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What was the drills' file name first time around?

The file was named along the lines of ABC01_A-1-4.drl.

The 'ABC01_A' portion indicates the project name and revision. '1-4' indicates that the holes should be drilled through layers 1-4, and .drl clearly isn't as meaningful as I thought it was!

Seriously... if you think you need a file, and there's exactly one file in the ZIP archive that hasn't been used yet, what would you do?

a) ask the customer to send the 'missing' file, or
b) check and see what the extra file you already have actually is?
Can someone please do a real test on the decoder functionality in the oscilloscope?

Really debug an SPI signal or a CAN bus signal, and use all 4 channels for the decoding.

Even on the 2 channel model which has been out there for quite some time, nobody on YouTube did a decent decoder test.

Connecting a sinus signal to the inputs is not really a decent test. For some people that's the best that they can do for some reason.
I agree. It is the advanced features like decoding and measurements where cheap scopes often fall flat on their face. Every scope can do squiggly lines and has a different user interface which a reviewer may like or not but that is just his/her opinion.
General Chat / Re: AQUAPOL - Bullshit Altert
« Last post by Bashstreet on Today at 09:24:07 AM »
The abstract concept is somewhat feasible but the application here is...   :-//

Why not? What's wrong with tying the grids together?


It works perfectly with both grids connected together. I don't know if this works with all tetrodes or if it's specific to the simulation model. I suppose the data sheet is the best place to start.

Needing to bias the grid negative to cutoff is expected behaviour. Connecting the grids together is an unusual thing to do (as in, almost never done) and I suspect that the simulation model is simply not representative in that configuration. I have no idea what the valve would do in the real world. What range of grid-cathode voltage does your simulation regulate with?

Usual valve operation is that it is "on" with the grid at 0 volts relative to the cathode, and you progressively reduce the current as you bring the grid more negative with respect to the cathode. This behaviour  is like an N-channel JFET or depletion-mode MOESFET. If you make the grid positive with respect to the cathode then you can on some types turn it slightly harder on but too positive and it will start to collect electrons, and current will flow into the grid. This is generally bad because the grid is not able to dissipate much power. Grid 1 current / power limits tend to be very low (but I can't actually find it in the datasheet). Sorry if some of this is obvious but you said you don't have much experience with valves. Hopefully it's helpful to someone anyway.

PL509 datasheet is here:

Page 7 shows current as a function of grid 1 voltage with the valve "triode-strapped", i.e. grid 2 connected to the anode and a fixed anode voltage of 160 V. Note that the range of Vg1 is 0 to -50 V.

Pages 8 and 9 show pentode operation with grid 2 held at a fixed +160 V, 175 V and 190 V relative to the cathode but the anode voltage varied with constant Vg1. The Vg1 range is 0 to -40 V.

edit: Ian.M has posted whilst I was typing. He makes a good point about the alignment of G1 and G2, but we're in agreement that the simulation model is probably junk for this configuration.
Thanks. I can see why my current limiting circuit is fatally flawed. I've managed to bodge it so it kind of works but it's still poor. The BJT limits the current first, then the short circuit current is determined by the characteristics of the valve. I imagine the valve's cut-off is extremely variable, like a JFET, so it won't work.

Last bad nubie valve circuit I promise.  ;)

With the memory mode you are running the memory in, you need U8:A & U8:B wired like grant's drawing. Pins 3 & 6 connect to ram/rom grant's way.
Pin 3 to ram WR
pin 6 to RAM & ROM OE

Yep, that's all in place still.

All Ram/rom address/data lines go to Z80
Except for A14 and higher.

A14 & A15 from the Z80 go straight to the MMU (670).  The Z80's A14 & A15 are now only connected to the rest of the address bus via the MMU.

Did you get the High 16k area of ROM programmed properly?
It should match first 16K except for those bytes in the message.

Yes, I've actually copied the monitor code into all 8 banks of the ROM earlier this evening (00000h, 04000h, 08000h, 0C000h 10000h, 14000h, 18000h and 1C000h) - so whichever ROM bank is selected, the SBC should boot.  It still doesn't, so this tells me that the ROM isn't selected at all by the MMU (which backs up the multimeter reading I took yesterday on Q4 being low.)  When I get more than 5 minutes to work on the issue, I'll get the oscilloscope out so don't worry, I won't be using the multimeter anymore. ;)

So, I've had little time today to look at the issue but I was able to program the ROM with monitor code in each of its 8 banks and try the SBC again.  It still doesn't boot, so this backs up my earlier observation that Q4 was low and thus the MMU wasn't selecting the ROM properly for boot.  I'll take a closer look at the MMU this weekend and check the voltages and signals to the 670.
Has anyone found anything remotely of interest in the Black Friday sales, I have to say that so far I've been disappointed with what I've seen.

Has anyone ever heard of test gear made by a company called PeakTech at all? Its a name that was brought in discussion today and I have never heard of them but I'm assured that they are considered big in test equipment in Europe?
You can get USB/PS2 adapters for pittance:

TBH I got annoyed with the lack of start + context menu keys with mine as well.
I ordered this one: before you post.
22€ exkl Tax.
Hopefully the work.
Curiously I have stumbled into those without warning, just as I did into the shared space scheme in Poynton. A quick glance at the road signs near the roundabout's entrance was sufficient to enable me to easily and simply navigate them.

Likewise, but as the "bell curve" neatly illustrates, 50% of people are likely below average. It also only takes one idiot to sink a ship and take everyone with it :)
Repair / Re: Scope blow, why?
« Last post by StillTrying on Today at 09:11:55 AM »
The Siglent SDS 1052DL+  .

 :) Very similar to my CML+.
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