Thanks Harvey for your reply. Yes, the 468 does not support remote operation. However it does support a remote WF request from the GPIB controller.
Replacing the CPU with a more modern microcontroller is the ultimate goal. That would replace all the ROMs as well as the System/Scratch RAM. However, the Acquisition RAM (512 bytes) and Display RAM (1K) are still needed since the 468 hardware autonomously accesses those. I' m more into AVRs then ARM myself.
At the same time, I have been able to change the address decoding logic so that I can now use the full 32KB ROM space, using an AT28C256 Eeprom, as well as added Serial I/O (with the existing 8085 CPU). I have decoded the Service ROM code and relocated it to run in the address space above the standard 16KB ROM range.
-Jan-
|
Some things to consider on this scope:
1) it is send only, IIRC, and was never designed for remote operation.
2) you set it up with the front panel controls, I don't think that any of the scope settings can be remoted.
3) IIRC, this was a "get waveform, press button, get printed copy" concept.
I did look at replacing the CPU, but that was going to be a plugin module of some sort, either just replacing the CPU or CPU/ROM etc.
Although, the original system RAM and ROM become more or less irrelevant once you put in an ARM processor.
Harvey
toggle quoted message
Show quoted text
On 2/17/2022 2:50 PM, jrseattle wrote: Hi, David.
I'm mostly interested in the DIGITAL internals of the 468: how does the 8085 CPU accomplish its tasks. Making the GPIB work is part of that.
As I mentioned, John (Twilight-Logic) created this AR488 GPIB controller which can be made for less than $20.00 (I made the pro-micro version, see for more info).
Problem with GPIB is, of course, that you need application software to process the custom GPIB commands and John provided that below - in Python which is another project :)
My cheap digital scope does all this much better, but making this 40 year old scope work the way it was intended is a goal in itself. Besides that, CRT scopes are much better at XY displays (see my Dutchtronix AVR Oscilloscope Clock). If anyone is interested in the 8085 firmware running the 468, please contact me.
What I really interested is is this: is there a way to produce "digital XY" mode on the 468? Currently, if you set the TIME/DIV knob to XY mode while the scope is in digital mode ("STORAGE" in Tek terminology), the scope gets into an undefined state.
While looking at the XY mode in Analog mode, I noticed the following: there is a separate path for Vertical Channel 1, which is the horizontal (X) signal in XY mode, but Channel 2 follows the normal path, including the delay line. This causes the Y signal to arrive later at the main amplifiers than the X signal. Is the delay so small that it doesn¡¯t matter, or is there a correction I have not found yet? For Channel 1, see J107 <1> going directly to <10>, the horizontal amplifier. For Channel 2, see <2> going to <3>, to the Delay Line, going to <5>, the vertical amplifier.
-Jan-
|
Hi, David.
I'm mostly interested in the DIGITAL internals of the 468: how does the 8085 CPU accomplish its tasks. Making the GPIB work is part of that.
As I mentioned, John (Twilight-Logic) created this AR488 GPIB controller which can be made for less than $20.00 (I made the pro-micro version, see for more info).
Problem with GPIB is, of course, that you need application software to process the custom GPIB commands and John provided that below - in Python which is another project :)
My cheap digital scope does all this much better, but making this 40 year old scope work the way it was intended is a goal in itself. Besides that, CRT scopes are much better at XY displays (see my Dutchtronix AVR Oscilloscope Clock). If anyone is interested in the 8085 firmware running the 468, please contact me.
What I really interested is is this: is there a way to produce "digital XY" mode on the 468? Currently, if you set the TIME/DIV knob to XY mode while the scope is in digital mode ("STORAGE" in Tek terminology), the scope gets into an undefined state.
While looking at the XY mode in Analog mode, I noticed the following: there is a separate path for Vertical Channel 1, which is the horizontal (X) signal in XY mode, but Channel 2 follows the normal path, including the delay line. This causes the Y signal to arrive later at the main amplifiers than the X signal. Is the delay so small that it doesn¡¯t matter, or is there a correction I have not found yet? For Channel 1, see J107 <1> going directly to <10>, the horizontal amplifier. For Channel 2, see <2> going to <3>, to the Delay Line, going to <5>, the vertical amplifier.
