Date   

Help required finding a Tek 466 power rail short

James55
 

Hi all.

Looking for some help to repair an old Tek 466 which I accidentally damaged.

The story is, that I bought it non-working and upon inspection found that the scope had been stored on it's face which had pushed the red 'VAR' button back into the horizontal channel, thereby breaking the potentiometer at the end of the rod.
Unable to find a replacement (as I am in Brazil), I was fortunate enough to be able to disassemble the board and do a workable repair. Further testing on the horizontal section revealed a shorted tantalum which when replaced led to the scope firing up fine and working fine.

Before putting it back in the case, I left it running to confirm that all was ok, and all was fine except I felt that rectifiers on the -8v and +5v rails were a little hot, so feeling confident set about upgrading them.
That all seemed to go fine, except for when I switched the scope back on, there was no longer had a trace.

What followed was that at some point (and for a reason I no longer remember) I decided to test the voltages on the J5 and J6 sets of pins which connect the main A6 board to the A2 vertical pre-amp board.

Whilst doing this, I slipped and momentarily shorted two pins.

This immediately blew the 1.5A fuse on the A6 board, sending the fan off at a higher speed and most of my LV power rail voltages out.

I don't remember the sequence of events following that, as I have since pulled and tested so many components that I can no longer see the wood for the trees.

The situation now, is that when it is plugged in to the mains it immediately blows the mains fuse, so if anyone has experience in locating shorted components then it would be greatly appreciated.


Re: 1502 TDR RECORD functions

Tom Gardner
 

On 01/12/21 21:51, fiftythreebuick wrote:
Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...
Now that hadn't occurred to me!

That's a really excellent example of using whatever is available to solve the problem at hand :)

Thanks!


Re: 1502 TDR RECORD functions

fiftythreebuick
 

Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...

Tom


Re: [OT} Peak DCA55 & Germanium

Brian
 

Hi Tim , I had that with a Chinese component analyzer with some 2N1516 and it was Tin wiskers . Once removed with a 15v psu it tested ok .
Brian (UK)

On Wednesday, 1 December 2021, 13:25:13 GMT, Tim Phillips <timexucl@...> wrote:

My Peak DCA55 often misidentifies some Germanium transistors as BiColor
LEDs.
In particular those such as 2N2209 with TO7 bases. (e-b-Case-c; the Case
lead has been clipped). Is this possibly Tin-Whisker or something about the
DCA55? My Chinese component analyser just says 'unknown component'  (I'm
going through my collection of 1S1s and 3T77s)
Tim
--
"Success is a collection of well-curated failures"


[OT} Peak DCA55 & Germanium

Tim Phillips
 

My Peak DCA55 often misidentifies some Germanium transistors as BiColor
LEDs.
In particular those such as 2N2209 with TO7 bases. (e-b-Case-c; the Case
lead has been clipped). Is this possibly Tin-Whisker or something about the
DCA55? My Chinese component analyser just says 'unknown component' (I'm
going through my collection of 1S1s and 3T77s)
Tim
--
"Success is a collection of well-curated failures"


Re: 1502 TDR RECORD functions

Tom Gardner
 

On 30/11/21 07:10, John Parkins G8KVP wrote:
Hello Reg,

The 1502 is the first time 2 of my hobbies have come together, electronics and woodwork.

I can get rolls of paper that fit our credit card machine and with a fine blade they can be cut down to the right size on the bandsaw. Not that I use a lot of paper.

You mention the the illumination....... Something I've looked at and it all seemed a bit tight, so it never got done. Keep us informed on how you go about it, then I might have a go. I have to say it's the only downside to my machine.
ISTR that the paper has holes down one side, and that a photodetector detects the holes.
ISTR that someone has synthesised the signal from the photodetector so that the chart recorder works without the holes.

I don't know since I've never bothered with a recorder; I simply bought a cheap XY output plugin.


Re: 1502 TDR RECORD functions

Tom Gardner
 

On 29/11/21 23:43, Reginald Beardsley via groups.io wrote:
All I have is the roll of paper that came with it. Since my post I've read the service manual and now understand the BNC output waveform. The narrow pulse is the sampling arm signal.

