Date   

Re: 6DJ8 substitute idea - reverse engineering

Carl Hallberg
 

Hi all,
I have a whole bunch? of EEC88 tubes. They have BRIMAR  and FOREIGN BVA written on them.  I got them from a tech school.  What are these particular 6DJ8's and where made?
Carl Hallberg (W9CJH)

On Monday, June 21, 2021, 09:42:16 AM CDT, Jim Adney <jadney@vwtype3.org> wrote:





On Sun, Jun 20, 2021 at 10:21 PM, Keith wrote:

Anyway, just an idea to kick around as a cost savings approach to keeping
older tube scopes running at reasonable performance levels without dropping
two hundred extra dollars on premium and scarce tubes.
Sounds like a reasonable suggestion. I checked my favorite vacuum tube source, Michael Marx at vacuumtubes.com, and he lists 6BQ7As for $4 and lots of variations of 6DJ8/ECC88s for $18 to over $100, depending on exactly what you want. Michael is a very reasonable guy, but a lot of the people he sells to fit in the Goldenears/Audiofool category, so don't be annoyed by some of the descriptions. The plain Jane 6DJ8 is probably what you want, but he also has them with gold pins, maybe even in Tek boxes. Just ask.


Re: explosion mystery on my 7104

Dave Daniel
 

There have been multiple posts on these forums (primarily on the HPAK and this forum) over the years that describe input line filters that have failed catastrophically. When I saw the first one many years ago (I believe the filter was a Schaffner), it made me wonder about all of the products which my company shipped during the 80s that contained Schaffner or Corcom line filters. I am pretty sure that some of those products ran off of 240 VAC when used in Europe and other places that commonly use 240 VAC. I wonder how many have failed over the years.

I also wonder about all of the line filters that are inside some

These line filters were used primarily as a defense against conducted emissions; there were, and I assume still are, pretty strict agency-imposed limits on the amount of noise that a product may couple back onto the power line. The filters were not intended to prevent noise from entering the power supply. The design of the power supply, product grounding scheme, etc. were (are)  supposed to deal with that.

DaveD

On 6/21/2021 7:48 AM, greenboxmaven via groups.io wrote:
Philco, Zenith, and General Electric all produced TV receivers containing non-electrolytic condensers that would often give LOUD unscripted sound effects.  The condensers were of sub-standard quality, and ran at  or above their ratings. I have never seen a power input filter on anything Tektronix or anything else for that matter explode or vent  when operating on 120 volts.  Today most condensers rated for power input noise supression have internal fuses in some form to prevent exciting events. Is there a possibilty that all of the switching power supplies in use today are on occasion creating line transients never imagined when the filters were made that  fry the condensers?

   Bruce Gentry,   KA2IVY




On 6/21/21 2:18, Dave Seiter wrote:
  Exploding electronics can be so much fun!
-Dave
     On Sunday, June 20, 2021, 02:38:27 PM PDT, Sparky99 <jnolan@iprova.com> wrote:
    even if the  wall does now need to be redecorated :)











--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus


Re: 475A Problem

Michael W. Lynch
 

Dick,

I would love to have that scope as a parts unit, if nothing else.

--
Michael Lynch
Dardanelle, AR


Re: 6DJ8 substitute idea - reverse engineering

Jim Adney
 

On Sun, Jun 20, 2021 at 10:21 PM, Keith wrote:

Anyway, just an idea to kick around as a cost savings approach to keeping
older tube scopes running at reasonable performance levels without dropping
two hundred extra dollars on premium and scarce tubes.
Sounds like a reasonable suggestion. I checked my favorite vacuum tube source, Michael Marx at vacuumtubes.com, and he lists 6BQ7As for $4 and lots of variations of 6DJ8/ECC88s for $18 to over $100, depending on exactly what you want. Michael is a very reasonable guy, but a lot of the people he sells to fit in the Goldenears/Audiofool category, so don't be annoyed by some of the descriptions. The plain Jane 6DJ8 is probably what you want, but he also has them with gold pins, maybe even in Tek boxes. Just ask.