-Jan-
|
No big deal, I just wanted to ensure the archive doesn¡¯t mislead the next guy. Once the OP has the multivibrator sorted out, there¡¯s a home-grown calibration technique that doesn¡¯t require the S-30 Delta Standard, just one precise capacitor and a frequency counter. (The latter wasn¡¯t commonly available when the 130 was created.) See ¡° /g/TekScopes/topic/tpe_130_l_c_meter_calibration/7656928¡±. If you see nonlinearity on the 3, 10, or 30 ranges, look at C94, C93, and C92. Even if they are not leaky, the paper or paper-plastic caps Tek used are prone to Dielectric Absorption and this application is sensitive to it. But take care not to over-correct ¨C those caps weren¡¯t particularly good even new, and Tek printed the meter scales to match them. I installed polypropylene caps only to find that I was (slightly) off in the opposite direction! Use polyester instead. Dave Wise From: [email protected] < [email protected]> On Behalf Of SCMenasian via groups.io Sent: Thursday, February 17, 2022 11:21 AM To: [email protected]Subject: Re: [TekScopes] Type 130 L-C Meter You're right. Sorry for the confusion. Stephen Menasian
|
You're right. Sorry for the confusion.
Stephen Menasian
|
On Thu, Feb 17, 2022 at 05:24 PM, Dave Wise wrote:
My manual scan covers serial numbers from the beginning to at least 10760.
During that time, the 130 used a 6BH6 for V110, Guard Voltage Cathode
Follower. It was always a 6BH6 and nothing else was ever a 6BH6. The V70
Multivibrator has always been a 6U8. The V76 Clamp Tube is ¡°Use 6DJ8¡± so
early instruments were probably 6BQ7, an older dual triode that Tek globally
replaced with 6DJ8 because the latter is more reliable.
Printed on chassis of S/N 8069: "V76 6DJ8/6922 6BQ7A". Albert
|
My manual scan covers serial numbers from the beginning to at least 10760. During that time, the 130 used a 6BH6 for V110, Guard Voltage Cathode Follower. It was always a 6BH6 and nothing else was ever a 6BH6. The V70 Multivibrator has always been a 6U8. The V76 Clamp Tube is ¡°Use 6DJ8¡± so early instruments were probably 6BQ7, an older dual triode that Tek globally replaced with 6DJ8 because the latter is more reliable. If the multivibrator is not switching, then the input may not be swinging past one of the threshold voltages, upper or lower. What¡¯s the frequency and amplitude of the AC part of the input waveform? What are the DC voltages? Dave Wise From: [email protected] < [email protected]> On Behalf Of SCMenasian via groups.io Sent: Thursday, February 17, 2022 5:12 AM To: [email protected]Subject: Re: [TekScopes] Type 130 L-C Meter Jerome, Are you sure the clamp tube should be a 6DJ8? I have a 130 (which I have converted to solid state) and the clamp tube is a 6BH6. Of course the 130 went through several iterations and your version may very well have a 6DJ8. The schematic I have shows a 6BH6 and the writing on the chassis near the tube socket says 6BH6. Mine worked well (until the main electrolytic capacitor in the power supply gave up the ghost); so, I'm fairly sure my tube is good. I am in Pennsylvania and can ship it to you for a nominal price, at your suggestion, including shipping. Stephen Menasian
|
Re: RTM/TM 506 Fan replacement
Well, mine is actually a very old one... I bought it decades ago.
Its much quiter because it doesn't run on nominal speed, the supply in the TM506 or TM5006 giving only 110V to the fan. The remaining noise is mainly from the bearings.
cheers
Martin
|
Will respond to you gentlemen when I get off of hell....er, work. Thank you
so much. You are amazing.
toggle quoted message
Show quoted text
On Thu, Feb 17, 2022, 8:11 AM SCMenasian <scm@...> wrote: Jerome,
Are you sure the clamp tube should be a 6DJ8? I have a 130 (which I have
converted to solid state) and the clamp tube is a 6BH6. Of course the 130
went through several iterations and your version may very well have a 6DJ8.
