Date   

Re: Tek power cables, older equipment

David Holland
 

https://www.lowes.com/pd/PRIME-6-ft-3-Prong-Gray-Air-Conditioner-Appliance-Power-Cord/1002462146


Something like that works on my 184 & 106....

May have to trim off the little nubbin on the female end, but it works well
enough...

David

On Sat, May 23, 2020 at 1:07 PM <sdturne@q.com> wrote:

For instruments like the 114 pulse generator, 184 time mark generator, and
more. Does anyone know of a good place to either get these power cables? I
have one, that came with my Type 114. With a 184 on the way, I'd like to
find another.

Thanks!

Sean




Tek power cables, older equipment

Sean Turner
 

For instruments like the 114 pulse generator, 184 time mark generator, and more. Does anyone know of a good place to either get these power cables? I have one, that came with my Type 114. With a 184 on the way, I'd like to find another.

Thanks!

Sean


Re: Tek 222/224 Battery Replacement - Project Update

Michael W. Lynch
 

Jeff,

Excellent Project! I do not have one of these little scopes, but if I did, I would be buying this kit!

Thanks for all your efforts.

--
Michael Lynch
Dardanelle, Arkansas


Tek 222/224 Battery Replacement - Project Update

Jeff Davis
 

Hi all,

I'm happy to announce that the Tek 222/224 Battery Replacement project is complete. I'm in the process of testing and shipping the first 25 orders from deposits received from folks here on TekScopes; after that, I've got another 14 boards available before I would have to go back and get some more built.

For those of you unfamiliar with the project, the Tektronix 222 and variants such as the 224 were sold originally with a sealed lead-acid (SLA) battery. Replacements for these SLA batteries stopped being manufactured a long time ago and, due to the form factor of the original battery, there are very few available SLA batteries that can be made to fit in the scope.

This kit allows the use of up to three readily available 18650 rechargeable lithium batteries to replace the now unavailable SLA battery. No modifications to the scope are required other than removal of the original SLA battery. Charging and protection circuitry is provided, allowing the use of unprotected 18650 cells. The kit consists of one assembled and tested battery charger circuit board, one 3D printed case, and some miscellaneous parts such as light pipes to bring the LED indicators to the front of the case and a jumper cable to attach to the scope’s battery connector. The kit does not include rechargeable 18650 lithium batteries (required for operation).

Here's a link to the order page: https://www.n0dy.com/product/tekcharger/.

For those of you interested in the history of the project, I maintained a status page with updates on progress at https://www.n0dy.com/2020/03/29/tek-222-224-charger-order-status/,

Some technical details from the original circuit designer can be found at http://kitsune-denshi.net/projects:tek222bat.

Best regards,
Jeff / N0DY
www.n0dy.com


________________________________
From: Jeff Davis
Sent: Thursday, March 26, 2020 10:02 AM
To: TekScopes <TekScopes@groups.io>
Subject: Tek 222/224 Battery Replacement

Hi all,

One of my customers approached me a few weeks ago about a project to replace the sealed lead acid battery (now unobtainium) in Tek 222/224 scopes with lithium ion cells that presumably will continue to be available for the foreseeable future. He pointed me to a really well done project with a public domain license. There's a YouTube video on it - https://youtu.be/LJ2VS3aohV0.

After a couple of weeks of capturing schematics, sourcing parts, etc. I'm about ready to hit Send on an order for the PCBs. Before I do that, however, I wanted to check with the community to see if there's sufficient interest to order more than the minimum quantity of boards.

How about it, Tek 222/224 collectors? Any interest in a battery pack replacement based on the design in the YouTube video above?

Regards,
Jeff / N0DY


Re: 7B80 sweeping off the screen

ik1zyw@...
 

Thank you Roger and Albert for the excellent advice.
I have the rackable 7603 and side-probing on the live system is not possible. But if the middle bay is left empty then signals can be brought outside easily, it just needs some planning since you connect test leads when the unit is on the desk and then carefully plug it in.

It turns out Q424 was bad. Socketed transistors are suddenly cool! The original part is 2N4122 which I replaced with a BC557 which has lower f_max but the same pinout. Other transistors mentioned by Roger are OK.

Now I will move to the calibration part of the 7B80 manual because the sweep is compressed: who knows what has been done to that 7B80 between 1974 and 2007 before I got it.

Thank you!
Paolo


Re: 475 questions

Leanna L Erickson <lle@...>
 

You may need to bend replacement FW Bridges to more horizontal after replacement.

