Date   

TDS520B - Part Locations

cmbath
 

On the TDS520B I am trying to repair I have stupidly removed either R25 or R26 (a 0ohm link) and have not taken note of which one it was (I thought I had the component service manual but this is only for serial numbers 3000 and above, mine is below this).

Can anyone who has an early serial number TDS520B tell me which location the 0ohm link is installed in? I would appear that this resistor selects between two outputs from a counter (74HCT393 (U1173) pins 5&6). I am guessing a selection between two different frequencies F and 2F.

Thanks,

Chris


Re: 2400 series PSU question

Paul Read <paulr@...>
 

Hi Victor,

 

Many thanks for the pointer, yes it was  a typo, should have been a 2445A, and yes I have a 2245A as well. Hopefully I will have a go at it over the Christmas break. I have the service manual from Ebaman and that does have the trouble shooting flowchart...it will live again. I do have another 2445 that may be for disposal next year if there is any interest, It is basically working, but by the look of the display, it could use the power supply caps being changed. Local pickup southern England preferred.

 

Cheers and Happy Christmas to All

Paul


Re: tek 7904A...

Greg Werstiuk
 

Interesting.  My 7904A has no fan at the rear.  The rear panel is solid except for a massive finned heatsink in the lower left corner.  The only fan is the one I described.

 

-

Greg

 


From: TekScopes@... [mailto:TekScopes@...] On Behalf Of David C. Partridge
Sent: Tuesday, December 22, 2009 12:24 AM
To: TekScopes@...
Subject: RE: [TekScopes] Re: tek 7904A...

 

 

The later 7904As had a REALLY NOISY PC type fan at the rear. Almost as
raucous as the 2430A (which is deafening).

The early 7904As with the same fan type as the 7834 etc. were nice and
quiet.

If ever there were a candidate for replacement with a modern quiet fan ...

Dave

-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com] On Behalf
Of Greg Werstiuk
Sent: 22 December 2009 07:45
To: TekScopes@yahoogroups.com
Subject: RE: [TekScopes] Re: tek 7904A...

You are correct the 7904A adds an air stirrer on the right hand side (when
faced from the front).


Accessories/spares for Sub-miniature probes (e.g. P6133, P6136 etc.)

 

www.testpath.com has a wide selection of Tek probe pieces/parts.

HankC, Boston


Re: Russian Tunnel Diodes ??

tmillermdems <tmiller@...>
 

Got mine today, Maryland. They physicly look nice but I have not had a chance to do anything with them yet.


Tom

--- In TekScopes@..., "Mike" <mikez11@...> wrote:

ditto for Boston, 3 weeks & counting


Re: 2400 series PSU question

victor.silva
 

I assume your midstream change from 2445A to 2245A is a mistake and you really have a 2445A.

A good 2445A LVPS should be able to power a good 2465B. There are some slight changes to some of the regulators on the 2465B. The 2445A PS will work but the resulting scope probably will not meet some noise spec.

Maybe there is something else wrong with your 2465B. Why not put the 2465B supply into the 2445A and see if it works? If it doesn't, remember you can still have two problems a bad 2465B supply and a short somewhere in your 2465B.

--Victor

--- In TekScopes@..., "paulxbe" <paulr@...> wrote:

Hi Guys,

I am having some fun with a 2465B that does not power up. I swapped the PSU out of a working 2445A and that would not power up either. I did find that there were some option power connectors missing on the 2245A PSU, but I was able to arrange alternative connections for that. The Question is, have I made a bold assumption about the interchangability of PSUs. I am considering putting the 2465B PSU into the 2245A, but I thought I would ask the question before I smoke the 2245A !
BTW I am getting a lot of practice removing the PSUs ! ;o), and it really is a 10 minute job.

Cheers

Paul


Bad link in the links section

tmillermdems <tmiller@...>
 

Is there a new link for this site and are the 400 series feet still available?