The schematic I have shows a 6BH6 and the writing on the chassis near the
tube socket says 6BH6. Mine worked well (until the main electrolytic
capacitor in the power supply gave up the ghost); so, I'm fairly sure my
tube is good. I am in Pennsylvania and can ship it to you for a nominal
price, at your suggestion, including shipping.
Stephen Menasian
|
Jerome,
Are you sure the clamp tube should be a 6DJ8? I have a 130 (which I have converted to solid state) and the clamp tube is a 6BH6. Of course the 130 went through several iterations and your version may very well have a 6DJ8. The schematic I have shows a 6BH6 and the writing on the chassis near the tube socket says 6BH6. Mine worked well (until the main electrolytic capacitor in the power supply gave up the ghost); so, I'm fairly sure my tube is good. I am in Pennsylvania and can ship it to you for a nominal price, at your suggestion, including shipping.
Stephen Menasian
|
Re: RTM/TM 506 Fan replacement
I have also replaced mine a few years ago with one (220v) I bought from my local electronics store.
I can¡¯t tell you the make off the top of my head, but it¡¯s much, much quieter than the original one.
I can only imagine that anything modern and new you replace it with will make a huge improvement.
|
bonjour ¨¤ tous
Have 130 LC since 1980s, from LLNL salvage was $0.30/lb,
Still working fine, uniquely wide,capacity compensation 75,pF.
generally the problems in older valve equipment is often leaky or open electrolytics, carbon composition resistors that drift higher, or were overloaded, and defective paper, oil or plastic capacitors.
hope this note,helps you
Jon
|
Re: RTM/TM 506 Fan replacement
I replaced the fan in my TM506 an TM5006 with 220volt Papst models. Mechanically identical, very quit.
As to the airflow: as long as the temperature of the outgoing air is moderate I do not see any problem. The modules remain cool compared to a TM503 without fans. And I usually do not operate the frame when ambient temperatures are above 35¡ãC - due to overheating of brains :-)
cheers
Martin
|
VintageTek received permission to post the three-part article. See
There's also a beautifully restored manual as well.
--Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
toggle quoted message
Show quoted text
On 2/16/2022 22:09, Kerry Burns wrote: Hello Jerome
In 2020 Silicon Chip magazine did a three part restoration feature on the Type 130.
The link to the first part is
Unfortunately it costs to access the full articles ¡¡
Regards
Kerry
From: <[email protected]> on behalf of Jerome D Leach <jeromeleach17@...>
Reply to: <[email protected]>
Date: Thursday, 17 February 2022 at 2:39 pm
To: <[email protected]>
Subject: [TekScopes] Type 130 L-C Meter
Greetings fellows.
Had this 130 for several years and decided to finally repair it.
Replaced all the paper capacitors, and the filter caps. have little
ripple so left them in.
Powered up, the needle moves up to zero, then drops back down slightly.
No effect when coarse adjust is manipulated. Checked PS voltages, and
they appear reasonable: +150 comes in at +149.9. The +270 unregulated is
a bit low at 257.8. Used the 'scope and determined that both the
variable and fixed oscillators are working along with the mixer. Good
waveform into the grid of V70B, a 6U8 used as the multivibrator. Looking
at the waveform on pin 6 of the 6U8 on my Tek 561A, I can manipulate the
coarse and fine adjust knobs on the faceplate and vary the frequency so
I assume everything back to the input UHF jack is fine. Output is pin 6
of V70A, and should be a square wave, but is a flat line. Checked all
the PS voltages going into V70 and they are fine. All components appear
good with no evidence of overheating, etc. Changed out the tube with two
other brand new 6U8s with no joy.
Looked at the clamp circuit and it's tube, a 6DJ8. All associated
discreet components look fine, and the supply voltages are correct.
Changed out the 6DJ8 with a couple known good tubes and still no joy.
Am a definite novice at diagnosing electronic circuits, so could use a
bit of advice as to what to look for.
