ADFS Upgrade board repair

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DaveLecky
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ADFS Upgrade board repair

Post by DaveLecky »

I took this upgrade out of my bbc b whilst cleaning and broke off 4 pins.

What is the best way to repair these pins or is it a bin job ?

Also the DFS chip above the board, is this correct for a bbc b or is it for a bbc b+ .

Can any one identify the exact type of upgrade and manufacturer...I’ve just bought this beeb.

A7859F98-30C9-49D7-A9E8-C9E5145A40CF.jpeg

Thanks

Dave
Last edited by DaveLecky on Thu Aug 15, 2019 4:12 pm, edited 1 time in total.
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cmorley
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Re: ADFS Upgrade board repair

Post by cmorley »

The neatest way would be to replace the header completely. These tall headers can still be bought from Mouser & Digikey etc but they are not cheap.

The cheap hack is to get a turned pin socket (pennies on eBay). Plug this into the socket and solder the broken pin stubs to the socket.

Either way repairable.
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Re: ADFS Upgrade board repair

Post by Coeus »

DaveLecky wrote:
Thu Aug 15, 2019 3:57 pm
Also the DFS chip above the board, is this correct for a bbc b or is it for a bbc b+ .
Originally a BBC model B would have had an i8271 and associated DFS. This was an old chip even when the upgrade was first released, dating from the 8" era, and soon became expensive. Various independent disc upgrade manufacturers made these daughter boards using the WD1770 chip and released an accompanying DFS ROM. Even with the expense of the daughter board these were cheaper. As far as the DFS itself working it is more a case of the DFS matching the daughter board concerned because not every board had the various registers at the same address.[1]

Acorn eventually joined the party and used a WD1770 in the B+ and also released their own daughter board with WD1770 for the BBC B, though I am not sure in exactly what order these were released. Acorn included their own 1770 DFS and some other daughter board manufacturers then came into line and used the Acorn addressing scheme for the registers in an updated version of their board so some of these later ones will work with the Acorn 1770 DFS.

As far as I know the only case where it matters if the machine is a B+ is where the B+ is a 128K machine, i.e. with sideways RAM. The 1770 DFS can have some sideways RAM utils tacked on the end. You can see that here in the HELP message from an emulated B+:
sram.png
see "SRAM 1.05". It looks like a separate entry but shares the ROM with the 1770 DFS. These sideways RAM utils will expect the B+ sideways RAM addressing scheme rather than something DIY.

[1] In a little more detail the WD1770 integrates a slighly different set of functions than the i8271. The i8271 has drive selection logic built in but the data seperator was external. The WD1770 has the data separator built in but drive selection is external. That means on the daughter board there has to be an extra latch to do the drive selection and in most cases also to control the density select pin on the WD1770. Some boards had the WD1770 at the lower addresses and the latch at the higher addresses and some had them the other way round. Then the assignment of the bits in the latch also vary. This is also discussed in much more detail in the thread about emulating various DFSes in the emulators forum. B-Em emulates Acorn, Watford, Opus and Solidisk but these are others too.
Last edited by Coeus on Thu Aug 15, 2019 5:04 pm, edited 2 times in total.
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Re: ADFS Upgrade board repair

Post by Boydie »

The Watford rom boards used a similar header, which was also just as vulnerable to trauma.
The cheapest solution I found was to remove the header, solder in a turned-pin dil socket, insert a couple of strips of male-male turned pins (from CPC, will try to dig out part number), then top it off with another turned-pin dil to keep it all stable and lined up. Finished height ends up pretty much the same as original header.
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DaveLecky
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Re: ADFS Upgrade board repair

Post by DaveLecky »

Thanks for the in depth info.

Dave
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Re: ADFS Upgrade board repair

Post by Coeus »

You also asked:
DaveLecky wrote:
Thu Aug 15, 2019 3:57 pm
Can any one identify the exact type of upgrade and manufacturer...I’ve just bought this beeb.
Not 100% but it looks more like the Acorn than the others. Acorn board at: http://8bs.com/see/acorn1770.jpg There are pictures of several of the 1770 boards at: http://8bs.com/seeboards.htm
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CMcDougall
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Re: ADFS Upgrade board repair

Post by CMcDougall »

does not look like a Acorn one, as the 1770 is in a socket, unless it's been fixed previously...

best is Acorn DFS 2.26 for B & B+ , the B+ has 1770 built onto board, no carrier as per pic.
the B+ originally came with Acorn DFS 2.0J , but it was VERY buggy like Solidisk, so hence updated to 2.26

the 1770 can handle 31/2" discs better too 8)
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richw
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Re: ADFS Upgrade board repair

Post by richw »

Back in the day, when I broke ROM legs, I would tin some wire and solder it on!to the stub. Then trim to size carefully. Has a high chance of breaking if you move the ROM again, but hey-ho...
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Re: ADFS Upgrade board repair

Post by Coeus »

CMcDougall wrote:
Thu Aug 15, 2019 9:03 pm
does not look like a Acorn one, as the 1770 is in a socket, unless it's been fixed previously...
I reckoned Acorn based on two chips on the underneath of the board which was very similar to the picture of a known Acorn board. All the other pictures I could seee had all the chips on the top. Having looked at one of the Acorn installation guides that looks like an Acorn ROM too. You can always put the ROM in and see what *HELP says.
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AndyF
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Re: ADFS Upgrade board repair

Post by AndyF »

I seem to recall the genuine ones suffered from this 'concern' :(

I remember that some third party ones did not do this as the construction was slightly different. 90% sure the RetroClinic ones are 'safe' but I don't have anything to hand as I write this to check.
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