On May 23, 2020, at 9:57 AM, Harvey White <madyn@...> wrote:

I'll give this a try, so my replies are in line

On 5/23/2020 12:48 AM, ciclista41 via groups.io wrote:
Hi Harvey,

So frustrating! I had a reply nearly as long as your post above, but accidentally hit some button and the entire thing evaporated. Oh well, maybe I will be less wordy and more to the point this time.
I used to have that problem, and then I took the entire "old" message, copied it to a word processor (notepad is fine), then did my editing, then pasted it back. Useful if you anticipate a long reply. As for emails, I use Thunderbird, and haven't had that problem.


Thanks for such a thorough set of suggestions and explanations! This sort of advice is so valuable to me. I understood the part about the rectifiers right away. The part about the linear voltage regulators will take some research on my part to get up to speed on that.
Ok, think of it in plumbing terms. You have a bucket from which you syphon water, that's the load. You have a water supply with a valve, that's the series/pass transistor. You've got a mechanism for measuring the water height in the bucket, and you set it for a certain level.

The bucket gets water removed, which we know. Think of that as the power going to the load (rest of circuit) and doing its job. So we have to adjust the valve to keep the amount of water going in equal to the amount going out. That's all the complicated circuitry. Measure height of water in bucket and adjust valve. Suppose we take less water? Then the bucket starts to get too full, and the mechanism closes the valve. Take more water? Bucket gets too low and we open the valve a bit more. Turn over the bucket, and we "ought" to go valve full on. However, if we don't want that, the little extra resistor and transistor act like a flow limiter so that you only get so much water going out.



I think I almost understand the part about NPN emitter followers, though. I'll be using all of that as well as everyone else's advice as I figure this thing out. Glad the advice has not been conflicting! Gives me confidence that I'm headed in the right direction.
You are. There's likely some good books on transistors out there, but one of the absolute best sources is the service manual itself. Tektronix (and HP) are noted for the quality of their service manuals.

Some on this list have been involved with electronics for years, and this kind of thing is familiar territory for them.

So, tacking a question on to this reply that's meant for anyone following the thread, since you've spent so much time already:

How do I know what generic components are best to replace the original parts? For instance, the tantalum caps come up a lot, but I assume when folks replace them, they don't use the same as the originals. What DO they use? There are so many types of capacitor, even in this one scope, and it's more than 37 years old. The large power supply caps are replaced with newer, smaller electrolytics, but I've heard that some brands are more reliable and last longer than others. What are some good choices?
Many tantalum capacitors can be replaced by aluminum ones. (standard aluminum electrolytics). Depending on the power supply, there are some parameters you want to follow. Others will want to amend these thoughts.

Capacitance, I'd personally use as much or a little more, but not double.

Voltage, going a bit higher is good, depending on where the part is. Early capacitors were thought to be capable of withstanding more of the voltage rating than not, so a 12 volt circuit might have a 15 volt rated capacitor. Time and evidence proved this wrong. Now, I'd use a 25 or 35 volt capacitor on the 12 volts. 25 being somewhat preferable to the 35 volt part. Get too high, and the capacitor doesn't work as well.

Temperature rating, most capacitors are rated at x thousand hours of operation at y degrees. You may not get to that temperature limit, but the typical temperatures are 85 degrees C and 105 degrees C. I'd use the 105 degrees C part.

Nichicon is a good brand, Panasonic is a good brand. Most people steer clear of clearly Chinese made parts which may not be made to appropriate standards.

I looked up one of the original rectifiers, an MDA960-3. I found a NOS of it on Ebay for almost $9 plus shipping. At that rate, this is going to get expensive very quickly. So what can I use instead? I assume that by looking up the specs on each original component that I end up replacing and finding something that meets or exceeds those specs, I'll probably be okay, but I could really use the voice of experience here.
Ask on the list. I think that a 960-3 is a bridge, 600 volts, and 3 amps. Any decent equivalent will work. A 5 amp bridge would work, but more than that and you may find that it's too big to fit properly. You could make an equivalent with (IIRC) 1n5400 series diodes, but that's awkward in a physical sense. The advantage of the bridges is that it's all one unit, and the case provides a heat sink. Any part with current (AC or DC) flowing through it will get hot. It may not be a measurable amount of heat, but there will be some. Generally, the higher power parts (semiconductors and resistors) have some method of dumping that heat, frequently into a chassis.