Thanks folks.
|
Hello Jerome In 2020 Silicon Chip magazine did a three part restoration feature on the Type 130. The link to the first part is Unfortunately it costs to access the full articles ¡¡ Regards Kerry From: < [email protected]> on behalf of Jerome D Leach <jeromeleach17@...> Reply to: < [email protected]> Date: Thursday, 17 February 2022 at 2:39 pm To: < [email protected]> Subject: [TekScopes] Type 130 L-C Meter Greetings fellows. Had this 130 for several years and decided to finally repair it. Replaced all the paper capacitors, and the filter caps. have little ripple so left them in. Powered up, the needle moves up to zero, then drops back down slightly. No effect when coarse adjust is manipulated. Checked PS voltages, and they appear reasonable: +150 comes in at +149.9. The +270 unregulated is a bit low at 257.8. Used the 'scope and determined that both the variable and fixed oscillators are working along with the mixer. Good waveform into the grid of V70B, a 6U8 used as the multivibrator. Looking at the waveform on pin 6 of the 6U8 on my Tek 561A, I can manipulate the coarse and fine adjust knobs on the faceplate and vary the frequency so I assume everything back to the input UHF jack is fine. Output is pin 6 of V70A, and should be a square wave, but is a flat line. Checked all the PS voltages going into V70 and they are fine. All components appear good with no evidence of overheating, etc. Changed out the tube with two other brand new 6U8s with no joy. Looked at the clamp circuit and it's tube, a 6DJ8. All associated discreet components look fine, and the supply voltages are correct. Changed out the 6DJ8 with a couple known good tubes and still no joy. Am a definite novice at diagnosing electronic circuits, so could use a bit of advice as to what to look for. Thanks folks.
|
Hi Jerome,
That's a nice unit and definitely worth fixing.
V70 is a straightforward Schmitt trigger, and there's not a lot that can go wrong. Measure voltages on the tube pins. Measure resistances (R72 and R73 in particular). If they've drifted far upward (including going open-circuit altogether), that would certainly kill the Schmitt. You'll find something quite obvious from those measurements.
Good luck!
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
toggle quoted message
Show quoted text
On 2/16/2022 19:14, Jerome D Leach wrote: Greetings fellows.
Had this 130 for several years and decided to finally repair it. Replaced all the paper capacitors, and the filter caps. have little ripple so left them in.
Powered up, the needle moves up to zero, then drops back down slightly. No effect when coarse adjust is manipulated. Checked PS voltages, and they appear reasonable: +150 comes in at +149.9. The +270 unregulated is a bit low at 257.8. Used the 'scope and determined that both the variable and fixed oscillators are working along with the mixer. Good waveform into the grid of V70B, a 6U8 used as the multivibrator. Looking at the waveform on pin 6 of the 6U8 on my Tek 561A, I can manipulate the coarse and fine adjust knobs on the faceplate and vary the frequency so I assume everything back to the input UHF jack is fine. Output is pin 6 of V70A, and should be a square wave, but is a flat line. Checked all the PS voltages going into V70 and they are fine. All components appear good with no evidence of overheating, etc. Changed out the tube with two other brand new 6U8s with no joy.
Looked at the clamp circuit and it's tube, a 6DJ8. All associated discreet components look fine, and the supply voltages are correct. Changed out the 6DJ8 with a couple known good tubes and still no joy.
Am a definite novice at diagnosing electronic circuits, so could use a bit of advice as to what to look for.
Thanks folks.
|
Crap, pin 6 on the brain. Input of V70 is pin 9, output is 6.
toggle quoted message
Show quoted text
On 2/16/22 22:14, Jerome D Leach via groups.io wrote: Greetings fellows.
Had this 130 for several years and decided to finally repair it. Replaced all the paper capacitors, and the filter caps. have little ripple so left them in.
