Acquired my first Model B today

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stuslayer
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Acquired my first Model B today

Post by stuslayer » Fri Apr 17, 2020 3:29 pm

Hiya,

As noted in the 'Today I received...' thread, I received my first Model B machine today. It was in good cosmetic nick for what I paid for it, and I was hopeful of something that would require minimal work to get running.

As promised, here are pictures of the insides:
20200417_144657.jpg
20200417_144701.jpg
20200417_144721.jpg
20200417_144805.jpg
20200417_144812.jpg
20200417_144910.jpg
20200417_145538.jpg
20200417_145601.jpg

So it looks to me like a completely unexpanded Model B, no hidden goodies or gems to be found. However it is in tidy condition with no obvious issues on the motherboard. Can anyone see anything missing from it?

I decided to take the risk of switching on before doing the PSU recap (I've ordered a RetroClinic cap pack), and got the boobip and BBC Computer 32K, BASIC, Ready! Yay! I got as far as typing *HELP to confirm very basic KB operation and that it accepted commands. got the OS 1.2 reply, then the caps fizzed and let out the magic smoke. First time for that experience, so I consider that a baptism of sorts!! It really does stink.

So, while I'm waiting for the cap kit to come, what upgrades would you good people suggest? I will be getting a disk controller and DFS (probably a 1770 kit with a later DFS ROM, I think?), what other items would people here consider 'essential'?
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Re: Acquired my first Model B today

Post by Wheel_nut » Fri Apr 17, 2020 4:35 pm

I would recommend a TurboMMC Adapter from Steve Picton (IFEL) who also sells a 1770 DFS kit. If you contact Steve direcly, he will sell you what you want directly from his Company IFEL at preferential prices to the eBay prices.Steve will also supply you an MMFS EPROM instead of the SPI EPROM on request.

Unless you have a lot of legacy Floppy Discs, you don't really need a Floppy Drive as all of the Game Images you could want are supplied on the TurboMMC SD Card. You can also use the SD Card to store and retrieve your data.

Welcome to the wonderful world of the BBC Micro.

Robin
#1 BBC Model B Issue 7 + 1770 DFS + Dual TEAC Floppy
#2 BBC Model B Issue 7 + 8271 DFS + Dual Floppy + Speech
#3 BBC Model B Issue 7 + 8271 DFS + Cumana Single Floppy + PiTubeDirect on KenLowe's Tube Level Shifter

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Re: Acquired my first Model B today

Post by stuslayer » Fri Apr 17, 2020 4:40 pm

Thanks, that's definitely an option :D

A quick question, the power cables to the motherboard spade connectors seem really secure, is it safe to just tug on these cables to disconnect? I'm slightly worried about pulling the spade connectors off the board!

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Re: Acquired my first Model B today

Post by anightin » Fri Apr 17, 2020 4:52 pm

Congrats on the new Beeb :D

Once the caps are done I'd also consider replacing the 16Mhz X1 crystal involved with display timing viewtopic.php?f=3&t=17709&hilit=Crystal

I'd also avoid new old stock on these parts too from experience.


Enjoy! =D>
Last edited by anightin on Fri Apr 17, 2020 5:04 pm, edited 1 time in total.

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Re: Acquired my first Model B today

Post by anightin » Fri Apr 17, 2020 4:54 pm

stuslayer wrote:
Fri Apr 17, 2020 4:40 pm
Thanks, that's definitely an option :D

A quick question, the power cables to the motherboard spade connectors seem really secure, is it safe to just tug on these cables to disconnect? I'm slightly worried about pulling the spade connectors off the board!
I found a gentle wiggle as close as you can to the top of the spade as you are pulling up on the cable usually does the trick.

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Re: Acquired my first Model B today

Post by tricky » Fri Apr 17, 2020 5:09 pm

Welcome,
I have never lost a spade connector, but have seen a few threads on here where people have.
First add-on if you have a CRT is a RGB to SCART cable and then maybe wire the speaker out to a jack and add that into the SCART plug.
If you already have a disc interface on order, I would go for a GOTEK, even if you already have a floppy.
I like the boobip (on here somewhere cmorley) 64K EEPROM expansion (takes one ROM slot) and the 32K sideways RAM (also one slot).
It really depends what you are going to do with it as to how much use you will get out of these last two.
In my beebs, I do the speaker mod, add sideways RAM and a speech chip, but that is because I use them for shows where I encourage people to play my games including AstroBlaster (my others are available on bbcmicro.co.uk

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Re: Acquired my first Model B today

Post by stuslayer » Fri Apr 17, 2020 5:42 pm

Thanks for the info so far, some useful stuff here. During the brief period I had the machine on (I have a RGB to SCART lead I use with my Electrons), I noticed no screen artifacts so unless it appears after regular use, I'll leave it alone. Thanks for the heads up on this potential issue though!

