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Trying to save a 576


Eric
 

Got a 576 that was supposed to be in working order but it seems it is not even close. After rebuilding the collector supply, I managed to get sweep again on the tube but the tube is VERY dim. I have a strong high voltage power supply and it is exactly where it should be. Given how faded the graticule lines are I have a suspicion the former owner stored it in the sun and it baked the tube. Is there any way I can safely drive the tube a little harder to try and get some brightness back. I also probed the 225V intensify pulse and it seemed it was stuck high it was not pulsing like it should. Any way to bring this on back or do I have a parts unit? The odd thing is the tube is uniformly dim it is but burned just not bright.


 

Hi Eric,

The 576 is a very valuable curve tracer. I may be possible to locate a replacement CRT from another instrument.
It uses a 154-0563-00 in serial numbers below B060000 and a 154-0563-01 in serial number B060000 and above.
Last month I helped fill in a small part of the information on a CRT Cross Reference list the VintageTEK museum is putting together from some of the microfiche they have. They may be able to tell you what other Tek instruments used that CRT.

Dennis Tillman W7PF

-----Original Message-----
From: Eric
Sent: Thursday, December 05, 2019 1:26 PM
Subject: [TekScopes] Trying to save a 576

Got a 576 that was supposed to be in working order but it seems it is not even close. After rebuilding the collector supply, I managed to get sweep again on the tube but the tube is VERY dim. I have a strong high voltage power supply and it is exactly where it should be. Given how faded the graticule lines are I have a suspicion the former owner stored it in the sun and it baked the tube. Is there any way I can safely drive the tube a little harder to try and get some brightness back. I also probed the 225V intensify pulse and it seemed it was stuck high it was not pulsing like it should. Any way to bring this on back or do I have a parts unit? The odd thing is the tube is uniformly dim it is but burned just not bright.




--
Dennis Tillman W7PF
TekScopes Moderator


Bob Koller <testtech@...>
 

You can set the mains input selector to the LOW position. This will increase the CRT filament voltage somewhat, and will increase the brightness at least a little. It also increases the LV regulator dissipation, but this is OK, at least in the short term.

Does the brightness "double peak" as the Intensity control is advanced? Does the spot defocus? If so, the CRT is just plain weak. Many of these were allowed to run 24/7, and wore out the tubes.
Is the CRT HV transformer black or brown potted? If brown, that is another problem, well documented.

Keep us posted on your progress, good luck!


Bob Koller <testtech@...>
 

Dennis, no other instrument used the 154-0563-xx CRT, unfortunately.


Ryan Scott
 

Hello, I have a 154-0563-05 CRT which came from the estate of a Tek collector.  I don't have a 576 so it's of no use to me.  You can have it for the cost of shipping from 97229 and take the gamble as it's in unknown condition.  Regards, Ryan Scott

On Saturday, December 7, 2019, 09:49:50 AM PST, Bob Koller via Groups.Io <testtech=yahoo.com@groups.io> wrote:

Dennis, no other instrument used the 154-0563-xx CRT, unfortunately.


Ed Breya
 

You may want to check that "intensify pulse" thing and circuitry to be sure it's working right. I don't recall if it should be active except in pulse mode. Speaking of which, are you sure you have the controls set up properly? Make sure it's not in pulse mode - there are buttons to select these, but I'm nowhere near a 576 right now, and can't see a panel to refresh my memory, so can't describe the right settings. You'll want it to be set for "normal" or "repetitive" or something like that.

If you figure out all the right operation, and the CRT is indeed very dim, it may be a candidate for rejuvenation, or replacement.

Ed


Ed Breya
 

One more thing - it's possible that the intensity and focus pot string resistors have drifted way out of spec. Depending on the circuit and drift direction, you may not have enough range for intensity setting all the way up. You'd have to study the circuit and make some measurements (they're elevated to near cathode voltage).

Ed


Tam Hanna
 

Hello,

on the risk of sounding like a broken record: please hang onto the DANAHER 576, 577 and 575 instruments with damaged screens.


Tamoggemon Holding k.s. currently is not in a position to make a public announcement re this, but we have something up our sleeve!


Tam

With best regards
Tam HANNA

Enjoy electronics? Join 15k7 other followers by visiting the Crazy Electronics Lab at https://www.instagram.com/tam.hanna/


Dave Voorhis
 

On 7 Dec 2019, at 21:18, Tam Hanna <tamhan@...> wrote:

on the risk of sounding like a broken record: please hang onto the DANAHER 576, 577 and 575 instruments with damaged screens.
Why do you call them _Danaher_ 576, 577, etc.?

I thought Tek wasn’t acquired by Danaher until 2007. Tek was still under independent ownership at the time the 575, 576, and 577 were made, wasn’t it?

If you’re naming it by current ownership, then wouldn’t it be more correct to call it Fortive?

Ownership often doesn’t reflect branding, anyway. E.g., a Vauxhall Corsa or Chevrolet Corvette is a Vauxhall Corsa or Chevrolet Corvette, not a General Motors Company Corsa or General Motors Company Corvette.

Or am I missing something here?


Eric
 

Bob you hit the behavior exactly square on the head. 0-75% intensity control the trace brightens then dims and brighten again and at full intensity it loses all resemblance of focus. So I think this tube is toast. Also this tube has a weird model number it is a 154-0563-05 I cant seem to find any reference to a tube version higher then 2. The High voltage transformer is the black silicone one.


