Date   

Re: DC503 Not Working

Stephen
 

On Mon, Jul 27, 2020 at 01:18 AM, <scm@...> wrote:


Check to see if the multivibrator capacitors are bad (possibly leaky?). Also,
check for signal on pin 10.
C330 and C335 read the right value within specs. they are not shorted And apparently not leaky. I read zero resistance across them.

Will check signal on pin 10 of U330 and report back soon.


Re: 11801 diagnostic help

Perdad
 

Hi All !

Thank you for good feedback ! I had to scroll the waveform all the way to the first rising edge to get a clean waveform.
The Calibrator is a 100 kHz square wave so the second edge is already 10 us away so to say. That second edge and the ones that
follow all have this very noisy behaviour.

See pictures https://www.dropbox.com/sh/h3so1ua0r9f7it6/AAAEGeur_rVDtRFczNsgVTXca?dl=0

My CSA seems to be out of specification with a 280 ps risetime (20-80%), should be less than 250 ps.
Not really sure if this makes a big difference or not when calibrating a head. Please enligthen me if you like.

Reg, I always use "initialize". This is the first thing I do. After that I 'select channel' and press 'Autoset'. This gives me 5 periods of the 100 kHz
Calibrator output. After that I have to dial in on the on the first edge of the waveform, which is quite tedious :o)
You must have a nose for business with the bargains you have made or do you have your own private eBay market place ;)
Thank you for the link with your endeavours into TDR-land !

"lccavalheiro", yes, I saw your post. Good that you found my question here.

)) Regards, Per


Re: TM506

Stephen
 

On Mon, Jul 27, 2020 at 05:46 AM, Stephen wrote:


Check and David,

You’re both very nice, And I really appreciate it. But I’ve already put
more money in trying to fix this device, than it’s actually worth.
So either I succeed in repairing it with advice from people, or I’ll scrap
it. But but I’m not going to send it anywhere.
Type sorry. Read “Chuck” of course.


Re: TM506

Stephen
 

Check and David,

You’re both very nice, And I really appreciate it. But I’ve already put more money in trying to fix this device, than it’s actually worth.
So either I succeed in repairing it with advice from people, or I’ll scrap it. But but I’m not going to send it anywhere.


Re: TM506

 

Yes there a quite a few here in UK ... myself included

D.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Chuck Harris
Sent: 27 July 2020 17:08
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM506

I am told that there are a lot of members of this group
in Europe...

-Chuck Harris

Stephen wrote:
On Mon, Jul 27, 2020 at 04:56 AM, Chuck Harris wrote:


Ask for help. There are many of us here that would do
it for you... some for a few bucks, some for free.

-Chuck Harris
That’s very nice. And I’m sure many would gladly help.
Unfortunately, being in Europe, it’s not worth it sending it back and forth.
For the price of shipping, i could probably buy 2 of these. And I already spent quite
a bit on parts. Learning expenses it will go to.




Re: TM506

Chuck Harris
 

I am told that there are a lot of members of this group
in Europe...

-Chuck Harris

Stephen wrote:

On Mon, Jul 27, 2020 at 04:56 AM, Chuck Harris wrote:


Ask for help. There are many of us here that would do
it for you... some for a few bucks, some for free.

-Chuck Harris
That’s very nice. And I’m sure many would gladly help.
Unfortunately, being in Europe, it’s not worth it sending it back and forth.
For the price of shipping, i could probably buy 2 of these. And I already spent quite
a bit on parts. Learning expenses it will go to.




Re: TM506

Stephen
 

On Mon, Jul 27, 2020 at 04:56 AM, Chuck Harris wrote:


Ask for help. There are many of us here that would do
it for you... some for a few bucks, some for free.

-Chuck Harris
That’s very nice. And I’m sure many would gladly help.
Unfortunately, being in Europe, it’s not worth it sending it back and forth.
For the price of shipping, i could probably buy 2 of these. And I already spent quite
a bit on parts. Learning expenses it will go to.


Re: TM506

Chuck Harris
 

Ask for help. There are many of us here that would do
it for you... some for a few bucks, some for free.

-Chuck Harris

Stephen wrote:

On Sun, Jul 26, 2020 at 11:54 PM, Glenn Little wrote:

Interleaved

Warm up the vacuum desoldering iron.
If they are TI low profile sockets, until you replace all of them, you
will have issues.
And this is precisely why I’m not going to do it.

I can remove 43 sockets in less that 30 minutes, if the pins are not
crimped down and RFM was followed.
I can’t.




Re: Need help with 11801 delay jitter #photo-notice

Chuck Harris
 

The 11801C specifically calls on the calibrator to be 250ps risetime.

I'm sure that I got the information about the 25ps risetime calibrator
being an option from one of you on this group. Maybe Leo?

It was during a show and tell session, and someone pointed out that
the calibrators with gold APC3.5 connectors were fast TDR compliant
calibrators, and were optional.

The 11801C manual I have doesn't discuss that option, though.

