Date   

Re: SC503 HV, long message

DaveC <davec2468@...>
 

Jerry,
I see sometimes you post to TekScopes, sometimes to TekScopes2, but rarely to both. And if only one, isn't TekScopes the better choice (larger membership)?

Is there method to your madness?

Dave
(posted this to both for you...)

-=-=-=-

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


SC503 HV, long message

Jerry Massengale <jmassen418@...>
 

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...

dnmeeks
 

You are headed in this direction, but I would suspect filter caps that have dropped in value. At light load, they would still work okay, but at heavier loads the ripple may get so large that regulators either drop out of regulation or otherwise pass the ripple along. I have had this same symptom with TM5xxx mainframes.

Having said that, I know nothing about the guts of a ‘7904 – whether the mainframe has rectifier / filter banks or not.

 

Good luck –

Dan

 

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Jim
Sent: Tuesday, December 22, 2009 5:09 AM
To: TekScopes@...
Subject: [TekScopes] Re: tek 7904A...

 

 

On Tuesday 22 December 2009 2:43:05 am d.seiter@... wrote:
> My 7904 (non-A) has no fan. The non-A's appear to have a picky power
> supply; my non-A is in tick mode(which has been resisting repair... and my
> -A is behaving nicely :-))

Does anyone have any advice on the "picky power supply" issue? My power supply
seems to be within spec. The plug-ins I'm using work fine on a 7514 and a
7704A. But on the 7904, if I try to use a full complement of four plug-ins
things usually get flaky (readout becomes garbled on some plug-ins, the 7D14
counter stops working, etc.). It works with three plug-ins, but does "tic" a
couple of times at start up.

I've been considering recapping the regulated supplies to see if that helps.

thanks,
Jim W4JBM


Re: What to do with legacy scopes etc

Tim Phillips <tim@...>
 

from Tim P (UK)
Hi, I am in London;
I would have the 1S1 and 1L10 off you if you want rid of them.
How much would you want ?
kindest regards
Tim P
 



Re: tek 7904A...

Jim
 

On Tuesday 22 December 2009 2:43:05 am d.seiter@... wrote:
My 7904 (non-A) has no fan. The non-A's appear to have a picky power
supply; my non-A is in tick mode(which has been resisting repair... and my
-A is behaving nicely :-))
Does anyone have any advice on the "picky power supply" issue? My power supply
seems to be within spec. The plug-ins I'm using work fine on a 7514 and a
7704A. But on the 7904, if I try to use a full complement of four plug-ins
things usually get flaky (readout becomes garbled on some plug-ins, the 7D14
counter stops working, etc.). It works with three plug-ins, but does "tic" a
couple of times at start up.

I've been considering recapping the regulated supplies to see if that helps.

thanks,
Jim W4JBM


Re: Scope Recommendations?

Mark Vaughan
 

Hi Dan

Does it have to be 300MHz

We just picked up an MS2024 for £3064, ex demo from Imex in the UK, it only has 8 preceding power ups on it, and is less than a month old, so as new and with full tek warranty and calibration sheets, and being ex demo they left a few extra’s in from the demo so we are a few hundred pounds up on what we expected.

 

Not 300MHz, but 200MHz four channel, long memory time, and MSO stands for mixed signal so it has an additional 16 channel logic analyser built in. You can also add modules that open up various serial and bus testing functions like I^2C, RS232, GPIB, OBD etc. And you can ask it to inspect your waveforms for anomalies which is very useful for those errors that occur when you looked away.

And it has a USB port, we also bought the network port mod that plugs in the back and allows it to sit on the network.

 

For higher frequencies I use a Lecroy 400MHz DSO which has GPIB, floppy drive and printer to get waveforms out. The lecroys are now available for a couple of hundred pounds, they are very nice scopes and while they might say 3dB is 400MHz it is actually just over 600Mhz on my 400MHz version and about 560MHz on my 300MHz lecroy. The only down side with the lecroy is that it isn’t as easy to drive as the tek’s are, all functions on teh tek are easy to find, but you can spend a lot of time wading the thick manual and fiddling to find some special functions on the lecroy’s.

