Date   
Re: troubleshooting Tek453 Mod 210H

Dale H. Cook
 

At 11:53 AM 10/10/2018, chuck wrote:

Second serial number is 005652 so I guess this monster is pre A.
Do you have Nuvistors in the front end and on the trigger board? If so you need the early 453 manual (serials below 20,000). It is at TekWiki:

http://w140.com/mmm/tek-453.pdf

Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/index.html

Re: troubleshooting Tek453 Mod 210H

Brendan
 

On Wed, Oct 10, 2018 at 08:55 AM, chuck wrote:

just bought a 453 and of course there are problems. The trace is fat! Using the 1Khz internal signal when I put it on either channel the trace is out of focus and really hi intensity. The focus knob works to an extent but the intensity knob does nothing.

Fabio,
Just thought of something.
So far I have yet to see a tube. Have only lifted the Z amp so far but
everything is Xstrs.
There will be two rectifier tubes inside the HV box unless someone has made mods, and if you have a below 20,000 serial # the other "tubes" will be nuvistors. The A version has a larger screen than the non-A version. I have 2 non-A 453s one nuvistor and the other is all transistor minus rectifier tubes, both have a screen size of 3 1/2 inches wide by 2 1/4 tall.

Re: 2465B SN 55xxx with TEST 05 FAIL 40

tekscopegroup@...
 

Right you are, only 4 SMD problem caps total. I need to have the board in front of me for facts to start falling in place. Definitively will carefully chop apart the caps before attempting removal. I did not intend to disturb any tantalums, unless really necessary. I've also read that the 20K trimmer pot near the DAC sometimes gets also damaged and needs to be replaced before the ref voltages are correct again. Maybe just order it too along the caps, just in case.

Your cleaning procedure makes a lot of sense, something I've not seen explained in detail anywhere else. Usually one would cringe at the idea of splashing water on a board like this, but now I am reassured it will be the best thing to do, even if corrosion damage appears to be light (due to fumes spreading on all nearby surfaces) its worth doing it right.

Do you by any chance know what Option 46 would be for this scope? Its the only field on the rear panel that has a punched hole in it.

Thanks.

Re: troubleshooting Tek453 Mod 210H

chuck
 

Kevin,
Thanks for your tip. Will check these out once I get the courage to get into the CRT circuit. LOL

Re: troubleshooting Tek453 Mod 210H

chuck
 

Fabio,
Just thought of something.
So far I have yet to see a tube. Have only lifted the Z amp so far but everything is Xstrs.

Re: troubleshooting Tek453 Mod 210H

chuck
 

Fabio,
First thank you for your very specific help. I know what I'm doing today now. LOL Anyway yes I have the service manuals (pdf) howver I think I have the A version and need the non A I can find that on the web.
Second serial number is 005652 so I guess this monster is pre A.

Re: 2445A calibration

Chuck Harris
 

Hi Maxim,

Everything in the scope is referenced to the DAC voltage reference
adjustment, and it is referenced to the +10V power supply adjustment.

Setting the reference is tricky in that it must be exactly a 2.5V
difference between the DELTA CCW and DELTA CW readings. I wrote a little
program for the TI-84 calculator (a castoff from my son) that helps with
that.

Wat are you using for your calibration voltages when doing CAL02 ?

-Chuck Harris

Max Vlasov via Groups.Io wrote:

Hello Chuck,

Thank you for the great help. Looks like we are moving forward with 2445a, slowly but surely. I've recaptured the photo of the calibration CAL02 step 111:

https://groups.io/g/TekScopes/photo/74577/17?p=Name,,,20,1,0,0

Now it seems that the dots are round. The problem was with the faulty coax (BNC plug was a bit loose).

However, all the CAL02 and CAL03 tests with the external signal generator generate LIMIT error regardless the channel number. I have assumed that the LIMIT is detected by the peak detector circuit in U500 by altering the trigger level signal generated by the DAC.
Also I've checked following your advice whether the CAL/NCAL Voltage pot can be left where it was or placed into the detent position. In both cases LIMIT error is generated....