I also have a Gotek I use with my Elk/Pegasus, I've bodged up an external power cable for it too, and I picked up some FD cables (straight, no twist) for pennies that are on the way. Once everything is up and running I may get another Gotek or look into the SD reader options for storage. I do have a 5.25" floppy drive I won on its way too (got it for £18 plus postage, BBC branded!), but no idea yet if it's in working condition.

I have no experience of using ROMs, so this is an area I'm interested in. I'd also like to start learning BASIC, so any recommendations in this area?

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Re: Acquired my first Model B today

Post by tricky » Fri Apr 17, 2020 7:13 pm

I use "mmc" (SD) readers on most of my beebs, but if you have a gotek, I wouldn't bother as although they are much faster, you will effectively have two copies of dfs and two sets of workspace eating your ram. The gotec will be more compatible and the beeb supports two double aided drives. You might like to try my gotek menu linked in another recent welcome thread.
I learnt all my basic from the user guide and there is a remastered version in a thread on here. I'm sure there are better books available now.
There are some ROMs that work with basic.
The beeb has sideways ROMs that bank switch in the third 16k with is support.
One is used by basic and the other three physical sockets could be used by DFSs and a basic editor.
The nice thing about the eeprom is it gives 4 16k slots and only takes on socket and you can swap them out using the beeb.

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Re: Acquired my first Model B today

Post by 1024MAK » Sat Apr 18, 2020 7:10 pm

stuslayer wrote:
Fri Apr 17, 2020 3:29 pm
So, while I'm waiting for the cap kit to come, what upgrades would you good people suggest?
Whoa! That's a deep sea you'll diving into :shock: :mrgreen: To give you an indication (hold that wallet tight mind) go here :wink:

So much information exists, it's hard to work out where to point you to. But for sideways ROM/RAM, start here if you want the technical details...

See also www.boobip.com

How much money have you got / want to spend, and do you have any particular interests in mind?

Mark

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 6:56 pm

1024MAK wrote:
Sat Apr 18, 2020 7:10 pm
stuslayer wrote:
Fri Apr 17, 2020 3:29 pm
So, while I'm waiting for the cap kit to come, what upgrades would you good people suggest?
Whoa! That's a deep sea you'll diving into :shock: :mrgreen: To give you an indication (hold that wallet tight mind) go here :wink:

So much information exists, it's hard to work out where to point you to. But for sideways ROM/RAM, start here if you want the technical details...

See also www.boobip.com

How much money have you got / want to spend, and do you have any particular interests in mind?

Mark
Hi Mark, sorry for the late reply! Yes, I'm spending freely while on lockdown, I got caught up in a bit of an eBay bidding frenzy, so I've ended up with the Beeb, an old BBC branded floppy drive (sadly the original 100K drive, but I got it for less than twenty quid, still need to find out if it works) an ANF03 tape recorder and cables...waiting for about 100 floppies I won on an eBay auction too. But I still might need another floppy drive, as the one I have is only SSSD.

I've just received today the PSU cap kit and a 1772 disc interface from IFEL.

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 7:03 pm

So, I have recapped my PSU successfully today. It's the first time I've attempted anything like it so I was flying by the seat of my pants! I watched a LOT of YouTube videos about it and I'm happy to say it was a relatively straightforward job in the end.

I have also received today IFEL's 1772 disc interface upgrade. I've fitted this, and all the supporting chips/wire links etc. I originally installed the Acorn DFS 2.26 ROM that comes with the kit, and this did not seem to work at all - no change to the startup banner etc. So after much pulling and reseating chips, taking out and adding back wire links, I decided to try putting in the Watford DDFS 1.54T chip. Turned on and hey presto! it appears on the startup banner.

