My rare old QL version AH

[badaman]

Today I opened one of my QLs that I had kept in a closet for a long time. At the time I changed the membrane, but I didn't notice any of the things. It is an Issue 5, with AH ROM.

It has, as you can see, a couple of cables that are disconnected. Possibly its previous owner used it for some type of expansion. or to power the ROM?

You can see something placed in the area that was going to be dedicated to the QL's watch battery. I don't recognize the piece.

It looks like a chip is missing from the socket above that clock area.

It also has an interesting label on the processor.

Can you help me identify these characteristics?

[Chr$]

What's the green serial number on the bottom?

The socket next to the ROM is present on early Iss 5 boards and can be used to house a 74LS00 and with the wire links configured differently the ROM sockets can be converted to use normal EPROMS instead of those mask ROMs.

I don't know what the number means on the sticker on the 8049.

[badaman]

What's the green serial number on the bottom?

Is D09-014922

[martyn_hill]

Hi badaman!

Your Issue-5 looks pretty standard to me, aside from:

A. That disconnected flying lead from (what appears to be) AS on the exp connector (B25) to the otherwise not-connected pin on the ROM Port. Perhaps the previous owner had a non standard device attached there. No value in reconnecting it otherwise.

B. The unusual label on the 8049 co-processor. No idea what that refers to.

All the usual factory mods appear in place, as far as can be seen in your photos.

Otherwise, all as expected for the later Issue-5's once the switch from EPROM to masked ROM was made (making IC217 redundant.)

Enjoy

[badaman]

Thanks to both. I'm left with the mystery of the 8049 label and what appears under the empty socket.

What is in the area that was going to be intended for a system clock battery what could it be?

[dilwyn]

I wonder if the labelling on the "8049" implies it could be one of the replacement 8049 chips, such as the Schön one? They were intended as anti- keybounce replacements for some keyboards. Had side effect of affecting serial comms in some ways.

[martyn_hill]

Hi again badaman

Thanks to both. I'm left with the mystery of the 8049 label and what appears under the empty socket.

When you say 'what appears under the empty socket.', what are you hoping to learn? There are some traces, but nothing that you need to worry about. The socket is there only as an artefact of the original Issue-5 build, to accommodate a different ROM configuration and is no longer wired in to anything active (the zero-ohm 'link' resistors just to the LHS of the socket route the ROMOEH signal directly to the two masked ROMs, circumventing the - now defunct/removed - logic IC.)

What is in the area that was going to be intended for a system clock battery what could it be?

Which area are you referring to?

Perhaps you could annotate the relevant photo and repost?

[badaman]

Perhaps you could annotate the relevant photo and repost?

I apologize for my bad English.

I refer to this in both comments.

[badaman]

I wonder if the labelling on the "8049" implies it could be one of the replacement 8049 chips, such as the Schön one? They were intended as anti- keybounce replacements for some keyboards. Had side effect of affecting serial comms in some ways.

Very interesting. Where could I get more information about this possible replacement?

[martyn_hill]

Hi badaman!

I refer to this in both comments.

Aha - ok, so that is just a tunable capacitor that was used on the Iss5 boards to tweak the 32kHz clock that drives the RTC timing on the ZX8302.

By the time the Iss6 boards came out, they just did away with that and used fixed timing for the RTC.