Date   

Re: Tek 2235A re-cap

 

On Tue, 02 Apr 2013 15:02:28 -0000, "vdonisa" <vdonisa@yahoo.com>
wrote:

It's me again... after doing a little bit more research (looking at other 2200 series oscilloscopes with fans) I came to the following conclusions:

- the case is designed so that the fan should be installed as an "exhaust" (outblow) fan; the air flow would be from the intake located on the left side near the middle of the CRT's length and gradually heat up until it flows along the hottest heat sink (the one between the 3 damaged caps) then gets exhausted through the rear vent

- installed like this it will also help with the power resistor located on the mainboard, under the CRT, near the intake - i saw some slight coloration of the PCB around it so I believe it heats up handsomely
Those resistors are the load resistors for the output of the CRT
vertical amplifier and they do run hot. They are a common failure
point in the 22xx series oscilloscopes that lack fans. I replaced a
set not too long ago and someone on the list here has also done so
recently.

Some of the 22xx series use 3 resistors in series on each side instead
of 2 which distributes the heat load somewhat.


Re: Tektronix 2230 power supply, which diode type is CR907?

Gregor
 

Thanks for the quick answer!

I am going to replace it with a HFA08TB60 because I can order it easily and it has much higher ratings (600V 8A 18ns).

--- In TekScopes@yahoogroups.com, "Tom Jobe" <tomjobe@...> wrote:

It is interesting that CR907 is listed as part number 152-0808-00 but with different amp ratings in different manuals that I have.
For example CR907 / 152-0808-00 is listed as a 1.0 amp part in the 2215A manual, and it is listed as a 1.5 amp part in the 2230 manual.
In testing, when you run the inverter of a 22xx scope from an external 43 volt power source, it does take more amperage to run the scope on the more complicated 22xx models.
Since it may be easy to get an ultra fast diode with a greater than 1.0 amp rating, it might be safest to put in that higher rated part.
tom jobe...


----- Original Message -----
From: Graziano Tedoldi
To: TekScopes@yahoogroups.com
Sent: Tuesday, April 02, 2013 6:58 AM
Subject: R: [TekScopes] Tektronix 2230 power supply, which diode type is CR907?




Hi,



this diode is DSR 3400X = ultra fast recovery diode 600V 1° 50 nS



BYE



Da: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com] Per conto di Gregor Ruf
Inviato: martedì 2 aprile 2013 14:31
A: TekScopes@yahoogroups.com
Oggetto: [TekScopes] Tektronix 2230 power supply, which diode type is CR907?





Hallo,

I need abit help by repairing my Tek 2230 power supply.

I have tiredit to get help on the eevblog form but I have found no help with my problem.



The problemwas a blown power mosfet (Q9070). I have replaced it and the Power supply worksfine now.

But whilereplacing the mosfet I have seen that the Diode CR907 was replaced by 2 otherdiodes in parallel (I think by the previous owner). These diodes are surely notoriginal and if you connect 2 diodes in parallel the power is unevenlydistributed.

So myquestion is which diode is CR907 in original? And which diode should I put inif the original isn't available anymore?

Here is anexcerpt of the service manual. I have marked the diode red:
Tek 2230 diode



I hope youcan help me with my problem.


Re: Tek 453 Mod 210H

John
 

The MOD210H is the version made for IBM: it has it's own option mumber due to the "Property of IBM" being photo-anodised onto the front panel. the only other departure from a "standard" 453 (that I'm aware of) was that these were supplied with longer probes (3 metres).

John

This particular scope was used by IBM because it has "IBM" printed on the front panel. Does anyone know the significance of Mod 210H?


Re: Tek 2235A re-cap

vdonisa
 

It's me again... after doing a little bit more research (looking at other 2200 series oscilloscopes with fans) I came to the following conclusions:

- the case is designed so that the fan should be installed as an "exhaust" (outblow) fan; the air flow would be from the intake located on the left side near the middle of the CRT's length and gradually heat up until it flows along the hottest heat sink (the one between the 3 damaged caps) then gets exhausted through the rear vent

- installed like this it will also help with the power resistor located on the mainboard, under the CRT, near the intake - i saw some slight coloration of the PCB around it so I believe it heats up handsomely

This being said I'm tempted to go for:

- Sunon HA60251V4-000U-999 fan (13.8dBa)
installed on
- Qualtek QLM-60-30-10 vibration dampening sleeve

The fan draws only 60mA from 12V so it should not be such a burden for the power supply. Also Tek is using (beefier) Sunon fans in other 2200 series models so the brand would not look out of place in the 2235A.

