Who else is building a Beeb from scratch?

[thedark]

Its almost not posible to do. You need a donor to do so. I cant help you on this one.
And it wil cost al lot of time an it is not cheap in the first place.

[BeebMaster]

2. Then I removed all econet ICs.

I've never heard of this before.

I can't imagine any Beeb works without Econet.

[!FOZ!]

Update: Raised new thread for my mode 7 issue viewtopic.php?p=401240#p401240

Success… well partial…

It is not easy to see with a still photo - but i am getting a rolling vertical screen in Mode 7 (not tried others yet).

(the picture makes it look like the text is duplicated - i don’t believe so - its just an aspect of my iPad photo taking i believe)

Output is via RGB via Scart and I have checked the lead and LCD TV is fine on my other Beeb.

I am running minimal configure hence no keyboard, IC3, IC69, IC4, IC7 and IC74 are not fitted.

Does anyone have any pointers on what to check here for a rolling vertical picture issue?

I did check the frequencies coming from IC6 per an earlier post and and did a few searches for rolling screens here and nothing sprang up.

Finally, wanted to note, that I have not at all adjusted VC1 since i fitted it - which has been a question I have been meaning to ask as well.

Update: Shared a video in the next post.

Update: I actually did find a useful post on RGB output here viewtopic.php?t=23440 - will probe some of IC48 pins tomorrow.

[!FOZ!]

Update: Raised new thread for my mode 7 issue viewtopic.php?p=401240#p401240

I also shared a video of my screen rolling issue

https://drive.google.com/file/d/1n38Fo6 ... p=drivesdk

p.s. from what I understand the continuous tone from the speaker is due to minimal setup - so I am ignoring that.

[!FOZ!]

Update: Raised new thread for my mode 7 issue viewtopic.php?p=401240#p401240

Installed additional chips and hooked up my keyboard, and apart from a rolling Mode7 display all other modes appear to work fine!

I am so happy right now - thanks to all the support thus far on this fine forum!

I have some mods to apply, and of course figure out a case strategy - but this is a big milestone.

P.S I will continue to research the mode 7 issue elsewhere on the forum - and raise a new thread on that issue if needed,

[KenLowe]

Well done. Looking very tidy .

[!FOZ!]

Well done. Looking very tidy .

Thanks Ken its a great feeling!

Now if I can only sort out this pesky mode 7 issue viewtopic.php?p=401240#p401240

[!FOZ!]

Very happy to report the Mode 7 issue has been resolve (need the Hitachi CRT), see viewtopic.php?t=27498

Started this process back in March, collecting parts and construction early July - its been a long road.

Clearly more sockets and connectors to fit and I have a host of upgrades to apply - and of course a custom case.

For now I will enjoy!

Good luck to those still building and hopefully the discussion here is helping folks present and future.

[!FOZ!]

Just had to share this as well. I have had a RBG2HMDI adapter for a while and with my older Beebs and VideoNula had so so results. But wow on this new build, just goes to show what new components can do! Click on the image and zoom.

[!FOZ!]

Finally got more sockets and connectors on (see attached pics) - all that remains is an analogue socket (i ordered a male one doh) and RF module (for completeness more than anything). I will likely pause a bit for now to enjoy, explore a few more upgrades and figure out my case plan…

Meanwhile here are some notes and recommendations thus far…

The replica PCB board itself
The heart of this is of course the board itself and it did not disappoint.

• The board (https://www.tindie.com/products/bobsbit ... b-replica/) I found to be very high quality, sturdy and easy to work with. Soldering components was a breeze and in cases where I needed to desolder also the same. In the later case, being a modern board its quite robust to some desoldering (especially if you are still growing skills here), but care should still be taken.

• It was very good to receive all the resistors with the board (paid extra), and saved on my Mouser order, including time. I did test all my resistors and none had any major faults, any tolerance variation was well within the Beebs own tolerances (see my earlier posts here). My board came with a small addendum for an error in the board, if yours does, photograph the instructions immediately. I also appreciated some of the enhancements made to the board to accept more modern components.

• Only minor thing was some of the link settings had already been shorted, which confused me, that said this is a “replica” so super super minor thing - only possible downside is fitting pin headers needlessly (see my comments below).

• This is an amazing PCB and offers an amazing and rewarding experience! Nice work Bob!