Cabinet Feet for 400 Series Portables
Reproduction feet are almost identical to original. Satisfaction guaranteed.
http://www.members.aol.com/hedgewarden/400feet/


Re: 2445 vs 2446

Robert Simpson
 

Tom,
My typo. yes 2445 vs 2246,
thanks, that answers my question.
Bob

--- On Tue, 12/22/09, tom jobe <tomjobe@...> wrote:


From: tom jobe <tomjobe@...>
Subject: Re: [TekScopes] 2445 vs 2446
To: TekScopes@...
Date: Tuesday, December 22, 2009, 3:45 PM


 



Hi Bob,
The 2446 must be a very rare model. I have never heard of it on this forum,
or seen one for sale.
The various 2246's are very common models of Tektronix oscilloscopes,
perhaps that is what you mean?
There is not much in common between the 224x and the 244x scopes.
tom jobe...

----- Original Message -----
From: "Robert" <go_boating_fast@ yahoo.com>
To: <TekScopes@yahoogrou ps.com>
Sent: Tuesday, December 22, 2009 3:31 PM
Subject: [TekScopes] 2445 vs 2446

Are there any similar parts in a 2445 compared to a 2446? I have a 2446 to
eventually repair and wondered if a
junk 2445 would be any help.
Bob



------------ --------- --------- ------

Yahoo! Groups Links



Re: 2445 vs 2446

tom jobe <tomjobe@...>
 

Hi Bob,
The 2446 must be a very rare model. I have never heard of it on this forum,
or seen one for sale.
The various 2246's are very common models of Tektronix oscilloscopes,
perhaps that is what you mean?
There is not much in common between the 224x and the 244x scopes.
tom jobe...

----- Original Message -----
From: "Robert" <go_boating_fast@...>
To: <TekScopes@...>
Sent: Tuesday, December 22, 2009 3:31 PM
Subject: [TekScopes] 2445 vs 2446


Are there any similar parts in a 2445 compared to a 2446? I have a 2446 to
eventually repair and wondered if a junk 2445 would be any help.
Bob



------------------------------------

Yahoo! Groups Links



2445 vs 2446

Robert Simpson
 

Are there any similar parts in a 2445 compared to a 2446? I have a 2446 to eventually repair and wondered if a junk 2445 would be any help.
Bob


re ; tektronics catalogs 1973 & 1975 sold !

walt_b5
 

thanks WALT


TDS544 CRT Free to a good home (154-0968-24)

dnmeeks
 

This came out of a TDS544, which had the LCD Shutter broken. The tube worked fine.

I have removed the LCD shutter, so this is just the CRT with the Yoke intact.

This same tube is probably used in a lot of the TDS5xx, 6xx, and 7xx scopes?

 

Tek PN 154-0968-24

 

Free for actual shipping.

 

Email off-list if you have questions or want a picture.

 

Thanks,

Dan


549 - cure for HV transformer disease

Marc van Endert
 

Hello,

if your 549 has the problem well known as "HV transformer disease" (HV supply breakdown after about 20 minutes due to aged epoxy potting) - there is a repair method I successfully tried today:

The HV transformer of the 549 can easily be replaced with the HV transformer of a 564 (not 564B!). Because the 564 transformer is bee wax insulated instead of the epoxy potting, it is not susceptible for the HV breakdown problem. Old 564's are easily obtaineable and very cheap - and it is much better to scrap a 564 to save a 549 instead of throwing away the valuable 549.

The transformer itself can be replaced 1:1 according to the schematic diagrams. The wire loops serving as secondary windings for the rectifier tubes of the 564 are removed, they are no longer needed. The transformers are identical in size; no drilling or other mechanical changes are needed.

Then proceed as follows:

1. Replace R807 (39K) with a 47K resistor.
2. Remove the wire bridge between C842/D836 and R834 and replace it with a 1.5M resistor.
3. Remove the green coded HV wire (leading to R837) from C842/D836 and reconnect it to R834 (to the other side of the 1.5M resistor).
4. Adjust the HV supply to -3700V according to the manual.
5. Adjust the intensity range according to the manual.

