The Adventures in repair and recalibration of the HP 331A

Here is my information on the repair and calibration of the HP 331A THD analyzer from the 1960's which is now in working condition and on the bench


Link to My post in EEVBLOG

Heres the Movie on Youtube

ST70 Resurrection PART 9

ST70 Resurrection PART 9

The first test of basic distortion displayed, we run some real tunes through it.  Notice the top of the waveform distorts before the bottom.   This will be covered in the next video

See Part 9 here.......

ST70 Resurrection PART 8

ST70 Resurrection PART 8

Testing of the input signals to the outputs of the 7199's are done showing two outputs exactly 180 degrees out of phase and an injection of an audio signal to display on the oscilloscope

See Part 8 here.......

ST70 Resurrection PART 7

ST70 Resurrection PART 7

This chapter deals with the summary of the electrolytics, testing and repair of the PC-3 board and other fun stuff

See Part 7 here.......

ST70 Resurrection PART 6

ST70 Resurrection PART 6

Revisiting the mistakes from the last video, everything is retested on the PCB and several tubes are selected until a good match is made

See Part 6 here.......

ST70 Resurrection PART 5

ST70 Resurrection PART 5

Revisiting the mistakes from the last video, everything is retested on the PCB and several tubes are selected until a good match is made

See Part 5 here.......

ST70 Resurrection PART 4

ST70 Resurrection PART 4

Here measuments are made of the bias circuit before and after replacing the two 50uf capacitors with higher rated 100uf caps, showing not only more stability but a cleaner DC signal.   Tests are made to the ABCD DC power for the plate voltages but A and B report high due to the missing 7199's to load them down

See Part 4 here.......

ST70 Resurrection PART 3

ST70 Resurrection PART 3

We replace the quad cap which allows us to introduce the rectifier and set up the bias.    We also get some good readings on the RF Choke and do some comparisons between both quad caps.  Final measurements determine that the power transformer is designed for 117VAC

See Part 3 here.......

ST70 Ressurection PART 2

ST70 Resurrection PART 2

Here we explore the power transformer and measure some voltages as the unit is slowly brought up on the VARIAC

See Part 2 here.......

ST70 Resurrection PART 1

ST70 Resurrection PART 1

Here is the amp I'd received from Mike from his brother Pat.  This is an overview of the amp as it arrived with 40 years of dust and other great stuff.  Also initial value collection of components and tube testing

See Part 1 here.......

Hantek 5072P testing videos

All of the Hantek 5072p testing videos are now in one group


See the listing here......

1962 Montgomery Ward C cell battery test

After getting the VTVM working, I was asked if it could then be used to test this early 60's C cell battery.   See the video below for the results!!



See the video here

Heathkit VTVM Turn up and test

My VTVM that I needed for work with Tube amps and antique radios arrived in pristine condition.  After an inspection of the device and testing of the tubes, a calibration was done and It works perfectly.


See the video here......

ST70 build pics from 2006

Photos from the Dynaco ST70 Build

First Run of SIO2PC on the Atari 800

Here is a video of my SIO2PC interface running between the Atari 800 and a Laptop running Ubuntu 14.10 64bit.

AspeQT is from SVN version 77 and compiled for AMD64 with QT5











This is an early attempt and the throughput has been greatly increased since the video was taken.

Understanding 6502 assembly on the Commodore 64 - (26) Intro to unsigned mathematics

Its time to talk about math.  Mathematics is naturally an important part to programming and can seem very confusing in machine language.  We have gotten comfortable with computers languages that allow for the easy computation of complex formulas.  It is quickly understood that mathematical routines may take many steps to complete a simple operation.



Click here for Chapter 26

Commodore 817 has been released

   After much work, the first version of commodore 817 is available for download.  At this stage, testing has been completed.  The test log and status is at the bottom of the page.

   The running main program takes up only 3299 bytes staying within my goal of under 4K.  Other smaller areas of memory deal with Disk/Printer I/O and uncrunching.  This was written in assembly using Relaunch64 and Tass64.  On actual hardware this was testing using the Glink232 on a stock C64 with an MPS-801 printer

The program has been tested with 1541, SD2IEC, NTSC, PAL.   As well as Vice.  See instructions for VICE below

Download D64 image here

Opening screen

The program reiterates the importance of backing up the calibration data of the radio.  The only way to fix it should it become corrupted is to send it back to the factory for recalibration.   