Cheers,
Valentin

--- In TekScopes@yahoogroups.com, "vdonisa" <vdonisa@...> wrote:

Hi Tom,

I already did, all electrolytic caps in the power supply were replaced with new, long life, 105C rated Panasonic and Rubycon. I was just musing that if that still doesn't work then I might go for 125 Celsius automotive rated ones :-)

But then I think the fan solution makes the most sense. As you mentioned, the 3 damaged caps were all having something in common - close proximity to the same heat sink (on one side or the other of it). A fan would blow right into that heat sink and help keep everything much cooler....

I just measured the distance between the holes and it appears that a 60mm fan (50mm hole distance) would fit just right. Mouser has in stock stuff like Ebm Papst 612FL - 12V, 0.4W, 11.2cfm, 16dBA - seems just right as a low noise solution. I'll wait though until you can get a look at the fan specs for the 2236A so I could know the proper voltage and max power it could draw. BTW I got my manuals from exactly the same source (together with a trigger knob) :-)

Thanks,
Valentin

--- In TekScopes@yahoogroups.com, "Tom Jobe" <tomjobe@> wrote:

Hi Valentin,
Do yourself a favor and change those three capacitors in the right rear corner. If your scope has cooked C970 on the front side of the heat sink, things have been getting very hot in there.
I don't have a copy of the 2236A service manual so I ordered one today from Qservice in Greece. I would like to see what component values are specified for the 2236A fan supply.
This very nice 2235A I have had some ordinary problems in the power supply which I fixed a year or two ago. It had one remaining problem with channel 2 which had not been fixed. It turns out that U180 was dead in the vertical amplifier, so I replaced it with the similar part out of a 2235 (which has a different part number). The channel 2 voltage gain is now too low, so I removed the U180 that came from the 2235 and ordered the proper U180 part number for the 2235A.
It will be a week or two before the U180 part and the 2236A service manual arrive. I will let you know what I find out about this fan mod, etc.
tom jobe...
PS If anyone has a 2236A service manual, could I get you to look up the values of a few components in the electrical parts list?



----- Original Message -----
From: vdonisa
To: TekScopes@yahoogroups.com
Sent: Monday, April 01, 2013 2:39 PM
Subject: [TekScopes] Re: Tek 2235A re-cap



Hi Tom,

Thanks for your answer!

I was thinking of a fan too (a low noise low RPM one that would just move the air a little bit without sounding like a vacuum cleaner like my HP 3325A lol). But then I was not sure where I could connect it without disturbing the power supply too much. Now that I know.... I do remember that connector, with an empty place for a capacitor nearby, I just didn't know what exactly it was for.

Otherwise if I can't find a decent fan solution, I already identified some 10u/100V that should be able to take some heat: Nichicon has them in their BT series (automotive 125 Celsius) also Rubycon in RX30 series.

Thanks again!

