Re: 2432A Chan Delay adjustment

Peter K

Thanks for the guidance.
From Scope’s SM I read, that I have to connect CH1 and CH2 through a 10X attenuator to generator and set it output amplitude to MAX. In specs for the PG506 is written that max output signal is 100V.
That means, that the scope expects fast rise signal with amplitude 10V and unknown frequency.
I tried different ones from 1 kHz to 1 MHz with no luck.
I will keep use it that way until I find a suitable calibration device .

Re: 7834 Missing Trace

Roger Evans

Thanks for doing all those measurements, if my understanding of U225 is correct (the manual doesn't describe its internals) it is something called a 'Gilbert Cell', which functions as a current multiplier. So if one current input is steady and the other is the signal then the steady current controls the gain of the cell for the signal input. You can also change the polarity of the steady current and make the amplifier effectively become an inverting amplifier. Being current driven, its inputs are always close to zero volts and I am not sure how significant are the small differences that you see. If you can find R551 on schematic <5> you can try adjusting it to get the +9V back to its nominal value and see how much the calibration changes. The -9V is derived from the +9V via an inverting op-amp and has its own adjustment, R570. Adjust +9V before testing the -9V.

In order to get the 7A12 working more nearly to its spec you can use the front panel gain adjustments to try and get the two channels somewhere near their nominal value. If you can borrow a second vertical plugin that would help enormously in being confident that the errors are in the 7A12 and not the mainframe.

Any progress in removing the 7A12 from the mainframe?



Re: 475 With a bowed display. . . .Ideas?

Steph L

Thanks Michael for added detail and photos.

Process elimination; - I'd be inclined to swap Y output leads at point of connection to tube and try make sense of result.

Also, re your screen shot 475-trace-bent-6.jpeg, in terms of geometry, the image appears to be trapezoid shape. That is, the distance from left to right across the top of the pulses is shorter than across the base line, for the same number of pulses. This is a good clue. Looking at the Horizontal (X) sawtooth linearity between blanking, might offer a reason.

Sorry if you have explained this earlier, but when the Vertical Shift is used to lower the trace, does the top (trapazoid) line width "expand" out such that when the tops of the signal pulses are across the bottom of the tube face, do they now match gratical exactly as they do in that photo?? If so, it reinforces point - the tube geometry is somehow trapezoidal instead of rectangular in a 10:8 ratio.

Steph Lancaster
Melbourne (Australia)

Re: Tektronix 2230

Saroj Pradhan

Hi satbeginner
Understood. After I am satisfied with my repair work I will connect those
wire directly to the FET.

On Sun, Aug 9, 2020, 8:14 PM <tekscopegroup@...> wrote:

On Tue, Aug 4, 2020 at 06:33 PM, Saroj Pradhan wrote:
Before, at the beginning when I started to repair 2230, I Googled many
thread and forum. Some body suggested to remove the molex connector that
goes to the FET for connection and solder the wire directly to the FET.
What might be the reason behind this?
That connector I understood is known to sometimes develop a bad or
intermittent contact which can upset or even interfere with the operation
of the prereg to the point of possibly causing a no start condition. The
effect is compounded due to the FET getting hot and transferring heat to
the pins and the connector contacts, and in turn to the nylon body as well.
Sometimes the nylon body of the connector even looks a bit "baked" a sure
sign that its overheating, most probably due to poor contacts and IR^2
losses on a high amp current path. Clipping off the connector and soldering
the wires directly to the FET pins restores/eliminates this potential
contact problem. Back then I did it not have to remove this connector on my
2213A, just made sure all contacts where clean and tight, but anyone's else
mileage may vary. As long as the legs of the FET and the contacts of the
connector look to be in good shape, and the nylon body is not deformed or
shows signs of overheating I think it would be ok to keep the connector as
it makes troubleshooting/replacing the FET much easier.

Re: 465M: No trace, No +5V, No +95V


I had a similar problem with my 465M. One of the raw supplies was low. I replaced all the can capacitors by cutting them off just above the fat part so I could save all the connections, removed the old stuff inside and soldered new caps into the bases. The capacitor mounting tabs are actually part of the circuit. Start by making sure you have all the raw supplies. There's a 2uf cap just to the left of the HV shield near the test point that went leaky and killed the +95V..