Create a build and test plan that allows you build, test, build, test etc

• This will help narrow down fault finding along the way, as you known whats change between build phases and can focus on that - in other words resist temptation to build it all at once! Note that in my case I even avoided risk of shorts on my connectors by putting them on last and only after I confirmed all other tests.

Component Sourcing

• A large part of the BOM lists Mouser parts and so far other than adjust one of the DIN sockets a bit, using only those parts and of course sourcing the rare ones elsewhere - I have a working build. I am using UMA 6502 and 6522 ICs and these are so far working very well. For those not listed in the BOM, study these forums for variations on manufactures and try to get exact matches on the ICs, such as the CRT IC (see my posts above).

• Oh I learnt, not all sockets are manufactured the same, I purchased most of mine from Mouser, and only some (i forgot in my original order) from another larger general purpose internet shopping site. The later felt cheaper, plastics wise and pins wise and indeed in one case, a pin dropped out during soldering!

Prep and BOM following

• I also followed the BOM line by line and resisted jumping around - keeping only the components I needed for the current step out on my workbench out. Testing and reviewing and labeling my components (especially ICs to which slot) also really helped. In other words, prep and testing time was also a key thing for me vs construction. In the end I am learning to diagnose issues, but anything I could do to avoid them is a major mitigation to my hitting walls later in the build given my skills at present.

Comfort and PCB standoffs…

• As you can see from my pictures I used some regular PCB standoffs to give the PCB height during the build and allow me to flip it over without impacting either side. It worked very well and a tip I owe to one of the many YouTube videos I watch these days. At the end of the day make your process comfortable - you will be doing this for many many hours - and comfort and ease = less mistakes - so optimize your experience.

Jumping settings

• You can just copy these from another Beeb if you have one, but I did find taking time to read through them all really helped me understand the machine even more. Also note that on the PCB some are already shorted on the PCB so you do not need to install pin headers and a jumper. Do check and double check them, some can have quite an impact on your machine working or not it seems. This was useful http://bbc.nvg.org/doc/A%20Hardware%20G ... _hw_04.htm

Add upgrades after you have a base machine working

• I am presently having some problems with SRAM upgrades in the ROM sockets (see elsewhere on the forum), but otherwise without them it functions flawlessly - with a DFS 1770 fitted and the rest basic standard spec.

Alternative keyboard via USB4C

• I will note that the firmware in the USB4VC module is at proof of concept status (per its author) so needs some fixes and updates it seems (it sends excessive interrupts for SHIFT and CTRL that halt the machine if the keys are kept down), but otherwise the all that works pretty well - and the feel of a modern mechanical keyboard is amazing. Note earlier in this thread some great shares on replica Beeb keyboards!

Where to ask questions?

• Try to use this thread to post about the actual build, share your progress, components questions (the schematic has bugs in it, see that post), testing approaches, questions about the replica PCB (mind needed a bodge wire) - rather than specific issues you are having, especially during later testing once its getting more to the state of a regular Beeb. These later questions (and answers already potentially) are what the rest of the hardware section on the forum is about. That said, do reference in making a new hardware thread post that it is a new build and the status you are at - x-ref to your latest posts here perhaps.

Other tips and tricks

• This thread already has great feedback and suggestions from the forum and those building and I hope it will continue to gather even more.

[!FOZ!]

Update:
It appears to the BOM is missing C25, per this thread viewtopic.php?p=402969#p402969 It does cause problems with the Analogue socket and use of joysticks. See advice in the thread on the component to order. I have also contacted Bob to let him know to add it to the BOM for future builders.

Update 2:
This missing C25 can also cause the machine to slow down it seems when ROM/RAM upgrades are fitted. So even if you are not using the Analogue port please still fit it. See here for more viewtopic.php?p=405594#p405594

[1024MAK]

VC1 only affects the colour encoding frequency for the TV/UHF and (if the link is fitted) composite video outputs. The RGB output does not use this circuitry.

If you have a couple of different TVs to test with and either the TV/UHF and (if the link is fitted) composite video outputs work okay in colour, don’t worry about it.

Mark

[!FOZ!]

VC1 only affects the colour encoding frequency for the TV/UHF and (if the link is fitted) composite video outputs. The RGB output does not use this circuitry.