Some also say the above tek I have is limited with its small screen, and yes it can get a bit busy with all inputs active including the logic, but it comes with a tek version of lab view so a lot can be pulled out to an adjacent PC, or you can simply plug a £100 flat PC screen in and hang it on the wall behind.

Tek do the MSO in higher frequency options but then the price goes up.

 

Regs Mark

 

Dr. Mark Vaughan Ph'D., B.Eng. M0VAU

Managing Director

Vaughan Industries Ltd., reg in UK no 2561068

Water Care Technology Ltd, reg in UK no 4129351

Addr Unit3, Sydney House, Blackwater, Truro, Cornwall, TR4 8HH UK.

Phone/Fax 44 (0) 1872 561288

RSGB DRM111 (Cornwall)

 

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Dan Meeks
Sent: 22 December 2009 04:00
To: TekScopes@...
Subject: [TekScopes] Scope Recommendations?

 

 

For work – we are looking for a relatively new (you know, a square CRT) scope, for as little money as possible.

Gotta have a USB port for saving waveforms, four channels, at least 300MHz, and digital.

 

Looks like this will be something like a used TDS3054C, but those are in the $6k range.

 

If anyone has a suggestion for something similar to the ‘3054C but less TD$, I would appreciate your opinion.

 

Dan

 


Re: What to do with legacy scopes etc

bobworsley92 <bobworsley92@...>
 

--- In TekScopes@..., "bobworsley92" <bobworsley92@...> wrote:

Hello group, been following the complaints about old scopes etc being disintegrated for their valves. Whilst I fully agree, on the other hand what do you do with them?

I have just re-inherited all the old test equipment I gave to my dad, he has recently died. I just don't have room for it, I could use it but it is not exactly portable like a 466 or similar. I also have a pile of 560 scope stuff of my own, and that now never gets used.

I did try selling some items on e(xpensive)bay but mostly no interest at all. On the second attept I sold the General Radio 1932A distortion analyser in almost new condition.

I was interested in the link to audiotubes web site, and the prices the valves get. As far as I can see that is the only way to get a reasonable sum for the scopes. At least part of them lives on.

Similarly the Sphere web site gives an idea on the prices for newer spares, prehaps all these 7704s I have are also for the chop.

Any suggestions other than giving it away? scrap prices are better than that.

Bob

Hello group, thanks for the replies. Firt thing, I am in the UK which limits posting stuff around.

At the moment I am looking at a 547, 585A (sure it is an A, can't see the front at the moment) and a 545A (I think, again). To come is a Solartron CD1212, Cossor 339 and anything else that comes out from under the bench, behind the bed, everywhere!

All of it did work, but Dad not used it really for a few years, was 97 when he died so a possible excuse there. I know the Solartron is missing its output valves, E55Ls, used in the Tek 560 amps which I have. There is also a 1S1 and 1L10, both were working but not used for years.

I also have a CRT (154-0448-00) and 11B2A (x2) and 10A2A for a 647. A 5T11A from a 661 and a HP 186A switching time tester, I am still waiting to get a 185A scope for it after 20 years.

The 7000 scopes and plug ins are items collected from government sales. I used to have a thriving electronics design business, legislated out of existance, then started selling on expensivebay. That is rubbish now, so have lots of stock. All needs testing, most never powered up, selling untested stuff is pointless, even if it is just the CRT or the custom chips. I have several 7704As, several R7704s and several storage types like 7313, 7813 and 7623 etc. Also 100 or so plug ins, mostly 7A18, 7B80, 7A26 type of thing, also some 7S11 and 7T11A sampling and one 7CT1N.

I am trying to sort my web site out to list all this, but not my favourite job.

Bob


Re: tek 7904A...

David C. Partridge <david.partridge@...>
 

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@... [mailto:TekScopes@...] On Behalf
Of Greg Werstiuk
Sent: 22 December 2009 07:45
To: TekScopes@...
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).


NEED Tek 496 attenuator

Jose V. Gavila <eb5agv@...>
 

Hello!

I am in need of a 496 attenuator in order to finish my repair of the unit.
Please, could somebody help me?. I could also use the attenuator pads only.

