547 HV Transformer: Bill Schell rewind failed


Dave Wise
 

In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working. It has sat unused in a dry basement since then.

Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part. (Fades out in ten minutes.)

Hours of warming have not restored it. I don't think it will. I used to think my Bill Schell transformer was wax-impregnated; now I don't. I think it's epoxy, and like Tek's, it has gone bad.

I hope other Bill Schell customers can check in with their status.

I have an ace in the hole. In my drawer is... a 2010 Chuck Harris rewind. To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it. I'll install it soon.

Dave Wise


Dave Wise
 

?Update.


I retract my doom and gloom. Further warming seems to be restoring it after all. I simply left the scope running, with the intensity control at a safe position. I don't have a visible trace yet but as time passes I have to advance the control less and less to get one.


This data point corroborates the theory of moisture-ingress or other reversible reaction.


I will report back later.


Dave Wise


Note: This 547 has the 6AU5 screen grid voltage limit mod.

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise via groups.io <david_wise=phoenix.com@groups.io>
Sent: Wednesday, March 03, 2021 8:06 AM
To: TekScopes@groups.io
Subject: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working. It has sat unused in a dry basement since then.

Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part. (Fades out in ten minutes.)

Hours of warming have not restored it. I don't think it will. I used to think my Bill Schell transformer was wax-impregnated; now I don't. I think it's epoxy, and like Tek's, it has gone bad.

I hope other Bill Schell customers can check in with their status.

I have an ace in the hole. In my drawer is... a 2010 Chuck Harris rewind. To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it. I'll install it soon.

Dave Wise


widgethunter
 

Talked to Bill Schell a couple of decades ago about taking over and buying his setup from him.Instead, I ended up contributing what I had learned to Chuck Harris' efforts.My recollection is that Bill did NOT use epoxy, but potted in straight beeswax.Chuck and I discussed this at length, considering beeswax vs paraffin.Chuck tested 10 mixtures and found best dimensional stability with a mixture of both.
I suspect incomplete impregnation or less than ideal coil pack resulting from his scatter winding method.Never heard of a Schell rewind failing until now.Bernie Schroder

-----Original Message-----
From: Dave Wise <david_wise@phoenix.com>
To: TekScopes@groups.io <TekScopes@groups.io>
Sent: Wed, Mar 3, 2021 8:06 am
Subject: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working.  It has sat unused in a dry basement since then.

Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part.  (Fades out in ten minutes.)

Hours of warming have not restored it.  I don't think it will.  I used to think my Bill Schell transformer was wax-impregnated; now I don't.  I think it's epoxy, and like Tek's, it has gone bad.

I hope other Bill Schell customers can check in with their status.

I have an ace in the hole.  In my drawer is... a 2010 Chuck Harris rewind.  To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it.  I'll install it soon.

Dave Wise


Roy Thistle
 

On Wed, Mar 3, 2021 at 08:06 AM, Dave Wise wrote:


I used to think my Bill Schell transformer was wax-impregnated; now I don't. I
think it's epoxy
Hi Dave:
Sorry to hear about your trouble.
Perhaps you don't remember... because the last time you handled the transformer was when you installed it... but, how does one mistake wax for epoxy?... or vice versa.


Dave Wise
 

?Roy,


I uploaded pictures to album "?547 HV transformer rewind by Bill Schell". Tell me what you think.


Dave Wise


Update:


Still improving; the intensified part of the trace is now visible at the original intensity setting.

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Roy Thistle via groups.io <roy.thistle=mail.utoronto.ca@groups.io>
Sent: Wednesday, March 03, 2021 8:47 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

On Wed, Mar 3, 2021 at 08:06 AM, Dave Wise wrote:


I used to think my Bill Schell transformer was wax-impregnated; now I don't. I
think it's epoxy
Hi Dave:
Sorry to hear about your trouble.
Perhaps you don't remember... because the last time you handled the transformer was when you installed it... but, how does one mistake wax for epoxy?... or vice versa.


Chuck Harris <cfharris@...>
 

Hi Dave,

That is interesting, as I never sold any transformers to Stan.

So, did I pass muster?

-Chuck Harris

Dave Wise wrote:

?Update.


I retract my doom and gloom. Further warming seems to be restoring it after all. I simply left the scope running, with the intensity control at a safe position. I don't have a visible trace yet but as time passes I have to advance the control less and less to get one.


