Electron Plus3 + ROM/RAM board problem

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rharper
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Electron Plus3 + ROM/RAM board problem

Post by rharper » Wed Jun 13, 2018 4:05 pm

I have a problem with a Plus3 and Prime's ROM/RAM board.
It was working.
Then it stopped accessing ADFS discs giving an error whether formatted previously on that drive or elsewhere but working OK with DFS discs.
Then (a week or so later) it powered on to a white screen with black stripes, Mode 6 style BUT this was on an Elk with a Master RAM board and it was OK in Turbo or Shadow modes and would access ADFS & DFS discs.
Also from the 'Normal' mode striped screen could switch to Turbo/Shadow, CTRL+BREAK and would be OK.
Now, can still get to Turbo/Shadow mode but accessing the drive in ADFS or DFS - no LED light, the drive spins but no response, ESC returns to BASIC.

I have tried the Plus3 on a basic Electron but just get the striped screen, similarly with lifting and resetting the ROM/RAM board in the Plus3.
I have sent this to Dave Hitchins to have a look at.
Dave or myself will report back on developments but it may be a while.
Ray :(
Raycomp

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CMcDougall
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Re: Electron Plus3 + ROM/RAM board problem

Post by CMcDougall » Thu Jun 14, 2018 9:52 pm

rharper wrote:
Wed Jun 13, 2018 4:05 pm
OK with DFS discs
well, well I never :lol:
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daveejhitchins
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Re: Electron Plus3 + ROM/RAM board problem

Post by daveejhitchins » Fri Jun 15, 2018 6:07 pm

Received the Electron and Acorn Plus 3 combination today.

First look shows that the Drive is not being accessed!
Step 1: Try another Plus 3 - everything works OK - so we can, probably, rule out the Electron and MRB . . .
Step 2: Ray's Plus 3 back (with lid off) and measure some Voltages.
This is where it gets interesting: +5V OK - +12V measures 16V ooooch! Drive is officially dead! Probably just the motor drive circuit - but more of that later.
Acorn Plus 3 Power Supply Schematic.png
The Acorn Plus 3 PSU Section
What's interesting is that the regulation is to the 5V rail - and the 12V rail is correct by design. So, how could we have +5V and +16V?

My thoughts are: That the regulator is not working - hence 16V on the 12V rail - and the 5V is being 'clamped' somewhere within the PSU - just to find out where and see if I can sort the regulation out.

More later . . .

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
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rharper
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Re: Electron Plus3 + ROM/RAM board problem

Post by rharper » Fri Jun 15, 2018 8:47 pm

daveejhitchins wrote:
Fri Jun 15, 2018 6:07 pm
This is where it gets interesting: +5V OK - +12V measures 16V ooooch! Drive is officially dead! Probably just the motor drive circuit - but more of that later.
Dave H :D
Ah well, I was thinking of having a Plus3 with a modern 3.5 inch drive to make it a 640K unit anyway.
I can have some fun making brackets so that it fits.
Ray
Raycomp

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daveejhitchins
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Re: Electron Plus3 + ROM/RAM board problem

Post by daveejhitchins » Fri Jun 15, 2018 8:56 pm

rharper wrote:
Fri Jun 15, 2018 8:47 pm
Ah well, I was thinking of having a Plus3 with a modern 3.5 inch drive to make it a 640K unit anyway.
I can have some fun making brackets so that it fits.
Ray
I have some laptop drives that were for that very purpose - Not sure yet if they'll work, but if you want to experiment (?) I'll send you one to play with . . .

I thought someone would have had some ideas about the fault, by now :? I'm going to 'study' the schematic . . .

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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1024MAK
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Re: Electron Plus3 + ROM/RAM board problem

Post by 1024MAK » Fri Jun 15, 2018 10:39 pm

Are you sure that the +12V being at or about +16V with the drive idle is not normal? Only with supplies that are unregulated, or regulated to another supply rail, they will tend to float at a higher voltage if there is no load. Further, I would not expect a 12V motor to necessarily die if it was supplied with 16V DC. It may get a bit hotter than normal, and may spin a bit faster...

The other possible reason for the +12V rail being high, would be the regulated +5V rail being more heavily loaded than normal. That is, there is more current being delivered by it, hence more power being delivered to the switching transformer, so the +12V rail is higher. The cause of the extra current on the +5V rail could be due to a semiconductor having partly failed and hence consuming more current.