Initial radio calibration check

The program also provides printouts of the calibration for a safe hardcopy

MPS-801 Output

The main screen shows both VFO and memory information currently running on the radio, as well as frequency, band information, CWID tag, tx/rx status, power levels, adjusted power levels, mode and squelch.A graphical Smeter also acts as the radios SWR meter during transmit.

Top menu functions include

NOISE BLOCKER - ON/OFF
AGC MODE           - SLOW/FAST/AUTO/OFF
VOX                       - ON/OFF
CW BREAKIN        - ON/OFF
FAST TUNER        - ON/OFF
SPLIT TX/RX         - ON/OFF
RF-GAIN/SQL        - TOGGLE SWITCH
DUAL WATCH       - ON OFF
CW KEYER            - ON OFF
CW PADDLE         - NORMAL/REVERSE
CW ID                   -  ON OFF
SCAN MODE        - OFF/UP/DOWN

Bottom menu functions include:

Change frequency - Also validates input for acceptable ranges and matches band

Toggle Mode - switches between all available modes

Toggle VFO - switches between VFO A/B

Toggle Power - switches between L1, L2, L3 , and High

A=B - copies all information from VFOA to B and matches current band

Charger ON/OFF

HELP -  An included help file

CHECK CAL - A utility that checks the calibration on the radio against the one saved on disk

check cal downloading cal data for testing

 Option to print after testing

 Portion of the Helpfile

Vice:


Vice requires that true drive emulation be enabled under Drive settings.

Under RS232 settings

Enable ACIA RS232 interface emulation
ACIA device - serial 1
ACIA Base address $DE00
ACIA interrupt - NMI
ACIA emulation mode - SWIFTLINK

SERIAL 1 DEVICE - whatever your serial port is    mine is /dev/ttyUSB0
Baudrate 9600


Under Printer Settings

Enable Printer #4 IEC Device
Driver MPS-803
Output Graphics
Text output device - Printer 1 (file dump)

Print text device 1...    [where to save and the file name]

Save settings












TESTING LOG:

6 FEB 15:
     Fixed an issue where program will hang when loading help or test cal if the button is pressed while squelch is open and radio receiving RF. Disable glink232 and its receive interrupt before loading disk

     Added disable all sprites before loading help or test cal so receive meter doesn't get stuck on the screen. SPENA to 00

Works in VICE on D64 and works on 1541 on c64, there is an unknown problem with SD2IEC.  Doesn't find calibration file nor save calibration file



7 FEB15:
     Fixed Dialogue when cal test fails

     Fixed check for calibration file code. now works with SD2IEC and 1541

     Fixed irq shutdown bit toggle 2 on GLINK232,    shuts just 2 instead of all bits
     Dumped undeeded vector relocation code used before help and check cal

     Added the don't touch radio medal when transferring A to B

      ADDED HANDLER FOR BAD DATA CAUSING OVERFLOW


8 FEB15:
    Removed extra 2 !! in A=B code

TO DO:

     

Chapter 2: Serial and network connection with Direwolf

This chapter will talk about programs that interface with Direwolf using serial communication or TCP.  This will not yet discuss AX.25 for network connectivity over packet and keep things simple

Click here to continue

Chapter 1: Intro to Packet Radio in the modern age with Direwolf

     Packet radio could be awesome.   By packet radio I do not mean APRS.  If APRS is your thing, you will also benefit from this document.  Consider if you would, the resurgance of BBS's now popping up everywhere, having replaced dial-up with telnet, and still allowing connectivity on antique computers using TCPSER as a conduit.

    Up until now, there have been issues with getting going on packet radio.  First was cost.  Does anyone really want to spend hundreds of dollars on a TNC in the hopes of finding someone else on the air who did the same thing.  Secondly, looking at 15 year old pages of ancient AX25 implementations on the web can be disheartening.  You could not be blamed for making an attempt and quickly giving up on unsupported code from 1.x kernels running under motif, followed by page after page of contradictory information.

Click here to read the Chapter

Converting a D64 image on SD2IEC to a floppy disk on the 1541

No special cables required here.   You can move SD2IEC images directly onto the 1541 with your Commodore 64, VIC20 or 128 with ease.

You only need a PC to put the correct files onto the SD card.


See how to do it here!