This data point corroborates the theory of moisture-ingress or other reversible reaction.


I will report back later.


Dave Wise


Note: This 547 has the 6AU5 screen grid voltage limit mod.

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise via groups.io <david_wise=phoenix.com@groups.io>
Sent: Wednesday, March 03, 2021 8:06 AM
To: TekScopes@groups.io
Subject: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working. It has sat unused in a dry basement since then.

Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part. (Fades out in ten minutes.)

Hours of warming have not restored it. I don't think it will. I used to think my Bill Schell transformer was wax-impregnated; now I don't. I think it's epoxy, and like Tek's, it has gone bad.

I hope other Bill Schell customers can check in with their status.

I have an ace in the hole. In my drawer is... a 2010 Chuck Harris rewind. To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it. I'll install it soon.

Dave Wise










Chuck Harris <cfharris@...>
 

Hi Bernd,

There have been several discussions about Bill's transformers of
late, and there is a picture on the group, that looks very much
like epoxy varnish, or some other non wax compound.

However, it is most definitely not scatter wound. It is a nice
looking, self supporting, universal wind.

Bill didn't use an outer tape covering on this transformer. The
naked winding is right there for you to see.

-Chuck Harris

widgethunter via groups.io wrote:

Talked to Bill Schell a couple of decades ago about taking over and buying his setup from him.Instead, I ended up contributing what I had learned to Chuck Harris' efforts.My recollection is that Bill did NOT use epoxy, but potted in straight beeswax.Chuck and I discussed this at length, considering beeswax vs paraffin.Chuck tested 10 mixtures and found best dimensional stability with a mixture of both.
I suspect incomplete impregnation or less than ideal coil pack resulting from his scatter winding method.Never heard of a Schell rewind failing until now.Bernie Schroder



Dave Wise
 

Chuck, your transformer worked great in 2010. A note reads that 6AU5 screen voltage was about 45V, and stable. That's way better than new.


Update.


With the intensity control at its original position, the trace is approaching original brightness.

My long-term-idle Bill Schell transformer is responding to baking.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Chuck Harris via groups.io <cfharris=erols.com@groups.io>
Sent: Wednesday, March 03, 2021 9:47 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Dave,

That is interesting, as I never sold any transformers to Stan.

So, did I pass muster?

-Chuck Harris

Dave Wise wrote:
?Update.


I retract my doom and gloom. Further warming seems to be restoring it after all. I simply left the scope running, with the intensity control at a safe position. I don't have a visible trace yet but as time passes I have to advance the control less and less to get one.


This data point corroborates the theory of moisture-ingress or other reversible reaction.


I will report back later.


Dave Wise


Note: This 547 has the 6AU5 screen grid voltage limit mod.

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise via groups.io <david_wise=phoenix.com@groups.io>
Sent: Wednesday, March 03, 2021 8:06 AM
To: TekScopes@groups.io
Subject: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working. It has sat unused in a dry basement since then.

Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part. (Fades out in ten minutes.)

Hours of warming have not restored it. I don't think it will. I used to think my Bill Schell transformer was wax-impregnated; now I don't. I think it's epoxy, and like Tek's, it has gone bad.

I hope other Bill Schell customers can check in with their status.

I have an ace in the hole. In my drawer is... a 2010 Chuck Harris rewind. To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it. I'll install it soon.

Dave Wise










Roy Thistle
 

Hi Dave:
Thanks for the reply... I'll check it the pic.
Hi it's Roy ( I'm a bit confused as.... usually.... if one doesn't address the O.P. directly by name... one is talking to the group... maybe that's not the convention? ) Also, I thought my "signature" in the footer was appearing?


Dave Wise
 

?Chuck, I think *I* bought that transformer from you - just to have a spare on hand - and loaned it to Stan for evaluation. Since my Bill Schell was happy, I wouldn't have swapped it out.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise via groups.io <david_wise=phoenix.com@groups.io>
Sent: Wednesday, March 03, 2021 11:24 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Chuck, your transformer worked great in 2010. A note reads that 6AU5 screen voltage was about 45V, and stable. That's way better than new.


Update.


With the intensity control at its original position, the trace is approaching original brightness.

My long-term-idle Bill Schell transformer is responding to baking.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Chuck Harris via groups.io <cfharris=erols.com@groups.io>
Sent: Wednesday, March 03, 2021 9:47 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Dave,

That is interesting, as I never sold any transformers to Stan.

