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Can't directly help with the problem, but you can by a 2245 (non-A) service manual for $12.50 from Artekmanuals.com. Very nice people; top quality.

Hi Jon,

I don't see anything in the manual change pages for those; however, those were initially fixed resistors and changed to potentiometers at serial number B080000 so perhaps they didn't update the manual with regards to adjusting them.

Thanks,
Barry

Hello,

Scratching my head on this one, and hoping it's something really simple that I forgot, or didn't hook up right.

I acquired a 2245 from a friend that was working fine, (albeit noisy traces) So I decided to pretty
much do a full recap on the power supply. (replaced all the 3 pin metal can electrolytics anyway)

Put everything back together, double checked ribbon cables and powered it up, only to see no traces.

Didn't see a 2245 service manual on the wiki page so downloaded the 2245A, thinking that would be close enough?

Running the "Diagnose" yields it starting the tests and stopping at "Triggers" with a
"Time Signal Too Small at A Trigger" message.

Wondering if anyone has run into this or something similar and where I should turn my gaze first..

Testing Voltages on the 13-pin pwr supply connector on the bottom of unit:

5.18V
5.18V
0V
0V
-5.20V
-15.99V
14.94V
7.51V
-7.56V
58V
130.8V
0V
0V

Thanks in advance,
Wade

Hi
i have just purchased a 575 curve tracer and the CRT has been necked in transit so i am looking to buy a Tektronix 154-0343-00 (154-343) T0520-31 (T52 P31) A.K.A 5CAP1 CRT, or Failing that a Tektronix T64 aka T533 aka T5330 which can be made to fit the 575 by connecting Pin 9 to pin 8 as this is done internally in the T5020

Hi sitzstange

if you want to part it out i would be willing to purchase the CRT as i have just purchased a 575 curve tracer and the CRT was smashed in transit so i am in dire need of a new CRT

Barry check SN scope vs manual, changes pages, end of,service manual

Jon

What reference point are you probing from? For now, forget the scope and do some DC DVM measurements while it's running. Clip the + lead on TP940, and leave it there for the following measurements.

Put the - lead on TP950. You should get the voltage applied from the external supply, roughly 42-43 V.
Then on the junction of CR946 and CR947. You should read around 40 V if it's regulating. If it is, then the regulator section is probably OK.
If not, write down the value, then check the bottom of VR943, which should be about 6.2 V as marked. If it's OK, check the emitters of Q938 and Q939.
That node should read around 5.5 V. Q938's base should read very close to the VR943 voltage when it's working, but won't be now if it's not regulating.
It should be close though, even if wrong. Calculate the expected voltage at the junction of R939 and pot R938, as a simple divider, using the previously measured voltage from CR946 And CR947. Then compare it to the voltage measured there. It should be fairly close, and if not, check C942 for leakage. Also feel C943 to see if it is hot, just in case.
Now check Q944's collector. It can show a very wide range, but should be maybe 38 to 1 V, indicating some current, and linear operation.

Now clip the DMM's - lead on TP950, and use the + lead for measurements.
Check Q944's emitter. This can get kind of weird because the B-E junctions of the output Qs act as rectifiers, and the transformer combines them and makes it symmetric, and it's superimposed on the R949 voltage, which varies with load. I think Q944's emitter can go from a little bit negative to a little bit positive, depending on conditions. The base should read that value plus the usual 0.7 V or so above the emitter.
I think normally, Q944 is only driven hard during startup, to activate the output Qs. Once the Royer operation is attained, T944 provides the base power, and Q944 adjusts the regulation point for the DC voltage drop - remember in this scheme the Qs are both linear regulators and switches.

Check the R949 voltage, which shows the main current, which should agree fairly closely with the output current shown on the external supply.

Anyway, that should answer some questions. Good luck.

Ed

I have checked (and replaced for good measure) Q938, Q939, and Q944. The base resistors R946 and R947 are fine too.

One weird thing I've noticed is that the voltage on the emitter of Q944 is negative. The base is at around 0V, while the emitter is at -0.7V. Measuring the collector voltage of Q947, it appears to go to -5V. I'm not sure why that is happening.

