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Looking more closely at your add on board, it seems to contain 4116 DRAMs (64k in total I think?). Mine has static ram, and ROMs, so is a different design. 4116 DRAM are 16k x 1 bit type. So eight of them gives 16k bytes. 4116 DRAM require +12V and -5V supplies in addition the the normal +5V supply...

There aren't lead fumes from leaded solder unless you evaporate it at ridiculously high temps. Which even high powered soldering equipment gets nowhere near. Try not to breath in the fumes from the flux (a fan helps here, as with no other airflow, your breathing will cause the fumes to drift toward...

KenLowe wrote: ↑

Fri Sep 21, 2018 10:46 pm

... and it will be nice to have the user port freed up for other things again.

Like UPURS

Mark

1024MAK wrote: ↑

Thu Sep 13, 2018 10:18 pm

Next week, time permitting, I'll post up some photos of one of my modified DS3231 RTC modules

See photos...

As you can see, I’ve removed the SMD resistor from the top right of the board (as viewed). This completely disables the dodgy charging circuit

Mark

I have been trying to PM Tricky to discuss options and buying a fully assembled and ready to go unit, but the forum says I need to participate more before I can PM anyone. Any ideas how I can get around this? Cheers Lee Lee, you can ask for PMs to be enabled by using the Contact us link at the bott...

Rather, in close proximity to a 74LS244 (Octal Buffers And Line Drivers With 3-State Outputs) chip and in close proximity to a nine pin SIL (single in line) resistor pack (RP) (also known as a resistor array).... As the resistors define the logic high level, the links (acting as switches) define the...

JGH is the person to ask. The whole point of the shadow RAM is that it is not normally in the CPU memory map. &3000-&7FFF shadow RAM (known as LYNNE) is available to machine code programs by manipulating the memory map latch (ACCess CONtrol) at &FE34. Details are in the Advanced Reference Manual for...

Could be a dry joint. Could be a poor plug or socket connection. Could be the contacts in the on/off switch. Could be the device that controls the demagnetisation of the screen. Could be a large electrolytic capacitor in the main power section.

Mark

First, just to be clear, LCD TVs may or may not work with unusual signals, but they work differently (being a completely different technology) so will not be damaged by a non-standard signal. Feel free to try anything you like with the signal to these. Any modern-ish CRT TV should also not be damage...

Yeah, I wouldn’t take the horizontal/line frequency down too low. Some 15625Hz CRT monitor’s and most CRT televisions use the line timebase running at 15625Hz to produce various supply rails for other parts of the set. And all generate the EHT voltage from the line output transformer. Most line time...

If you want proper sub-directories, there's only one option...

danielj wrote: ↑

Mon Sep 17, 2018 9:09 pm

Any better?

Only with beer goggles on...

The gotek uses USB by default, but it can use a very small one! (e.g. a Sandisk Ultrafit) :) Thanks, Daniel - List updated - Don't suppose there's a schematic that's black-on-white? See attachments :wink: Note: also included as a zipped file to get around the overzealous forum image compressor. Als...

So 5V at 2A is not uncommon. It may be possible to find a better quality PSU.

Yes, the extra terminal for grounding would be on the signal generator.

Mark

Yes. But in the longer term, you would be better off adding a 4mm green coloured socket or a “grounding” combined screw and 4mm terminal. Another way to make something floating with respect to the mains, is to feed the existing SMPSU via an isolating transformer (230/240V primary, 230/240V secondary...

You may also want to consider Dave’s latest cartridge, the Retro Hardware ARA III - Low Cost Writable ROM Cartridge - For the Electron and Master

Mark

And now breathe out...

Nice

Mark

Following the famous phrase ‘if in doubt add another Pi’ could you put a Pi zero in a box with level shifters etc. and an econet connecter and use this purely to bit bang? It would take in raw econet data and convert it to something that the Pi server could use. It would also take meaningful data f...

See also the links in this post

Mark

Micro Gotek by Zaxon at SellMyRetro
Zaxon’s web site with photos of the connections

Mark

To answer the original question regarding use of the ROM sockets vs. sideways RAM, here is an extract from the Master Service Manual : LK18 plug, made West: Paged ROM/RAM Select. Two position link. When fitted in the West position, this link causes 16Kbyte of RAM to appear in each of the "sideways" ...

Does this system make use of a Drive Ready/Disk Changed (/RDY, pin 34) signal?

Or it’s timed out waiting for another signal from the drive?
Pin 26 /TRK00 Track 0
Pin 8 /INDEX Index

If one of these signals is missing, would this cause these symptoms?

Mark

If the wiring loom for the top head is removed from the connector on the board, that would do it! Alternatively, there could possibly be a link in the logic circuits that select which head to use. Or the input control from the control and data (the 34 way ribbon) cable by be disconnected somewhere. ...

I'd fear for the fidelity of the power supply... Never mind that, imagine the scene in summer: the place stacked out with warm Beebs and other retro gear, everywhere rather toasty with the heat. Hence the air conditioning going at full pelt. Then a Rifa capacitor lets go... Followed by a mass stamp...

As with anything else, after a good visual inspection, the next step is to work out (by testing) what power supply rails are okay and which ones are missing or low. No need to worry about testing the EHT though.

If the tube heater is not glowing, that normally means it has lost it’s supply.

Mark

Colin’s comments remind me that poor quality, or poorly stored tapes sometimes are the cause. For some reason, the friction between the spool(s) and the case increases, hindering the free movement of the spool(s). A hexagon shaped pencil is useful for seeing who difficult a spool is to rotate. I kee...

Any electronic or electrical component that is overheating, being overloaded or self destructing can be the cause of smoke. I recommend that you open it up and carry out a visual inspection by eye (under a good light) looking for any physical trace of the cause of the smoke, such as soot marks, blac...

Tape chewing is normally a mechanical fault with the take-up spool drive running slower than the capsan (the rubber roller near the tape read/write head). Sometimes due to a slipping belt. Also ensure that the tape path and head is clean. And that the capsan rubber roller is slightly grippy and not ...

Are you sure C10 is a tantalum capacitor? It may be another type. Normally film capacitors are used in audio circuitry. Anyway, it's best if you include a 100nF capacitor between the wiper of your variable resistor / pot / preset and pin 3 (the LM386) input to seperate the different DC levels. And t...