

I've been swapping between 2 different p/supplies but have a third so could double check. Also I haven't actually checked the p/supply on its own so I'll do that as well.

I expect the Medic disk i/face will be putting a fair load on the power, some kind of power drop might be my problem.

Thanks

Dave