Re: Tek 4654M; No Trace, No +5V, No +95V; Help


Thank you Dick. As happens, I stumbled onto the source of the 95V shortly after posting. Regardless, I am still struggling on getting this unit repaired. I thought I saw issues with diode CR582 (in the 95V supply) and transistor Q742 (transistor in the +5V circuit). Replaced both components but no measurable difference in results after doing so. At a loss of where to go from here. My basic electrical theory and understanding of this unit may just be too weak. With the +5V TPs reading -.749 and the 95V TP reading +5.71V it points to a component going to ground. Maybe a cap, resistor, or perhaps a faulty transistor or diode. I just am not seeing where the circuits seem to go bad. I've been wondering if I could have an issue in transformer T550 or in U550 the HV module. For instance, should I have +95 on pin 2 of T550? Currently I don't. Harrison N1FAM

Re: 475 With a bowed display. . . .Ideas?


Micheal, you asked for ideas and I am no expert on Tek scopes like Chuck Harris and others,
but is it possible that the gain of the horizontal (x) amp is being affected by the vertical (y) amp signal in some way?
I do not suggest that I know of a way the circuits could interact in this way, but the "tilt" towards the center at the top of the screen suggests this.
Experts, please say why this is not possible.

Re: 2465 Fan Collet Thingy


He probably made them himself. This part is so small I don't think the
weight will make a difference to the motor bearings. If nobody else has
time I could make some.


On Sun, Aug 9, 2020, 9:32 AM victor.silva via <daejon1=> wrote:

On Sun, Nov 10, 2019 at 01:46 PM, Siggi wrote:

I did machine a batch of these collets from delrin/acetal, and those will
work just fine - delrin will hold the thread just dandy. (I've been
shipping these out for postage, but I'm out of stock now - alas).


Will you be having more produced? Depending on the cost I would like to
have 10 or 20.
If you aren't about to order some, can you release the manufacturer of the
Delrin collet to sell some to a third party?
I would place the group order myself.

Although I collaborated with Tom Jobe for the design of the Brass collet
that led to the 2D in the files section,
I never liked the fact the initial samples were made of brass. Brass made
the impeller much heavier than it needed to be
putting unnecessary stress on the motor bearings.


Re: Tek 4654M; No Trace, No +5V, No +95V; Help



See Schematic FO-10

+95V originates at T550 - 1/2 wave rectifier D582, filter C582, L582 - jumper - C584, CR584 - TP+95V

Dick K9FFK

On 8/6/2020 10:14 AM, @HHSIII wrote:
Greetings; I am more of a mechanical guy than electronic guy. That said I am trying to troubleshoot a 465M scope that has no trace, no trace with beam finder, no +5V nor +95V. I was testing for the +95V at the TP on the left side of the A11 Interface board forward of the power supply area and the +5V on the TPs on each side of the A11 board (right side in the rear and left side outboard of the +95V TP.. Unit does power up and CRT illumination is present. I am using a Air Force Service Manual (465M Operation and Maintenance) that I found on line. I have been tracing +5 voltage from the T700 transformer forward. Things seem good before the Q742 transistor. After the transistor I was looking for +4.9V and had -0.121V (basically zero. Q742 is a 2N222 NPN transistor. My thought was to replace it to see if that restored the +5V. My issue with the +95V is I at a loss to determine where the +95V originates. I would really appreciate some "adult supervision and guidance" on both the +5V and the +95V issues and any suggestions, advice and guidance in general. Thank you very much. Stay safe and healthy. Harrison N1FAM

Re: 2465 Fan Collet Thingy

Li Gangyi

Just experimented a whole bunch more.

With a FDM printer and PLA material, ,vertical printing is tough, even with
the collet split 3 ways I have layer adhesion issues, perhaps a different
material might work (PLA has almost no give), horizontal printing will
sorta work, you'd have to sand / machine away the exterior (scale it a
little bigger for that), however there is no good way to put a thread on
there (I tried printing it with a 4mm shaft but trying to tap on that shaft
just shreds layers away). You'd have to use the model with a pilot hole,
drill it out and push in an insert with say a soldering iron.

I do have access to an SLA printer, but I've not set it up as of yet. Would
be interesting to know if I can just print the threads as is (no
machining). Update with results later probably.