As I've no experience using these devices, and have yet to test it out with my Gotek, can anyone tell me:

1. If the Watford DDFS shows up on the startup banner, does that mean that everything should work as intended, or is it simply that the Beeb sees the ROM so reports it as installed? Would it show up if the 1772 was removed?

2. Is it possible/likely that the Acorn 2.26 DFS ROM is faulty, therefore didn't show up?

I am going to be doing more testing this evening, but anyone got any pointers?

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Re: Acquired my first Model B today

Post by LordVaderUK » Thu Apr 23, 2020 7:05 pm

stuslayer wrote:
Thu Apr 23, 2020 7:03 pm
So, I have recapped my PSU successfully today. It's the first time I've attempted anything like it so I was flying by the seat of my pants! I watched a LOT of YouTube videos about it and I'm happy to say it was a relatively straightforward job in the end.

I have also received today IFEL's 1772 disc interface upgrade. I've fitted this, and all the supporting chips/wire links etc. I originally installed the Acorn DFS 2.26 ROM that comes with the kit, and this did not seem to work at all - no change to the startup banner etc. So after much pulling and reseating chips, taking out and adding back wire links, I decided to try putting in the Watford DDFS 1.54T chip. Turned on and hey presto! it appears on the startup banner.

As I've no experience using these devices, and have yet to test it out with my Gotek, can anyone tell me:

1. If the Watford DDFS shows up on the startup banner, does that mean that everything should work as intended, or is it simply that the Beeb sees the ROM so reports it as installed? Would it show up if the 1772 was removed?

2. Is it possible/likely that the Acorn 2.26 DFS ROM is faulty, therefore didn't show up?

I am going to be doing more testing this evening, but anyone got any pointers?
Stu - currently a number of Beeb experts (I don't include myself in this description!) are online in a virtual user group. If you're free, we could invite you?
Loving my BBC Master 128

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 7:18 pm

LordVaderUK wrote:
Thu Apr 23, 2020 7:05 pm

Stu - currently a number of Beeb experts (I don't include myself in this description!) are online in a virtual user group. If you're free, we could invite you?
Hiya, thanks for the invite - how long are you going to be on for? I have the kids to put to bed but may be available in around 30 minutes?

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Re: Acquired my first Model B today

Post by LordVaderUK » Thu Apr 23, 2020 7:19 pm

It's slated to run until 9pm.
Loving my BBC Master 128

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 7:21 pm

LordVaderUK wrote:
Thu Apr 23, 2020 7:19 pm
It's slated to run until 9pm.
In that case I'd love to. What channel are you guys on?

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Re: Acquired my first Model B today

Post by LordVaderUK » Thu Apr 23, 2020 7:23 pm

Stand by, I have asked the organiser to send you a PM with joining details.
Loving my BBC Master 128

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 7:26 pm

Brill, thanks :D

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 8:18 pm

Thanks for the invite, I joined for a bit but not really got into the swing of it.

Any easy tests I can run to make sure my hardware is working as it should be? Just generally, not necessarily for the disk interface.

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 9:56 pm

OK, something isn't working right. I have my Gotek hooked up. I have an .ssd file on, alongside the correctly configured FF.cfg file, running flashfloppy 2.13. When I type *CAT, the drive noise whirrs for a second, then stops. The screen is stuck at >. Nothing cures it except an Escape.

Also, CTRL Break or Shift-Break only seem to work intermittently. Any ideas? Otherwise all seems ok. Any BASIC diagnostics I can run?

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 10:14 pm

Ok, got a bit further. Hadn't cut S9. Did this, and more success. The disc now CATs. However, When I try to load a couple of SSD's on there, I get this:
20200423_221138.jpg
Any ideas?

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Re: Acquired my first Model B today

Post by stuslayer » Thu Apr 23, 2020 10:31 pm

...and it's dead. Now i just get the constant low beep, and nothing onscreen. Caps lock light is on, but that's it :(

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Re: Acquired my first Model B today

Post by jonnyboy » Thu Apr 23, 2020 11:18 pm

I had similar unpredictable things happening recently with an sd card reader (different port I know but the same principle). Have you cleaned the disk drive port pins with IPA? Try re-inserting the connector 5/6 times and try again. My port pins looked really clean before I did this but it worked for me! I'm merely passing on received wisdom! :)

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Re: Acquired my first Model B today

Post by tricky » Fri Apr 24, 2020 7:50 am

I haven't tried that ROM, but the ones I have tried always announce themselves on power on.