I'm aware of Digikey and Mouser. I ordered some diodes from Digikey several years ago to build a rectifier that I used to convert the power from a hub generator on my touring bike to charge my phone as I rode. It even worked, although my buddy said the one I built for him killed his phone. Mine had some issues that I never resolved. I'm hoping to soon have the ability to design my own circuit, rather than copying someone else's, and have it be rock-solid! But, I digress...
There are some places you can also buy parts. All Electronics, Electronics Goldmine are two of them. They operate as "dump surplus/excess inventory" and as such, if you see it, buy it and enough for future needs. No guarantees that they will have it again once sold out. James Electronics operates more as a hobby distributor, and has a more consistent inventory. You may find older parts there as well.

Mouser and Digikey are, of course, industrial distributors. If I buy resistors from them (I use surface mounted parts), I would consider buying in lots of 100 for the best price, perhaps even 1000, depending on my history of using the part. You'll see the economies of scale if you go to building things. Replacement parts are another matter, though, since you are not likely to need 100 each of 47 uf/200 volt capacitors. (certainly not at what I think they go for).

You may also find in your area, depending on where it is, some surplus electronics stores that have stocks of parts. Florida has at least two that I know of. Those stores are hard to find, though.

Harvey



Thanks again, Harvey!

Bruce




Re: 475 questions

Albert Otten
 

On Fri, May 22, 2020 at 04:02 AM, <ciclista41@...> wrote:


Yes, I re-read them just after turning the scope off, before my last reply,
and I re-read them just now. All three are shorted regardless of the polarity
with which I measured them. So it's surprising to me that the board doesn't
pop, get hot, or release magic smoke when I run it.
Hi Bruce,
Strange indeed that you measure 0 ohms at some LV lines while they come up to several volts when the 'scope is powered up. Is there any chance that something is wrong with your analog meters? As a test you might measure the resistance of those low-ohmic current sensing resistors R1478 (3 ohms) and R1468 (0.6 ohms) if these are easy to access.
Albert


Re: Update on my 7854 diagnostics project

Holger Lübben
 

Hi!

The trick is: In this case the front panel is also a pcb ;-)

This board is 0.8mm thick, white soldermask and black silk screen.
Here is a closeup of one of my red & white ones:

http://w140.com/tekwiki/images/7/77/P7001_program_overlay_card.jpg

If you look closely you can see the copper borders under the silkscreen

There a two downsides:
1) You can't get inner holes with sharp corners - usually you have to deal with 3mm corners. Thats the reason why my 7854 keyboard overlay card has a big hole per keyboard row - compared to individual holes for each key on the original card
2) I've tried a local pcb manufacturer and one of those cheap chinese ones and both reuqire at least one pad on the pcb. Thats the reason for the two pads on my panels.

But beside from that: They are great and look even better in real world.

If you want to have professional front panels you can also use services like www.schaeffer-ag.de. That's one of the local german ones, but I think you'll find such a company in every country.

Holger


Re: Tek 7K flex extenders available again

John Griessen
 

On 5/23/20 6:50 AM, evdsp39 wrote:
HI John,
I am very interesting to buy the 7k flex extender so plese tell me the cost included the shipping at this address :
COLISEXPAT - ref.276174
10, rue Eugène Hénaff
93000 - BOBIGNY
FRANCE
tel: 01.84.74.03.75 Mob : 06.76.40.32.22
I will pay by PAYPAL or AMEX card
Thank you for answer.
Etienne.
I sent you a paypal invoice.

--
John Griessen


Re: 475 questions

Harvey White
 

I'll give this a try, so my replies are in line

On 5/23/2020 12:48 AM, ciclista41 via groups.io wrote:
Hi Harvey,

So frustrating! I had a reply nearly as long as your post above, but accidentally hit some button and the entire thing evaporated. Oh well, maybe I will be less wordy and more to the point this time.
I used to have that problem, and then I took the entire "old" message, copied it to a word processor (notepad is fine), then did my editing, then pasted it back.  Useful if you anticipate a long reply.  As for emails, I use Thunderbird, and haven't had that problem.


Thanks for such a thorough set of suggestions and explanations! This sort of advice is so valuable to me. I understood the part about the rectifiers right away. The part about the linear voltage regulators will take some research on my part to get up to speed on that.
Ok, think of it in plumbing terms.  You have a bucket from which you syphon water, that's the load.  You have a water supply with a valve, that's the series/pass transistor.  You've got a mechanism for measuring the water height in the bucket, and you set it for a certain level.