Re: 475A Problem

Dick
 

Replacing all 6 of those large, and expensive, caps
is deal breaker. I have another 475A, plus two 485's
and a few of the larger TEK scopes.

I'll put it into the Goodwill pile.

Thanks for all the replies,

Dick, W1KZS
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Renée <k6fsb.1@gmail.com>
Sent: Sunday, June 20, 2021 11:05 AM
To: TekScopes@groups.io <TekScopes@groups.io>
Subject: Re: [TekScopes] 475A Problem

48V is low.....the other issue I noted on my 475 is when the main caps
allow too much ripple...the tants start to go due to Peak voltages
exceed ratings.
Renée

On 6/20/21 10:47 AM, Jeff Dutky wrote:
The 50 V rail plays the same role on the 475/A as the 55 V rail on the 465. No idea why they are different, but here we are. 46 V is well out of spec for the 50 V rail, even 48 V is suspiciously low. I second Mark’s suggestion to check the rectifier and caps. Once that’s fixed I would verify all the power rails, voltages and ripple currents. If the electrolytic on the 50 V rail have gone dry there may be others that need replacement as well.

— Jeff Dutky





Re: Email adresses of group exposed

Jim Adney
 

On Sat, Jun 19, 2021 at 04:59 AM, Jean-Paul wrote:

Hello all: Somehow the masking of our email adresses after the poster's name
has been compromised.
When I view Tekscopes messages either on the web site or in the digest I don't see the poster's email address, unless he has included it in his sig file. I DO see full email addresses for attributions in some quoted material, which may be due to the 2nd responder's email program.

I admin several groups.io lists, and one of the options is to hide email addresses. It appears that his has been done for Tekscopes.

For those of you getting too much spam on your phone, I recommend nomorobo.com. It's free for landlines and $5/mo for cell phones. It doesn't work on all carriers, but you can check it out at nomorobo.com. It works by monitoring calls around the country (world?) and identifying spam calls. If your incoming call is spam, nomorobo answers it, so a call that only rings once is a robo call. We wait for the second ring to answer. It's not prefect, but it helps.

As for email spam, that's completely dependent on the spam filters at your email server. Some are good, some, like mine, are non-existent. I get 100-125 emails a day, of which 90% are spam. I use Pegasus Mail, which makes sorting and deleting the spam quite quick and easy.

Since this thread has evolved a bit to suggest changes in our groups.io configuration, I'd like to recommend one change: Enable posters to edit their own messages.


Re: Email adresses of group exposed

John Clark
 

Whether or not someone uses one email provider or another, or has super duper computer security they think is the best, or uses an email address they don't care if they get spam in. These email addresses should NOT be visible in a Google search like this. It doesn't matter if you think the Internet is broken or that you have no privacy anyway, so why try?

Someone needs to take a look at this and see why it's happening and what needs to be done to stop it.

John

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Seiter <d.seiter@att.net>
Sent: Monday, June 21, 2021 2:44 AM
To: TekScopes@groups.io <tekscopes@groups.io>
Subject: Re: [TekScopes] Email adresses of group exposed

Yahoo does do a good job, quite the opposite of AOL, which I stopped using almost completely about 15 years ago. I keep it for ebay, which itself generates about 4-5 junk emails on the average day. A few years ago I deleted about 23K junk and spam emails that had built up over the years. It's nice to have a selection of addresses for various uses.
-Dave
On Sunday, June 20, 2021, 11:07:07 PM PDT, Greg Muir via groups.io <big_sky_explorer=yahoo.com@groups.io> wrote:

I did see my address on Google. However, non-priority things such as this site are assigned to other collateral email accounts other than my “real” private one with my ISP. In this case my Tek & HP email address is one of five Yahoo accounts I have for various reasons so I don’t worry too much about spamming since it is a relatively non-important account and never deals with sensitive information. Besides, Yahoo takes fairly good care of incoming spam. If I am lucky I may see one or two spam emails a month in the Yahoo account.