But good news are that after running CAL03, even though the LEVEL error was generated every time, I don't have a problem any more with AUTO LVL. So, when I press the AUTO LVL on channel 1/2/3/4 the scope automatically finds 50% voltage level of the selected trace. So, now it really works. IMHO, there is nothing wrong with U500. Also checked attenuators for CH1/2 in all the modes and all the V/DIV positions. They work properly, no problem (also I assumed that a film resistor is blown on channel 1, but can't find a fault).
By looking at the vertical trace levels when the external signal is applied, it seems like they are off by 1-2%, which is a small error (calibration should take care of that, but it doesn't).

Looks like the scope is fully functional...

Maybe the problem is with DAC and/or with the demultiplexer and sample&hold? I'll try checking the DAC reference. Also I wonder how symmetrical the DAC calibration should be (when judging by voltage measurements on J119). Also I wonder how precise the main voltage reference must be set (10.000V)? Likely I have omitted an important step somewhere, therefore the FW can't close the calibration loop.
I plan to re-check the power supply, DAC output voltages. I wonder if anybody else had anything similar to that....

Thank you again,

Best regards,

Maxim

Re: 2465B SN 55xxx with TEST 05 FAIL 40

Siggi
 

On Tue, 9 Oct 2018 at 22:20 <tekscopegroup@...> wrote:

I've been reading up on this A5 board bad caps situation and have found
similar good tips and information.
You should probably just change those SMD caps on sight. If you want to
conclusively trace the wandering traces to the DAC reference, you can do
that by measuring the 1.36 and -1.25 reference voltages on the A5 board.
Those should be spot-on and pure DC, if they wobble around as the traces
move, then you know the DAC reference is compromised.
If you don't see those wobble around with the traces, it means you have
other and/or additional problems.

It's also useful to measure those voltages after your repair to validate
that you've brought the DAC in spec.

Re: troubleshooting Tek453 Mod 210H

Fabio Trevisan
 

Hello Chuck,

When it comes to intensity control inoperative, and highly intense trace, I`m afraid that you're going to set your fears aside about the CRT circuit and playing around it (with all its indeed intimidating High Voltages)...
Still, a lot of those circuits can be troubleshoot on the "Low" side, and what can't, can be troubleshoot by rising one lead of the components and measuring them (with scope turned off).
The regular caution is advised though... To keep one hand in the pocket, to remember to discharge the H.V. points before poking around and, preferably, don't be isolated in the bunker with nobody around.

About the focus, I think you probably don't have a problem in that dept. The trace is fat and the focus can't tame it because it's too intense and the beam is "bloomed".

An inoperative intensity control can have many causes, from a short between grid (G1) and Cathode (K) of the CRT tube, to problems (mostly leakage currents) in the DC restorer circuitry, to defects around the CRT bias circuitry, which encompasses the Intensity control pot and the CRT bias control (usually a trimpot).

All that I`m saying above is general to CRTs and not exactly specific to the 453.

In order to get more specific, anyone in the group will ask you 2 things:
1. If you have a manual, whether in Paper or PDF form (which for the 453 vintage is simultaneously a user and service manual). Some options to download here:
http://w140.com/tekwiki/wiki/453
2. What is the serial number? And if it's really a plain 453, or if it's a 453A.

Please let us know... and we take from there.

Kindest Rgrds,

Fabio

On Wednesday, October 10, 2018, 2:38:26 AM PDT, chuck
<@chuckyorbalinda> wrote:

Folks,
just bought a 453 and of course there are problems. The trace is fat!
Using the 1Khz internal signal when I put it on either channel the trace is
out of focus and really hi intensity. The focus knob works to an extent but
the intensity knob does nothing. I traced the signal thru the z amp and it
behaves as it should as I adjust the knob the signal at the output stage
(prior to going into the CRT control circuit) changes. I'm intimidated by the
CRT circuitry and would love to get some feedback so that I'm not going in
blind. The Tek troubleshooting guide talks about Typical High Voltage problems
but does not really point me in a direction.
Any help would be appreciated. I have a couple of DVM's and a pocket
scope (Chinese knock off) to work with.
Chuck


Re: 2445A calibration

Max Vlasov
 

Hello Chuck,

Thank you for the great help. Looks like we are moving forward with 2445a, slowly but surely. I've recaptured the photo of the calibration CAL02 step 111:

https://groups.io/g/TekScopes/photo/74577/17?p=Name,,,20,1,0,0

Now it seems that the dots are round. The problem was with the faulty coax (BNC plug was a bit loose).