Thanks and best regards,

JOSE

--
73 EB5AGV - JOSE V. GAVILA - IM99sm La Canyada - Valencia(SPAIN)
Vintage Radio and Test Equipment........... http://jvgavila.com
RadioRepair BLOG............... http://radiorepair.blogspot.com


Re: tek 7904A...

Greg Werstiuk
 

Brain fade.  Was thinking the 7904 had a separate power supply fan.  You are correct the 7904A adds an air stirrer on the right hand side (when faced from the front).

 

-

Greg

 


From: TekScopes@... [mailto:TekScopes@...] On Behalf Of victor.silva
Sent: Monday, December 21, 2009 11:37 PM
To: TekScopes@...
Subject: [TekScopes] Re: tek 7904A...

 

 

I'm no expert on the 7904, but I believe it's the other way around. The later model 7904A is the one with the fan.

I assume it was added to improve instrument cooling.

--Victor

--- In TekScopes@yahoogroups.com, "Greg Werstiuk" ...> wrote:
>
> Tek was in the habit improving their equipment. The catalog pages for the
> 7904 and 7904A described the specification differences. I don't have them
> at my fingertips but the "A" has greater bandwidth and faster risetimes.
>
>
>
> As I recall, the 7904 had a fan which is eliminated in the "A" which reduced
> noise and eliminated a point of failure. (Completely different power
> supplies between the two.)
>
>
>
> -
>
> Greg
>
>
>
>
>
> _____
>
> From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com] On Behalf
> Of Goran
> Sent: Monday, December 21, 2009 11:17 AM
> To: TekScopes@yahoogroups.com
> Subject: [TekScopes] tek 7904A...
>
>
>
>
>
> 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
>


Re: tek 7904A...

d.seiter@...
 

My 7904 (non-A) has no fan.  The non-A's appear to have a picky power supply; my non-A is in tick mode(which has been resisting repair... and my -A is behaving nicely  :-))

Dave

----- Original Message -----
From: "Greg Werstiuk"
To: TekScopes@...
Sent: Monday, December 21, 2009 11:56:01 PM GMT -07:00 US/Canada Mountain
Subject: RE: [TekScopes] tek 7904A...

 

Tek was in the habit improving their equipment.  The catalog pages for the 7904 and 7904A described the specification differences.  I don’t have them at my fingertips but the “A” has greater bandwidth and faster risetimes.

 

As I recall, the 7904 had a fan which is eliminated in the “A” which reduced noise and eliminated a point of failure.  (Completely different power supplies between the two.)

 

-

Greg

 

 


From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Goran
Sent: Monday, December 21, 2009 11:17 AM
To: TekScopes@...
Subject: [TekScopes] tek 7904A...

 

 

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


Re: tek 7904A...

victor.silva
 

I'm no expert on the 7904, but I believe it's the other way around. The later model 7904A is the one with the fan.

I assume it was added to improve instrument cooling.

--Victor

--- In TekScopes@..., "Greg Werstiuk" <greg_werstiuk@...> wrote:

Tek was in the habit improving their equipment. The catalog pages for the
7904 and 7904A described the specification differences. I don't have them
at my fingertips but the "A" has greater bandwidth and faster risetimes.



As I recall, the 7904 had a fan which is eliminated in the "A" which reduced
noise and eliminated a point of failure. (Completely different power
supplies between the two.)



-

Greg





_____

From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of Goran
Sent: Monday, December 21, 2009 11:17 AM
To: TekScopes@...
Subject: [TekScopes] tek 7904A...





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


Re: Scope Recommendations?

stefan_trethan
 

You can go a lot cheaper if you give up the USB port. It came relatively late in scopes and you will be limited to very new models.
It is convenient, but for the price difference you can likely stick a PC or laptop there to get your waveforms out.

Also look at LeCroy, Agilent, Yokogawa as well as Tektronix.

ST


On Tue, Dec 22, 2009 at 5:00 AM, Dan Meeks <dan-meeks@...> wrote:


For work – we are looking for a relatively new (you know, a square CRT) scope, for as little money as possible.

Gotta have a USB port for saving waveforms, four channels, at least 300MHz, and digital.