Sounds like you may have another problem with your beeb or may have caused a chip to loose contact with the board flexing associated with inserting chips.

I would try wiggling/reconnecting several times the keyboard cable or cleaning its pins as they are known to oxidise and cause a beeb not to boot.

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Re: Acquired my first Model B today

Post by stuslayer » Fri Apr 24, 2020 8:33 am

Thanks all. Definitely has other issues. I'm going to get it (somehow) to RetroClinic for a professional fettling.

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Re: Acquired my first Model B today

Post by Kazzie » Fri Apr 24, 2020 10:04 am

stuslayer wrote:
Thu Apr 23, 2020 7:03 pm
So, I have recapped my PSU successfully today. It's the first time I've attempted anything like it so I was flying by the seat of my pants! I watched a LOT of YouTube videos about it and I'm happy to say it was a relatively straightforward job in the end.
The existence of Youtube videos makes learning new skills such a different game these days: I managed to do a head gasket replacement on my car a few years back, having done nothing more mechanical that bicycle maintenance before then!
stuslayer wrote:
Thu Apr 23, 2020 7:03 pm
1. If the Watford DDFS shows up on the startup banner, does that mean that everything should work as intended, or is it simply that the Beeb sees the ROM so reports it as installed? Would it show up if the 1772 was removed?

2. Is it possible/likely that the Acorn 2.26 DFS ROM is faulty, therefore didn't show up?

I am going to be doing more testing this evening, but anyone got any pointers?
Acorn's DFS and NFS ROMs are written so that they check for the presence of their respective hardware when booted, and don't load themselves if they're absent. I wouldn't be surprised if the Watford DDFS behaves similarly.

The Sideways ROMs are read in a specific order when powering the machine on. Different Language ROMs (BASIC, LOGO, etc) can be in the machine at the same time, but the one in the highest priority socket will be active at boot. In the case of DFS, I suspect that your DFS and DDFS ROMs might behave similarly: if DDFS is loaded first, DFS may notice there's already a disk filing system installed, and disable itself. The easy way to check this is to take one of them out, and see if the other is recognised.
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
RiscPC 600 under repair
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Re: Acquired my first Model B today

Post by Kazzie » Fri Apr 24, 2020 10:21 am

Sorry I didn't notice you at yesterday's meetup: I was head-down with a soldering iron for a lot of it. :oops:

The screenshot you posted above has some tokens splurging across the screen (OSCLI, LINE, OR, LEN, MOD, etc). These kinds of symptoms have shown up on other machines with a loose contact on a pin in the OS ROM socket. There's one similar case here, and I'm sure there are others on the forum that I didn't spot at a very quick glance just now.

If you fancy having a closer look yourself, continuity testing between the pins of the OS ROM and the 6502 could be a good start. If you have a multimeter to hand, there are a few other simple checks that can be done on the clock circuitry and other areas. Let me know if you'd like a hand in doing this. :)
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
RiscPC 600 under repair
Acorn System 1 home-made replica

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Re: Acquired my first Model B today

Post by stuslayer » Fri Apr 24, 2020 10:40 am

Hi Kazzie,

Thanks for your replies. I could have another look - I was going to send it off because it's like being in a wood at night with no torch for me!!

With regards to the DFS ROMs, The Acorn DFS was in on it's own and did not come up, I swapped it out for the DDFS and this worked, so either there's something wrong with the DFS ROM itself or some other issue which I have no clue about.

If I do find a problem with the OS ROM connections, how would I go about fixing it? I have zero clue what I'm doing with this, so would need some extreme hand holding...

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Re: Acquired my first Model B today

Post by stuslayer » Fri Apr 24, 2020 11:55 am

Scratch the above, thanks for the offers of help. I want a working machine as soon as possible, and to be confident it's been done right, so it's off to RetroClinic.

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Re: Acquired my first Model B today

Post by Kazzie » Fri Apr 24, 2020 12:28 pm

We're more than happy to give a helping hand. :D

We'll put the DFS issues to one side for now, as it'll be tricky to diagnose without the rest of the machine up and running.

Firstly, just to check, when you power up the machine, you have a long beep, and do you see anything on your monitor? A black screen, a black screen and a flashing cursor, or no video signal at all?