However, all the CAL02 and CAL03 tests with the external signal generator generate LIMIT error regardless the channel number. I have assumed that the LIMIT is detected by the peak detector circuit in U500 by altering the trigger level signal generated by the DAC.
Also I've checked following your advice whether the CAL/NCAL Voltage pot can be left where it was or placed into the detent position. In both cases LIMIT error is generated....

But good news are that after running CAL03, even though the LEVEL error was generated every time, I don't have a problem any more with AUTO LVL. So, when I press the AUTO LVL on channel 1/2/3/4 the scope automatically finds 50% voltage level of the selected trace. So, now it really works. IMHO, there is nothing wrong with U500. Also checked attenuators for CH1/2 in all the modes and all the V/DIV positions. They work properly, no problem (also I assumed that a film resistor is blown on channel 1, but can't find a fault).
By looking at the vertical trace levels when the external signal is applied, it seems like they are off by 1-2%, which is a small error (calibration should take care of that, but it doesn't).

Looks like the scope is fully functional...

Maybe the problem is with DAC and/or with the demultiplexer and sample&hold? I'll try checking the DAC reference. Also I wonder how symmetrical the DAC calibration should be (when judging by voltage measurements on J119). Also I wonder how precise the main voltage reference must be set (10.000V)? Likely I have omitted an important step somewhere, therefore the FW can't close the calibration loop.
I plan to re-check the power supply, DAC output voltages. I wonder if anybody else had anything similar to that....

Thank you again,

Best regards,

Maxim

Re: troubleshooting Tek453 Mod 210H

Kevin Clark
 

On the 22xx series of scopes this fault is related to the focus string resistors gone bad. Something similar maybe ?

Kevin


On 10 October 2018 at 11:11 "Jeff Pederson via Groups.Io" <jpederson32=yahoo.com@groups.io> wrote:

Probably obvious, but have you checked the trace find circuit, if that is an older one with tubes I have one for parts if interested.

On Wednesday, October 10, 2018, 2:38:26 AM PDT, chuck <@chuckyorbalinda> wrote:

Folks,
just bought a 453 and of course there are problems. The trace is fat! Using the 1Khz internal signal when I put it on either channel the trace is out of focus and really hi intensity. The focus knob works to an extent but the intensity knob does nothing. I traced the signal thru the z amp and it behaves as it should as I adjust the knob the signal at the output stage (prior to going into the CRT control circuit) changes. I'm intimidated by the CRT circuitry and would love to get some feedback so that I'm not going in blind. The Tek troubleshooting guide talks about Typical High Voltage problems but does not really point me in a direction.
Any help would be appreciated. I have a couple of DVM's and a pocket scope (Chinese knock off) to work with.
Chuck


Re: troubleshooting Tek453 Mod 210H

Jeff Pederson
 

Probably obvious, but have you checked the trace find circuit, if that is an older one with tubes I have one for parts if interested.

On Wednesday, October 10, 2018, 2:38:26 AM PDT, chuck <@chuckyorbalinda> wrote:

Folks,
just bought a 453 and of course there are problems. The trace is fat! Using the 1Khz internal signal when I put it on either channel the trace is out of focus and really hi intensity. The focus knob works to an extent but the intensity knob does nothing.  I traced the signal thru the z amp and it behaves as it should as I adjust the knob the signal at the output stage (prior to going into the CRT control circuit) changes. I'm intimidated by the CRT circuitry and would love to get some feedback so that I'm not going in blind. The Tek troubleshooting guide talks about Typical High Voltage problems but does not really point me in a direction.
Any help would be appreciated. I have a couple of DVM's and a pocket scope (Chinese knock off) to work with.
Chuck

troubleshooting Tek453 Mod 210H

chuck
 

Folks,
just bought a 453 and of course there are problems. The trace is fat! Using the 1Khz internal signal when I put it on either channel the trace is out of focus and really hi intensity. The focus knob works to an extent but the intensity knob does nothing. I traced the signal thru the z amp and it behaves as it should as I adjust the knob the signal at the output stage (prior to going into the CRT control circuit) changes. I'm intimidated by the CRT circuitry and would love to get some feedback so that I'm not going in blind. The Tek troubleshooting guide talks about Typical High Voltage problems but does not really point me in a direction.
Any help would be appreciated. I have a couple of DVM's and a pocket scope (Chinese knock off) to work with.
Chuck

Re: free - tek 453 scope manual printout

chuck
 

just bought a 453. Do you want to talk about selling the parts donor also?
I would love to get the manual in any case I assume it is the service manual.

