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I finally go around to trying the XY display. It works quite well. As for the stretching characters, I don't see any of that; however, I'm waiting to get the replacement IC for the vertical board to see how much it still stretches with that. I should get that Monday and can do further testing once I get that installed.

Thanks,
Barry - N4BUQ

Thanks Mark, I hope my story helps others.
It would be a shame to junk a nice 'scope for the sake of a 10c resistor.
Peter

On Sat, Mar 9, 2024 at 6:42?PM Mark Vincent <orangeglowaudio@...>
wrote:

Peter,

Glad to hear you fixed it. I had wondered about that resistor. Knowing it
has 140V across it, I will note that in case mine gives the same trouble
then change to a 1/2W.

Mark

Peter,

Glad to hear you fixed it. I had wondered about that resistor. Knowing it has 140V across it, I will note that in case mine gives the same trouble then change to a 1/2W.

Mark

My last message did not display well using copy and paste but the information is there.
To summarize and answer my own questions.
The problem appears to have been an intermittent R1031 which was temperature sensitive. It took the PWM control just out of range so it kept resetting.
I'm not sure why the repair triggered the CT Test 81 Fail 01 but it might have been the defect in pin 7 of the 7 pin connector next to the ribbon cable on the right side that plugs into the buffer board. The repair and the new problem happened at the same time.
About the CTT adjustment procedure: I used a pulse generator but it has to have an offset ability. Set it to an accurate 0.5 uSec pulse width and an accurate 1 MHz frequency (use a frequency counter) and an amplitude of 1 volt. Then set the DC offset so the pulse is centered about ground. Now perform the calibration. When they talk of upper Mode and lower Trigger they mean select up for upper and down for lower. Don't forget to move the P501 jumper back.
After doing the calibration the error message no longer appears.
My 2465 is now rock stable and working.
Thanks for all the help. I have noted them down in case of more problems. It seems the components under high voltage stress are most vulnerable. R1031 has 140 volts across it.

Christian,

Any chance that you could post some pictures of sliding out the drawer? I’m also curious to hear what your gray encoder solution is. Currently suffering with that issue on my 370.

Regards,

George KD6NEW

Does anyone have experience with calibrating the CTT? What did you use for
a pulse generator?

*Check the U1030 circuits*

· Circuit operation: An output voltage is fed through high voltage
isolator U1040 where it is compared to a voltage derived from REF2.

· Wires were connected to check the U1030 circuits.

Black on REF2

Blue on TP81

Red on pin 15 of U1030

Green on pin 4 of U1040

· When powered on the ‘scope started without problems but showed:

*CT Test 81 Fail 03* which can be cleared by pressing *A/B/Menu*, and the
‘scope worked normally.

TP81 had normal signals.

Pin 15 of U1030 was at 152 mV, it should be 0.8 volts.

Pin 4 of U1040 was at 2 mV which is what it should be.



*Analysis*

· Something has changed. The red wire was clipped onto R1031 which,
although it measured at 330k, could have altered its value during the test.

· Why is the voltage at R1031 wrong and why the error message? Are
they related?

· Or there could have been a component that finally failed on the CT
board. The symptoms do not support this theory.

· There was some movement of the traces along with primary AC current
jumps which settled down and in subsequent power up the current is steady
at 0.95 amps. A previous intermittent load has gone away. (It was at 1.1
amps and unsteady)

· The original symptoms: The PS runs well with a load on its own. In
the 'scope it does its resetting and clicking for several to many minutes
then starts to work normally. Hot air speeds the recovery. Something needs
to warm up.



*Actions*

· R1030 was changed.

· All wires were removed to eliminate pickup as a cause of the error
message.

· It was discovered that pin 7 (on the right end) of the connector
that goes to the Buffer board was not connected properly, part of the
housing was missing. A new housing was installed. Nothing changed.

· The ‘scope powers up immediately but with a different error message:

*CT Test 81 Fail 01 *is this different because of the connector repair?

· Could the connector problem have created a new fault?

· *CT Test 81 Fail 03* is not listed.

· *CT Test 81 Fail 01* is listed as *Delay Offset constant Board
Tests out of Limit. Recalibrate the CTT.*

· The power supplies were checked at the 14 pin socket on the main
board:

1 -15.01 v

2 +4.98 v

3 -18.8 v

4 +10.00 v

5 -4.99 v

6 +14.98 v

7 0.0 v

8 +87.0 v

9 +42.4 v

10 varies up to 0.25 v then starts again from 0

11 -8.03 v

12 +4.97 v

13 +14.98 v

14 0.0 v

On Thu, Mar 7, 2024 at 10:49?AM peter bunge via groups.io <bunge.pjp=
[email protected]> wrote:

I found out how to send pictures of the 'scope screens
This link shows TP75 on schematic 9 in yellow and the collector of Q1062 in
Purple. 10 uS/div and 5v/div
The 'scope ground is on Ref 1 just marked REF on the 2465 schematic (see
2465B schematic to compare the two reference * and **)


and this shows the same signals at 1 second/div


I hope everyone has access.
I am moving my attention to the U1030 circuit and how it regulates.
This has to be a common fault. Two out of Four 2465 that myself and a
friend own have the problem of clicking for several minutes before settling
down.
Several people have told me it is a common problem. No one says what causes
it. The common repair is to replace all capacitors and a few other
components.