After this modification, my 549 performs as new: All HV voltages are as they should be; focus and astigmatism pots are centered when correctly adjusted as well as the intensity range potentiometer. And no more HV breakdown, even after hours of operation... :-)

Regards

Marc


Re: tek 7904A...

ditter2
 

--- In TekScopes@..., "Craig Sawyers" <c.sawyers@...> wrote:

There are major internal changes between the non-A and the -A versions. Tek
moved across to using Hypcon hybrids from the earlier generation hermetic
canned types. In addition they moved the HT from being inside the box to
the more regular 4-bay location on the main chassis. And the mode select
buttons were no longer illuminated.

Essentially there is much in common, electrically and visually (including
Hypcon hybrids) with the 7104. Although the nominal bandwidth of the -A is
the same as the earlier 7904 scope, in practice it comfortably exceeds it by
a big margin. There is a view that Tek knew this, but did not mention it in
the specifications since (MCP based CRT notwithstanding) it was sufficiently
close to the 7104 in bandwith terms to be competitive.

Craig
I was not aware of the similarities with the 7104. I know a similar thing happened when the 7704 changed to the 'A' model. The CRT was the same one used in the 7904, and I think the vertical amp hybrid is also the same (might be wrong on that), although the channel switch is not the same. The net result is that the 7704A has considerably more real BW and faster rise time than the original non 'A' model. Of course a big change in the A model was the ability to separate the base unit from the display. By adding a crude digitizer module in between, Tek had its first DSO. Not very user friendly, but none of the early DSOs were, including the 2430/2440

- Steve


Re: tek 7904A...

 

--- In TekScopes@..., "Goran" <goran.krusell@...> wrote:

Hello,

the model 7904A is a redesigned and improved version of the 7904. Does anyone know why this was done? Cost, reliability or production margins?
Is there any description available except for the service manual?

Regards
Göran
-----------------------
Here's what the 7904A MSR dated May 83 said:

//I. Product Description and Specifications

The 7904A will replace the 7904. All spec's will remain the same. The 7904A will have the following improvements.

1. Split casting used in 7800's, 7104 for easier servicing.

2. Power supplies and other parts will be common to existing 7800's, 7104 mainframes.

3. Improvement in reliability and performance made in the 7800's, 7104 will be incorporated in the 7904A.

4. Front and rear panel controls will be the same as the 7104.//

/Håkan


2400 series PSU question

paulxbe <paulr@...>
 

Hi Guys,

I am having some fun with a 2465B that does not power up. I swapped the PSU out of a working 2445A and that would not power up either. I did find that there were some option power connectors missing on the 2245A PSU, but I was able to arrange alternative connections for that. The Question is, have I made a bold assumption about the interchangability of PSUs. I am considering putting the 2465B PSU into the 2245A, but I thought I would ask the question before I smoke the 2245A !
BTW I am getting a lot of practice removing the PSUs ! ;o), and it really is a 10 minute job.

Cheers

Paul


Re: tek 7904A...

Craig Sawyers <c.sawyers@...>
 

There is one thing I do know. At the time the 7904 went to
the "A" model, Tek had a policy that the model suffix would
not increment unless there was a significant specification or
feature change for the customer. Improved reliability,
manufacturing cost savings, fixing the annoying power supply
start up, etc, would not merit the "A" model for the 7904.
There are major internal changes between the non-A and the -A versions. Tek
moved across to using Hypcon hybrids from the earlier generation hermetic
canned types. In addition they moved the HT from being inside the box to
the more regular 4-bay location on the main chassis. And the mode select
buttons were no longer illuminated.

Essentially there is much in common, electrically and visually (including
Hypcon hybrids) with the 7104. Although the nominal bandwidth of the -A is
the same as the earlier 7904 scope, in practice it comfortably exceeds it by
a big margin. There is a view that Tek knew this, but did not mention it in
the specifications since (MCP based CRT notwithstanding) it was sufficiently
close to the 7104 in bandwith terms to be competitive.