Re: Tek 485 - does anyone recognise these 485 power supply transistor markings?

Andre de guerin
 

Will check my box of scraps. Also can anyone make use of some fast switching diodes and other parts?
www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered. $Deity knows what happened."

On Tuesday, 9 October 2018, 21:53:14 BST, Reed Dickinson <reed714@...> wrote:

The Tek P/N 151-0324-00 is a PNP, Silicon, audio frequency power amp in
a TO-126 package with the collector connected to the metal center
mounting plate.  Connections are E-C-B.  It is rated 80V BVcbo at 40W
max Pd.  Equivalent devices are ECG185, 2N4918, 2N4919, 2N4920, 2N5193,
2N5194, 2N5195.  Use a mica washer when mounting on a metal surface.

Reed Dickinson



On 10/9/2018 6:43 AM, zenith5106 wrote:
On Mon, Oct  8, 2018 at 05:37 AM, Lorenzo wrote:

it's a Motorola TO-126 package marked B428 & T0324. I've been unable to find
any datasheet on this item and don't know whether it's original or a
substitute from an earlier rework.
T0324 actually means 151-0324-00 so it's the right one for S/N B143850 and up.
I'll bet the B in B428 is an 8 and if so 8428 is a date code.
/Håkan



Re: free - tek 453 scope manual printout

Dale H. Cook
 

At 01:16 AM 10/10/2018, Bill Noble wrote:

I printed out about 1" or maybe more of paper for a tek 453 that I wanted to troubleshoot
Bill -

You need to specify whether it is for serials below or above 20,000 - that was the dividing point between Nuvistors and FETs in the 453.

Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/index.html

free - tek 453 scope manual printout

william_b_noble
 

I printed out about 1" or maybe more of paper for a tek 453 that I wanted to troubleshoot - it has a bad HV supply so I've decided not to fix it - if anyone wants this printout (it's not an original manual, it's printed from the PDF file), just let me know and cover postage (probably $4 or so) and I'll send it to you - otherwise it will go into the recycling after I dispose of as much of this scope as I can


Regards, Bill Noble
www.wbnoble.com<http://www.wbnoble.com/>

Re: 2465B SN 55xxx with TEST 05 FAIL 40

Chuck Harris
 

Hi Alex,

No, it is only 4 electrolytic capacitors. There are
a couple of tantalums, but leave them alone.

I mean put the board in the kitchen sink, put an inch
of warm to hot water in the sink, and a good squirt of
Dawn, or other detergent, and scrub the area around the
capacitors with a toothbrush. That is the only way I
have found that will really clean up the leaked electrolyte.

The electrolyte goes everywhere, and spreads as fumes, so
it will be both above and below the capacitors when they
are in the position they were in when the leak occurred.

If you must use alcohol, the 70% is best, though 50% would
be better. The electrolyte is a polar compound, and will
only dissolve in a polar solvent, like water. It will not
dissolve at all in 99% IPA, as there is no water, and alcohol
is not polar enough.

If you are worried about water infiltration into the pots,
you can put a piece of electrical tape over them, but I
haven't found that to be necessary. Shake the board dry,
and them put it in a convection oven. Nothing else will
be bothered by the water in the least bit.

Do not try to remove the capacitors as complete units if you
are going to use a single point soldering iron. That is
virtually guaranteed to destroy the board. Cut them apart.

-Chuck Harris


tekscopegroup@... wrote:

Hi Chuck,

Thank you for the very detailed input on the procedures. I've been reading up on this A5 board bad caps situation and have found similar good tips and information. In any case I hope the corrosion will not be that severe, but who knows given the symptoms. Guess I'll find out once the scope gets to me in what I hope will be about 2 weeks if all goes well. In any case I feel confident and have experience with SMD soldering using a fine tip conventional iron, which in this case would have been my choice as well to solder the new caps in to keep it simple. Also, if I am not wrong its really 5 SMD capacitors that need to be replaced on the A5 board, 4 on one side of the board, and another one on of the opposite corners I think?