Valentin

--- In TekScopes@yahoogroups.com, "Tom Jobe" <tomjobe@> wrote:
>
> Your observation that heat might be what kills those capacitors in the right rear corner of the mainboard, is probably worth considering.
> The 2235A has a much improved aluminum heat sink for Q946, Q947 and Q9070 which might further aggravate the situation for those capacitors, while helping the transistors and the MOSFET attached to the heat sink.
> Something you might consider is to use the onboard power supply for the 2236A case fan. The 2235A has the complete fan circuit less the capacitor C965. All of this is just in front of that aluminum heat sink, and the place for C965 is marked "2236A only". The back panel on the 2235A has a hole pattern to accept a standard 12 volt fan (50mm square bolt pattern on a 60mm diameter fan?), and the pins to connect the fan's power are just ahead of the heat sink and marked "W9965".
> If you look at the power supply schematic for a 2232 or a 2236A you will see the fan circuit and component numbers. I may have a copy of the fan schematic around here somewhere, but I think there is a free copy of the 2232 manual in several places. You don't even need the schematic if you decide to do this mod, just connect the fan with the polarity that moves the air in whichever direction you prefer.
> I have added this fan circuit to several 22xx scopes. Many of the older 22xx scopes had some kind of an undocumented fan circuit on the mainboard but you had to populate it. The 2215A and 2235 scopes would be examples that had the undocumented fan circuit.
> tom jobe...
>
>
>
> ----- Original Message -----
> From: vdonisa
> To: TekScopes@yahoogroups.com
> Sent: Saturday, March 30, 2013 6:19 PM
> Subject: [TekScopes] Re: Tek 2235A re-cap
>
>
>
> This is interesting, maybe the gentleman that replaced C942 & C943 with 4.7u/250V knew something, anyway his repair has lasted. In my case C925 was OK and looked like being the original one.
>
> Maybe I should find some 10u/250v although by looking at the schematic I can't understand how they would get so much voltage. Unless there's some weird transient action there at power turn on/off.
>
> Other than this it might be the heat in that compartment, I probably should pull out the infrared thermometer and check what's going on.
>
> Thanks!
>
> --- In TekScopes@yahoogroups.com, "Tom Jobe" <tomjobe@> wrote:
> >
> > For whatever reason, the three capacitors in the right rear corner of the mainboard fail on the 22xx scopes with your kind of power supply (C925, C942, C943) but they are easy to change without removing anything. Also in the same corner of the mainboard the SCR Q935 often fails on 22xx scopes, but your 2235A probably has the upgraded MCR72-4 SCR just like this one has, so you may have no worries there. I was just looking inside of this 2235A power supply to see how it differs from an ordinary 2235 and it is all quite similar, but upgraded in several ways.
> > tom jobe...
> >
> >
> > ----- Original Message -----
> > From: vdonisa
> > To: TekScopes@yahoogroups.com
> > Sent: Saturday, March 30, 2013 8:57 AM
> > Subject: [TekScopes] Tek 2235A re-cap
> >
> >
> >
> > Hi All,
> >
> > I just finished replacing a bunch of old aluminum capacitors in a recently received 2235A and I'm posting here to share my experience and ask a few questions. This is my first post here so please bear with me :-)
> >
> > The scope was in working status so it was about replacing any easily accessible capacitor in sight :-) So far I replaced only those located on the main board that can be accessed without removing the daughter boards. This means complete power supply cap replacement plus a few other cap spread elsewhere on the main board.
> >
> > What I noticed:
> >
> > - there was a previous repair work on C942 ad C943 (both 10u/100V), they were replaced with 4.7u/250V of types not normally found in a Tek; this looked like an old repair (not recent)
> >
> > - C970 (4700u/10V, +5V supply filter) was bulged and cracked at the base rubber vent and sitting in a weird position (because of the bulge lol)
> >
> > - all other caps were looking OK
> >
> > For replacements I used mainly Panasonic EEU-FR and EEU-ED series except C906 (Panasonic EET-ED) and the 10u/100V ones where I used Rubycon YXF.
> >
> > Now for the questions:
> >
> > - does this look like a decent choice of caps or could I have done better? (I'm looking at it as a "restoration of memorabilia" for myself; I'm interested in doing good work, cost is no objection)
> >
> > - there's a bunch of small electrolytics on the daughter boards, they seem to be mostly 22u/10V of Nichicon VX type, should I have a second session and replace these too? Are these prone to fail?
> >
> > - looking on the schematic C942 ad C943 don't seem to be stressed too much, any known reason why they failed and needed to be replaced (long time ago)? Should I over spec them (higher voltage than the original 100V)?
> >
> > - any good source for C906 270u/450V with 4 pins? I couldn't find any so I used a standard 10mm pin spaced snap-in, fortunately the PCB layout helped me and I was able to drill 2 extra holes and fit it there?
> >
> > - anything else that you gentlemen know to be frequently failing and should be replaced?
> >
> > Thanks!
> >
>


Re: Tektronix 2230 power supply, which diode type is CR907?

Tom Jobe <tomjobe@...>
 

It is interesting that CR907 is listed as part number 152-0808-00 but with different amp ratings in different manuals that I have.
For example CR907 / 152-0808-00 is listed as a 1.0 amp part in the 2215A manual, and it is listed as a 1.5 amp part in the 2230 manual.
In testing, when you run the inverter of a 22xx scope from an external 43 volt power source, it does take more amperage to run the scope on the more complicated 22xx models.
Since it may be easy to get an ultra fast diode with a greater than 1.0 amp rating, it might be safest to put in that higher rated part.
tom jobe...
 
 

----- Original Message -----
Sent: Tuesday, April 02, 2013 6:58 AM
Subject: R: [TekScopes] Tektronix 2230 power supply, which diode type is CR907?

 

Hi,

this  diode  is  DSR 3400X  =   ultra fast recovery  diode    600V  1°   50 nS

BYE

Da: TekScopes@... [mailto:TekScopes@...] Per conto di Gregor Ruf
Inviato: martedì 2 aprile 2013 14:31
A: TekScopes@...
Oggetto: [TekScopes] Tektronix 2230 power supply, which diode type is CR907?

 

Hallo,

I need abit help by repairing my Tek 2230 power supply.

I have tiredit to get help on the eevblog form but I have found no help with my problem.

The problemwas a blown power mosfet (Q9070). I have replaced it and the Power supply worksfine now.

But whilereplacing the mosfet I have seen that the Diode CR907 was replaced by 2 otherdiodes in parallel (I think by the previous owner). These diodes are surely notoriginal and if you connect 2 diodes in parallel the power is unevenlydistributed.

So myquestion is which diode is CR907 in original? And which diode should I put inif the original isn't available anymore?

Here is anexcerpt of the service manual. I have marked the diode red:
Tek 2230 diode 

I hope youcan help me with my problem.


Re: Vacuum?

Dave Daniel
 

Thanks for all the replies.

I have an air compressor, but I don't, in general use it for cleaning anything that is static sensitive or where "pushing" rather than "pulling" can force debris into places where I don't want it.