The bucket gets water removed, which we know.  Think of that as the power going to the load (rest of circuit) and doing its job. So we have to adjust the valve to keep the amount of water going in equal to the amount going out.  That's all the complicated circuitry.  Measure height of water in bucket and adjust valve. Suppose we take less water?  Then the bucket starts to get too full, and the mechanism closes the valve.  Take more water? Bucket gets too low and we open the valve a bit more.  Turn over the bucket, and we "ought" to go valve full  on.  However, if we don't want that, the little extra resistor and transistor act like a flow limiter so that you only get so much water going out.



I think I almost understand the part about NPN emitter followers, though. I'll be using all of that as well as everyone else's advice as I figure this thing out. Glad the advice has not been conflicting! Gives me confidence that I'm headed in the right direction.
You are.  There's likely some good books on transistors out there, but one of the absolute best sources is the service manual itself.  Tektronix (and HP) are noted for the quality of their service manuals.

Some on this list have been involved with electronics for years, and this kind of thing is familiar territory for them.

So, tacking a question on to this reply that's meant for anyone following the thread, since you've spent so much time already:

How do I know what generic components are best to replace the original parts? For instance, the tantalum caps come up a lot, but I assume when folks replace them, they don't use the same as the originals. What DO they use? There are so many types of capacitor, even in this one scope, and it's more than 37 years old. The large power supply caps are replaced with newer, smaller electrolytics, but I've heard that some brands are more reliable and last longer than others. What are some good choices?
Many tantalum capacitors can be replaced by aluminum ones. (standard aluminum electrolytics).  Depending on the power supply, there are some parameters you want to follow.  Others will want to amend these thoughts.

Capacitance, I'd personally use as much or a little more, but not double.

Voltage, going a bit higher is good, depending on where the part is.  Early capacitors were thought to be capable of withstanding more of the voltage rating than not, so a 12 volt circuit might have a 15 volt rated capacitor.  Time and evidence proved this wrong.  Now, I'd use a 25 or 35 volt capacitor on the 12 volts. 25 being somewhat preferable to the 35 volt part.  Get too high, and the capacitor doesn't work as well.

Temperature rating, most capacitors are rated at x thousand hours of operation at y degrees.  You may not get to that temperature limit, but the typical temperatures are 85 degrees C and 105 degrees C.  I'd use the 105 degrees C part.

Nichicon is a good brand, Panasonic is a good brand.  Most people steer clear of clearly Chinese made parts which may not be made to appropriate standards.

I looked up one of the original rectifiers, an MDA960-3. I found a NOS of it on Ebay for almost $9 plus shipping. At that rate, this is going to get expensive very quickly. So what can I use instead? I assume that by looking up the specs on each original component that I end up replacing and finding something that meets or exceeds those specs, I'll probably be okay, but I could really use the voice of experience here.
Ask on the list.  I think that a 960-3 is a bridge, 600 volts, and 3 amps.  Any decent equivalent will work.  A 5 amp bridge would work, but more than that and you may find that it's too big to fit properly.  You could make an equivalent with (IIRC) 1n5400 series diodes, but that's awkward in a physical sense.  The advantage of the bridges is that it's all one unit, and the case provides a heat sink.  Any part with current (AC or DC) flowing through it will get hot.  It may not be a measurable amount of heat, but there will be some.  Generally, the higher power parts (semiconductors and resistors) have some method of dumping that heat, frequently into a chassis.



I'm aware of Digikey and Mouser. I ordered some diodes from Digikey several years ago to build a rectifier that I used to convert the power from a hub generator on my touring bike to charge my phone as I rode. It even worked, although my buddy said the one I built for him killed his phone. Mine had some issues that I never resolved. I'm hoping to soon have the ability to design my own circuit, rather than copying someone else's, and have it be rock-solid! But, I digress...
There are some places you can also buy parts.  All Electronics, Electronics Goldmine are two of them.  They operate as "dump surplus/excess inventory" and as such, if you see it, buy it and enough for future needs.  No guarantees that they will have it again once sold out.  James Electronics operates more as a hobby distributor, and has a more consistent inventory.  You may find older parts there as well.

Mouser and Digikey are, of course, industrial distributors.  If I buy resistors from them (I use surface mounted parts), I would consider buying in lots of 100 for the best price, perhaps even 1000, depending on my history of using the part.  You'll see the economies of scale if you go to building things.  Replacement parts are another matter, though, since you are not likely to need 100 each of 47 uf/200 volt capacitors.  (certainly not at what I think they go for).