Craig


Re: SC503 HV, long message

Tom Miller <tmiller@...>
 

It looks like the measurements you are seeing are good. Without the 33 volts, the inverter will certainly not work.
 
The negative to counteract the two plus supplies (and the HV adj from <10>) comes from the neg 1900 HV through the 25 Meg resistor.
 
I would check the two inverter transistors and all the transformer windings to ground for a shorted condition. The blown track means someone tried a larger fuse or jumper to force a condition.
 
Check all the output caps and diodes.
 
 
 
Good luck,
Tom
 
 

----- Original Message -----
Sent: Tuesday, December 22, 2009 10:32 AM
Subject: [TekScopes] SC503 HV, long message

 

Hi,
 
An SC503 I recently bought did not power up and the +33V fuse was blown. After replacing 2 transistors and a shorted tantalum in the +5V regulator, the LVPS is good and powers up. I replaced Q7031 and Q7032 in the HV oscillator circuit and cleared a short on the +33V load. I installed a 1amp fast blow fuse and found that with the power switch in the STBY position I had no voltage on the collector of Q7031. I quickly found that continuity was intermittent from +33V to Q7031 collector, I found a damaged pad where T7041 is mounted, repaired with a solid jumper and found good voltage at Q7031-C. Turned power switch to CH1 and found 1amp fuse blown. No voltage at Q7031-C, 0.65V at Q7031-B, U6021-6 at -10.5V, .4885V at U6021-2 and .0003V at U6021-3. The negative output turns Q6031 on, causing the .65V to turn on Q7031. I grounded U6021-2 to see if pin 6 would go positive. I found that grounding U6021-2 does not cause U6021-6 to change. Is grounding pin 2 enough? The book says pin 2 should be near zero during normal operation. This causes me to wonder where the negative comes from to counter the +12V and +110V. I checked the HV ADJ line and found it zero. What should the HV ADJ line normally be?
 
jerry


Re: tek 7904A...

ditter2
 

--- In TekScopes@..., "Goran" <goran.krusell@...> wrote:

Hello,

the model 7904A is a redesigned and improved version of the 7904. Does anyone know why this was done? Cost, reliability or production margins?
Is there any description available except for the service manual?

Regards
Göran
I don't have the specs in front of me to compare, but with some effort I could find an old catalog with the non"A" model to see what changed.

There is one thing I do know. At the time the 7904 went to the "A" model, Tek had a policy that the model suffix would not increment unless there was a significant specification or feature change for the customer. Improved reliability, manufacturing cost savings, fixing the annoying power supply start up, etc, would not merit the "A" model for the 7904.

Consider the 7A13 upgrade to the electronic DMM for displaying the comparison voltage. The old "odometer" version was prone to mechanical alignment problems that caused it to bind up and ultimately strip its plastic gears. I don't think I have ever seen an old one that was actually well used that did not suffer this problem. The DMM totally eliminated this reliability problem, and changed a significant portion of the circuitry and mechanical parts list. Yet the model remained a 7A13.

This was not always the case. The 310A is essentially the same circuitry as the 310, with no change in performances or features. It returned to ceramic strips. The original 310 tried out this new technology of "etched circuit boards" but before plated through holes were invented. Using rivets for feed throughs proved intermittent, resulting in a reliability nightmare. Sometime in either the late 1960's or early 1970s Tek adopted the policy to denote major internal changes with no performance enhancement using large serial number breaks rather than model number increments.

- Steve


Fluke (Montronics) Model 207-5 WWVB Receiver/Comparator

salcornacchia1 <salccor@...>
 

Hello Group Members, I have a Fluke (Montronics) Model 207-5 WWVB Receiver/Comparator with various problems to many to mention on this list, if someone has any experience with this model and would like to help out please contact me off list salccor@... Thank you for helping out.
Sal C. Cornacchia
Electronic RF Microwave Engineer (Ret.)

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