I often use a pair of discarded makeup brushes that I got from my ex-wife a long time ago, supplemented where necessary by cloth and isopropyl alcohol, to clean out debris. But sometime the debris is way too much for that approach (as is the case for this power supply).

I did see the hose-diameter converter kits, and I have several shop vacs and one canister vac. While that set up would work fine for this power supply, having that as a general purpose tool in the lab would not work because I would not be able to use it for anything that is static sensitive. I went from working on this stuff in Florida to now working on it in Colorado, and I am reasonably paranoid about creating ESD events in this arid climate. In Florida it was different, of course.

My recollection of the ESD-proof vacs we used to use on printers was really what prompted me to post the question. Several people pointed me at several manufacturers of those, and I think that is what I want for a dedicated "lab vac". The 3M ones are good. Those look like what I remember. I am still looking at the other two manufacturers - it is not clear from their websites that these are ESD-proof.

Thanks.

Cheers,
DaveD

--- In TekScopes@yahoogroups.com, Dave Daniel <kc0wjn@...> wrote:

Does anyone use a vacuum with a small-diameter hose to vacuum dust and
debris out of electrical equipment? I have an HP power supply that
defies normal cleaning methods, and I am looking for a small 110V vacuum
cleaner that has a hose and nozzle that can get into reasonably tight
places. We used to use something similar to vacuum out toner from
non-impact printers, but I haven't had much finding anything on the web
except tiny little USB-powered keyboard vacs and the like.

Thanks,
DaveD


Re: Curve Tracer vs. Octopus

Glydeck
 

Magnus,

Very nice.  The album as a whole makes for a well documented project that will be helpful for someone starting out.

George

On Apr 1, 2013, at 3:19 PM, "magnustoelle" <magnustoelle@...> wrote:

 



Hello Rob,

as you have asked for it, I have scanned the schematics of my overly simple component tester today.
Please refer to the picture here:
http://groups.yahoo.com/group/TekScopes/photos/album/1220275392/pic/1002421185/view?picmode=&amp;mode=tn&amp;order=ordinal&amp;start=1&amp;count=20&amp;dir=asc

The symbols are IEC/European style (i.e. we use rectangular boxes instead of zig-zagged lines for resistors), but I suppose these schematics are so easy to read anyway...

Again, there is nothing magic here that many other group members have not already mastered.

Have fun when designing and building your own unit!

Cheers,

Magnus


R: Tektronix 2230 power supply, which diode type is CR907?

Graziano Tedoldi
 

Hi,

 

this  diode  is  DSR 3400X  =   ultra fast recovery  diode    600V  1°   50 nS

 

BYE

 

Da: TekScopes@... [mailto:TekScopes@...] Per conto di Gregor Ruf
Inviato: martedì 2 aprile 2013 14:31
A: TekScopes@...
Oggetto: [TekScopes] Tektronix 2230 power supply, which diode type is CR907?

 

 

Hallo,

I need abit help by repairing my Tek 2230 power supply.

I have tiredit to get help on the eevblog form but I have found no help with my problem.

 

The problemwas a blown power mosfet (Q9070). I have replaced it and the Power supply worksfine now.

But whilereplacing the mosfet I have seen that the Diode CR907 was replaced by 2 otherdiodes in parallel (I think by the previous owner). These diodes are surely notoriginal and if you connect 2 diodes in parallel the power is unevenlydistributed.

So myquestion is which diode is CR907 in original? And which diode should I put inif the original isn't available anymore?

Here is anexcerpt of the service manual. I have marked the diode red:
Tek 2230 diode 

 

I hope youcan help me with my problem.


Re: Help Needed - 2465 -- No Beam

cmjones01
 

On 02/04/2013 14:30, Chin Siang Lim wrote:
3. If spots come up, then your HV section is OK. You need to check the
horizontal section. The biggest fear is a dead U800.
In my recent experience of a 2465 with a dead U800, the beam was very much still present: if I pressed the beam finder switch, everything looked normal, in the centre of the screen. Releasing the beam finder made the beam disappear off the right hand side of the screen. I accept that there may be different failure modes of U800, though.

Chris


Re: Help Needed - 2465 -- No Beam

cslim388
 


Hi Yair, 
I assumed that when you switch on the scope, you are able to see the self-test sequence - lights in the vertical position square moving from left to right thru the two rows of buttons. This is the self check process. 

1. Turn up the intensity button clockwise and press beam finder? If nothing, switch off scope, set intensity to midpoint,  take out scope cover and do 2.

2. Locate U800, the horizontal output IC. Follow pins 4 and 9 along the two resistors to the horizontal inputs of the CRT. 
Desolder the two  horizontal input wires and leave it hanging in the air in the open square. 

Now switch on the scope and see if you can see any dots. Move the vertical positioning knobs up and down thru its full range, vary the intensity knob.  