I just made a test with the chart recorder removed and I get a proper sweep. So it appears that the fault is in the Y-T chart recorder. The X-Y module attached to an Ardinuo/MSP430/STM32 to dump digits to a USB flash drive or SD card should be far more useful. I suspect a bspoke module for that would not be difficult to make.
The XY module is trivial to make; the mechanics are more difficult than the electrics. The schematics are in the manual.

Do have a look at the PSU caps. On mine C6246 and C6341 had spewed acid across the track. Fortunately the simple PCB was easily repaired.


I'm getting TDR responses with the 1502 from RF adapters and connectors which look to my eye to be quite comparable to the 11801/SD-24.
The 1502 is a fun instrument to use; I've a bit of a fetish for them.

Fortunately mine is calibrated in metres, so I don't have to mentally work out what 0.1ft is :)


A working 11801 & SD-24 are difficult to find, 10x+ as much money and have *no* component schematics available.
I suspect that schematics would have to include a symbol for "black arts employed here". Even the 485 schematics include capacitors that aren't on the board, because they are in the board or are other parasitics :)

The 1502 has schematics and appears to be easily hacked to be a very useful RF connector TDR system.
And take it to hamfests to measure cable impedance and  length :) People like looking at the hypnotic twinkling trace.


Re: USB interface for the DPO / P7001

magnustoelle
 

Very impressive work, Holger - well done!

And I am now aware that the abbreviation DPO once stood for "Digital Processing Oscilloscope" in Tektronix speech - but my TDS5054 D igital P hosphor O scilloscope strongly disagrees with this :-) I was just loooking at it over my shoulder. Youngsters these days...

Cheers,

Magnus


Re: hp fails selftest #photo-notice

-
 

I doubt it, the HP self tests are pretty accurate in my experience. It
sounds like you got someone's parts mule. Their in an HP group on groups.io,
you might check with them.

On Tue, Nov 30, 2021 at 12:10 PM <quadzillatech@...> wrote:

Hi all,i hope its ok asking this here but here goes,i brought a hp 54503a
scope with dead nvram and a dead psu,i swapped the psu,now it powers up but
i get no trace,running self test brings up analog trigger fail,D/A
converter fail and A/D converter fail,my question is will the new nvram
chip result in a fix for these as ive not fitted it yet?,cheers in advance.






Re: 453 trigger issues

Michael W. Lynch
 

I would start with any Transistor or FET that is located in the trigger generator or sweep generator circuits (this is an extensive list, refer to your specific instrument schematic). Start with the components closest to the Tunnel Diodes and work out. Keep in mind that you have a "B" trigger circuit which is almost identical and uses many of the same components. You can substitute the "B" components into the "A" circuit until you get a working "A" Trigger. Process of elimination. I have only repaired one Model 453, but I use that same technique in the 465/475 whenever possible. This assumes that your major components are installed using sockets, which makes the swapping of components pretty simple. Soldered in components are more trouble, especially tunnel diodes.

--
Michael Lynch
Dardanelle, AR


Re: Repairing a 148-0034-00 Relay

 

Barry: The vintageTEK Museum has a stock of these relays and we can set up a special ebay sale for you.

--
Bob Haas


hp fails selftest #photo-notice

quadzillatech@...
 

Hi all,i hope its ok asking this here but here goes,i brought a hp 54503a scope with dead nvram and a dead psu,i swapped the psu,now it powers up but i get no trace,running self test brings up analog trigger fail,D/A converter fail and A/D converter fail,my question is will the new nvram chip result in a fix for these as ive not fitted it yet?,cheers in advance.


Re: 453 trigger issues

quadzillatech@...
 

any idea where to start checking then?,is there any common components can cause this?


Re: Sick TG501 Main 1Mhz ref not running.

Roy J. Tellason, Sr.
 

On Monday 29 November 2021 02:09:55 pm Harvey White wrote:
Would a standard 14 pin oscillator package work?  14 = vcc, 7 = gnd, 8 =
output, and no other pins are connected.  A 14 pin wirewrap socket with
pins removed (and an under socket jumper on the socket) would save
having to make a board.