Eric
 

Ryan, I would defiantly be interested in that especially if it has been in a box. The 05 is currently what is in there at the moment.


Bob Koller <testtech@...>
 

Eric,

Too bad the tube is weak, but very typical, I probably at least a dozen bad 576 tubes up in the loft, that I can't quite bring myself to toss.
You have the later HV transformer, so no worries there.
As for the dash number on the CRT, don't worry about that, all are usable, install any CRT that works!


Eric
 

On Sat, Dec 7, 2019 at 12:37 PM, Ed Breya wrote:


One more thing - it's possible that the intensity and focus pot string
resistors have drifted way out of spec. Depending on the circuit and drift
direction, you may not have enough range for intensity setting all the way up.
You'd have to study the circuit and make some measurements (they're elevated
to near cathode voltage).

Ed
CRT voltages tested at the neck pins.

1) -3815 Vdc
2) -3841 Vdc
3) -3840 Vdc
4) -2667 Vdc
5) NC
6) NC
7) 100 Vdc
8) 100 Vdc
9) 100 Vdc
10) 109 Vdc
11) 52 Vdc
12) NC
13) -3814 Vdc
14) - 3814 Vdc


Heater voltage ping 1-14) 5.9Vac


Mlynch001
 

I have a very early and a very late model 576. The CRT in the later one is an -05 at the end of the part number. The early one is a -00 or -01 if Memory serves me. The older one suffers from a bad HV transformer, which I am currently trying to get a replacement for.

--
Michael Lynch
Dardanelle, AR


 

Hi Ryan,
That was a very generous offer.
Hi to Kim!
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Ryan Scott via Groups.Io
Sent: Saturday, December 07, 2019 12:13 PM
Subject: Re: [TekScopes] Trying to save a 576

Hello, I have a 154-0563-05 CRT which came from the estate of a Tek collector. I don't have a 576 so it's of no use to me. You can have it for the cost of shipping from 97229 and take the gamble as it's in unknown condition. Regards, Ryan Scott

On Saturday, December 7, 2019, 09:49:50 AM PST, Bob Koller via Groups.Io <testtech=yahoo.com@groups.io> wrote:

Dennis, no other instrument used the 154-0563-xx CRT, unfortunately.




--
Dennis Tillman W7PF
TekScopes Moderator


Kurt Swanson
 

Eric,
I've had real good luck restoring cathode emission in TEK manufactured CRTs. A number of testers intended for the TV repair market can do this: the gold standard is the Sencore CR7000, but the Sencore CR70, as well as testers from Beltron, Heathkit, etc. also work well. You want the type of tester that uses a current limited supply to pull current between the cathode and G1 of the CRT, not the type of tester that applies a high energy pulse to the cathode. The current limited type of operation is usually referred to as cleaning or restoration as opposed to rejuvenation. Scope tubes, with their small structures, call for careful work with short duration, but I've had close to 100% success, including tubes that were so dim the trace could barely be seen in a totally dark room.

This process takes some finesse, so I would not start learning on a precious tube - If you happen to know anyone who used to work on CRT TVs, or someone who is into arcade games, they may be able to help, or point you to someone who can.

Good luck here. Bottom line: this technique is always worth trying on a weak tube - after all, you have nothing to lose.

Regards - Kurt


Miguel Work
 

The last tube crt monitor tube that I fixed was using a 576 as cathode bias power supply. ;)

Some examples in crt tube restorantion:

http://www.ke5fx.com/crt.html



-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Kurt Swanson
Enviado el: domingo, 8 de diciembre de 2019 18:43
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] Trying to save a 576

Eric,
I've had real good luck restoring cathode emission in TEK manufactured CRTs. A number of testers intended for the TV repair market can do this: the gold standard is the Sencore CR7000, but the Sencore CR70, as well as testers from Beltron, Heathkit, etc. also work well. You want the type of tester that uses a current limited supply to pull current between the cathode and G1 of the CRT, not the type of tester that applies a high energy pulse to the cathode. The current limited type of operation is usually referred to as cleaning or restoration as opposed to rejuvenation. Scope tubes, with their small structures, call for careful work with short duration, but I've had close to 100% success, including tubes that were so dim the trace could barely be seen in a totally dark room.

This process takes some finesse, so I would not start learning on a precious tube - If you happen to know anyone who used to work on CRT TVs, or someone who is into arcade games, they may be able to help, or point you to someone who can.

Good luck here. Bottom line: this technique is always worth trying on a weak tube - after all, you have nothing to lose.

Regards - Kurt


Eric
 

Working in the low voltage section of the 576. This is an older low voltage board all gold traces. The power supply keeps resetting itself. I was monitoring the -75 volt rail yesterday and it was rock solid for about 20 minutes. Then the power supply starts to rise to 0. Then it totally collapses and starts oscillating. And as it is doing that all the relays in the unit start to chatter and stutter. Any one have any ideas what might cause this or am I in for a hunt?


Mlynch001
 

HV transformer is going out. Look to see if it has the brown encapsulated HV transformer.
--
Michael Lynch
Dardanelle, AR


Eric
 

This one does for sure the brown potted one. The serial number is 22XXX. I would have never guessed that one would have spent the night banging my head agents the power supply. Is there a test I can do to confirm the transformer?