Much appreciate the tips on heating cautions on the corroded pads, and definitively the sliding and not lifting the caps seems to make a lot of sense to further protect the board from heat delamination. Always a good thing to heed to the voice of experience, specially on Tek equipment this nice that would be a shame to ruin just because of a bad soldering technique.

One question comes to mind: when you say "wash it again with warm water and dish soap, and a tooth brush", once all the affected pads are clean and tinned, do you mean to wash the whole affected area and then just rinse off with water? Guess there are no parts nearby that can be damaged by the water. In other situations sometimes I had good results cleaning up residual corrosion on a board by using 70% alcohol and a soft toothbrush. I had to redo the cleaning/scrubbing process several times. Advantage of alcohol is that it will evaporate quickly, and much less water will be left behind in comparison to using dish soap and plain water throughout the cleaning process. But then of course this was a very different kind of board, only two layers, low density, etc. So if you could please elaborate a bit about the washing/rinsing procedure.

I've worked so far on three other Tek scopes, a 2247A, a 222, and a 2213A. The 2213A was my first scope repairing experience back around 2004-ish (power supply issues/bad T948 against all odds). Back then it took a me a while to troubleshoot that devilish inverter power supply, but with quite a bit of help from the amazing Dennis Cobley, and Dean Smith fedexing me a donated almost complete main board with the needed transformer, in the end that humble scope came back to life. But when it comes to a 2465B, which is a classic and must have, I consider myself a rookie at best. But I digress...

Thanks again.
-Alex

Re: 2465B SN 55xxx with TEST 05 FAIL 40

tekscopegroup@...
 

Hi Chuck,

Thank you for the very detailed input on the procedures. I've been reading up on this A5 board bad caps situation and have found similar good tips and information. In any case I hope the corrosion will not be that severe, but who knows given the symptoms. Guess I'll find out once the scope gets to me in what I hope will be about 2 weeks if all goes well. In any case I feel confident and have experience with SMD soldering using a fine tip conventional iron, which in this case would have been my choice as well to solder the new caps in to keep it simple. Also, if I am not wrong its really 5 SMD capacitors that need to be replaced on the A5 board, 4 on one side of the board, and another one on of the opposite corners I think?

Much appreciate the tips on heating cautions on the corroded pads, and definitively the sliding and not lifting the caps seems to make a lot of sense to further protect the board from heat delamination. Always a good thing to heed to the voice of experience, specially on Tek equipment this nice that would be a shame to ruin just because of a bad soldering technique.

One question comes to mind: when you say "wash it again with warm water and dish soap, and a tooth brush", once all the affected pads are clean and tinned, do you mean to wash the whole affected area and then just rinse off with water? Guess there are no parts nearby that can be damaged by the water. In other situations sometimes I had good results cleaning up residual corrosion on a board by using 70% alcohol and a soft toothbrush. I had to redo the cleaning/scrubbing process several times. Advantage of alcohol is that it will evaporate quickly, and much less water will be left behind in comparison to using dish soap and plain water throughout the cleaning process. But then of course this was a very different kind of board, only two layers, low density, etc. So if you could please elaborate a bit about the washing/rinsing procedure.

I've worked so far on three other Tek scopes, a 2247A, a 222, and a 2213A. The 2213A was my first scope repairing experience back around 2004-ish (power supply issues/bad T948 against all odds). Back then it took a me a while to troubleshoot that devilish inverter power supply, but with quite a bit of help from the amazing Dennis Cobley, and Dean Smith fedexing me a donated almost complete main board with the needed transformer, in the end that humble scope came back to life. But when it comes to a 2465B, which is a classic and must have, I consider myself a rookie at best. But I digress...

Thanks again.
-Alex

Re: Tek 485 - does anyone recognise these 485 power supply transistor markings?

Lorenzo
 

Thanks to Reed & Håkan for the confirmation that this is likely the original part or good replacement - I didn't pick up the 0324 link to the part number, but guess I wouldn't have been confident even if I had. And closer inspection shows you're right that it's 8428 not B428. My eyes are not what they used to be. In this case the device is connected to a large pad on the -5.5V rail through the attaching bolt and there's no mica pad in place. Seems that's the way it should be. I'll presume for now the 2N5195 is working OK and move on.

Laurence