EPROM burning 21/25V 2.

 As it wasn't a big deal project, I made the drawings fast, and ordered the boards. Also as I didn't want to use some fancy SMPS for the boost voltage conversion, so I picked the good old MC34063 used a switchable feedback divider and that's it.

The board is arriving from the JLCPCB, with the cheapest manufacturing and shipment method. I left this project laying around for a long while now. I'm not willing to pay any extra for my laziness.

EPROM burning 21/25V 1.

 After my last Fake in China post, I continued to work on the 2716 EPROM burning. I ordered a second batch of 2716's from a different source. The new series looks more promising:

Same chip size, two different date code. I think this is still a chinese copy, but may works.

Also, I've a different issue here, what I just barely realized last time.

The TL866II programmer what I use, doesn't support the 21V Vpp printed on the top of the case. Even, according to the original ST documentation, it should be 25V. The programmer only support 18V. It is not enough, even the chips would be genuine.

I found a solution in a forum: https://pinside.com/pinball/forum/topic/program-21v-25v-roms-in-lower-voltage-programmers

This is great, just I don't like it.

This is a hack solution to me. I want to have a proper adapter, I'd like to see the pin detect function still works, I want to use a regular wall wart adapter instead of a lab supply, I want to have the 21V/25V programming voltage switchable, I want to protect my TL866II from faulty chips.

I asked a question on a forum, how the pin detect function of the programmer works. On the side I had a cloudy idea in my head:

What if: I just connect the original programmer pint to the chip through a diode, while clamp the programmer side to the ground with a high value resistor. In addition use one n-channel mosfet, with a zener to detect if the voltage from the programer is more than - let say - 12V. With this n-channel mosfet pull to the ground a p-channel mosfet's gate connected to the external programming voltage and the chip's Vpp.

On the side of why even you need those chips, why you not build another programmer from scratch like answers I got to relevant:

The schematics of the TL866II:

https://proghq.org/wiki/images/3/3c/TL866II_Schematic.pdf

And a kind of solution from a german site:

https://www.dr-bosch.com/volker/umbau/index.html?#VppAdapter

This later link contains a schematic, what is exactly the same what I have in my mind except it was realized with bipolar transistors instead of mosfets

Károly Molnár, István Sümegi - Thank you for the links.

So the project starts here. The real programming in this case can wait.

In addition to the mentioned circuit I plan to add a boost converter with switchable output (21V/25V from a 12V input), plus a zener and a resistor for every pin to protect the programmer.

This is how my abandoned projects are come into existence. :-D

The design will be available here when it is ready for this:

https://gitlab.com/suf/suf-electronics-TL866II-HV-EPROM

Hi-Fi Rack - Motorized turntable tray 3.

This year I decided, to complete some previously abandoned projects of mine. I'd like to finish one of those in every month. It is just a plan and not a promise (I don't want to fell into the trap of unkept new year's resolutions).

The first one in the row (for January) is my motorized turntable tray. The previous posts about it can be seen here:

• https://pakahuszar.blogspot.com/2019/12/hi-fi-rack-motorized-turntable-shelf.html
• https://pakahuszar.blogspot.com/2020/01/hi-fi-rack-motorized-turntable-tray-2.html

Since I restarted January, many things happened with it:

• Added the final electronics
• Changed the TI DRV8825 stepper driver to Trinamic TMC2209
• Almost completely rewritten the code, based on TMCDriver and AccelStepper, while keeping the original touch sensor library.
  
• There was an achievement from my side, that after a long struggling period, my 3D printer is back online and working stable, so I was able to add 3D printed parts. This way a new cable management arm come into picture instead of the unreliable tape used previously. It is used for the touch sensor cable and the mains cable. For the audio cable I may create a second arm sometime.
• I also 3D printed the holder for the connector at the back panel.
• Created a kind of power breakout box (temporary solution until the proper supply is made):
  It has:
• +12V - Wall Wart adapter for a time being
• +5V  - Wall Wart adapter for a time being
• Earthing (for the touch sensor)
• Serial connection
• Mounted it into it's final place

While I was writing the serial communication part of the code (it will be used later), a weird issue raised.