I think that 1 Mhz is available.   you could do something similar with a
half-dip size and a few more jumpers.
I happen to have a whole pile of those, if anybody wants one. Feel free to contact me off-list...

Harvey


On 11/29/2021 1:54 PM, Zentronics42@... wrote:
Dealing with the gate inputs is easer said then done. On this one they tied the inputs together at the board level under the IC socket. I am starting to think getting this running will be a redesign of the clock. If I shoot out 1Mhz at pin 8 at a TTL level that should get the unit up and running again. So I might be in to making an adaptor board. That can use the socket to get 5 Vdc and output the 1Mhz. would most likely add to the stability as well with modern parts.

Zen

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of SCMenasian
Sent: Monday, November 29, 2021 12:29 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Sick TG501 Main 1Mhz ref not running.

I reasoned that this was a really poor way of building an oscillator and that, since TTL really isn't a good analog part, circuit operation could be dependent upon the individual part's characteristics. When I build oscillators from logic parts, I usually use Schmitt trigger parts; Tektronix didn't. 74HC132, 74hct132 or 74ls132 might work like a chram. Not wanting to reengineer the Tektronix circuit (and parts of it using the other 2 sections of the part), I took the path of least resistance and dug around in my junk bin of little used ancient parts and came up with another 74L00. The part I used was old - possibly older than Tektronix's part. The circuit sprang to life and that was good enough for me.

Crystal oscillators can be tricky since individual crystal characteristics can vary widely. You might be able to get it to run by playing with the capacitances; however, you might not be able to calibrate the frequency. Try lifting one leg of C105. A 74HC00 might be interesting to try. You can always try an LS00 or an HCT00. Note that you can reduce capacitive loading a bit by lifting one input of each gate and conecting it to +5V.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin


Re: 1502 TDR RECORD functions

John Parkins G8KVP
 

Hello Reg,

The 1502 is the first time 2 of my hobbies have come together, electronics and woodwork.

I can get rolls of paper that fit our credit card machine and with a fine blade they can be cut down to the right size on the bandsaw. Not that I use a lot of paper.

You mention the the illumination....... Something I've looked at and it all seemed a bit tight, so it never got done. Keep us informed on how you go about it, then I might have a go. I have to say it's the only downside to my machine.

Good luck.


Monday, November 29, 2021, 11:43:40 PM, you wrote:

RBvgi> All I have is the roll of paper that came with it. Since my post I've read the service manual and now understand the BNC output waveform. The narrow pulse is the sampling arm signal.

RBvgi> I just made a test with the chart recorder removed and I get a proper sweep. So it appears that the fault is in the Y-T chart recorder. The X-Y module attached to an Ardinuo/MSP430/STM32 to dump digits to a USB flash drive or SD card should be far more useful. I suspect a bspoke module for that would not be difficult to make.

RBvgi> I'm getting TDR responses with the 1502 from RF adapters and connectors which look to my eye to be quite comparable to the 11801/SD-24.

RBvgi> A working 11801 & SD-24 are difficult to find, 10x+ as much money and have *no* component schematics available.

RBvgi> The 1502 has schematics and appears to be easily hacked to be a very useful RF connector TDR system.

RBvgi> First up is LED graticule illumination.

RBvgi> Have Fun!
RBvgi> Reg


RBvgi>





--
Best regards,
John mailto:john@...


Re: 1502 TDR RECORD functions

Reginald Beardsley
 

All I have is the roll of paper that came with it. Since my post I've read the service manual and now understand the BNC output waveform. The narrow pulse is the sampling arm signal.

I just made a test with the chart recorder removed and I get a proper sweep. So it appears that the fault is in the Y-T chart recorder. The X-Y module attached to an Ardinuo/MSP430/STM32 to dump digits to a USB flash drive or SD card should be far more useful. I suspect a bspoke module for that would not be difficult to make.

I'm getting TDR responses with the 1502 from RF adapters and connectors which look to my eye to be quite comparable to the 11801/SD-24.

A working 11801 & SD-24 are difficult to find, 10x+ as much money and have *no* component schematics available.

The 1502 has schematics and appears to be easily hacked to be a very useful RF connector TDR system.

First up is LED graticule illumination.