3. If spots come up, then your HV section is OK. You need to check the horizontal section. The biggest fear is a dead U800. 

Pl share your findings. 
cslim


Re: Tektronix 2230 power supply, which diode type is CR907?

Tom Jobe <tomjobe@...>
 

Hi Gregor,
CR907 is listed as a 400 volt, 1.5 amp, 50 ns recovery time.
Any ultra fast diode should work if it has at least those specifications.
I just looked on Mouser Electronics and they have some diodes like that with a 2.0 amp rating in stock.
Your local supplier might have a similar part.
tom jobe...
PS I would guess that the person put in a pair of the common 1.0 amp ultra fast diodes that are so common.
 
 
 
 
 
 
 

----- Original Message -----
From: Gregor Ruf
Sent: Tuesday, April 02, 2013 5:30 AM
Subject: [TekScopes] Tektronix 2230 power supply, which diode type is CR907?

 

Hallo,

I need abit help by repairing my Tek 2230 power supply.

I have tiredit to get help on the eevblog form but I have found no help with my problem.


The problemwas a blown power mosfet (Q9070). I have replaced it and the Power supply worksfine now.

But whilereplacing the mosfet I have seen that the Diode CR907 was replaced by 2 otherdiodes in parallel (I think by the previous owner). These diodes are surely notoriginal and if you connect 2 diodes in parallel the power is unevenlydistributed.

So myquestion is which diode is CR907 in original? And which diode should I put inif the original isn't available anymore?

Here is anexcerpt of the service manual. I have marked the diode red:
Tek 2230 diode 


I hope youcan help me with my problem.


Tektronix 2230 power supply, which diode type is CR907?

Gregor
 

Hallo,

I need abit help by repairing my Tek 2230 power supply.

I have tiredit to get help on the eevblog form but I have found no help with my problem.


The problemwas a blown power mosfet (Q9070). I have replaced it and the Power supply worksfine now.

But whilereplacing the mosfet I have seen that the Diode CR907 was replaced by 2 otherdiodes in parallel (I think by the previous owner). These diodes are surely notoriginal and if you connect 2 diodes in parallel the power is unevenlydistributed.

So myquestion is which diode is CR907 in original? And which diode should I put inif the original isn't available anymore?

Here is anexcerpt of the service manual. I have marked the diode red:
Tek 2230 diode 


I hope youcan help me with my problem.


Re: OT?..Why not design together a usefully and cheap usb sampler scope?

Jon Kirwan
 

On Tue, 02 Apr 2013 08:01:03 -0000, John G. wrote:

--- In TekScopes@yahoogroups.com, Jon Kirwan <jonk@...> wrote:

On Tue, 02 Apr 2013 05:21:15 -0000, John Gord wrote:

Gabriel,

Here is a link to a company that makes a USB sampling oscilloscope:

<<http://www.fastsampling.com/PHP/products.php>>

I have the DS800, it works as advertised.
Hmm. Out of stock.

http://www.fastsampling.com/PHP/order_form.php?product_id=20

Jon
Yes, but the DS800E is listed as in stock. (Might even be true.)
Ah, but that's a different unit. ;) And you don't get a nice
picture with it, either!! (Least wise not on my Chrome
browser.) :)

Jon


Re: OT?..Why not design together a usefully and cheap usb sampler scope?

John Gord
 

--- In TekScopes@yahoogroups.com, Jon Kirwan <jonk@...> wrote:

On Tue, 02 Apr 2013 05:21:15 -0000, John Gord wrote:

Gabriel,

Here is a link to a company that makes a USB sampling oscilloscope:

<<http://www.fastsampling.com/PHP/products.php>>

I have the DS800, it works as advertised.
Hmm. Out of stock.

http://www.fastsampling.com/PHP/order_form.php?product_id=20

Jon
Yes, but the DS800E is listed as in stock. (Might even be true.)

--John


Re: OT?..Why not design together a usefully and cheap usb sampler scope?

Jon Kirwan
 

On Tue, 02 Apr 2013 05:21:15 -0000, John Gord wrote:

Gabriel,

Here is a link to a company that makes a USB sampling oscilloscope:

<<http://www.fastsampling.com/PHP/products.php>>

I have the DS800, it works as advertised.
Hmm. Out of stock.

http://www.fastsampling.com/PHP/order_form.php?product_id=20

Jon


Re: Repackage AM503B

Dave Casey <dcasey@...>
 

To follow up, I checked my notes and the way I powered the AM503 from a 7k scope (7854 to be exact) was:
 
1. Removed U410 (regulator IC).
2. Wired +/-15V from mainframe slot to nets of U410.5 and U410.6, respectively. This powers the +/- 16V bus directly from +/- 15V as Steve suggested.
3. Replaced R452 and R462 with 2k parts.
4. Wired +/-50V from mainframe slot to C402 pos and C406 neg, respectively. This, along with the resistor change maintains the proper output for the +/- 19.3V regulators within the AM503.
 