The Vertical Interface in a 7704A (Schematic 5) has two potentiometers, R2234 and R2284, connected to the LEFT & RIGHT VERTICAL PLUGIN_SELECTOR IC (U2230 - a 0022 chip) for which I can't find any references in the calibration chapter of the service manual. Have I simply overlooked it? If not, does anyone know if those should be part of a calibration and, if so, how to do that?

Thanks,
Barry - N4BUQ

The boards say (c)1978 so I’m thinking 1979 low serial is probably closer.

Did you check or replace Q944? It's possible for it to be damaged during output transistor failure. If Q944's B-C junction blows open, it's possible for Q939 to supply enough base drive through R944 and Q944's remaining B-E, to start up and run poorly, without the current gain it would normally provide. Measure Q944's collector voltage to make sure some reasonable current is flowing through R945. Also check the base resistors R946 and 947.

Ed

The 107437 is a Tektronix Guernsey numbering - unrelated the Bxxxxxx number from Beaverton - I imagine there's a correspondence but I doubt it was documented.

You best bet is to compare the board level revisions against those the low/high Bxxxxxx manuals.

David

I all.

I am a lucky owner of an old DSA602 From tektronix. It work fine but the batteries (Memory and CPU) are tired. On power up, the scope show an battery error.

Is anybody know what type of battery i need to replace them (techno, voltage, reference, distributor in europe). Is exist a special procedure to replace them. Is this replacement risky?

Thank's in advance for your answer.

Best regards

The scope shots in the last post were taken on the output

I probed the collector and emitter voltages and it looks like the transistor is in saturation.




The first two show the transistor emitter and collector voltages on the input side. You can see that the collector voltage (trace in yellow, with a 10x probe) goes all the way down to zero, so the transistor seems to be hard switching.

The third one shows what happens when the scope fails to start properly. The power supply oscillates at 1 MHz.

I replaced the transistors with a more matched pair (hFe for both transistors was 73 at a Vbe of 550 mV).

The circuit still does not start up reliably. There is another mode of oscillation at a few hundred kHz which the circuit sometimes falls into. I had to crank the 8.6V potentiometer all the way to get it to start.

Here are the oscilloscope captures.




There is still ringing.

Just got the pictures from the seller, it is the old type/brown one.
So not sure where to go from here and if it even make sense to start restoring it or sell it for parts (again)..

On Tue, Feb 13, 2024 at 07:59 AM, Tom Phillips wrote:
"...The "high" serial numbers for the 465B are S/N B0600000 and up..."
That should read "B060000 and up."
Apologies for the typo. I sure wish we were allowed to edit our own posts.
Cheers,
Tom

On Mon, Feb 12, 2024 at 02:46 PM, Eric wrote:

I could be interesting in doing a pickup if there is enough to make the trip worth it.

Local pickup would be ideal. I'm told there is more Tek stuff, but I haven't seen it yet. The owner now knows there's interest, so there's likely to be more info soon.

--
Jim Adney
Madison, WI USA

On Mon, Feb 12, 2024 at 02:35 PM, Dale H. Cook wrote:

The subject line of this thread says "near Madison, WI, USA."

And I THOUGHT I had also set that up in my sig file, but now I see that it's not there. Now it is.

--
Jim Adney
Madison, WI USA

On Tue, Feb 13, 2024 at 04:19 AM, Don - AC2EV wrote: "How does one tell if the scope is a low serial number or a high serial number? My unit is #107437 as indicated on the front face. There’s no letter indicator."
The "high" serial numbers for the 465B are S/N B0600000 and up. That's how it is stated on the cover of the high S/N version of the 465B service manual.
The 465B high S/N manual is marked copyright 1982. The previous version was marked copyright 1979.
The leading alpha character designates the manufacturing location and I am not sure how Tek controlled the assigned numeric characters with respect to the alpha characters. Hopefully, someone can clarify that.

Note that the High/Low break point is different for the 465 Model.