One again the models I have created are over at

Re: Tektronix 475


I was able to check the cathode voltage (-2450V) using a VTVM which goes up to 3000V. I have some chunky test probes, but it makes me sweat in this heat. I figured that the PDA voltage must be fairly high to light a neon bulb through a a 22 MΩ resistor. Now that I have the CRT out I might try the arc test, but I am not too keen. My assumption was that the high voltage multiplier module would fail terminally. I suppose it could limp along at a lower voltage, but that should have been enough to get a spot on the screen.
I cannot understand why the beam finder did not produce a spot with 50 V on both X plates and 10 V on both Y plates. Apart from reducing the X and Y gains it also shorts the Z blanking signal to -8 V and should bias the tube into the right ballpark.
I will have to check the X and Y amplifiers methodically.

Re: 2465 Fan Collet Thingy

Tam Hanna

I volunteer to print one, but do not have the scope. Physical location is Budapest, Hungary, Europe.

With best regards
Tam HANNA (emailing on a BlackBerry PRIV)

Enjoy electronics? Join 14k other followers by visiting the Crazy Electronics Lab at

Re: 7834 Missing Trace


Ok, last one hopefully. I went through the supply test points and found that the +9V pin is supplying 8V. This voltage is also on pin 13 of U225. The test point labeled inv is supplying the 0.13V, and the one labeled pos is supplying about -0.045V. The rest seemed to be normal.


Re: 7834 Missing Trace


Addition: The measurements I linked were using channel 1. In channel 2 the voltage stays at about 0.13VDC in both positive and inverse settings.


Re: 7834 Missing Trace


The behavior of the noise is as you describe it, at least in my testing. My 7A12 is actually missing the left cover, so I have access to U225 with it still in the scope. I measured (what I'm pretty sure is) pin 12, I will link an album. The positive setting gives me 0.1346VDC, and the inverse gives me -0.1057VDC.

Here is the album:


Re: Tektronix 475


On Sun, Aug 9, 2020 at 07:35 PM, Raymond Domp Frank wrote:

readjusting the CRT bias
Obviously, I meant Grid bias (3x).


Re: Tektronix 475


If I understand correctly, you have a brightness and a (time base) deflection problem. There may be two problems or they may be two results of one (power supply?) fault.
Did you try readjusting the CRT bias and check for any light? CRT bias isn't critical, as long as you keep brightness within limits. Just make sure that once everything is ok, you readjust CRT bias so that the screen can be set completely dark with intensity fully CCW at intermediary timebase speeds (or X_Y).


Re: Tektronix 475


On Sun, Aug 9, 2020 at 05:58 AM, <tenareze32@...> wrote:

Here in SW France it cools a bit at night. We have AC in the house, but not in
the workshop. 37°C at 18:00 today.
39deg C in Paris. Cools down to 29 at night. AC died on us.

Re: Tektronix 475


On Sun, Aug 9, 2020 at 01:29 PM, <tenareze32@...> wrote:

An absence of spot or trace generally indicates an HT fault, but all HT
voltages are OK.
Depending on the voltage between grid and cathode, HV and PDA may be ok but still no light visible.


Re: Tektronix 475


On Sun, Aug 9, 2020 at 02:45 AM, <tenareze32@...> wrote:

I am wondering if there is a way of testing it without extensive disassembly.

I went ahead anyway and the HT was OK, it lit up a neon bulb through a 22MΩ resistor.
Are you talking about the HV (-2450V) or the HV multiplier (PDA) voltage output?
Checking either (HV and PDA voltage) the way you did it is not a good indication of functionality: Since a neon bulb needs only a few hundred volts to light and less than a mA or so to stay lit, that is not an indicative test.
There are two easy tests for the PDA:
1. Often, with relatively low air humidity (!), a very slight crackling may be heard immediately after switching the 'scope on after it's been off for a while and approaching the screen immediately after switching on sometimes causes the same sound, unless your 'scope has the EMC screen in front of the CRT.
2. Switch the 'scope off and pull the two parts of the high voltage cable apart at the connector in the pink wire. If all is well, this is not without risk of shock; use gloves if you can. Be especially careful to keep the ends away from any electronics or you'll zap them, again, if all is well... Approach the chassis with the protruding metal end of the CRT cable. You should see and hear a discharge with a spark length of at least 3 mm. Be aware that usually, not all charge is gone after the one spark.