Looks like I may have put too little voltage in.
From 43 - 48V, the circuit outputs 8.56V, so it is in regulation. The current is 900 mA. Unfortunately, I still can't run it of the wall outlet (the power supply makes a high pitched sound every second or so). Any ideas on what the problem could be?

On Fri, Mar 8, 2024 at 03:23 AM, stevenhorii wrote:

The calculator takes unusual batteries - like current button cells, but
quite a bit thicker. Fortunately, they have not leaked. Unfortunately, they
are dead so I don’t know if the calculator works.

If you have access to a lathe it's a trivial task to make up a spacer that allows modern button cells to be used in place of those obsolete thicker ones (that possibly contained mercury). I have done that for old clocks with good results.

Obligatory Tek content: Mercury button cells were used in the 7S14 sampling plugin and possibly other products. The best substitute hack has been described on this group and doesn't requite machine tools!

Morris

Chris,

There is a TR-20 on eBay - for USD $16,800!


<>


and an EAI 180 for even more:


<>

Where are you located?

A friend of mine has one but wants to keep it. He uses it - after doing a
lot of repair work on it (power supply, many of the op amps). Besides doing
some analog computer work, he also uses it as a music synthesizer. He
thinks that besides the “young folks” who grew up during the
microprocessor-based computers and have an interest in early computing
stuff (and money to buy it - you probably heard about the Apple I that sold
for an astronomical price) there are those who have gained an interest in
analog music synthesizers and are partly responsible for driving up the
price on analog computers.

Steve H.


On Fri, Mar 8, 2024 at 12:43 Chris Wilkson via groups.io <cwilkson=
[email protected]> wrote:

I just missed out on a fully loaded EAI Pace TR-20 a few years ago. I'm
happy/sad about that. They aren't light and they aren't small!
I hesistated on shipping cross country. At the time they popped up fairly
regularly so I was hoping to see one within driving distance. I'm still
waiting....

On a happier note, I built a dedicated analog computer to implement a 1-
or 2-player Vector Pong game with score and sound. It drops into a stock
Asteroids Deluxe (cabaret style) arcade machine and makes use of the built
in power supply and audio amp/speaker and that glorious X-Y monitor. It's
a big hit when I take it to public arcade shows. I had obsessed over
Pong's unfortunately square ball ever since I was a small child. That itch
has been eliminated. Vector Pong draws a true circle! :)

I just missed out on a fully loaded EAI Pace TR-20 a few years ago. I'm happy/sad about that. They aren't light and they aren't small!
I hesistated on shipping cross country. At the time they popped up fairly regularly so I was hoping to see one within driving distance. I'm still waiting....

On a happier note, I built a dedicated analog computer to implement a 1- or 2-player Vector Pong game with score and sound. It drops into a stock Asteroids Deluxe (cabaret style) arcade machine and makes use of the built in power supply and audio amp/speaker and that glorious X-Y monitor. It's a big hit when I take it to public arcade shows. I had obsessed over Pong's unfortunately square ball ever since I was a small child. That itch has been eliminated. Vector Pong draws a true circle! :)

With analog computing, it's not a revival of the classical analog computer. We're at the cradle of something totally new coming up.

Try running up the external supply to a higher level. It's not precise. If it runs and ultimately regulates according to closed-loop conditions, it should be good to go. You know now how to tell if that's the case. The input should work around 43V, but a little more should be OK. If it has to reach say over 46 V, then maybe there are more problems. The main thing is to reach the closed-loop condition at a reasonable input, which should proof the circuit operation.

Ed

I got the TIP41C transistors and I swapped them in.

The power supply no longer oscillates at 1MHz, but the -8.6V rail is at -8.2V when I feed in 42V, and that's with the potentiometer turned all the way up.

Would it be a smart idea to bodge a 10k resistor in parallel with R937? Is there a better way of getting the voltage to match -8.6V? The current consumption is 800 mA, which seems a bit low. When I plug in the scope, it still doesn't power up.

How about pictures of the slide calculator, both sides.

Forgive my error in terminology. It is not grey as in color, it is Gray named for the author of the patent who gave it the name Reflected Binary.

I recently bought a “hybrid” - a slide rule with an electronic calculator
on the back. These were made by Faber-Castell but it was not long before
they were eclipsed by the electronic calculators that did the various
functions that slide rules do. To some extent, this makes sense - you don’t
do addition and subtraction on a slide rule. There was an earlier version
that that had an “addiator” on the back.

The calculator takes unusual batteries - like current button cells, but
quite a bit thicker. Fortunately, they have not leaked. Unfortunately, they
are dead so I don’t know if the calculator works.

I also have a Curta “pepper mill”. I’ve also used the Friden calculators. I
swear it’s where the term “crunching numbers” comes from. It’s amazing that
the Curta can do the same operations as the Friden though it does require a
lot of turns of the crank.

I still have my HP-35 calculator and it still works (with the AC adapter).
I have not gone through the effort of rebuilding the battery pack.