Have Fun!
Reg


Re: OTish: ROM/RAM bank switching in the 2467 et al.

Mark Litwack
 

I did. It was a bit of tedious work to derive the equations from the gate programming. Afterwards I noticed the source where I got the JEDEC file had also posted the original equations from which the JEDEC file was generated (doh!).

Can't wait to see your GUI rendering of a 24xx front panel in MAME!

-mark

On Mon, Nov 29, 2021 at 01:06 PM, Siggi wrote:
...

Ah, that's cool. Did you reverse the full definition of the PAL?


Repairing a 148-0034-00 Relay

n4buq
 

After getting my 7B50 to produce a sweep, I noticed that the x10 magnification function isn't working and traced that to a bad K780 relay (P/N 148-0034-00). I noticed the TekWiki page for the various relays has links for some repair techniques and, since my relay's coil checked open circuit, I decided to open it up.

Fortunately, the wires are intact and it appears that because those were wrapped around the pins and, possibly, micro-welded(?), enough resistance has built up over time between the wire and pins such that there's not a good contact anymore. I can get the relay to function if I apply 15VDC directly to the wires at the pins but that doesn't work if I just touch the pins where they protrude through the bottom of the relay.

I'm wondering if I can wrap a fine copper wire around the existing wire/pin, secure it as snugly as I can get it, and then, perhaps a very light soldering job might be enough to repair this.

Anyone else tried to repair these and, if so, any good advice as to how to proceed? That's some extremely fine wire and, apparently, very easily broken so I'm wanting to tread as lightly as possible.

Thanks,
Barry - N4BUQ


Re: 1502 TDR RECORD functions

Tom Gardner
 

Do you have a good supply of paper for the chart recorder? If not, whether the chart recorder works is moot! Personally I think the X-Y output module is more useful: at least that can be fed to a digitising scope.

The service manual is worth reading. There are minor differences between the civilian and the military (Patriot battery) manuals, but nothing that I have found significant.

On 29/11/21 22:14, Reginald Beardsley via groups.io wrote:
My 1502 arrived today.

Unfortunately, I either have a fault in the RECORD function or completely misunderstand the manual.

The paper feeds if I push the switch up. However, I do not get an accurate trace and the CRT sweep stops until I power cycle it. If I push the switch down and hold it for a photo the sweep also stops. When I release the switch the paper feeds.

I did get a couple of sweeps in the form of a vertical line about 1 division high which tracked the shorted BNC connector waveform but nothing I would interpret as a "flood" of the CRT at the end of the sweep to make the graticule visible..

I fed the BNC signal to a 200 MHz DSO which revealed that the 1502 is producing alternating 4.8 and 11.1 microsecond pulses at ~25.5 kHz.

I'd planned to measure the rise time of the 1502 pulse on an 11801 but I can't see how I can do that if the pulse periods alternate.

Happily, it does appear to be able to resolve discontinuities in cable adapters and connectors in a manner comparable to and 11801 &SD-24.

Can anyone explain what is going on? I'm about to start reading the service manual.


1502 TDR RECORD functions

Reginald Beardsley
 

My 1502 arrived today.

Unfortunately, I either have a fault in the RECORD function or completely misunderstand the manual.

The paper feeds if I push the switch up. However, I do not get an accurate trace and the CRT sweep stops until I power cycle it. If I push the switch down and hold it for a photo the sweep also stops. When I release the switch the paper feeds.

I did get a couple of sweeps in the form of a vertical line about 1 division high which tracked the shorted BNC connector waveform but nothing I would interpret as a "flood" of the CRT at the end of the sweep to make the graticule visible..

I fed the BNC signal to a 200 MHz DSO which revealed that the 1502 is producing alternating 4.8 and 11.1 microsecond pulses at ~25.5 kHz.

I'd planned to measure the rise time of the 1502 pulse on an 11801 but I can't see how I can do that if the pulse periods alternate.

Happily, it does appear to be able to resolve discontinuities in cable adapters and connectors in a manner comparable to and 11801 &SD-24.

Can anyone explain what is going on? I'm about to start reading the service manual.

Reg

7481 - 7500 of 195575