If you have a couple of different TVs to test with and either the TV/UHF and (if the link is fitted) composite video outputs work okay in colour, don’t worry about it.

Mark

Thank you sir - for completeness I do plan on testing composite, and fitting a UHF box - so now I know what to fiddle with.

[!FOZ!]

Ok, fitted a new UHF modulator, and after a few hours fiddling with VC1 no dice with the color (on screens should be red and yellow), same for composite. Though without S39 fitted for composite, its black and white picture is pretty good - so that’s good.

Regarding, VC1, having initially rotated it and then reading (https://www.vishay.com/docs/28527/bfc2808-75mm.pdf) it has a max of 10 rotations i suspect its now busted. It is of course not a huge problem as I am using RGB, which is super sharp. Just a bit of a shame I will know its not working…

I could fit a new trimmer of course and try again, but given the risk of damage to the board in doing so its not worth it given I will likely never use it. I have not btw adjusted the control on the top of the UHF modulator (assume that’s purely the channel output). My BITD Beeb on the same TV does show the correct colors, but its actually not that brilliant a picture either tbh.

This was the last component to fit to the board!

[1024MAK]

I have not btw adjusted the control on the top of the UHF modulator (assume that’s purely the channel output).

Yes, it’s best not to try to adjust this, it’s made of a brittle material. It adjusts the oscillator frequency and hence the channel frequency. Even when new, forty years ago, the frequency output was never spot on. These days, the frequency may have drifted far more. But analogue TVs did not care. A good modern TV should be able to cope. Although not all can.

I wouldn’t say VC1 is busted. More that you are now outside the manufacturer’s guaranteed specifications.

To be honest, it’s better to adjust it if you have a frequency counter or a ‘scope that displays the waveform frequency. And it’s best to view the output on the composite output with link S39 fitted.

But if you are not using the UHF TV output or composite video (with colour), I would not worry about it too much.

Mark

[!FOZ!]

I seem to get some color (wrong ones), then the TV reverts after a few seconds to black and white. I have done a full rotation, very slowly. First pic shown for reference is RGB.

[1024MAK]

Please note, I’ve edited my post above…

[1024MAK]

Is the TV in ‘PAL I’ (that’s I for India) mode?
I found that some get confused. If (and not all do) possible, can you manually select PAL?

Mark

[!FOZ!]

Please note, I’ve edited my post above…

Thank you - I have another TV attached and attached composite with S39 fitted. VC1 seems to have no impact on the picture here. And picture quality in general is worse. VC1 does not seem to have a stop and a start, inspect the device it does seem like it just rotates. I guess its possible there is another fault somewhere in the circuit driving UHF/Composite….

[!FOZ!]

Is the TV in ‘PAL I’ (that’s I for India) mode?
I found that some get confused. If (and not all do) possible, can you manually select PAL?

Mark

Yeah, the other TV (Samsung) has a few more settings -and does confirm PAL.

[1024MAK]

Alas, your thinking what I’m thinking…

Do you have a copy of the service manual?
Do you have, or have access to a ‘scope?

Mark

[!FOZ!]

Alas, your thinking what I’m thinking…

Do you have a copy of the service manual?
Do you have, or have access to a ‘scope?

Mark

BBC service manual, yes I have that downloaded and yeah I have a scope.

[thedark]

A litlebit silence here. Anybody still working on one?

[dominicbeesley]

I've still not started yet if that counts. Got some of the bits but by no means all

[eelco108]

Yes, still building ... very slowly. So many parts ...

But I am doing two at the same time

[Zeb]

Wow. Where do I get a replica board from please? Bearing in mind I'm in the UK. Saw a link in an earlier reply that was in dollars - would prefer to avoid having to have one imported if possible.

I've always wanted to build a new computer. Was looking at an Amiga 1200 but this seems a much better route to go down.

[!FOZ!]

Wow. Where do I get a replica board from please? Bearing in mind I'm in the UK. Saw a link in an earlier reply that was in dollars - would prefer to avoid having to have one imported if possible.

I've always wanted to build a new computer. Was looking at an Amiga 1200 but this seems a much better route to go down.

https://www.tindie.com/products/bobsbit ... b-replica/

[thedark]

Kost bij deze site 42 pond ex postage
The parts you have get a donor and New parts.