Mark
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daveejhitchins
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Re: Electron Plus3 + ROM/RAM board problem

Post by daveejhitchins » Sat Jun 16, 2018 7:13 am

Are you sure that the +12V being at or about +16V with the drive idle is not normal? Only with supplies that are unregulated, or regulated to another supply rail, they will tend to float at a higher voltage if there is no load. Further, I would not expect a 12V motor to necessarily die if it was supplied with 16V DC. It may get a bit hotter than normal, and may spin a bit faster...
Yes, I did check without a drive attached - I'll check again. The drive was tested in another Plus 3 - so definitely a dead drive. I'll put a 'load' on the +12V rather that risk a drive. I'd have thought that the +12V current, with no drive activity, would be very small - I'll measure it along with several other Voltages and mark-up the schematic.

The other possible reason for the +12V rail being high, would be the regulated +5V rail being more heavily loaded than normal. That is, there is more current being delivered by it, hence more power being delivered to the switching transformer, so the +12V rail is higher. The cause of the extra current on the +5V rail could be due to a semiconductor having partly failed and hence consuming more current.
Nothing getting warm - I need to check that the drive is getting the correct signals. Once I've sorted the +12V out or eliminated it, I can test with an alternative drive More later today . . .

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Electron Plus3 + ROM/RAM board problem

Post by daveejhitchins » Sat Jun 16, 2018 8:36 am

OK - PSU just fine - the number of engineers I've told, over the years "don't measure open circuit e.g. not loaded, supplies - you'd think I'd practice what I preach - D'oh! :oops:

Just faulty drive. Ray, I can replace this with the same model of drive or let you play with alternatives - let me know.

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

rharper
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Re: Electron Plus3 + ROM/RAM board problem

Post by rharper » Sat Jun 16, 2018 9:04 am

daveejhitchins wrote:
Sat Jun 16, 2018 8:36 am
Just faulty drive. Ray, I can replace this with the same model of drive or let you play with alternatives - let me know.

Dave H :D
I'll try to make it a 640k drive. I have several modern 3.5" drives that should do - I expect it will need a twisted cable to make it Drive 0.
Would there be any advantage to a laptop drive?
Ray
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Re: Electron Plus3 + ROM/RAM board problem

Post by daveejhitchins » Sat Jun 16, 2018 3:29 pm

rharper wrote:
Sat Jun 16, 2018 9:04 am
I'll try to make it a 640k drive. I have several modern 3.5" drives that should do - I expect it will need a twisted cable to make it Drive 0.
Would there be any advantage to a laptop drive?
The advantage would be two drives :D the disadvantage is you'll need to source a suitable lead (see photos).
IMG_2452.jpg
NEC - I have 2 of these
IMG_2453.jpg
NEC
IMG_2454.jpg
NEC
IMG_2455.jpg
Epsom - I have 6 of these
IMG_2456.jpg
Epsom
IMG_2457.jpg
Epsom
Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
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Re: Electron Plus3 + ROM/RAM board problem

Post by Prime » Sun Jun 17, 2018 8:55 am

Glad it wasn't either of my boards, but at least you found the problem.

Cheers.

Phill.

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Re: Electron Plus3 + ROM/RAM board problem

Post by daveejhitchins » Sun Jun 17, 2018 9:22 am

Prime wrote:
Sun Jun 17, 2018 8:55 am
Glad it wasn't either of my boards, but at least you found the problem.
Phill . . . I'm currently looking at an issue involving the MRB - I need to check if it's your MRB, a generic problem with MRBs or nothing at all to do with MRBs. I'll start a new thread, when I have more information.

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
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Re: Electron Plus3 + ROM/RAM board problem

Post by Prime » Sun Jun 17, 2018 7:18 pm

daveejhitchins wrote:
Sun Jun 17, 2018 9:22 am
Prime wrote:
Sun Jun 17, 2018 8:55 am
Glad it wasn't either of my boards, but at least you found the problem.
Phill . . . I'm currently looking at an issue involving the MRB - I need to check if it's your MRB, a generic problem with MRBs or nothing at all to do with MRBs. I'll start a new thread, when I have more information.
Do you have one of the original Slogger boards? As I have one so could possibly do comparative tests if needed.

Cheers.

Phill.

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