The connection to the PC just created unusable data stream. A complete mess. Even I changed the USB-Serial adapter. I didn't understood why. Then an idea pop into my mind, and...

Yes, I used a 12MHz crystal instead of 16MHz. This means, everything working correctly, except the serial communication. When I used 115200 on the arduino side and 86400 on the terminal side, the communication eventually started to work normally.

I didn't wanted to keep it this way, so changed:

The complete electronics, in it's place with the motor and the cable management arm

The power breakout box

Now only a few things left to do:

• A better GT2 pulley mount
• A second cable management arm for the audio cable
• The next phase of the project, what will contain the proper power supply also

Working on my desk:

Project finished, mounted into it's final place:

The design and the code reside here:

https://gitlab.com/suf/suf-hifi-rack

Fake in China (EPROMs)

 When I opened the HP 8903B Audio Analyzer I realized, that the rom memory on the processor board is assembled from various chips from various providers, what I not really like. The EPROMs anyway need reprogramming after a few decades, to keep the instrument working in stability.

As I didn't want to erase the originals, I had the plan to create a complete new EPROM set. The 2716 and 2516 EPROMs are not available anymore from any of the regular suppliers. So I went to the eBay to find some. Ordered 20pcs. Arrived from China:

I know, that the manufacturers time to time change the process of the devices kept on the market. But come one! Three different chip size, with the same date code?

Guys, you can do better job than this! :-D

Anyway, I tried. One out of the twenty acted like an EPROM in the programmer, even this one was failing during the programming cycle.

HP 8903B Audio Analyzer - WIP 1.

 I started to work on my instrument control software months ago (http://pakahuszar.blogspot.com/2020/09/instrument-control-1-beginning.html). When my audio analyzer related things started to work, I realized that the analyzer itself is off from the specifications, so I can't really continue the work on it as I planned. Actually I put the whole project aside for a while.

Now I feel it is the right time to continue to work on it.

The unit functionally working correctly, just some calibration (maybe recapping needed). For the calibration I would need a few raiser cards, to be able to measure things on the boards. The original raiser cards (08901-60084, 08901-60085, 08903-60018) are unobtainable. Even for the last one the schematic diagram is also missing. Fortunately the unit has no functional problems, so the processor board doesn't need troubleshooting (the last card is for this).

As the cards are not available, I ordered the matching 44 and 30 pin 3.96mm pitch connectors on the aliexpress, and designed suitable raiser cards. To make my work easier, added two things to the new cards:

• additional 44 (30) pin 2,54mm headers to be able to measure easier on the bus.
• additional 44 (30) pin edge connector to be able to break out the cards in 90 (instead of 180) degree (I don't know if this will be useful, we will see)

The boards at jlcpcb for manufacturing:

In addition to those, I have doubts on the EPROM long term stability. Unfortunately those 2k x 8 EPROMs doesn't exists at the regular suppliers I use. So I ordered some from the eBay.

Waiting for the things to arrive, to be able to continue.

Antenna holder

In the last few years I actively building my retro Hi-Fi sets (I don't know, when and why this started, but this is the case).

I still listen FM radios. Unfortunately the cable provider at my home upmix the FM stations into the TV frequencies and also provide them as digital channels also TV compatible. This make me impossible to listen radio on my collection of FM tuners, without proper antenna.

First option would be to build antenna to the roof of my house. I drop this idea immediately didn't want to invest the money/time to do this.

Tried to find some in room antenna, but my efforts failed. They are only selling TV antennas.

Finally I found some antennas on the Aliexpress, what was built for boomboxes or for those inexpensive FM capable bluetooth amplifiers widely available. Those also have F plug connectors, what I used several times previously.

First attempt to use this give me little success. While it was working the tightening it to the back of the radio, wasn't working properly.