Dave Casey
 

----- Original Message -----
From: dcasey@...
Sent: Monday, April 01, 2013 4:14 PM
Subject: Re: [TekScopes] Re: Repackage AM503B

 

Thanks for the extra tips, Steve. I'll have to go back and check my
notes, but I'm pretty sure I was already headed down the +/- 15V route
because I specifically remember having to consider the impact of the
voltage change on the circuitry it fed.

My original plan was (and is) get the whole thing grafted together in
one box, then test it to see what it can and can't do, and work toward
iterative improvements to have something useful.

This project is way on the backburner for me, as I shelved it a couple
years ago. I'm basically only sustaining my 7k scopes for the benefit
of having analog when I need it.

Dave Casey

Quoting Steve <ditter2@...>:

> --- In TekScopes@..., "Dave Casey" wrote:
>>
>> Yes. Haven't spent much time on it beyond proving that the AM503
>> (no suffix) can be powered from a 7k mainframe with a simple power
>> supply modification. My plan was to graft the electronics with
>> those of a 7A16A (the gain is right without the attenuator).
>> All the right bumps are on the attenuator drum of the AM503 to
>> implement the readout.
>> It's just a matter of making the boards fit in the shared space and
>> making the front panel pretty, which I haven't spent the time on yet.
>>
>> Dave Casey
>
> Dave,
>
> Operating an AM503 from 7000 series power supplies is not
> straightforward. The voltage/current combinations are not matched.
> You can not simply drop the higher voltages to the values used in
> the TM500 design.
>
> The AM503 bucking amplifier driver stage operates on +/- 16 V,
> produced from a power supply in the AM503 which gets its raw power
> from rectifying and filtering the 25 V AC windings in TM500.
> Operating it from the 7000 series+/- 50 V supplies would greatly
> exceed the per slot r current rating. It would also dissipate too
> much heat in the plug-in from the transistor you added to drop the
> voltage.. If you tried this, the amplifier would work but with a
> high current flowing through the probe, the AM503 would pull down
> the 50 V supplies, possibly current limiting the scope power supply
> if other plug-ins were also using the supply.
>
> A better solution would be to operate the bucking amp from the +/-
> 15 supplies. You would need to bypass the power supply circuit in
> the AM503, which needs more overhead to operate correctly. Dropping
> the collector voltage on the output stage by 1 volt on each side
> would lower the available peak power for the bucking amp. However
> this is not a problem for even operating on the 15 V 7000 series
> supplies, the AM503 bucking amp will pull more than the recommended
> design limit from these supplies when the probe is fully loaded, or
> overloaded. This can be prevented by limiting the swing of the op
> amp that drives the bucking amp output stage. This technique is
> used in the 11000 series version of the current probe amplifier.
> The peak power rating of some of the probes is reduced from their
> rating when used with the AM503.
>
> Finally, even with the amplifier swing limited to prevent
> overloading the +/- 15 V supply, driving the probe with large
> amplitude medium frequency currents, such as would be found in a
> SWPS, the current drain on the 15 V supplies will exceed di/dt
> design rating. When this happens, ripple is introduced into the
> internal power supplies which may cause gain and offset modulation
> to appear in adjacent plug-ins or the scope itself. We had this
> problem during the design of the TekProbe interfaced versions of
> the A6302. This effect can be mitigated by putting large bypass
> capacitors on the internal +/-15 V power supplies. These need to be
> really large – a few thousand microfarads. But charging these puts
> a real demand on the power supply during turn on, so it may be
> necessary to add a soft start circuit in power supply input, before
> it connects to the caps. A common implementation is power MOSFETs.
> A time constant turns the FET on slowly during power up.
>
> So while it is possible to operate the circuitry of an AM503 in a
> 7000 series slot, a fair amount of modifications need to be made to
> the AM503 circuitry.
>
> Steve
>
>
>


Re: OT?..Why not design together a usefully and cheap usb sampler scope?

John Gord
 

Gabriel,

Here is a link to a company that makes a USB sampling oscilloscope:

<<http://www.fastsampling.com/PHP/products.php>>

I have the DS800, it works as advertised.

--John Gord

--- In TekScopes@yahoogroups.com, "iglesia_cristiana_arpas_eternas" <iglesia_cristiana_arpas_eternas@...> wrote:

I hope not be off topic!!.
Here in this forum, are the best and smart people about electronics and scope Science...why not all of us together design a simple ,cheap an nice front end sampler connected to PC...?
Like this:
2Ghz BW..or more if possible.
1M/50 input impedance.
Microcontroler based (A/D,USB connection,time base..etc) .
On a first step with out input attenuator, with +-10V range input.
Seems very ambitions ??.
Gabriel.


Re: Vacuum?