[BeebMaster]

Bit disappointing that the boards are in UK, the seller is in UK, but the website listing them uses a foreign currency.

Clearly the days when "the British Pound is the admiration of the world!", as George Banks once said to Admiral Boom, are long gone.

[!FOZ!]

Some updates…

Being careful does not just stop at construction…

• Pay attention Bond!
  I have had a small set back, a stupid one! I was happily installing expansions into it and got the polarity wrong wiring up the 1Mhz shifter to be powered from the CoPro shifter and was met with a small but alarming firework show! Thankfully (ish) it was on the expansion card itself not the Beeb itself! After collecting myself, the damage is thankfully minimal - my PSU (the ATX2VC modern alternative), expansion itself and my SCART splitter is all - the core of the build is fine.

Upgrades

• SRAM/Flash
  Since the above, I have been applying other upgrades! I have the amazing BooBip modules installed, for 64k SRAM and 64k Flash. I have these in my BITD Beeb and they are amazing. I am going to run the fly leads under the PCB and solder directly onto the pins via some DuPont connectors. See latest pictures. Also related was a missing capacitor (see in update above viewtopic.php?p=403172#p403172), and this thread causing slow down (in theory) without fitted viewtopic.php?t=27522

• BeebOPL and BeebSID
  I am also attempting to get a new build BeebOPL build running on it, which works fine on my BITD Beeb but not this new build. After originally thinking my 1MHZ bus was faulty and then finding no faults (I have done extensive diagnostics on that port before) - I tried my BeebSID which works fine. I then tried the BeebOPL on my BBC Master, and it also fails (differently though) - so this might be something to come back to I dunno.

• Speech
  I had the opportunity to find the original chips on eBay and have fitted them, working perfectly so far, very pleased.

• 1770 DFS
  No surprises here, works as expected, and looks way nicer than the original tbh.

• Black Cables
  Purely because I like to keep the number of colors minimal on things and well why not! Oddly quite hard to find, but I managed to get some old floppy drive cables and refitted the connectors without the pin adjustments.

Connector testing

• Working
  The following work and have been tested, RGB, Analog, Userport, Disc, 1Mhz and CoPro have all been tested and checkout. I updated my summary post above with a missing capacitor from the BOM that effects the Analog port and it seems the performance of the machine, in my case with the modules above fitted. I tested the userport with my own BeebLED board (viewtopic.php?t=26047 ) and an AMX mouse, all good! If you do not have a 1Mhz bus device, you can use the testing approach in this thread, viewtopic.php?f=3&t=10931, you will need a scope though.

• Not Working
  As yet the UHF and Composite are partially working, in respect to quality and/or color of the picture. I posted on this thread some of my issues with these and mostly decided the value vs risk to the board was not enough. However I have been very interested in this latest post (viewtopic.php?t=27403) and the following comment… so may go do that test just to see, as I have fitted per the BOM an 820ohm resistor in R109.
  

  It appears the duration of the colour-burst is controlled by D19, C45, and R109. R109 has no fixed value on the schematic.
  According to other posts on here, its value varied according to which batch IC41, 74LS02 came from.
  I replaced D19 (1N4148) and C45 (10nf). No change. Leaving only R109, which on my board was 1.8k.
  I replaced it with a 5k multiturn trim pot. There's just enough space to squeeze it in.
  
  Hey Presto !!!!!
  
  Upshot:
  If the colour is non existent or vanishes, suspect this resistor, especially if you have replaced IC41.
  If you have a scope, check the duration of the colour-burst on IC41, pin 4.

• Not Tested
  I may try to dig out my old cassette player to test the cassette port. Econet tbh is likely not going to be tested as I really do not want to go down that rabbit hole (famous last words).

Case Thoughts
I have yet to put much effort into thinking about what I want from a case. I do know that I want it to sit in our living room along with my other consoles. As such it needs to be easy to switch on and use with wireless devices. This is mainly why I am going down the experimental path with the BBC adapter for the amazing USB4VC project. That still has some kinks to workout, but its generally doing what I need. I think in the end I will likely find just a simple box type case made in clear perspex that can be mounted on the wall with just a power input and HDMI output (i will blend the audio in). For now though I just want to focus on the main build and keep what I have made safe and secure when not working on it.

Thats all for now -for those of you still building - keep at it - the reward is worth it - its the best thing I have ever built!