It’s easier to set up security methods in advance rather than pay the price later.

Greg


Re: Type CA module in a 545

Jim Adney
 

On Sun, Jun 20, 2021 at 02:32 PM, David Kuhn wrote:

Everything looked the same except the filament resistance. Pin 15 to
ground is supposed to be ~65 ohms. On the good module is ~74 ohms. On
the weak one, it is 100 ohms.

So I guess I am looking at some old/bad tubes.
I'd be surprised if the actual filaments changed resistance that much. Check the pin to pin resistances right on the tubes and then see if there's a high resistance connection somewhere else. Frankly, 74 Ohms sounds much too high for a cold filament. There must be something else in that path.


Re: 2465B 5v Digital ripple and other issues

Mark Vincent
 

Allan,

The filters on the power supply need to be a high temperature low ESR type. Examples are Nichicon ULD/UHE. I do not know what brand and series you used. Condor Audio says to increase the capacitance of the filters for the 180 and 250mfd to 330mfd. Mouser has 470mfd 16V types in stock in the UHE version at the time of this post. These would be ones to use for the 5V supplies and any 8V supply. If you have used this or equal quality caps, move on. The TO-220 rectifier is suspect as these can go bad. The 47mfd types on the boards should be changed. I used ULD types in mine.

The intensity should go from 0 to 1,36V at the wiper and pin 16 on P120. You may not have put this back in fully. Reseat this. That may be all that is wrong. See if there is a bad solder joint to the control or flex cable. I am assuming the readout intensity is working by your post. You may have to trace the voltage back through the 10,000 ohm resistor back to the IC it goes to. The IC could be bad. This is an unlikely case.

What you said and looking at the schematic is the best I can do for now. You may find the problem easily. Let us know what you find as your problem(s).

Mark


Re: 7603 variations

 

Read all about it here:

<https://w140.com/tekwiki/wiki/7603>

Raymond


Re: 7603 variations

Eric
 

Tom,

That is a late model, if I remember correctly. The fan was an early
modification to cool the lv board. The nec plug was a late modification.

Eric

On Mon, Jun 21, 2021, 8:37 AM Tom Phillips <bumpstart21@gmail.com> wrote:

Hey Folks,

I just picked up a 7603 to replace the one someone dropped a few years ago!

Is info on the model changes/evolution on the 7603 available somewhere?

This new one has the integrated IEC plug, a small fan and was built in
the Netherlands.

-Tom P.






Re: Another interesting Tektronix web site

Keith
 

re: fan vibration isolators, p/n 348-008 and similar

Well, I've looked at these some already, and I am about to have to address this on my 575 rebuild. I'm toying with the idea of adapting Sorbothane and forming my own version of isolator replacements for Tek 348-008. I know it won't be original, but Sorbothane will outperform rubber any day of the week for vibration isolation. I hate fan vibration noise.

Sorbothane is fairly easy to find and comes in different elasticity values. Here are examples;

As equipment feet: https://www.scientificindustries.com/shock-absorbing-feet-microplate-genie-4.html?gclid=CjwKCAjw8cCGBhB6EiwAgORey0tSiIJkrFdHmkW8wP__jf58xSHbQzOQ1nzrseGZL9EtzNimuAH6jBoCWScQAvD_BwE

As disc bushings adaptable to various uses; https://www.amazon.com/Isolate-Sorbothane-Vibration-Isolation-Circular/dp/B00X6R47N0/ref=asc_df_B00X6R47N0/?tag=hyprod-20&linkCode=df0&hvadid=343351339353&hvpos=&hvnetw=g&hvrand=13667055082900351822&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9025850&hvtargid=pla-692662753862&psc=1&tag=&ref=&adgrpid=67841369743&hvpone=&hvptwo=&hvadid=343351339353&hvpos=&hvnetw=g&hvrand=13667055082900351822&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9025850&hvtargid=pla-692662753862

I've used this before. It is really a much better material than Buna-N rubber.