Rob <rgwood@...>
 

*laugh*

I should have figured someone would sale one. I have the same “Kit” . Only mine consists of the parts stolen from a “key board vacuum” (I believe found in a truck stop for $1.98  or perhaps came with a Happy meal I forget).

 

The hose the repurposed pieces plug-into is connected to my shop vac hose with duct tape (no bailing wire in this case) and the other end has the nozzle of the “key board vacuum” duct taped into it (after skillfully removing same from afore mentioned implement with my Dremell look alike).

 

Mine literally whistles now. Although the kit version shown may have something on mine as I am pretty sure they have taken static generation into consideration. I was fortunate with mine as the piece of hose that was lying around is forgiving in that aspect as well. However, I do give credence to the possibility of generating some significant static.

 

Anyway, struck my funny bone sorry. For $10 it is a pretty good deal all things considered.

Rob    

 

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of Robert
Sent: Monday, April 01, 2013 5:10 PM
To: TekScopes@...
Subject: [TekScopes] Re: Vacuum?

 

 

How's this?
http://www.totalvac.com/23-4900-04.html?zmam=6843742&zmas=1&zmac=18&zmap=23-4900-04

Vacuum mini attachment kit

Bob

--- In TekScopes@..., Dave Daniel <kc0wjn@...> wrote:
>
> Does anyone use a vacuum with a small-diameter hose to vacuum dust and
> debris out of electrical equipment? I have an HP power supply that
> defies normal cleaning methods, and I am looking for a small 110V vacuum
> cleaner that has a hose and nozzle that can get into reasonably tight
> places. We used to use something similar to vacuum out toner from
> non-impact printers, but I haven't had much finding anything on the web
> except tiny little USB-powered keyboard vacs and the like.
>
> Thanks,
> DaveD
>


Re: Curve Tracer vs. Octopus

Rob <rgwood@...>
 

>>>”Have fun when designing and building your own unit!”<<<

 

I will. All received and stored for future reference.

Thank you.

Rob


Re: Tek 2235A re-cap

vdonisa
 

Hi Tom,

I already did, all electrolytic caps in the power supply were replaced with new, long life, 105C rated Panasonic and Rubycon. I was just musing that if that still doesn't work then I might go for 125 Celsius automotive rated ones :-)

But then I think the fan solution makes the most sense. As you mentioned, the 3 damaged caps were all having something in common - close proximity to the same heat sink (on one side or the other of it). A fan would blow right into that heat sink and help keep everything much cooler....

I just measured the distance between the holes and it appears that a 60mm fan (50mm hole distance) would fit just right. Mouser has in stock stuff like Ebm Papst 612FL - 12V, 0.4W, 11.2cfm, 16dBA - seems just right as a low noise solution. I'll wait though until you can get a look at the fan specs for the 2236A so I could know the proper voltage and max power it could draw. BTW I got my manuals from exactly the same source (together with a trigger knob) :-)

Thanks,
Valentin

--- In TekScopes@yahoogroups.com, "Tom Jobe" <tomjobe@...> wrote:

Hi Valentin,
Do yourself a favor and change those three capacitors in the right rear corner. If your scope has cooked C970 on the front side of the heat sink, things have been getting very hot in there.
I don't have a copy of the 2236A service manual so I ordered one today from Qservice in Greece. I would like to see what component values are specified for the 2236A fan supply.
This very nice 2235A I have had some ordinary problems in the power supply which I fixed a year or two ago. It had one remaining problem with channel 2 which had not been fixed. It turns out that U180 was dead in the vertical amplifier, so I replaced it with the similar part out of a 2235 (which has a different part number). The channel 2 voltage gain is now too low, so I removed the U180 that came from the 2235 and ordered the proper U180 part number for the 2235A.
It will be a week or two before the U180 part and the 2236A service manual arrive. I will let you know what I find out about this fan mod, etc.
tom jobe...
PS If anyone has a 2236A service manual, could I get you to look up the values of a few components in the electrical parts list?



----- Original Message -----
From: vdonisa
To: TekScopes@yahoogroups.com
Sent: Monday, April 01, 2013 2:39 PM
Subject: [TekScopes] Re: Tek 2235A re-cap



Hi Tom,

Thanks for your answer!

I was thinking of a fan too (a low noise low RPM one that would just move the air a little bit without sounding like a vacuum cleaner like my HP 3325A lol). But then I was not sure where I could connect it without disturbing the power supply too much. Now that I know.... I do remember that connector, with an empty place for a capacitor nearby, I just didn't know what exactly it was for.

Otherwise if I can't find a decent fan solution, I already identified some 10u/100V that should be able to take some heat: Nichicon has them in their BT series (automotive 125 Celsius) also Rubycon in RX30 series.

Thanks again!