You may also find in your area, depending on where it is, some surplus electronics stores that have stocks of parts.  Florida has at least two that I know of.  Those stores are hard to find, though.

Harvey



Thanks again, Harvey!

Bruce



Re: Update on my 7854 diagnostics project

Ke-Fong Lin
 

Hi Holger,

If that's not a secret, where did you have your keyboard overlay card manufactured?
There's multiple sources of PCB fabs that are very good quality, and cheap.
But I've trouble finding a suitable front panel manufacturer.
Thank you.

Best regards,


Re: 7B80 sweeping off the screen

Roger Evans
 

Albert,

Thank you for that particular insight, my suggestion was just to have a single plugin (the 7B80) in the 7603 and move it to whichever slot gave best access for probing. Your suggestion is much better since you are using the working parts of the 7603 to diagnose the part which is not working. I have previously suggested that if you have one channel not working on a normal double channel (not mainframe plus plugins) scope you can use the working channel to probe the non working channel from the input connectors as far as the channel switch.

Roger


Re: Looking for P7001 / GPIB ROM images

Holger Lübben
 

Hi Raymond,

Thanks for your help.

My board and ROM layout matches your description.
Here is a picture of my board:
http://w140.com/tekwiki/images/f/f0/P7001_GPIB_adaper_right_dismounted.jpg
As you can see someone changed some of the ROMs in the past - maybe thats the source of my problems.

It would be nice to get the files in "plain binary format" (*.bin), but I can reformat nearly every format.

Holger


Re: Looking for P7001 / GPIB ROM images

 

On Sat, May 23, 2020 at 02:12 PM, Holger Lübben wrote:


Is there anybody with a P7001/GPIB combo in this group who could provide me
with working copy of the ROM files?
Hi Holger,
I may have a way to read the ROMs in my unit.
Just to verify we're talking about the same hw/fw versions: My interface (board 670-4882-03) contains 7 pcs. 2708, numbered 160-0174-00.. 160-0810 in ink handwriting. Also, they all have "37-78" written on them in pencil. Could be a date code.
If these are what you're looking for, what format should the ROM code files preferably be in (Intel, Motorola, Tek, TI)?

Raymond


Re: 7B80 sweeping off the screen

Albert Otten
 

On Sat, May 23, 2020 at 12:42 PM, <ik1zyw@...> wrote:


First of all, on the "+ sawtooth" output in the back of the mainframe, the
working 7B53A produces a down sloping negative signal, sweeping between -4.5V
(trace @left) and -5.5V (trace @right). Measured on the low-ish impedance
analog voltmeter.

OTOH the 7B80 produces an up going positive "+ sawtooth" signal between +1V
(theoretical left) and +10V (theoretical right). Its frequency follows
time/div changes. Trigger is honoured (no sweep in single-shot for example).

Which reading is correct?
Hi Paolo,

The 7B80 reading is correct. If you change the Hor Pos control you might notice that the signal is actually between 0 V and +10 V. Just checked this in my similar 7633 (with 7B80 and 7B53A) and the Calibration procedure also mentions that 10 V amplitude.

In addition to Roger's comments (if this is not already what he meant), note that you might also use the 7603 as ordinary 'scope with 7B80 in the Left bay and some 7A in the middle bay and the 7B53A as time base. Trigger the 7B80 externally with some Line frequency signal and set the 7B53A also for Line triggering. Now you can probe the 7B80 internal circuitry and display wave forms via the 7A module. (Of course this makes it impossible to probe the rhs of the 7B80 though.)

Albert

Albert


Re: 475 questions

Michael W. Lynch
 

Bruce,

No worries about not responding personally to my post. You have been inundated with advice and in my experience with this forum, most people do not expect a personal reply for every piece of advice they offer.

As for desoldering tools you will not be sorry for the route you have taken. I did the same thing when I got started in this hobby almost 3 years ago. You are spot on about the heat, I did not mean to discourage the use of the Weller method, Just cautioning about too much heat for too long a period. You see to have that figured out. I have a Weller for those "Big" jobs as well.

With the powered desolder station, you can use the iron of choice to apply quick heat (supplementing the desolder pump heat) and suck the solder up quickly. Quicker is better. No need to rush, The first cap will take longer and you will gain proficiency as you do each subsequent cap.