-Chuck Harris

John Gord via groups.io wrote:

Chuck,
The 11801 Service Reference Manual has a test (page 2-44) calling for the 11801 to measure its own calibrator at 35ps or better for the sampler/calibrator combination.
No mention is made of any optional calibrator versions. I don't know about the options that might have been available for the A/B/C versions.
--John Gord


On Sun, Jul 26, 2020 at 05:58 PM, Chuck Harris wrote:


I'm pretty sure that the 20ps calibrator is an option available
on the entire series, and standard to none.

-Chuck Harris



Re: TM506

Stephen
 

On Mon, Jul 27, 2020 at 01:17 AM, John Griessen wrote:

Not annoyed. It helps create searchable threads when you put a relevant
subject line.
You are perfectly right. My apologies.


Re: DC503 Not Working

Stephen
 

On Mon, Jul 27, 2020 at 01:18 AM, <scm@...> wrote:


Check to see if the multivibrator capacitors are bad (possibly leaky?). Also,
check for signal on pin 10.
Will certainly do when I get back home.
Will report back.

Thank you gain.


Re: DC503 Not Working

Stephen
 

On Mon, Jul 27, 2020 at 02:16 AM, Roger Evans wrote:


Stephen,

So is either C548 or C549 showing high leakage (low resistance) with one leg
unsoldered?

Roger
I haven’t had the opportunity to check yet. I’m not home at the moment. Will report back when I do, Roger.

Thank you for your help.


Re: DC503 Not Working

Roger Evans
 

Stephen,

So is either C548 or C549 showing high leakage (low resistance) with one leg unsoldered?

Roger


Re: DC503 Not Working

SCMenasian
 

Check to see if the multivibrator capacitors are bad (possibly leaky?). Also, check for signal on pin 10.


Re: TM506

John Griessen
 

On 7/27/20 3:58 AM, Stephen wrote:
Some people are apparently annoyed to see this posted in my original topic about the TM506 and the modules I got with it.
Not annoyed. It helps create searchable threads when you put a relevant subject line.


Re: DC503 Not Working

Stephen
 

On Mon, Jul 27, 2020 at 12:22 AM, Roger Evans wrote:


Stephen,

If you have almost zero volts across C548 then the -22V regulated supply is at
almost zero volts. The most likely culprits are C548 itself and C549 which
sits after L549 to provide an additional stage of smoothing. You should lift
one pin of each of C548 and C549 to check that they are OK. You might as well
check L549 for continuity while the other parts are disconnected.

Roger
L549 is fine. When I checked the voltage across C548, that top board was removed. Hence L549 wasn’t connected.

Thank you for pointing that out Roger


Re: DC503 Not Working

Stephen
 

On Mon, Jul 27, 2020 at 12:05 AM, <scm@...> wrote:


U330B and U330C are the scan clock multivibrator.
This is one single chip, right? U330. Believe it or not, I have Clean the socket, and replaced that one too.
I have actually replaced 98% of all the chips on that board. This is insane!

If these stop or stop
intermittantly, the symptoms you describe will appear. U332B
Also replaced and socket cleaned.

is part of the counter which,
along with U333 (which you have already changed) controls the
display multiplexer. There is a scan clock disable line shown in the block
diagram. It may be stuck. Look for bad connections as well as bad ICs
associated with these circuits. Try adding an external test point by soldering
a 1 foot wire to U330, pin 10 as a start to bring the scan clock signal out so
you can see it. Move it around, depending on what you see.
I'm looking at the right manual now.
Thank you

One funny thing though, whether a digit is there, or if nothing appears on the display at start up, when I turn the 506 off, digits appear randomly where none where before, before fading off for lack of power.


Re: DC503 Not Working

Roger Evans
 

Stephen,

If you have almost zero volts across C548 then the -22V regulated supply is at almost zero volts. The most likely culprits are C548 itself and C549 which sits after L549 to provide an additional stage of smoothing. You should lift one pin of each of C548 and C549 to check that they are OK. You might as well check L549 for continuity while the other parts are disconnected.

Roger


Re: TM506

Stephen
 

On Sun, Jul 26, 2020 at 11:54 PM, Glenn Little wrote:

Interleaved

Warm up the vacuum desoldering iron.
If they are TI low profile sockets, until you replace all of them, you
will have issues.
And this is precisely why I’m not going to do it.

I can remove 43 sockets in less that 30 minutes, if the pins are not
crimped down and RFM was followed.
I can’t.


Re: DC503 Not Working

SCMenasian
 

U330B and U330C are the scan clock multivibrator. If these stop or stop intermittantly, the symptoms you describe will appear. U332B is part of the counter which, along with U333 (which you have already changed) controls the display multiplexer. There is a scan clock disable line shown in the block diagram. It may be stuck. Look for bad connections as well as bad ICs associated with these circuits. Try adding an external test point by soldering a 1 foot wire to U330, pin 10 as a start to bring the scan clock signal out so you can see it. Move it around, depending on what you see. I'm looking at the right manual now.