Valentin

--- In TekScopes@yahoogroups.com, "Tom Jobe" <tomjobe@> wrote:
>
> Your observation that heat might be what kills those capacitors in the right rear corner of the mainboard, is probably worth considering.
> The 2235A has a much improved aluminum heat sink for Q946, Q947 and Q9070 which might further aggravate the situation for those capacitors, while helping the transistors and the MOSFET attached to the heat sink.
> Something you might consider is to use the onboard power supply for the 2236A case fan. The 2235A has the complete fan circuit less the capacitor C965. All of this is just in front of that aluminum heat sink, and the place for C965 is marked "2236A only". The back panel on the 2235A has a hole pattern to accept a standard 12 volt fan (50mm square bolt pattern on a 60mm diameter fan?), and the pins to connect the fan's power are just ahead of the heat sink and marked "W9965".
> If you look at the power supply schematic for a 2232 or a 2236A you will see the fan circuit and component numbers. I may have a copy of the fan schematic around here somewhere, but I think there is a free copy of the 2232 manual in several places. You don't even need the schematic if you decide to do this mod, just connect the fan with the polarity that moves the air in whichever direction you prefer.
> I have added this fan circuit to several 22xx scopes. Many of the older 22xx scopes had some kind of an undocumented fan circuit on the mainboard but you had to populate it. The 2215A and 2235 scopes would be examples that had the undocumented fan circuit.
> tom jobe...
>
>
>
> ----- Original Message -----
> From: vdonisa
> To: TekScopes@yahoogroups.com
> Sent: Saturday, March 30, 2013 6:19 PM
> Subject: [TekScopes] Re: Tek 2235A re-cap
>
>
>
> This is interesting, maybe the gentleman that replaced C942 & C943 with 4.7u/250V knew something, anyway his repair has lasted. In my case C925 was OK and looked like being the original one.
>
> Maybe I should find some 10u/250v although by looking at the schematic I can't understand how they would get so much voltage. Unless there's some weird transient action there at power turn on/off.
>
> Other than this it might be the heat in that compartment, I probably should pull out the infrared thermometer and check what's going on.
>
> Thanks!
>
> --- In TekScopes@yahoogroups.com, "Tom Jobe" <tomjobe@> wrote:
> >
> > For whatever reason, the three capacitors in the right rear corner of the mainboard fail on the 22xx scopes with your kind of power supply (C925, C942, C943) but they are easy to change without removing anything. Also in the same corner of the mainboard the SCR Q935 often fails on 22xx scopes, but your 2235A probably has the upgraded MCR72-4 SCR just like this one has, so you may have no worries there. I was just looking inside of this 2235A power supply to see how it differs from an ordinary 2235 and it is all quite similar, but upgraded in several ways.
> > tom jobe...
> >
> >
> > ----- Original Message -----
> > From: vdonisa
> > To: TekScopes@yahoogroups.com
> > Sent: Saturday, March 30, 2013 8:57 AM
> > Subject: [TekScopes] Tek 2235A re-cap
> >
> >
> >
> > Hi All,
> >
> > I just finished replacing a bunch of old aluminum capacitors in a recently received 2235A and I'm posting here to share my experience and ask a few questions. This is my first post here so please bear with me :-)
> >
> > The scope was in working status so it was about replacing any easily accessible capacitor in sight :-) So far I replaced only those located on the main board that can be accessed without removing the daughter boards. This means complete power supply cap replacement plus a few other cap spread elsewhere on the main board.
> >
> > What I noticed:
> >
> > - there was a previous repair work on C942 ad C943 (both 10u/100V), they were replaced with 4.7u/250V of types not normally found in a Tek; this looked like an old repair (not recent)
> >
> > - C970 (4700u/10V, +5V supply filter) was bulged and cracked at the base rubber vent and sitting in a weird position (because of the bulge lol)
> >
> > - all other caps were looking OK
> >
> > For replacements I used mainly Panasonic EEU-FR and EEU-ED series except C906 (Panasonic EET-ED) and the 10u/100V ones where I used Rubycon YXF.
> >
> > Now for the questions:
> >
> > - does this look like a decent choice of caps or could I have done better? (I'm looking at it as a "restoration of memorabilia" for myself; I'm interested in doing good work, cost is no objection)
> >
> > - there's a bunch of small electrolytics on the daughter boards, they seem to be mostly 22u/10V of Nichicon VX type, should I have a second session and replace these too? Are these prone to fail?
> >
> > - looking on the schematic C942 ad C943 don't seem to be stressed too much, any known reason why they failed and needed to be replaced (long time ago)? Should I over spec them (higher voltage than the original 100V)?
> >
> > - any good source for C906 270u/450V with 4 pins? I couldn't find any so I used a standard 10mm pin spaced snap-in, fortunately the PCB layout helped me and I was able to drill 2 extra holes and fit it there?
> >
> > - anything else that you gentlemen know to be frequently failing and should be replaced?
> >
> > Thanks!
> >
>

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