For those "hole fillers". using a piece of 3/8" brass rod, I machined a small brass bushing with a 1/16 hole in the center. OD is then turned to just fit into the large holes vacated by the ground lugs on the caps and with a thin flange or "brim" on one side (the result looks like an old fashioned straw hat only with a small hole where the wearers head would go.). Drop these into the 3 big holes in the board for each cap and solder into place. Now you have a 1/16" hole for the little pins of those boards to solder into, instead of trying to fill that huge hole with solder. I wish now that I had taken pictures of what I did. It worked very well for me. I am sure that there are many efficient methods to accomplish this, I just had the time and the lathe available to do what I did. Once you get it apart, you will see what I mean and come up with some suitable method to accomplish the task.

One piece of advice that I will offer is to get into a systematic method of diagnosis, don't be tempted to "Shotgun" the task. You are started in the correct place, the main LV power supply. This is common to almost any instrument that you will encounter, going forward. Get all the power supplies working before you try to "Fix" any other problems.

I found the 465 manual P/N 070-1861-00 has an excellent troubleshooting section and is almost identical to the 475. If nothing else, this section can give you an idea of the flow of the power and how to work systematically to isolate the various supplies and locate your shorts or excess loads. You will find that certain manuals for certain instruments do a better job of explaining a particular portion of the circuit than others. The nice thing about the 465/465B 475, 475A and other derivatives is that they are all very similar, so you might glean some insight by looking at a similar section of a different instrument manual in the series (if that makes any sense).

When digging into a problem, spend a lot of time understanding the "Theory of Operation" or "Circuit Description" Section of the applicable manual, this is you best resource. This section cuts through the complexity of the circuit and the schematic diagram. This section is the "Cliff Notes" version, if you will, and directs you to the primary operations or critical components of each circuit.

Ask lots of questions and carefully consider all advice. People in this group are eager to help, you will find no better resource for your project.

Finally, Keep at it, I was where you were just s few short years ago, no previous experience in this sort of electronics, just the desire to learn and time to do so. .

Best of luck in your journey.

--
Michael Lynch
Dardanelle, Arkansas


Update on my 7854 diagnostics project

Holger Lübben
 

Hi

As promised an update about my 7854 diagnostics project:

I've finished all tests with my ROM card replacement. After that I've tweaked the layout a little bit and ordered a final sample.
These are pictures of the earlier prototypes:

ROM card:
http://methodyn.de/p/proto11.jpg

Keyboard-overlay card:
http://methodyn.de/p/proto12.jpg

Last week a good friend borrowed me his MicroLab. So at the moment I have a (nearly) complete 7854 digital diagnostics sytsem at home.
Pictures of the system can be found on Tekwiki:

http://w140.com/tekwiki/wiki/067-0911-00
http://w140.com/tekwiki/wiki/067-0961-00
http://w140.com/tekwiki/wiki/MicroLab_I

I've also uploaded the bin files.

Next step is to analyze and understand the system in detail.

Holger


Looking for P7001 / GPIB ROM images

Holger Lübben
 

Hi!

The GPIB interface in my P7001 does not work correctly. I did some debugging and I'm pretty sure the error is in the firmware.
Is there anybody with a P7001/GPIB combo in this group who could provide me with working copy of the ROM files?

The files on Tekwiki come from the ROMs in my device - so they are also buggy.

Thanks

Holger


Re: Tek 7K flex extenders available again

evdsp39
 

HI John,

I am very interesting to buy the 7k flex extender so plese tell me the cost included the shipping at this address :

COLISEXPAT - ref.276174
10, rue Eugène Hénaff
93000 - BOBIGNY
FRANCE
tel: 01.84.74.03.75 Mob : 06.76.40.32.22

I will pay by PAYPAL or AMEX card

Thank you for answer.

Etienne.


Re: 7B80 sweeping off the screen

Roger Evans
 

You can operate the 7B80 in any of the three slots of the 7603 and it will drive the vertical deflection if you put it in a vertical slot. So if you insert only the 7B80 and take all side panels off both the mainframe and the plugin you have some options for probing but you will need to run in auto trigger mode to have the time base sweeping with no trigger. If you don't have a second scope but do have an analogue multimeter you can run on the slowest possible sweep speed and the voltages should largely follow what is in the manual but obviously on a slower timescale.

If you probe test point TP345 (waveform 4) you can confirm that the sweep generator is producing the correct sweep voltage range and polarity. Measuring the waveform at the collectors of Q448 and Q458 (waveforms 8 and 9) you should see if either half of the paraphase amplifier is causing the problem. Then you need to follow the signal through Q428 etc to track down the culprit. If the transistors are socketed ( mine aren't) I would just begin by testing Q424, Q428, Q434, Q438.

Regards,

Roger

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