Steve H.

I remember them being advertised in so many techie magazines 50+ years ago. We called them "math grenades". I now have one, they are a work of art. The massive desktop calculators by Marchant, Monroe, Friden, and Burroughs are simply amazing as well.

?? Bruce Gentry, KA2IVY

Another marvel analog mechanical calculator , of more modern vintage
is the " Curta " , popular in the 1950's to 1970's, but then eclipsed by the pocket calculator.

I found out how to send pictures of the 'scope screens
This link shows TP75 on schematic 9 in yellow and the collector of Q1062 in
Purple. 10 uS/div and 5v/div
The 'scope ground is on Ref 1 just marked REF on the 2465 schematic (see
2465B schematic to compare the two reference * and **)

and this shows the same signals at 1 second/div

I hope everyone has access.
I am moving my attention to the U1030 circuit and how it regulates.
This has to be a common fault. Two out of Four 2465 that myself and a
friend own have the problem of clicking for several minutes before settling
down.
Several people have told me it is a common problem. No one says what causes
it. The common repair is to replace all capacitors and a few other
components.




On Wed, Mar 6, 2024 at 10:32?PM peter bunge via groups.io <bunge.pjp=
[email protected]> wrote:

Thanks Mark, I replaced R1020 although it was not bad. The troubleshooting
for that circuit using a power supply says the switch should activate from
20 to 25 volts. Mine latches at 17.5 volts. I don't think it is
significant.
I replaced C1024 with no change.
The RIFAs look good so I did not change any. They don't fit with the
symptoms.
I don't know if C1051 would cause my problems. I won't discount it.
CR1110 would show in the current sensing if it was shorting. There is no
evidence of a problem after T1060.
I don't think the doublers would cause my symptoms but I may change them. I
have the ones recommended.
I'm thinking that something in the U1030 circuit is acting up.Maybe U1040
feedback optocoupler? I need to see what its supposed to do.
I have good 'scope pictures of the signals but cannot post them. They show
the drive signals suddenly stopping after running from 1 to 5 seconds. The
recovery to working happens when the interval DECREASES. It seems that
there is something like overvoltage that needs to drift down to a control
range.
Peter

On Wed, Mar 6, 2024 at 8:15?PM Mark Vincent <orangeglowaudio@...>
wrote:

Peter,

R1020 is known to go bad. That should be 2W. Make sure to get a resistor
that is about 15mm long. Some 2W resistors are 3.68 x 8.72mm which is
smaller than a 1/2W. C1034 is originally a tantalum. I replaced the three
on that board with 50V film types to ensure low ESR. C1055 and a few

others

are the clear amber tinted RIFAs that are known troublemakers. I used

630V

film types to replace them. C1051 is another condenser that is a RIFA

type.

Look to see if those were replaced. CR1110 is known to go bad. It is a
Schottky rectifier. I replaced mine with a Si type and it worked with the
proper voltage out. Mine is 200V, I think, because I have some in stock.

If

you decide to replace the doubler condensers, I suggest using Nichicon

LGR

types. I put in 390mfd in mine. Make sure the diameter is small enough to
fit where the originals are. Add wires from the lugs/pins of the LGR type
to the board.

Mark

Thanks Mark, I replaced R1020 although it was not bad. The troubleshooting
for that circuit using a power supply says the switch should activate from
20 to 25 volts. Mine latches at 17.5 volts. I don't think it is significant.
I replaced C1024 with no change.
The RIFAs look good so I did not change any. They don't fit with the
symptoms.
I don't know if C1051 would cause my problems. I won't discount it.
CR1110 would show in the current sensing if it was shorting. There is no
evidence of a problem after T1060.
I don't think the doublers would cause my symptoms but I may change them. I
have the ones recommended.
I'm thinking that something in the U1030 circuit is acting up.Maybe U1040
feedback optocoupler? I need to see what its supposed to do.
I have good 'scope pictures of the signals but cannot post them. They show
the drive signals suddenly stopping after running from 1 to 5 seconds. The
recovery to working happens when the interval DECREASES. It seems that
there is something like overvoltage that needs to drift down to a control
range.
Peter

On Wed, Mar 6, 2024 at 8:15?PM Mark Vincent <orangeglowaudio@...>
wrote:

Peter,

R1020 is known to go bad. That should be 2W. Make sure to get a resistor
that is about 15mm long. Some 2W resistors are 3.68 x 8.72mm which is
smaller than a 1/2W. C1034 is originally a tantalum. I replaced the three
on that board with 50V film types to ensure low ESR. C1055 and a few others
are the clear amber tinted RIFAs that are known troublemakers. I used 630V
film types to replace them. C1051 is another condenser that is a RIFA type.
Look to see if those were replaced. CR1110 is known to go bad. It is a
Schottky rectifier. I replaced mine with a Si type and it worked with the
proper voltage out. Mine is 200V, I think, because I have some in stock. If
you decide to replace the doubler condensers, I suggest using Nichicon LGR
types. I put in 390mfd in mine. Make sure the diameter is small enough to
fit where the originals are. Add wires from the lugs/pins of the LGR type
to the board.

Mark