So, did I pass muster?

-Chuck Harris

Dave Wise wrote:
?Update.


I retract my doom and gloom. Further warming seems to be restoring it after all. I simply left the scope running, with the intensity control at a safe position. I don't have a visible trace yet but as time passes I have to advance the control less and less to get one.


This data point corroborates the theory of moisture-ingress or other reversible reaction.


I will report back later.


Dave Wise


Note: This 547 has the 6AU5 screen grid voltage limit mod.

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise via groups.io <david_wise=phoenix.com@groups.io>
Sent: Wednesday, March 03, 2021 8:06 AM
To: TekScopes@groups.io
Subject: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working. It has sat unused in a dry basement since then.

Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part. (Fades out in ten minutes.)

Hours of warming have not restored it. I don't think it will. I used to think my Bill Schell transformer was wax-impregnated; now I don't. I think it's epoxy, and like Tek's, it has gone bad.

I hope other Bill Schell customers can check in with their status.

I have an ace in the hole. In my drawer is... a 2010 Chuck Harris rewind. To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it. I'll install it soon.

Dave Wise










Dave Wise
 

?Roy, your signature is not included in the groups.io footer. Thanks for including your name in the message body.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Roy Thistle via groups.io <roy.thistle=mail.utoronto.ca@groups.io>
Sent: Wednesday, March 03, 2021 11:33 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Dave:
Thanks for the reply... I'll check it the pic.
Hi it's Roy ( I'm a bit confused as.... usually.... if one doesn't address the O.P. directly by name... one is talking to the group... maybe that's not the convention? ) Also, I thought my "signature" in the footer was appearing?


Chuck Harris <cfharris@...>
 

Hi Dave,

I have long believed that the reason there were so few
failures with beeswax HV transformers is "wet" beeswax will
get hot and melt, letting the water out. Because the
windings are so close together, they act like a sponge,
and as long as the beeswax isn't made to boil, its surface
tension should keep it in the coil... It shouldn't drip
everywhere.

-Chuck Harris

Dave Wise wrote:

Chuck, your transformer worked great in 2010. A note reads that 6AU5 screen voltage was about 45V, and stable. That's way better than new.


Update.


With the intensity control at its original position, the trace is approaching original brightness.

My long-term-idle Bill Schell transformer is responding to baking.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Chuck Harris via groups.io <cfharris=erols.com@groups.io>
Sent: Wednesday, March 03, 2021 9:47 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Dave,

That is interesting, as I never sold any transformers to Stan.

So, did I pass muster?

-Chuck Harris

Dave Wise wrote:
?Update.


I retract my doom and gloom. Further warming seems to be restoring it after all. I simply left the scope running, with the intensity control at a safe position. I don't have a visible trace yet but as time passes I have to advance the control less and less to get one.


This data point corroborates the theory of moisture-ingress or other reversible reaction.


I will report back later.


Dave Wise


Note: This 547 has the 6AU5 screen grid voltage limit mod.

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Dave Wise via groups.io <david_wise=phoenix.com@groups.io>
Sent: Wednesday, March 03, 2021 8:06 AM
To: TekScopes@groups.io
Subject: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

In 2017, my 547 with Bill Schell HV transformer (installed around 2000) was working. It has sat unused in a dry basement since then.

Today, in March 2021, that transformer exhibits the same thermal runaway symptom as the original Tek part. (Fades out in ten minutes.)

Hours of warming have not restored it. I don't think it will. I used to think my Bill Schell transformer was wax-impregnated; now I don't. I think it's epoxy, and like Tek's, it has gone bad.

I hope other Bill Schell customers can check in with their status.

I have an ace in the hole. In my drawer is... a 2010 Chuck Harris rewind. To ice the cake, it's the one Stan Griffiths was evaluating - he gave it to me after he was done with it. I'll install it soon.

Dave Wise


















snapdiode
 

Whoah, that's odd. My 547 has a Bill Schell transformer, also installed many years ago, and my 547 was working fine yesterday, but it didn't run for more than 30 minutes.