Powered up, the needle moves up to zero, then drops back down slightly. No effect when coarse adjust is manipulated. Checked PS voltages, and they appear reasonable: +150 comes in at +149.9. The +270 unregulated is a bit low at 257.8. Used the 'scope and determined that both the variable and fixed oscillators are working along with the mixer. Good waveform into the grid of V70B, a 6U8 used as the multivibrator. Looking at the waveform on pin 6 of the 6U8 on my Tek 561A, I can manipulate the coarse and fine adjust knobs on the faceplate and vary the frequency so I assume everything back to the input UHF jack is fine. Output is pin 6 of V70A, and should be a square wave, but is a flat line. Checked all the PS voltages going into V70 and they are fine. All components appear good with no evidence of overheating, etc. Changed out the tube with two other brand new 6U8s with no joy.
Looked at the clamp circuit and it's tube, a 6DJ8. All associated discreet components look fine, and the supply voltages are correct. Changed out the 6DJ8 with a couple known good tubes and still no joy.
Am a definite novice at diagnosing electronic circuits, so could use a bit of advice as to what to look for.
Thanks folks.
|
Quick update here: It turns out that there are 2 Python modules exporting the name "serial", one called serial, one called pyserial. I had to do "Python -m pip uninstall serial", followed by " Python -m pip install pyserial" before it worked. Found this by searching for the error message.
I was able to download exactly 1 WF from my 468 using the micro-pro based AR488 controller (configured as a controller) but after that no more communication.
A while ago, I posted this on eevblog:
================
I was able to talk to a Tektronix 468 (with GPIB option) using the micro-pro version of AR488 (thanks so much for this design).
The program I used was the Prologix Configurator from KE5FX (this means I had to change the AR488 version string to match prologix).
The 468 was configured as device 3 and the TALKONLY option was DISABLED.
Commands I issued before turning the 468 on:
++addr 3
++srqauto 1
++eor 7
The 468 (which is ONLY a talker, not a listener) issues an SRQ value 1 on startup (called Power On SRQ).
==============
the AR488 handles this SRQ using these settings. With this setting, the GPIB LED on the side of the 468 is turned off because the "Power On SRQ" request is now handled.
-Jan-
|
Greetings fellows.
Had this 130 for several years and decided to finally repair it. Replaced all the paper capacitors, and the filter caps. have little ripple so left them in.
Powered up, the needle moves up to zero, then drops back down slightly. No effect when coarse adjust is manipulated. Checked PS voltages, and they appear reasonable: +150 comes in at +149.9. The +270 unregulated is a bit low at 257.8. Used the 'scope and determined that both the variable and fixed oscillators are working along with the mixer. Good waveform into the grid of V70B, a 6U8 used as the multivibrator. Looking at the waveform on pin 6 of the 6U8 on my Tek 561A, I can manipulate the coarse and fine adjust knobs on the faceplate and vary the frequency so I assume everything back to the input UHF jack is fine. Output is pin 6 of V70A, and should be a square wave, but is a flat line. Checked all the PS voltages going into V70 and they are fine. All components appear good with no evidence of overheating, etc. Changed out the tube with two other brand new 6U8s with no joy.
Looked at the clamp circuit and it's tube, a 6DJ8. All associated discreet components look fine, and the supply voltages are correct. Changed out the 6DJ8 with a couple known good tubes and still no joy.
Am a definite novice at diagnosing electronic circuits, so could use a bit of advice as to what to look for.
Thanks folks.
|
I'm trying to get the Python program that John (Twilight-Logic) posted below to run.
I was able to comment out the "termios" lines but now I'm running into a different issue. Python claims that module "serial" has no attribute "Serial":
Python 3.10.2 (tags/v3.10.2:a58ebcc, Jan 17 2022, 14:12:15) [MSC v.1929 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license()" for more information.
========== RESTART: C:\electronics\Tek468\468plot-main\src\468plot.py ==========
Traceback (most recent call last):
File "C:\electronics\Tek468\468plot-main\src\468plot.py", line 728, in <module>
ser = serial.Serial()
AttributeError: module 'serial' has no attribute 'Serial'
I installed "serial" as follows: Python -m pip install serial
John, thank you so much for your brilliant AR488 design!
|
jrseattle
Martin
Jean-Paul