 

Looks like this will be something like a used TDS3054C, but those are in the $6k range.

 

If anyone has a suggestion for something similar to the ‘3054C but less TD$, I would appreciate your opinion.

 

Dan

 



Re: tek 7904A...

Greg Werstiuk
 

Tek was in the habit improving their equipment.  The catalog pages for the 7904 and 7904A described the specification differences.  I don’t have them at my fingertips but the “A” has greater bandwidth and faster risetimes.

 

As I recall, the 7904 had a fan which is eliminated in the “A” which reduced noise and eliminated a point of failure.  (Completely different power supplies between the two.)

 

-

Greg

 

 


From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Goran
Sent: Monday, December 21, 2009 11:17 AM
To: TekScopes@...
Subject: [TekScopes] tek 7904A...

 

 

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


Re: tek 7904A...

 

Some reasons for the redesign:

1) Better performance (higher bandwidth) because of improved ICs.
2) Simplified circuitry made it easier and more cost effective to build.
3) Greater profit margins.

Dennis

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of Goran
Sent: Monday, December 21, 2009 11:17 AM
To: TekScopes@...
Subject: [TekScopes] tek 7904A...

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


Scope Recommendations?

dnmeeks
 

For work – we are looking for a relatively new (you know, a square CRT) scope, for as little money as possible.

Gotta have a USB port for saving waveforms, four channels, at least 300MHz, and digital.

 

Looks like this will be something like a used TDS3054C, but those are in the $6k range.

 

If anyone has a suggestion for something similar to the ‘3054C but less TD$, I would appreciate your opinion.

 

Dan

 


Re: 2430A error 4000

victor.silva
 

You should also ask the serial number. I don't know what price you're getting but IMO serial numbers below B012xxx are good for parts only.

There are just to many of these at rock bottom prices to waste your time on s/n ranges that are full of problems and old firmware.

I would recommend getting serial no. B030xxx or higher. (B042xxx is close to the latest serial number.)

You want to see versions V2.31 / V2.5 on the Extended Diagnostics page.

--Victor


2 TEKTRONIX catalogs for sale

walt_b5
 

1973 and 1975 catalogs for sale

over 300 pages each .

$ 8 plus shipping

i do paypal

for pix go to www.waltbelsito.4t.com page 8 fotos

thanks WALT


tek 7904A...

Goran <goran.krusell@...>
 

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


Re: What to do with legacy scopes etc

jvanderwall1941
 

You have indeed come to the right place. I, for example, would like to hear more of the 7704s! Any sampling plug-ins? SMA cables? Tell us more.

Regards,

Jonathan

--- In TekScopes@..., Jerry Massengale <jmassen418@...> wrote:

Bob,
 
You have come to the right place. This group of crazies will buy any damn thing. Must be from Louisiana. I suggest you generate a list of what you have and ask the group for offers for the value plus shipping. I would be very interested in Tektronix SC50X scopes as parts units and working units. Please feel free to contact me off list. And give your location. I need SC50x parts.
 
Jerry

--- On Mon, 12/21/09, bobworsley92 <bobworsley92@...> wrote:


From: bobworsley92 <bobworsley92@...>
Subject: [TekScopes] What to do with legacy scopes etc
To: TekScopes@...
Date: Monday, December 21, 2009, 11:56 AM


 



Hello group, been following the complaints about old scopes etc being disintegrated for their valves. Whilst I fully agree, on the other hand what do you do with them?

I have just re-inherited all the old test equipment I gave to my dad, he has recently died. I just don't have room for it, I could use it but it is not exactly portable like a 466 or similar. I also have a pile of 560 scope stuff of my own, and that now never gets used.

I did try selling some items on e(xpensive)bay but mostly no interest at all. On the second attept I sold the General Radio 1932A distortion analyser in almost new condition.

I was interested in the link to audiotubes web site, and the prices the valves get. As far as I can see that is the only way to get a reasonable sum for the scopes. At least part of them lives on.

Similarly the Sphere web site gives an idea on the prices for newer spares, prehaps all these 7704s I have are also for the chop.

Any suggestions other than giving it away? scrap prices are better than that.

Bob

150941 - 150960 of 194745