Roy Thistle
 

On Wed, Mar 3, 2021 at 01:19 PM, snapdiode wrote:


my 547 was working fine yesterday, but it didn't run for more than 30 minutes.
It didn't run for more than 30 minutes, and then failed ... or you didn't run it for more than 30 minutes? .... and then you turned it off. (In which case the working state is unknown.)


snapdiode
 

I powered the 547 for 30 minutes and everything was normal for that time. Then I turned it off.


Roger M
 

Just another flashlight probing the darkness...

Back in December I received some mis Tek goodies from a kind member of the "Old Tek Scopes"
Facebook group,.. some obviously appearing to be HV transformer rewinds. One has the hand written
notation on the tape holding the core halves: "0308 6-6-94 W.A.S." (could be W.R.S.) on one side,
"Either 547 or 454 Good" on the other This specimen has what appears (by fingernail test and sight)
to be a beeswax coating. Defiantly not epoxy. The wind job also looks to be a professional universal,
and hasn't been put to use since re-manufacture.

-Roger


Dave Wise
 

?Update.


This morning it ran for an hour maintaining normal brightness. I think it's healed. I guess it absorbed moisture over the four years it sat, and yesterday I baked it out.

I can't explain why it didn't become lossy during other years-long idle periods between 2003 and 2017.


Carry on.


Dave Wise

________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Roy Thistle via groups.io <roy.thistle=mail.utoronto.ca@groups.io>
Sent: Wednesday, March 03, 2021 2:58 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

On Wed, Mar 3, 2021 at 01:19 PM, snapdiode wrote:


my 547 was working fine yesterday, but it didn't run for more than 30 minutes.
It didn't run for more than 30 minutes, and then failed ... or you didn't run it for more than 30 minutes? .... and then you turned it off. (In which case the working state is unknown.)


widgethunter
 

Hi Chuck;Assumed scatter because of the larger size of Schell rewinds.It has been a looong time, but I think I'd remember if he'd said anything about epoxy...B

-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Wed, Mar 3, 2021 9:57 am
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

There have been several discussions about Bill's transformers of
late, and there is a picture on the group, that looks very much
like epoxy varnish, or some other non wax compound.

However, it is most definitely not scatter wound.  It is a nice
looking, self supporting, universal wind.

Bill didn't use an outer tape covering on this transformer.  The
naked winding is right there for you to see.

-Chuck Harris

widgethunter via groups.io wrote:
Talked to Bill Schell a couple of decades ago about taking over and buying his setup from him.Instead, I ended up contributing what I had learned to Chuck Harris' efforts.My recollection is that Bill did NOT use epoxy, but potted in straight beeswax.Chuck and I discussed this at length, considering beeswax vs paraffin.Chuck tested 10 mixtures and found best dimensional stability with a mixture of both.
I suspect incomplete impregnation or less than ideal coil pack resulting from his scatter winding method.Never heard of a Schell rewind failing until now.Bernie Schroder
 
 


Roy Thistle
 

Roger:
If's beeswax (It could be paraffin wax, or a silicone wax, or some other wax type potting...or not even wax)
If it's beeswax... and you want to verify... put a tiny scraping of it in a spoon, and hold it in the steam of a boiling kettle... it will soon melt.
Also, beeswax has a pleasant fragrance.
--
Roy Thistle


Chuck Harris <cfharris@...>
 

Hi Bernd,

I guess the biggest indicator of a scatter wind would be
the presence of a spool. The universal wind doesn't require
any additional support.

In addition to talking to you, I talked to Deane Kidd, and
Deane talked about Bill using beeswax, like tektronix did in
the earlier transformers.

But, like you, it has been a looong time, and I don't think
our memories are getting any better.

-Chuck Harris

widgethunter via groups.io wrote:

Hi Chuck;Assumed scatter because of the larger size of Schell rewinds.It has been a looong time, but I think I'd remember if he'd said anything about epoxy...B



-----Original Message-----
From: Chuck Harris <cfharris@erols.com>
To: TekScopes@groups.io
Sent: Wed, Mar 3, 2021 9:57 am
Subject: Re: [TekScopes] 547 HV Transformer: Bill Schell rewind failed

Hi Bernd,

There have been several discussions about Bill's transformers of
late, and there is a picture on the group, that looks very much
like epoxy varnish, or some other non wax compound.

However, it is most definitely not scatter wound.  It is a nice
looking, self supporting, universal wind.

Bill didn't use an outer tape covering on this transformer.  The
naked winding is right there for you to see.

-Chuck Harris