Of course, we have to accept that it won't look quite NOS original, which will definitely cost us points at the Concours d'Elegance judging events for our restored scopes. :-)


Re: 6DJ8 substitute idea - reverse engineering

Keith
 

Hi Tom,

Yes, makes sense - and also begs another question. I wonder when Tek stopped merely swapping in the newfangled 6DJ8 and actually started designing circuits that more fully exploited this tube's capability - thus making the reversion to 6BQ7 no longer an option? The 1961 announcement seemed fairly casual and broad-stroke. "We recommend 6DJ8 as direct replacements for 6BQ7A's"...

So I wonder when Tek started consciously pushing plate voltages out of the 6BQ7 range, thus turning what was essentially a 1961 technical bulletin announcement of "sub for better performance" into a "requires 6DJ8" specification? Maybe never? Dunno. They made a lot of scopes that survived a couple decades of design advances. Ah, the mysteries of Tek history.

Hi Sergey,

Yes, I'm well aware of 6N23P (and other Russian-sourced tubes.) I have some. With respect to Russian "equivalent", and with genuine love to all my Russian brothers, I would not personally put Russian branded parts in my Tektronix equipment. I tried it once, and when I turned the scope on half the on-screen information was in Cyrillic. It took months for me to sort it out. :-)

But all kidding aside - yeah, this is another option and similar in spirit to the idea of "going back" to 6BQ7. FWIW, I bought NOS 6BQ7 a hundred at a time for $1 a tube, which is even cheaper than the 6N23P you point out on Fleabay.

So, yes - if you want to buy more 6N23P than you need and want to sort through them (and if you want to allow Russian parts in your Tek scopes) the 6N23P offers something similar in cost to reverting to 6BQ7, perhaps with more plate voltage capability and maybe similar performance specs to 6DJ8 depending on how good the factory was running the day they were assembled or how honest the importer is, etc.

Remember that Tek burned in and sorted 6BQ7A for section balance before putting them in their scope applications. AFAIK there is no "special quality" mil-spec version of this tube, so 6BQ7 were really "average" quality consumer equipment tubes on which Tek did their usual extra purification/selection process. Of course, in the US circa 1961 "average quality" tubes were still generally very good. Not sure how sharp the 6N23P production line is these days, but you know at least that the tooling must be "vintage" at this point. :-0

My point is this; With any non-Tek prepped NOS 6BQ7 OR current production 6N23P we could do the very same thing. Burn in and section balance measurements are not very difficult to do. You just have to tell yourself the truth when measurements show that you have to to reject six of those seemingly "economical" 6N23P. Allowing for waste, these seemingly less expensive tubes might suddenly "cost" you $5 or more a pop, plus the time wasted burning in and measuring. For me, the duds would be write-offs, as I can't personally resell tubes I've tested and found wanting. I suppose those are just my old fashioned scruples.

In contrast, with just about any vintage NOS US/European sourced 6DJ8, I would be very comfortable plugging them right in my average Tek application after nothing more than a routine pass through the tube tester to check for shorts and gas. But of course, we can't get vintage US/Euro 6DJ8 for $2 a tube these days. Fortunately, I have about a hundred of them too - so I don't personally need to worry about this.

I guess I was thinking about the next generation of guys and gals who catch the bug and want to keep these old tube Tek scopes going. They probably DON'T have a big back stock of tubes they've collected in preparation for the coming electronic apocalypse. :-) By then the Audiophools will probably have driven the price of 6DJ8 to $200 a tube, just like 6550A. :-/

So, here's to hoping some future Tek enthusiast now in middle school might find this post after we are long dead and say "wow! I can use 6BQ7 in my 1960 model 315? No kidding?"

Anyway, just a thought thread. Maybe inconsequential.