Later I had the Idea, to 3D print some kind of holder for it. So I designed one:

Printed:

Assembled:

It will be glued to the Hi-Fi rack with double sided tape:

In place:

Instrument Control 1. - The Beginning

 Convergence.

This is the word what pop into my mind when I think about this project.

I feel this is the point where my lab building, instrument collection, instrument/interface building and measurement efforts connected together, giving me some higher level capabilities, than the things what I have on hand.

Where this is started?

I was building audio equipment in my childhood. Later when I restarted this hobby, was the plan, to continue to work audio electronics. I was lack of test equipment (had just a dying DMM). I wanted to build instead of buying. This lead me to the digital electronics.

Later I bought lots of equipment. At a point of time, I bought a HP 8903B Audio Analyzer, to be able to draw various graphs on amplifier performance. But the problem is, connecting an XY recorder is an outdated solution. For connecting to a computer, you need an interface. I wasn't happy with the readily available GP-IB interfaces, so my GP-IB interface is born.

Later, I was looking into the available controller software for the HP 8903B, and didn't like it. In addition, I wanted to connect/control my other instrument to a PC, having more ideas than just controlling the audo analyzer. So after a few control experiment, my "Virtual Instrument" project is born.

After two years, with many struggling, restarting and redesign, it looks like the system started to work.

The concept:

I wanted to create something flexible, while it able to use without programming skills. I wanted something can be used for serious measurements, can be used with many of the instruments I have. Compatible with several communication interface types. The whole system need to be use plugins for the future development.

I created a few object types  

Controller:

Something run the show. Starting the measurement series, even providing some base data for the instruments. Currently I implemented these:

- Continuous controller: Just runs the measurements one after the other. This is the usual work scheme most of the instruments, like multimeters.

- Single shot controller: Just run one measurement, then stops

- Variable controller: Can be setup for a series of measurements. It provide a linear or logarithmic dataset. It is originally created with the HP8903 in my mind. In the first trials I used it as a logarithmic frequency source for the integrated sine wave generator

Instrument:

Some device (typically hardware), can measure something. Can consume measurement results from the previous instruments (or controller) in the chain and/or provide measurement results for the next object.

Currently two type of instruments created: HP8903 Audio Analyzer, HP3478A 5,5 digit DMM

The instruments always working in single shot triggering mode. The reason: The controllers above are running the show and not the instrument's internal controller.

Filter:

It is originally designed for filtering, running maths, converting the results. During the development I realized, that similar functions are needed between the instruments also. So I realized that keeping filter plugins separately from the instruments has no added value.

I'll drop the filter functionality and create the filters as instruments.

Target:

Something can display or save the measured results. Currently two target available:

- Digital Display: can display the currently measured data, also provide min, max and average displays, with variable number of digits displayed

- Chart Display: Capable of displaying the measured data in a chart, using multiple series of data, using linear or logarithmic axes (this is not completely ready)

Connections:

Not part of the measurement chain. It is used by the instruments as communication interface. Currently available:

- AvrGPIB - My own GPIB board (on the development I wrote a few articles)

- IVI VISA - The standard instrument interface. I tried it with the Keysight stack and a Keysight USB/GPIB interface. Actually it was quite unstable, so future development is needed

- Serial - It is implemented and not. Actually it is used by the AvrGPIB, but I never tested directly, so it can have problems

So, this is what I have right now. I tested with the HP 3478A:

And later with the HP 8903B:

It is just AC Level measurement, the input directly connected to the output with 20-20000Hz sweep, 1V AC. Actually you can see some error:

Later with some modifications on the graph (still not finalized):

You can see around 2% error. So the instrument need some repair (at least replace of the filter caps).

So I intend to continue the development, adding support for other instruments and I have many improvement idea.

The code is written in C#.Net with Visual Studio 2019. The repository is located here: 

https://gitlab.com/suf/suf-electronics-VirtualInstrument

Anybody like this project, have spare time, some programming knowledge, and willing to help in the development effort, wellcome.