In terms of working out what's where in the Beeb, and what it does, this page of the 8BS website is a really good resource: it has a picture of the mainboard that lets you click on a chip to see a description of what it does. A copy of the circuit diagram is useful when you're trying to work out what should be connected to what; there are a number of scans of original paper diagrams online, but I tend to work from this redrawn diagram. If you want to do some in-depth reading, the BBC Micro Service Manual has a lot of technical information on how the machine works, but don't worry if you leave that one on the shelf for now. ;)

I'm working on the assumption that you have a multimeter, and are confident in how to use it. If I'm going too fast, let me know. (And for that matter, shout out if you have any other testing equipment, such as a logic probe or oscilloscope.)

Here are a few tests that can help us work out what is or isn't working in your Beeb at the moment:

:arrow: As has been mentioned earlier, give each socketed chip a firm press, to make sure they're in securely and haven't loosened over time. Then turn on the machine and see if anything good shows onscreen.

:arrow: Take a DC voltage reading of pins 4, 5, 6, 7, and 8 of IC6 (the 5C094 Video ULA Chip) with the machine switched on. Pin 8 is the master 16MHz clock signal for the board, and it's divided into 8, 4, 2, and 1MHz clock signals for the rest of the board by IC6. If these are missing, the Beeb's chips won't know when they're meant to do anything.

Incidentally, IC pins are numbered counter-clockwise from the notch or dot at one end of the chip, e.g.:
Image

A DC voltage is effectively an averaged measurement, so the average of a good square wave clock signal that's oscillating between 0V-5V would be around 2.5V. (From memory, pin 8's voltage may be slightly different to the other four.) An oscilloscope or logic probe would give us extra information, but we can manage without for now.


:arrow: Measure the DC voltage on pin 40 of IC1 (the 6502 CPU) with the machine switched on. This is the Reset input to the CPU, which tells it to get its act together and start running. Note what happens to the voltage when you press and release the Break key on the keyboard. It should be 3-5V, going down to ~0V when you press Break.


:arrow: Locate jumper S25, in the North-East of the board near the RGB video output. This jumper configures how much RAM is available to the Beeb (think Model A vs Model B). It's normally in the North position for a Model B, to enable both of the 16K RAM banks. Switch the machine off, then move the jumper to the South position, and see if the machine will boot. Then try it again with S25 removed. This helps test whether there's a fault in one of the RAM chips, by disabling half of them at a time. (Put S25 back North again at the end if you don't see any change.)


:arrow: Check continuity between the OS ROM and the CPU. You'll want to switch your machine off for these tests. The OS (in IC51) has sixteen address lines and eight data lines that connect it to the CPU. These can be identified from the circuit diagram:
BBCB-IC1.png
BBCB-IC51.png
We see from these, for example that pin 25 of IC1 and pin 1 of IC51 both correspond to line A15 of the address bus. These should be connected together electrically, and the continuity function should give a loud beep if there is such a connection through the two probes and the circuit they're touching.

To test A15, place one probe on the shoulder of pin 25 of IC1, and the other probe on pin 1 of IC51. Putting the probes on the shoulders of the chip itself, rather than the socket, means we'll also be testing the connection between the chips and their sockets. :)

Repeat this process for all of the address and data pins, double-checking and noting any that don't pass the continuity test. If you have some failures, re-seating the two chips may help. Use a small flat-head screwdriver alternately under either end of the chip, and gently lever the chip up a few millimetres, before pressing it back down with your hand. Repeat the continuity test again, to see if the fault is gone.
Last edited by Kazzie on Fri Apr 24, 2020 5:08 pm, edited 1 time in total.
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
RiscPC 600 under repair
Acorn System 1 home-made replica

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Re: Acquired my first Model B today

Post by Kazzie » Fri Apr 24, 2020 12:30 pm

stuslayer wrote:
Fri Apr 24, 2020 11:55 am
Scratch the above, thanks for the offers of help. I want a working machine as soon as possible, and to be confident it's been done right, so it's off to RetroClinic.
That's no problem, if you're happier doing it that way. Whatever works best for you. 8)
BBC Model B 32K issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM, ZIDEFS with 512MB CF card
RiscPC 600 under repair
Acorn System 1 home-made replica

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