Cheers,
Keith
CBG


Re: 'splitting' A2 and A3 PCBs when recapping Tek 2465

Jared Cabot
 

Beaten to it, but here I show how to work the clips in a restoration video:

https://youtu.be/NjHbfbtNhyY?t=645


7603 variations

Tom Phillips
 

Hey Folks,

I just picked up a 7603 to replace the one someone dropped a few years ago!

Is info on the model changes/evolution on the 7603 available somewhere?

This new one has the integrated IEC plug, a small fan and was built in the Netherlands.

-Tom P.


Re: 'splitting' A2 and A3 PCBs when recapping Tek 2465

Jon Nicoll
 

Reply to my own message... I've managed to do this fine after a bit closer examination. I just use a small pair of pliers to squeeze the inner 'jars' of the clip.s Everything came away fine. I have mostly completed the recapping boards A2 and A3...


Re: 6DJ8 substitute idea - reverse engineering

greenboxmaven
 

The 6BQ7, 6BK7, and 6DJ8 were all used extensively as cascode RF amplifiers in receivers and tuners. If my recollections are right, the 6DJ8 had better intermodulation tolerance than the others and could make the difference in receiving weaker FM stations when a powerful FM or television transmitter was nearby. The higher voltage rating of the 6DJ8 allowed it to be reliably operated with higher plate voltage and grid bias, which reduced the chances of a strong signal driving the grid positive or causing other intermodulation effects. I rarely if ever saw a 6BQ or BK7 used in an audio amplifier, but for some reason some manufacturers and the AudioPhools go ape$#1T for the 6DJ8. They are also very picky about the number and location of getters, the color and shape of the plates, age, and of course manufacturer.

    Bruce Gentry, KA2IVY

On 6/21/21 1:18, Tom Lee wrote:
Yes, the two types are indeed pretty much interchangeable. The ft values are neary identical, the transconductances differ by only about 10%, and the electrode capacitances are also within about 10% of each other. One thing to note, though, is that the 6DJ8 is rated for a higher plate voltage, so subbing with a 6BQ7 can't be done completely casually in all cases.

-- Cheers,
Tom


Re: TEK DMM830 True RMS Multimeter.

Colin Herbert
 

I always thought that the Service Manuals included the User Manuals, but maybe not in this case, if you say so.
I take it you have tried eBay, Telford Electronics and Artek. I also take it that you want a hard-copy, rather than an electronic copy - if not take a look at Tekwiki, it's a source of all sorts of info.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Ken Wright via groups.io
Sent: 21 June 2021 12:49
To: TekScopes
Subject: [TekScopes] TEK DMM830 True RMS Multimeter.

I have just purchased a Tektronix TEK DMM838 True RMS multimeter, I have found service manuals for it, but not a user manual. I have tried a the usual places but keep coming back to the service manual, any suggestions for the UK.
Regards.Ken WrightM0KHW


TEK DMM830 True RMS Multimeter.

Ken Wright <kenwright309@...>
 

I have just purchased a Tektronix TEK DMM838 True RMS multimeter, I have found service manuals for it, but not a user manual. I have tried a the usual places but keep coming back to the service manual, any suggestions for the UK.
Regards.Ken WrightM0KHW


Re: explosion mystery on my 7104

greenboxmaven
 

Philco, Zenith, and General Electric all produced TV receivers containing non-electrolytic condensers that would often give LOUD unscripted sound effects.  The condensers were of sub-standard quality, and ran at  or above their ratings. I have never seen a power input filter on anything Tektronix or anything else for that matter explode or vent  when operating on 120 volts.  Today most condensers rated for power input noise supression have internal fuses in some form to prevent exciting events. Is there a possibilty that all of the switching power supplies in use today are on occasion creating line transients never imagined when the filters were made that  fry the condensers?

   Bruce Gentry,   KA2IVY

On 6/21/21 2:18, Dave Seiter wrote:
Exploding electronics can be so much fun!
-Dave
On Sunday, June 20, 2021, 02:38:27 PM PDT, Sparky99 <jnolan@iprova.com> wrote:
even if the  wall does now need to be redecorated :)








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